Turn off or standby?

[gohan2091]

In terms of general health and battery life, is it better to leave the n900 on standby or turn it off when not in use for long peroids of time (e.g. sleeping)

[schettj]

Unless you're planning on sleeping for more then a couple days, I'd go with standby

[nikolajhendel]

not sure about N900 (which I have only had for a week). For prior generations N8x0 it was better to leave on than turn off, as the boot ate battery. With N900, not so sure. 3G seems to suck energy, but if you are at home and connected to WIFI, battery drain is probably not that bad.
I have no hard info, as I keep the N900 plugged in overnight.

[Death Scythe]

Standby. I think it might even use more power booting up than being on standby for a night.

[Mara]

I put it in offline mode and leave it on standby overnight.

[chowdahhead]

I'd vote for standby too. If you don't need it to be connected, switch it to offline mode. It barely uses any battery overnight.

[magnuslu]

If it uses more battery power to shut down and restart than to leave it switched on overnight, it should be easy enough to test it.

1
a) Fully charge the N900
b) Leave it on standby/offline until it dies (This is the hard part as you're supposed to simulate that you're sleeping so you should be doing absolutely nothing on it for days!!)
c) Record how long time it lasted. This will be X hours.

2
a) Fully charge the N900
b) Switch it on and off as many times as you can until it will not power on because of lack of battery power.
c) Record how many times you could do that. This will be Y times.

Now divide X/Y. This will give you how many hours you can sleep per night. If it is less than you are comfortable with, switch off the phone, otherwise leave it on standby.

[benny1967]

I put it in offline mode and leave it on standby overnight.

I used to do that. There's this annoying bug though that brings up a "do you wnat to leave offline mode" message soon after you enter offline mode... and then, when you really want to go online again in the morning, claims it doesn't find any connections (even though it's about to connect to the wifi the very moment it says it doesn't find it).

im very annoyed about this sloppiness and therefore leave it on - usually charging overnight.

[gohan2091]

I left it on standby last night for 10 hours, the battery hardly moved so that's good. I have wi-fi set to manual connection and never use 3G so I think standby is the best way.

[TA-t3]

I used to do that. There's this annoying bug though that brings up a "do you wnat to leave offline mode" message soon after you enter offline mode... and then, when you really want to go online again in the morning, claims it doesn't find any connections (even though it's about to connect to the wifi the very moment it says it doesn't find it).
I've never seen this, I just go to "disconnected" mode every night and "connected" in the morning. Very convenient. I don't see any messages. Is the 'offline' mode you mention something different from what you see in the menu when you hit the power button? Are we talking about the same function?

[ksh]

I've never seen this, I just go to "disconnected" mode every night and "connected" in the morning. Very convenient. I don't see any messages. Is the 'offline' mode you mention something different from what you see in the menu when you hit the power button? Are we talking about the same function?

Sounds like your just disconnecting the WLAN or GPRS, hit the on/off button and you will see and "Offline mode" button on the right, then when you want to go back online do the same again but this time you will see a "normal mode" button

[jukkar]

I used to do that. There's this annoying bug though that brings up a "do you wnat to leave offline mode" message soon after you enter offline mode... and then, when you really want to go online again in the morning, claims it doesn't find any connections (even though it's about to connect to the wifi the very moment it says it doesn't find it).


That is this bug https://bugs.maemo.org/show_bug.cgi?id=3979

Although it is annoying to see the question, you can just press cancel as the autoconnect will handle the situation and you do not have to scan.

[benny1967]

That is this bug https://bugs.maemo.org/show_bug.cgi?id=3979

Although it is annoying to see the question, you can just press cancel as the autoconnect will handle the situation and you do not have to scan.

actually, it's this bug:
https://bugs.maemo.org/show_bug.cgi?id=8090

the bug you're referring to is the second part of what happens. it shouldn't ask me to leave offline mode in the first place.

[benny1967]

I've never seen this, I just go to "disconnected" mode every night and "connected" in the morning. Very convenient. I don't see any messages. Is the 'offline' mode you mention something different from what you see in the menu when you hit the power button? Are we talking about the same function?

mhm... do you just disconnect or do you really go to offline mode?

also, what are the settings of your RSS-application? do you have the RSS applet on the desktop? does it auto-refresh?

[Mara]

I used to do that. There's this annoying bug though that brings up a "do you wnat to leave offline mode" message soon after you enter offline mode... and then, when you really want to go online again in the morning, claims it doesn't find any connections (even though it's about to connect to the wifi the very moment it says it doesn't find it).

im very annoyed about this sloppiness and therefore leave it on - usually charging overnight.

I confirm also not having this issue. For the record I do not use the RSS applet.

[DaveP1]

I searched for this answer when I got my N810. Unfortunately, I have never seen any hard facts. The consensus, dating back to the N770, is that keeping devices in standby for a day consumes less battery than booting up once because of the need for the device to load the OS on boot up. There are also suggestions, as mentioned here, that going to offline mode (which should shut down Bluetooth and Wi-Fi radios) saves a bit of battery while in standby. As far as overall battery life over the years, it shouldn't make any difference.

[TA-t3]

mhm... do you just disconnect or do you really go to offline mode?
Offline. I click the power button, then button just below 'Lock unit' (second down from the right).


also, what are the settings of your RSS-application? do you have the RSS applet on the desktop? does it auto-refresh? I don't use the built-in RSS application.

[gohan2091]

There are also suggestions, as mentioned here, that going to offline mode (which should shut down Bluetooth and Wi-Fi radios) saves a bit of battery while in standby. As far as overall battery life over the years, it shouldn't make any difference.

My bluetooth is always off and my Wi-Fi is set to manual, only connecting when I request it to, yet I don't set the device to offline mode when I sleep. My method though mimics offline mode though... right? Or should I still be going to offline mode?

