brainstorm: extending n900 battery life (mods) [Archive] - maemo.org

ossipena

2009-09-28, 19:30

I just ordered 3pcs 1100mAh backup batteries for n900. Now I started thinking ways to have longest possible continous battery life.

Of course driving battery to the limit and wait until device dies and then switching batteries is an option. but why not consult the community about it. hope we come up with different ideas.

power over usb to keep device running when switching batteries(experts opinion needed)
hardmod one battery with connectors continously plugged in and glue it into cover(probably too extreme but doable)
other way to feed power to keep the device alive during battery switch
tweaking os for hibernation?!?!

any suggestions?

remember!! also stupid ideas count!!!! there can be a modification that makes a stupid idea brilliant!

Den in USA

2009-09-28, 19:41

I just ordered 3pcs 1100mAh backup batteries for n900. Now I started thinking ways to have longest possible continous battery life.

power over usb to keep device running when switching batteries(experts opinion needed)
hardmod one battery with connectors continously plugged in and glue it into cover(probably too extreme but doable)
other way to feed power to keep the device alive during battery switch
tweaking os for hibernation?!?!

!

I vote for your second option, except I would glue all three batteries together and wire them in parallel and mount to the back of your N900. Of course, then, you must wire three chargers also in parallel to handle the increased current of three batteries.:rolleyes:

ossipena

2009-09-28, 19:49

I vote for your second option, except I would glue all three batteries together and wire them in parallel and mount to the back of your N900. Of course, then, you must wire three chargers also in parallel to handle the increased current of three batteries.:rolleyes:

that could be solved with a switch. 3 batteries bundled together is so big that one could attach multiple dip/other switches and the size wouldn't chance so much :)

Den in USA

2009-09-28, 19:51

that could be solved with a switch. 3 batteries bundled together is so big that one could attach multiple dip/other switches and the size wouldn't chance so much :)

Great idea, except use mini relays instead of the dip switches.:rolleyes:

fnordianslip

2009-09-28, 19:56

zkyevolved

2009-09-28, 20:00

OK... Maybe I'm just thinking in the box... but why not just an EXTENDED battery. Or: I have a mini/micro usb charger that's 1700 mah, and I keep it in my bag. OR: I liked the first option. Run the device on USB while switching out the battery and replacing it. That's my fav.

lorelei

2009-09-28, 20:01

I vote for your second option, except I would glue all three batteries together and wire them in parallel and mount to the back of your N900. Of course, then, you must wire three chargers also in parallel to handle the increased current of three batteries.:rolleyes:

And don't forget the fork-lift for carrying around your N900 (or pants with very very large pockets) :) All those batteries will make a non-negligible mass to carry...

(edit: I approve the continuous supply from the USB port)

Den in USA

2009-09-28, 20:03

How about building an external power-pack from the two spare batteries, with a USB cable to attach to the device. Of course you are still left with the problem of charging the power-pack. I've used a PowerMonkey with my N800, but I might need to get a new adaptor for the N900 when it arrives.

Remember, he ordered three extra batteries in addition to the battery that come with his N900. If he decides on building up the external power pack that you suggest, I think he should order three more batteries for even more power!

edgar2

2009-09-28, 20:11

i know next to nothing about electricity, but would this be possible: having thin wires connected to the surface where the battery connects to the device - to those wires could a second battery be connected (even if only by holding it together) for the short while the almost dead battery gets removed and a third battery gets inserted. alternatively one could try to slide the second battery in place and then quickly remove the wires.

Texrat

2009-09-28, 20:16

remember!! also stupid ideas count!!!! there can be a modification that makes a stupid idea brilliant!