[TA-t3]

I mainly use offline mode to turn off the phone for the night, without turning off the N900. And if any other radio happens to be active at the time it'll also be shut off, of course.

[lazart]

hello,
i couldn't find a clear answer to the question, what's better: turning the device off by night or leave it in standby with all network stuff disabled.
did anybody measure it, for example with the battery graph app?

[ndi]

It's been one and a half years, but let's see.

Stand by eats more than off, obviously. A powerup cycle takes about one percent of the battery. A normal sleep cycle takes about 8%, about one per hour. You can get that from quoted standby times from product page.

So, surprisingly, turning something off eats less battery.

Also, you can install battery graph yourself.

Also, you can search forum for batterygraph screens, battery threads that span for years and some efforts from several people that do battery tests (such as the battery test thread).

Have fun.

[nicholes]

it looks charging the battery of n900 is costly for you,why don't buy a charger instead of getting it on rent!!

[Estel]

I tested it few times with bq27200-0 module (cause batterygraph and other programs like that use stock battery info sources, that are incorrect). Results were as follows (N900 always charged "from 0" to full, then left for 30 minutes before test):

------

cat /sys/class/power_supply/bq27200-0/capacity = 99

Turn off - Wait 8 hours - turn on

cat /sys/class/power_supply/bq27200-0/capacity = 98

------

cat /sys/class/power_supply/bq27200-0/capacity = 99

Off-line mode for 8 hours

cat /sys/class/power_supply/bq27200-0/capacity = 94

------

Surprisingly, it turns out that standby mode eats more battery. Long time ago, in stone era of mobile devices, i was turning it off for night. Then, following popular opinion that in smartphones / extra low-power mobile computers world bootup eat more battery, i switched to offline mode for night. did it also for my N900 for weeks, but i always felt that my battery last shorter. So finally did this test and coming back to switching off :)

[ndi]

Erm, popular opinions aside, no device eats less in standby other than off, ever. If anything, that little red LED eats a few as well.

As for powerup consumption, that's another myth-y thing that popular opinion is wrong about. If it were true, and powerup took something hefty, like 10% of the battery, then there ideas would be true:

a) Plug it in, it powers up, unplug it after 10-15 seconds after power up and it would be full. It's not, it can't be.

b) A battery is typically over 1000 mAh at 4.2 volts, that's 4.2 watts. N900 is 5000 mWh, and 10% of that is 500 mWh. That's 500 mW for 3600s, that's 1800Ws, and on a 10 second powerup you'd need to eat 180W (my math may be off it's really late). Point is, it would be glowing inside, smoke would come out, stuff would be having funny smells. In reality, 1% approx (actually, less than 1%, tests on forum have shown) spread over 30 seconds give us about half a watt, which is also a nice guess for a powerup cycle. n900 can eat up to 2W if you really try and boot-up isn't particularly heavy. Video encoding isn't up, e.g.

c) If that were true, no device would ever turn off, not really. It would just pretend-off, but actually stand by really deep, so it would insta-boot. Many devices do this. Some DSLRs do this to have instant-on, some notebooks, some PCs (ASRock has a nice instant-boot trick).

Normal appliances don't really turn off for convenience of touch button start, TVs and such need to keep time and the IR receiver. Non-touch ones, like toasters are really-off.

All this started a while ago, when someone with a poor grasp of math and physics (isn't that how all myths start?) found out that lights experience a surge when powered up, because cold filaments have a lower resistance. While true, the surge is the equivalent of 0.1 seconds of consumption (rounded), so it's not really there. And from there on, it spread like wildfire. As did battery formatting, battery memory, charging techniques that are almost always wrong.

It's so deeply embedded into the history that so called experts compile this info into whole books of unknowledge and then it ends up on lesser manufacturer's sites, in "expert's" training and I have seen manuals that came with batteries that gave plain wrong advice for the chemistry they sold.

(
Good information if you want it can be found on wikipedia, high-end manufacturer sites and specialty sites that don't have a Geocities-looking site. For batteries, batteryuniversity.com (http://batteryuniversity.com/) is a good read if you have the time. Professional charger manufacturers also have the right idea, like Maha. Those guys built chargers 3 years before Panasonic recommended the same charging technique (burst charges).
)

This includes self-discharge times, load types and profiles and many more.

As for the ultimate battery advice, here's the bottom line:

* Li-Po batteries hate the heat. Keep them cool. (Really)

* Li-Po self discharge (very slowly)

* Li-Po hates being fully charged or discharged when stored.

* Li-Po has a shelf life of about 10 years if charged 40-60% and kept in a dry environment at 4 degrees Celsius.

* Under normal use, a Li-Po has about 1000 cycles until it starts to be visibly lacking, that's about 3 years. Also, they tend to get ruined because they aren't kept in a half-charge at 4 degrees, so they start to break down after about 3 years. So, charge daily or you're saving for the dead.

Personally, I plug the device at night (about 2 AM) and pick it up at 9-10 AM, fully charged (96%). Every day. If it runs dry, I charge for a short while. After 18 months+, there is no visible damage.

Oh, and, because of the charging technique:
* Batteries charge faster from wall wart than USB or other emergency chargers

* Batteries charge faster in the lower range than higher. It sucks up 10-15% in 10 minutes when at 20%, but it takes 30 minutes from 86 to 96. So if you have a choice, aim low.

That's it for now.

[Estel]

ndi, thank You for very useful info. I will definitely look at site You mentioned - anyway, i think that i was ''victim'' of one of those myths, no matter that I'm not totally newbie in terms of battery maintenance. Even with Li-poly i tried to discharge them at least to 3,5 V before charging to full - yea, i know that origins of this come from NiCd/NiMh batteries, but i thought that 40-60% charge should be used purely for storage, i.e days/weeks/months without use.

So, we can sum up, that letting li-poly to go down only to 40%, then charging to semi-full is best to keep them alive and healthy? That is what you do by charging every night, or i missed something?

Also, just one little correction - N900 stock battery got 5W (4,9W in fact), so bootup can't use 0,5W, cause it would be... mentioned 10% :D Anyway, I got main rationale. Maybe someone will correct Your calculations, but that is pure cosmetic thing. I won't cause im after 24h without sleep so my calculations can get even ''better'' results.

[petur]

A small correction: your power calculation is flawed, because the voltage isn't a constant.

Apart from that, my unscientific experience is that the powercycle and a night in offline are not very far off, so I take the fastest and most convenient way - I have AlarmD switch it to/from offline mode automatically :)

EDIT: did two powercycles and battery-eye shows a 3-4% drop caused by the reboot.

If we're talking 1 day or more, I agree it is better to power it off.

[AndyNokia232]

Do the same as me: charge your N900 at work. Save some pennies on your electric bill ;)

[Estel]

petur:battery-eye, battery graph and other things like that seems to cheat. According to both, i many times run for hour or so with under 0 capacity ;) I would rely on bx2700 module, which is showing 1% for powercycle - as ndi already mentioned, it is something under 1% in fact.

Ps.

It's funny how battery-eye/graph react for powercycle - doing it all the time in loop for 20-30 times you Can probably reach -50 capacity (but wasn't be able to see it on graph, line will be just under visible area) and then use N900 for half a day.

[ndi]

Even with Li-poly i tried to discharge them at least to 3,5 V before charging to full - yea, i know that origins of this come from NiCd/NiMh batteries, but i thought that 40-60% charge should be used purely for storage, i.e days/weeks/months without use.

Actually, that's not true of NiCd nor NiMh. It doesn't help a NiCd to discharge below a voltage unless you are in very confined, non-standard scenario, like the memory droop. The effects of partial charging to a battery is negligible.

So, we can sum up, that letting li-poly to go down only to 40%, then charging to semi-full is best to keep them alive and healthy? That is what you do by charging every night, or i missed something?

I charge as I can, and I try to make it to home. Sometimes I charge at night at 40, sometimes at 56 (if I forget about the phone) sometimes at 0.

Ideally, a pattern exists, but if you go ideal you can't use the phone or it forces you to shut down or stop using.

Lithium Ion (BTW, it's the same chemistry as LiPo, the differences are negligible, in fact it's called Polymer Lithium Ion) is quite delicate in some areas, quite strong in others. Don't worry too much, try not to abuse it.

abuse:
* heat (bad)
* cold (ok)
* overcharge (very, very bad)
* overdrain (very bad)

The last two are managed by the chip inside the battery AND the N900, so it's fine. Keep it at a reasonable temperature.

It eats cycles if you charge it for no reason - some people charge 5 minutes when in an office. This is bad, a 5 or 10 minute cycle counts as a cycle, and if you do this 3 times a day, in a year it'll be dead.

Also, it is very bad for it to be discharged. Phone shuts down when it's low, but if you leave it like that for a week it will go below the safe level and be destroyed.

So, you know, as needed. If you try to charge every OTHER day but don't make it ans it has to stay for hours on zero, it will probably give out before a battery that has been charged daily. If you charge 5 times a day, again, bad.

So charge as needed, try to charge fully so it would have autonomy and not go through cycles (that's why I charge overnight, full charge every time). Mine usually takes me through the day. If it doesn't, I charge it again when it becomes low. This means that, on average, I get 1.1-1.2 charges a day.

Also, just one little correction - N900 stock battery got 5W (4,9W in fact), so bootup can't use 0,5W, cause it would be... mentioned 10% :D

No, actually, you missed the unit. N900 battery has 5 Wh (the little h isn't a typo). That's watts-hour, meaning it can put out 5 watts for an hour. The bootup sequence eats 0.5 W (notice no h). To eat 10%, it would have to boot for an hour straight.

When peaking, the device eats 2W, so 5Wh lasts for 2.5 hours.

And yes, as it was mentioned, my calculation is off. The battery doesn't do 1250 mAh at 4.2V, since the voltage drops. If it is linear, it averages 3.8 (4.2 to 3.6), by 1320 mAh(as per specs) is 5.016 Wh.

I knew it was 5 so I just cheated the math and pasted the result :P

Anyway, I got main rationale. Maybe someone will correct Your calculations, but that is pure cosmetic thing. I won't cause im after 24h without sleep so my calculations can get even ''better'' results.

Ehmmm ... I can't really find much fault with the calculations, actually. It was an approximation to start with, and battery really is 5Wh, 10% is still 500 mWh and dissipating 10% of battery charge in a matter of seconds still yields blue smoke.

And explodes (lights, actually, it's a rapid flame) the battery, most likely, assuming a phone thingy can output anywhere near the required power to heat the core over 60 Celsius. Point is, it's not 10%.

As for using battery module as opposed to native HAL, it's not like that. Battery level is a complex thing without some electronics, and the percentage is a decaying average based on consumption, load and voltage.

It is not wrong, it is helpful. Rebooting the phone erases that backlogged average so the phone guesses based on voltage alone. That's why reboots mess up the percentage, not that percentage is unreliable.

I found the battery kernel module to be incredibly annoying. The thing simply assumes that voltage is percentage and it varies wildly. After quiet periods, it shows 75% even though the battery is over 50% gone. Other times, it simply panics when I know it's fine.

Overall, the Nokia percentage calculation is pretty good, if you know how it works. Batteryeye is a nice program, and it logs and shows, it does not presume to show any percentage, it is up to you to determine droop, fall rate and guess your own capacity.

Good capacity software could be written, but Maemo is kinda dead and the few good people we have are busy fixing stuff, not polishing battery guesstimates. And good for them.