I think I love you. :D

Den in USA

2009-09-28, 20:17

zehjotkah

2009-09-28, 20:19

Good idea, except how about using conductive paint that also glows in the dark. Then you can find you N900 in the dark. :rolleyes:

i would be scared from a glowing ghost n900 in the dark... O.o

fnordianslip

2009-09-28, 20:19

If you make the wires thin enough, they will glow, but only for a short time.

debernardis

2009-09-29, 04:30

/me thinks hibernation is cool :-)
That's also the easiest way since involves no hardware modding.
Not that I have any idea how to start though...

spinnukur

2009-09-29, 04:39

Why wouldn't this work? It works with the N810.

http://www.nokiausa.com/find-products/accessories/all-accessories/power/chargers/dc-8?r=-1

ysss

2009-09-29, 04:49

I'm hoping #1 works. That'll open up so many simpler options:
- external charger\reserve battery packs
- temporary power for battery swaps

spinnukur

2009-09-29, 05:27

Just found this on JR.com, it has a bigger lith-ion rechargeable battery built in, so even more juice for the N900.

http://www.jr.com/nokia/pe/NOK_DC11/

ossipena

2009-09-29, 09:22

Why wouldn't this work? It works with the N810.

http://www.nokiausa.com/find-products/accessories/all-accessories/power/chargers/dc-8?r=-1

that would be the greatest solution. if it really works that way. because i think new symbian phones will shut down even when charged if you remove the battery...

and bundle 2 batteries together to usb reserve could be the smartest solution. one could first use two batteries with no external gadgets. and when second is wearing out, with external pack one could almost double the uptime(1100+1100mAh vs 1350mAh+1100mAh)....

on an other hand, regulator eats some of the batteries power when connecting 2x3,7v -> >7v and regulating to usb 5v. so it isn't really 2200mAh compared to plugging batteries to battery contactors. maybe the simplest solution would be 6pcs cheap AA-batteries and a 5v regulator just to keep the device running during the change.

could someone confirm that does the device stay on when removing battery while charging?

chemist

2009-09-29, 10:03

the hibernation seems a good idea.

the backplate could be extended to the edges of the camera and stand to fit a bigger battery.

the whole case could be painted with CIGS to have it charged or at least assisted.

I dont want the mod to change overall sizelimits to still fit in my pockets and I dont want to carry any additional stuff with me apart of a spare battery (hibernate change)

spinnukur

2009-09-29, 17:36

that would be the greatest solution. if it really works that way. because i think new symbian phones will shut down even when charged if you remove the battery...

and bundle 2 batteries together to usb reserve could be the smartest solution. one could first use two batteries with no external gadgets. and when second is wearing out, with external pack one could almost double the uptime(1100+1100mAh vs 1350mAh+1100mAh)....

on an other hand, regulator eats some of the batteries power when connecting 2x3,7v -> >7v and regulating to usb 5v. so it isn't really 2200mAh compared to plugging batteries to battery contactors. maybe the simplest solution would be 6pcs cheap AA-batteries and a 5v regulator just to keep the device running during the change.

could someone confirm that does the device stay on when removing battery while charging?

If it's USB reserve, the link I posted from JR.com has both a USB plug and standard power plug built in on the portable charger

Bratag

2009-09-29, 17:38

Um wouldnt hibernation kind of defeat the whole point of this device being a phone as well as a tablet. I cant see myself ever wanting to miss phone calls etc.

quingu

2009-09-29, 17:42

power consumption in idle is near zero anyway...

ossipena

2009-09-29, 18:44

well if you say that one can switch battery without hibernation & without reboot, we can close this thread right away.

zkyevolved

2009-09-29, 22:28

power consumption in idle is near zero anyway...

Not from what I've read :P some blogs say that you can get a few days out of it in standby mode without GSM radio turned on! So... near 0 is far from correct if your phone dies 2 days after no radio usage and in idle-sleep mode.

allnameswereout

2009-10-02, 00:47

Hibernation and most suggestions on lesswats.org aren't or are barely interesting on ARM and other mobile/embedded devices. You'd need to write all the data in RAM to swap, and read all that again when powering it up. That uses a lot time, and also resources/juice, while the ARM in idle mode barely uses juice. You might as well leave no application open instead, put all receivers and transmitters off, or only leave voice open for phone/SMS, or suspend an application which uses a lot of resources. When battery almost empty Symbian has option to disable cellular data. Alternatively, something like powertop or iotop or htop could help debug (in SDK or on real device). All these 3 run on Linux/ARM.