Other phones have the same battery and charging principle and work to the percent because they gave a *** when they wrote the OS. Nokia didn't, because Nokia still uses indicators that read "full, full-ish, 'bout half, empty-ish and red". For that kind of precision (and they round up to counter human factor) there is no need to estimate anything.

You and your percentage. Kids these days.

[shadowjk]

I'd like to see some references for your claim that a partial cycle equals a full cycle.

Considering that what the N900 (and almost everything else) does once the battery reaches full is let it discharge 2-5% and then top it up again, it should be burning through a large amount of "cycles" once it reaches full. (And the green light comes on independent of whether the battery is actually full at that time or not, and stays green until charger is disconnected)

[Estel]

Hey, that simple threat becomes very interesting battery knowledge source!

Most of ndi post is very useful for me, but I think that shadowjk got a point here. If you let the phone charge overnight, in fact it is just charged to full in few hours, then discharged to 95%, then charged again to 100, etc... It's true that RGB diode is green all the time, also battery-eye show it as "full" part of cycle. Unfortunately, N900 doesn't use power directly from charger when plugged - it just use the battery, charging in the same time. When battery reaches "full", power is cut off until battery drop to 95% or so. You can easily monitor it with bq27200 kernel-power module, by:

cat /sys/class/power_supply/bq27200-0/current_now

...when plugged in, you got value under 0 (for example, "-2475") which is exactly (charge current)-(current used by phone to "live"). When battery reach "full", current_now report just positive (i.e used actually) current - exactly the same as if plug is disconnected = non charging.

So, that would mean You got 10-20 cycles every night...

Also, after short logic check i totally disagree with Your calculations about powercycle drain. Precisely, your calculations are correct, but upside down - it is not 180W in couple of seconds, but 0.180W = 180mW!

Look ndi. N900 battery rounded up got 5Wh - You're right at that. It's capable to safe deliver for our needs 1315 mA constant current @ 3.8V (rounded from 3.3V-4.2V, doesn't matter for our calculations) for time of 1 hour. Also, it can deliver 657 mA constant current for 2 hours, etc. Every fluctuation of current change total time, but after C (current)*V (voltage)=5W or higher, battery is already at 3.3V and is discharged, aka "dead".

Then, if we want to calculate how much power could be drained if powercycle would use 3% of battery capacity, we need to keep in mind that Wh = Ch*V, so (Wh = Ch*V) / h -> W=C*V - we need to divide by h, not multiply by h as you did.

Using known values, we want to get 3% power during, lets say, 15 seconds of bootup - it is W*3/100=C*V, V is constant four our calculation (3.8V), W after /h is just 5. 5*3/100=0.15.

We want C (current), so C=W/V (or, if you prefer that, Ch=Wh/V, doesn't matter at all for us now), we get 0.039=0.15/3.8. Our 0.039 is in A, so it is 39mA. When we don't use /h, we get 3% of battery power = 39mAh. If You want to check for mistakes, 39mAh *33.33 = 1299.87 mAh - thats our 1315 mAh capacity :) rounded down.
@ 3.8V it is 5Wh.

So, we already know and proofed (if anyone understand my not so self-explanatory calculations ;) ), that 3% of battery power is 150 mW (yea, it's logical, but we wanted hard proofs, doesn't we?). 10%, then, is 500 mW, 10% battery capacity use is just 500mW. No need for blue smoke and other things.

---

Also, if we treat serious Your calculations about 10% beign 180W, that would mean we got 1800W at 100% - real beast. That would allow us for powering up high-power driller for an hour, just using our little battery, no need for wall plug ;) I got nothing against that idea, but for now we must be happy with 5W thing...

I tried to explain calculations as easy as it can be, but I'm again after sleepless night, so sorry for any hard to understand shortcuts. We can pull here dr_frost from "3000mAh battery mod" thread, he use high W batteries in his RC machines, so maybe he will be able to explain it more user-friendly ;)

[ndi]

I'd like to see some references for your claim that a partial cycle equals a full cycle.

Considering that what the N900 (and almost everything else) does once the battery reaches full is let it discharge 2-5% and then top it up again, it should be burning through a large amount of "cycles" once it reaches full. (And the green light comes on independent of whether the battery is actually full at that time or not, and stays green until charger is disconnected)

And that's why I said half charge. Small cycles don't count almost at all. Also, N900 charges to about 98 then doesn't charge until approx 86. Standby and self-discharge doesn't take that much overnight in normal circumstances. So, actually, N900 only chages one cycle overnight. Should it take longer, it tops it off again. My phone still says battery full if standby overnight.

And yes, battery does go away if phone is left plugged in for extended periods.

As for how much a cycle counts for a chemistry, I already linked battery university.

but I think that shadowjk got a point here. If you let the phone charge overnight, in fact it is just charged to full in few hours, then discharged to 95%, then charged again to 100, etc...

He does, just not under normal circumstances.

power is cut off until battery drop to 95% or so.

We already went through this in another thread. Also, if you decide to use a different metric, the battery module versus Nokia's, the we can't talk numbers, now can we? The module you use does not make the charge decision, bme does.


So, that would mean You got 10-20 cycles every night...

And that's why we don't use that module for reference. If bme says 90 percent and you plug it in, N900 says "battery full" and doesn't charge. If you want to see how bme works, ask bme via lshal.

Look ndi. N900 battery rounded up got 5Wh - You're right at that. It's capable to safe deliver for our needs 1315 mA constant current @ 3.8V (rounded from 3.3V-4.2V, doesn't matter for our calculations) for time of 1 hour. Also, it can deliver 657 mA constant current for 2 hours, etc. Every fluctuation of current change total time, but after C (current)*V (voltage)=5W or higher, battery is already at 3.3V and is discharged, aka "dead".

You have long lost me. In my post I said that IF IT REALLY ATE 10 PERCENT in a few seconds, dissipated power would be in the order of 100s watts. Nothing above has anything to do with my post. You seem to be on about what it really eats, my post was about what it would eat if.

If you still think I'm off, please quote the segment so we are on the same page.

Then, if we want to calculate how much power could be drained if powercycle would use 3% of battery capacity, we need to keep in mind that Wh = Ch*V, so (Wh = Ch*V) / h -> W=C*V - we need to divide by h, not multiply by h as you did.[QUOTE]

Power multiplied by time is capacity/energy. If capacity is the same, small time equals big power. If you used C as discharge factored as capacity per hour, then the equation is:

Capacity = power multiplied by time.
Capacity = volt times ampere times time.

if you factor hour, you get WATT equals Amp times Volt. Which is what we already know. You substituted C oddly. There is no Ch. C is an abstract-ish concept, in which a battery is drained in one hour, so A equals Ah. No operations using h is allowed.

Wh = W * h
Wh= V * A * h
5 Wh = 3.8V * 1.3A * 1h

If you make 1 to be 0.1, or 6 minutes, and volts is the same, then Amp jumps tenfold.

5 Wh = 3.8V * 13A * 0.1h

Same bucket spilled in half the time means twice the intensity.

So, if instead of 3600s you do 36 seconds, that's 100 times current, and 1.3 A becomes 130 amps, so, you know, some 500W.

[QUOTE=Estel;1004643]
Also, if we treat serious Your calculations about 10% beign 180W, that would mean we got 1800W at 100% - real beast. That would allow us for powering up high-power driller for an hour, just using our little battery, no need for wall plug ;) I got nothing against that idea, but for now we must be happy with 5W thing...


You missted the h again. 5 Wh is 5 * 3600 watts second. That's 18 kWs. Notice the s, it's not plural. Same battery can power a high power drill for a second not for an hour.

1 Ws is 1 watt for a second, 1 kW for a miliwecond or a wris****ch for a year.

Assuming zero internal resistance.

ETA: Haha, forum censored wris****ch. Wrist Watch. Timepiece. Portable clock. Heh.

[shadowjk]

It is true that the battery module does not control charging. This is a good thing, because that means any observations we make through it do not change bme's behaviour.

bme's charge control actually seems to run independently of bme's battery meter in a number of ways.
First, when charging it will display "battery full" before charging actually stops or reaches full. Then it will display green forever even if it charges and stops charging.
Secondly, if the battery is near full, like 90-100% in real terms (not the percentages reorted by bme, hal and so on), and you connect charger, it will often go straight to "Battery full" green led. This doesn't mean it's not charging, it does charge, and typically the charge rate is 2 - 3 times higher than when green light is triggered during a charge started from lower initial state of charge.

How "full" the battery is charged depends on a few factors:

Before PR1.3:
CC/CV @ 950mA to 4.2V, Charge termination at 50mA during CV stage.
The charge chip current sensor can not distinguish between system load and current going into battery. (Check leaked schematics and you'll see it).
Additionally there are some PCB losses between charging chip and system+battery amounting to about 0.125 Ohms.

Let's investigate two scenarios here: Idle phone, and not quite idle phone.
An idle N900 has a power consumption of about 6mA.
This decreases the termination current (at the battery) to 44mA, while the charger chip is outputting 50mA @ 4200mV.
By ohms law, The voltage drop across .125 Ohm is 6.25mV. Let's call it 6. The voltage at the battery will then be 4194mV.

So, charge ended at: 4194mV, 44mA.
Manufacturer recommended charge is CC/CV to 4200mA @ 0.7C with C/20 cutoff. Or, 924mA, 66mA.
The end voltage was lower, but so was the termination current, meaning more power was put into the battery.
Very close to the specs recommended by battery manufacturers anyway.

For the highly loaded N900, let's take 350mA system load. This is typical of heavy browsing on edge or wifi, or heavy IM activity on 3g, screen on.

Charge will never terminate, as 350mA > 50mA.
Voltage drop due to losses in path between charger and system: 0,35A * 0,125 Ohm = 43,75mV. Let's call it 44mV.
The battery voltage eventually stabilizes at 4200mV - 44mV, 4156mV, with the charger chip float charging it indefinitely.

The end voltage is lower, but then it has floated at that voltage for much longer than in the previous example.

After PR1,3 (but not with some community kernels) there's a minimum system load of about 60-80mA, which means that the charge never ends.


From a battery longevity point of view, time spent at 3.7-3.9V degrade the battery the least. Time spent over 4.1V accelerate aging. Time spent at 4.15 trickle charging (charging never stops) accelerates aging even more.
Likewise, time spent at low voltages also accelerate aging.

What this mean is that the battery is happiest when it's at 40-80%.

Anyway, after 100 cycles (where a partial cycle from 60-40-60 would be counted as one fifth of a cycle) and spending 8-12 hours a day on the charger, my battery tests out as 1261mAh (was 1300 as new). Seems to hold up much better than N8x0 BP-4L and BP-5L batteries :)

[ndi]

I actually regret not having a spare charger I can destroy by hooking up a multimeter. :)

[Estel]

Agree with shadowjk, i will only clarify that indeed i used bx module only to measure, not to control charging - as joerg mentioned in other thread, bx module can't be used for that caused it occupy hardware doesn't allowing other monitors (also bme) to work in parallel.

1 Ws is 1 watt for a second, 1 kW for a miliwecond or a wris****ch for a year.

sorry, but i can;t agree with logic of that sentence - i feel that either You or me is very wrong in understanding what other mean.

Calculations i posted on last post were NOT for actual capacity use, but for our teoretical 3% or 10% capacity (whatever, i calculated for both). I proved that using 10% of battery power during 15 seconds boot time WILL NOT produce 150W or any other similiar high value, but 150 mW.

Also - maybe I fail to understand it, what is possible - battery that is 5Wh can deliver 5 W after a 1 hour of work with 1C drain. That doesn't mean that it can deliver 10 W for 0.5 hour! You multiply it when time decrease, what is wrong. Battery CAN work for an 2 hour if C is 0.5 etc. In Your calculation, when time decrease, C remain the same, what is wrong.

Thats also why battery charge for an hour if charged with 1C (with 0 internal resistance etc), for 0.5 hour if charged with 2C, etc...You can not just multiply Wattage, when time decrease, ignoring C decreasing. Thats why in your calculations 10% of battery power would produce 150-180W energy during 15 seconds, what is wrong. Just because You don't decreased C in calculations.

[mece]

...
I proved that using 10% of battery power during 15 seconds boot time WILL NOT produce 150W or any other similiar high value, but 150 mW.


That is just plain wrong. Battery is 1250mWh so 10% is 125mWh so 125 mW PER HOUR. So 15 seconds would be 1/240 hours, 0.00416667 hours. now to get the Wattage used during that time when 125mWh was spent, we divide away time, which is 0.00416667 hours. in so we get 125 / ~0.00416667 mW which is 30000 mW or 30W.

EDIT: erm ok that ^^ is also just plain wrong. but if you replace all W's with A's it will be correct :) and multiply with some nice V, 3.9 or so, to get the W.

[Estel]

http://talk.maemo.org/showpost.php?p=923472&postcount=657

Post by joerg-rw, currently working on jrbme that is replacement for closed-source bme, for HEN project.

He stated that 1W won't exceed 30% of battery capacity... Because all capacity is 5W, You can call it 5Wh if You want to count with mAh, but that doesn't matter :)

I link this only because joerg-rw is very respected community member, and maybe that will help sceptics to understand that our belowed BL-5J is beast capable of store high W values :) In fact, that citation is not needed, cause basic math skills tell you than when on both side of "=" you got same multiplier - h in this case - You can drop it by dividing both sides /h.

sorry to call basic math skills - i don't want to offend anyone, but I;m just running out of ideas how to prove basic things that has been proved by calculation itself...

BL-5J can deliver max POWER of 5 W (no matter of time which it was used) what is CAPACITY of 5Wh independent of voltage (theoretically, You can use transformer to obtain 5Wh with for example, 12V, in 0 power loss during transforming, what is of course theoretical only), or 1300 mAh at 3.7.

Power != Capacity

Capacity is constant (unless our battery degrade ;P )

10% of 5Wh battery is damn 0.5Wh, and using that 10% of capacity during 15 seconds is using damn 0.5W = 500mW in 15 seconds.

I don't know how to write it in simpler words.

[dr_frost_dk]

i have just been browsing through an can't really be sure what has been concluded here but some ref here from someone that uses battery's to a greater extent then normal

the 1320mAh battery can in no way supply over 24W they are not built for high power delivery but high capacity and the 24W is based on 5C which they cannot deliver anyway, the circuit can defiantly not deliver much more the 5-10W

On the charge cycles, well you will already feel a slight drop (very low tho) from 5 cycle, and after 300 cycles it will have lost some % capacity, and here it really depends on the quality of the battery.

I have not been nice to my EV Ciao battery through the last year an it has lost a little over 20%, next time (in the near future) im getting LiFe instead.

[ndi]

Ok, everyone:

@dr_frost_dk: "the 1320mAh battery can in no way supply over 24W they are not built for high power delivery"

You are correct, I said ideal battery on purpose back there, even mentioned resistance.

The proposition was, booting the battery decreased charge by 10% as shown by the indicator. I said it can't be, because bootup is 30 seconds and if you killed 10% in 30 seconds that would be many-a-watt, so it can't happen. For many reasons, one being battery can't deliver, another being the phone would fry. Nobody is claiming it can happen. Au contraire.

@mece
That took about 10 minutes to understand, but yes, you are correct. Roughly 30A, or ~100W, in 15 seconds, that's 180W for 10 seconds.

@shadowjk
My measurements disagree with your last part, but I have a custom kernel. I'm fairly sure that my phone doesn't charge battery at all if left connected after end-of-charge, because the consumption slope is identical when connected and not connected.

Will dig further.

@Estel:
"A candle that burns twice as bright burns half as long". We can all agree to that. 5Wh is 5Wh and nobody is changing that (we wish).

5Wh = 5W in 1h
5 Wh = 10 W in 30 minutes

You said:
"10% of 5Wh battery is damn 0.5Wh, and using that 10% of capacity during 15 seconds is using damn 0.5W = 500mW in 15 seconds."

You again mix hours and seconds like they are the same.

10% of 5Wh battery is damn 0.5Wh(1), and using that 10% of capacity during 15 seconds is using damn 0.5W(2)(see what you did here?) = 500mW in 15 seconds.

Herein lies your problem. You said that 10% of 5Wh is 0.5W. It's not. It's 0.5 Wh. Since 10% of a kilometer is not 0.1 oranges. You should keep the measurements to the end of the equation.

You used 5Wh (at 1), and said that 10% is 0.5W (2). It's actually 0.5Wh, which is 0.5W FOR AN HOUR. Not 15 seconds. 0.5W for an hour, but delivered in 10/15 seconds.

If you still have issues with this, I suggest you take the simplistic approach to physics. Go with metric basic measurements. They are volt, ampere and second. I'll use the extended Watt as V*A.

A 5Wh battery delivers 5W for one hour, that's 5W for 3600 seconds. The measurements is watt hour, NOT watt per hour, mind you, it's not a division. Watt per hour implies flux of energy, watt hour is capacity.

A faucet delivers water at 1 liter per hour, meaning that left alone for an hour, it produces a liter. That allows for a bucket that gets filled in one hour to be one liter (1l/h*1h simplifies to liter). So, Wh is capacity, and Wh per time (hour) is W.

We simplify to metric, so the equation becomes:

5W * 1h = 5W * 3600 seconds = 18000 Ws

Note that when you do math with measurements, measurements keep the operands. So, two apples times two oranges makes four apple*orange. We write that as apple orange.

When you multiply watts and seconds, the result is watt second, or Ws. A grand total of 18,000 Ws. That's it. 18000 watts second. If you take 18000 seconds (5 hours) that's 1W. Makes sense. Also, if you take one second, it's 18000W. Whole battery.

10% is 1800Ws. If it boots in 10 seconds, it's 180W dissipated power, vast majority in heat. It'll glow like a light bulb (well ... -ish).

My original post read:
"A battery is typically over 1000 mAh at 4.2 volts, that's 4.2 watts. N900 is 5000 mWh, and 10% of that is 500 mWh. That's 500 mW for 3600s, that's 1800Ws, and on a 10 second powerup you'd need to eat 180W (my math may be off it's really late)."

Considering the hour, I was surprisingly accurate.

[dr_frost_dk]

what ndi means here is that it uses 180Ws (Watt seconds) not 180W, he just forgets the s at the end (e.g. Ws)

Because as i wrote the BL-5J cannot deliver much in terms of POWER, even in a 1 second spike you wont even get 20W

Now i don't know why he insists on using Ws instead of just Wh.
This then calculates to 10% being drawn in 30 sec = 1320mAh / 10 = 132mAh
In watts thats 132mAh * 3.8V = 0.5Wh that have been draw

But the fact is here that this is equal to 12C for 30sec which i can assure you that the battery or circuit can't handle

Now i know that it does not use 10% on a reboot/boot, because if you measure the battery in REAL TIME then you will see the voltage go up when it is done with the boot, e.g. it "recovers" some %, the real drain is more like max a few %, but why keep speculating, someone here please charge their battery full up, and then do either
10 Boot
20 Wait 10sec after idle
30 Shutdown
40 GOTO 10
or
10 Reboot #after full charge
20 Wait 10sec after idle
30 GOTO 10
and then report back how many boots or reboots the 1320mAh battery can handle, or any other battery you have.

[Estel]

In watts thats 132mAh * 3.8V = 0.5Wh that have been drawn

That is what i tried to say, but i agree with ndi that i messed a little with units (''appleoranges" ;) )

[cheve]

...but why keep speculating, someone here please charge their battery full up, and then do either
10 Boot
20 Wait 10sec after idle
30 Shutdown
40 GOTO 10
or
10 Reboot #after full charge
20 Wait 10sec after idle
30 GOTO 10
and then report back how many boots or reboots the 1320mAh battery can handle, or any other battery you have.

fwiw, here is the result of a test run:

# chrge volts %
0 1070 4052 85
1 974 3976 --
2 920 3976 72
3 963 3976 76
4 954 3941 75
5 964 3935 77
6 910 3952 72
7 921 3923 73
8 876 3947 69
9 910 3947 72
10 838 3923 66
11 887 3917 70
12 838 3905 66
13 810 3917 64
14 824 3911 65
15 796 3899 62
16 810 3894 64
17 782 3888 61
18 768 3882 60
19 729 3852 58
20 711 3823 55
21 743 3858 58
22 729 3870 57
23 687 3847 53
24 673 3829 53
25 673 3799 53
26 660 3847 52
27 648 3829 51
28 648 3823 51
29 639 3817 50
30 638 3799 50

I stopped the test run after the 30th boots. My guess is that it would take 110 to 120 boots to kill a 100% charged battery:). I have rechecked for any possible typo and there is none.

This is what I did:
=============
Between boot 1 to 9:
1. power on
2. waited for all icons at desktop(#4 view) to show up.
3. wait 10 sec
4. launch battery graph to record the values
5. close battery graph
6. switch off
7. wait about 30sec and Goto 1 again.

Between boot 10 to boot 30th.
1. power on
2. waited for all icons at desktop(#4 view) to show up
3. waited until the CPU load widget showing 1 bar.
4. wait 10 sec
5. launch battery graph to record the values
6. close battery graph
7. switch off
8. wait about 1.5 to 2 min and Goto 1 again.

A few notes about my setup:
=====================
My unit has power 47 kernel loaded(but only the default N900 voltage profile is used).

At boot 0th, the % battery was from the advanced power plugin.

At boot 1st, I forgot to record the % battery.

Wifi is enabled, but there is NO internet connection.

Bluetooth is switched off as shown by the advanced interface switcher.

N900 General Profile is used with System sounds set at level 1; speaker volume is set to OFF.

Brightness is set at max level.

Cheers,

[dr_frost_dk]

good work 'cheve' :)

Facts instead of speculation, that the way we like it.

Can see that at boot #30 the voltage was 3.8V which mens that there where about 50% left at that point, so the battery can take up to 60 boots on a charge with your setting and method.

So just doing boots without the waiting etc, it should do up to 100 boots, meaning that the actual drain on the battery is about 1% e.g. 14mA used. but for the sake of the 60 boots we get 1.66% or 22mA used (mA was rounded up)

And for the sake of W we get
3.8V * 14mA = 0.05W (180Ws)
3.8V * 22mA = 0.08W (288Ws)

the Ws was for 'ndi' :)

[ndi]

Dr frost:

For your first post, it makes me feel you didn't read my last post :). I have explicitly stated that I was referring to an impossible scenario. I don't know what more to say.

For your second post, I use Ws because of SI units (http://en.wikipedia.org/wiki/International_System_of_Units#Units). Also, for clarity.

@cheve
I read your initial post but couldn't find it again. You posted this experiment before, right?

[cheve]

@cheve
I read your initial post but couldn't find it again. You posted this experiment before, right?

no, it is the 1st time.

i hope it is somewhat helpful

[ndi]

Ah, it was Matan (http://talk.maemo.org/showpost.php?p=778643&postcount=5). I knew I read this before.

[dr_frost_dk]

no, it is the 1st time.

i hope it is somewhat helpful

very useful, thanks for taking the time to put this "myth" to rest. :D

[ME2g]

[...]
So finally did this test and coming back to switching off :)

I always switched off the mobiles that I had.
Maybe that is the reason why I get up to 3 days with my
N900.
;-)

Since I have my N900 as only phone I even wonder about the strange habit that we all had with landline phones keeping them "online" all night long.
;-)

[ndi]

Stock N900 does maintenance overnight - checks for updates, cleans up calendar, etc.

[Estel]

Unless You change that behavior to do it in noon/twilight/whatever ;) Anyway, shall we mark this topic as "concluded" and maybe do some wiki article? what do you guys think?

[reinob]

I still haven't seen any reports on battery usage during the night leaving the phone "as is", as I always do (GSM on, all data off).

Checking by battery-eye history, when idle my N900 uses about 0.5% per hour, so about 4% of the battery is used during the night.

Probably putting it in offline mode and unloading the WLAN driver would also save a bit. At least for me it's not worth it, prefer to be available at night (e.g. in case of emergency), and the battery lasts for a good 3+ days (OK, I'm not a heavy user..)

[reinob]

@ndi,

Do you have any references regarding that overnight maintenance?

[Estel]

Reinob, please read whole thread, not only last few posts (especially, that this one is short, only few pages...). Overnight off-line/powercycle was compared and published here long time ago.

[reinob]

@Estel,

Must have missed your post, but I have read and followed the thread from the beginning :)

[dr_frost_dk]

I still haven't seen any reports on battery usage during the night leaving the phone "as is", as I always do (GSM on, all data off).

Checking by battery-eye history, when idle my N900 uses about 0.5% per hour, so about 4% of the battery is used during the night.

Probably putting it in offline mode and unloading the WLAN driver would also save a bit. At least for me it's not worth it, prefer to be available at night (e.g. in case of emergency), and the battery lasts for a good 3+ days (OK, I'm not a heavy user..)

I also leave it on all night, but i have every thing on (and i do mean everything) i have a drop of about 5% and here we a talking about the 3000mAh battery, so it really looses some %, a normal battery would be closer to 10%, unless you charge up at night (keep charger connected when sleeping) then it chargers for 1-2 hours of the night and then starts to drop.

Ref. i charge when needed, really no pattern, i never charge doing sleep, and sometimes when im in a hurry and can see that it's low on power i charge it for 10-15minuts, but this still gives me 625mA (half of a normal battery)
For more info on my charging look to post #2 in my battery thread

[Estel]

Reinob, if that is the case - sorry about that. Maybe we're all getting little too sensitive about thread reading, but don't worry - i also read every post in thread that i write to, and also been ''accused'' of not doing so same day, except that from little different cause.

Sorry for this little off-topic, but i think that keeping good atmosphere was worth posting that - as a reminder, also for myself.

[reinob]

@Estel, no worries. I'm a very "passive" user here so I tend to read a lot and post very little.. but of course sometimes a detail or two can escape my attention :)

[iscio]

sorry for my bad english but at the end what is the result? turn off or offline mode to consume only a bit the battery? :-)

[reinob]

@iscio,

If you turn off the phone during the night the battery goes down by about 1% (due to the shutdown and restart), while leaving the phone idle during the night takes around 4-5%.

So if you don't need to be available during the night, turning the phone off saves some battery.

[ndi]

@ndi,

Do you have any references regarding that overnight maintenance?

Not at hand, but you can use Google to check, there is a bug on Bugzilla about Calendar being open in the morning, Nokia said it performs maintenance at 4 am.

Also, if you want you can check alarque.ini for all the scheduled tasks. The list is quite large. Also on this forum you will find tutorials on how to move/disable updating overnight.

As for wiki, not sure if "off eats less than on" deserves its own page.

[iscio]

@iscio,

If you turn off the phone during the night the battery goes down by about 1% (due to the shutdown and restart), while leaving the phone idle during the night takes around 4-5%.

So if you don't need to be available during the night, turning the phone off saves some battery.

sorry but I don't need to be available during the night but I asked if turn off or use offline mode. Here you can see my screen about night, it seems more than 4-5%

[dr_frost_dk]

The 4-5% is in "power saver" mode, if you like me have no power saving steps in place you will be looking more at 10% (for a 1320mAh battery), also the voltage in the battery is not the easiest to understand

Look at this graph then you will see that a 10% drop in battery graph is not necessarily equal to a 10% drop in capacity, thats why i made my battery meter like i did, it simulates the REAL graph quite good.
20167

In batterygraph it goes linear from top to bottom, but as you can see in the graph it is more log than linear

[Estel]

"Off eats less than on" maybe not, but our measurements - hell yea. And, as you posted few pages ago, this is quite popular urban legend (about standby = less battery drain), so i think it may be worth wiki'ing (viking). Sure, maybe not in "power-user" section, but "beginners" seems ok for me.

And sure - i know that i can do it myself, probably ;) Just wanted to know what others thing about it, and eventually discuss it.

// Edit

Maybe it should be integrated into one wiki page about battery @ all? With info about voltage/capacity ratio fr_frost presented here, short info and link to "3000 mAh battery mod" (other info regarding "how to buy less faked n900 battery, or real rocking one" is also there), and near-future "hotswap during heavy load" topic... If there is other battery-regarded info on wiki (i don't remember one now, but I may be wrong), we ca integrate it also.