A battery pack is interesting. Theoretically one could have one which supports the Nokia charger, but also one which supports USB charging. The latter allows one to also use other devices to charge via USB. However, USB charging is slower than using the official Nokia charger.

You could even use USB on your laptop to charge your N900. Not sure that works when laptop is on suspend or hibernation mode (I doubt it, may depend on case-by-case, hardware guru can clarify hopefully). Why would you do that? Well because you're on the go and your laptop is not required right now whereas your phone is. Then better give juice to the phone then. Or you actually only use your laptop as battery for your N900. Or the reserve battery of your laptop. I think I've seen such 'mods' for iPhone. Problem with reserve batteries is to store them for longer time you need to have them not fully charged, instead 40%, and that doesn't yield much, although OTOH a laptop battery would. And it could be a life saver so to say.

When I was in train from Belgrade to Munich I had only one power source, and I had to switch my laptop and phone constantly (tethering drained the phone's battery). Had I been able to charge my phone on my laptop's USB I would not have to switch them whole time.

ossipena

2009-10-04, 10:18

ok so hibernation is totally off limits because it would be probably the same as shutting device down, switching battery and turning it on again.

I think that I'll order a holder 4xAA plus one 5v regulator and usb connector after someone confirms that the tablets stays on when plugged in and battery is removed or then i'll test it myself later when my n900 comes knocking to my door...

tomraider

2009-10-04, 10:37

I like the look of the PortaPow USB battery, from £17.50. Anyone tried one?

http://www.portablepowersupplies.co.uk/usbliionbatterypack.htm

f(x)

2009-10-04, 18:18

if you are going to extend it through portable charger, why not thinking about solar? Either you attach it to n900 or modifying the portable charger.

Also, check this out: http://www.instructables.com/id/DIY-Solar-Powered-radio-for-%245/
If someone up to try this, try to link AAA batteries together (I am not sure about 5800/N900 battery size/space so probably this might or work. Anyway linking 4 of AAA's batteries with each 800mAh (you can find higher) this means 3200mAh.

Now for people who are interested to know the difference this will gave them , simply use the ratio to determine your extra running time.

Now if I remember n900 is having 9 hours as a call time (Forget this , unless you want to compare your gain to it) I will consider 6 hours in extreme using

(3200mAh/1350mAh)* 6 hours = 14 hours and 22 minutes in extreme using conditions
now for the talk time:
(3200mAh/1350mAh)* 9 hours = 21 hours and 20 minutes of continues talking

konttori

2009-10-04, 19:15

that reserve battery will do just fine, but device will reboot when you switch the battery. I think the HW itself supports the hibernate mode for some seconds, but it's not enabled. Time to start looking at omap3 docs and do some kernel hacking. (eh, for some of you, me, I'm just fine with the battery as it is)

mattiviljanen

2009-10-04, 20:09

tomraider

2009-10-04, 20:11

With the talk about mAh, what about the differing voltages? i.e. a NiMH battery is typically 1.2v, so 2100mAh isn't the same as a 5v USB battery extender rated 2100mAh.

tomraider

2009-10-04, 20:16

I've had a look at the solar panels available after not having much luck in the UK with a fairly big twin solar panel charging 5x AA batteries... and the output of such panels maxes out at about 100mA in optimum conditions. Maybe good in LA or somewhere :)

geneven

2009-10-04, 20:51

Charging at a distance seems to have become practical, judging from newspaper articles I've seen. Easier charging is almost as good as having a longer battery life.

shadowjk

2009-10-04, 21:08

(3200mAh/1350mAh)* 6 hours = 14 hours and 22 minutes in extreme using conditions
now for the talk time:
(3200mAh/1350mAh)* 9 hours = 21 hours and 20 minutes of continues talking

You need to compare energy. 3.2Ah * 1.2V versus 1.35Ah * 3.7V:

3.84Wh vs
4.995Wh

In reply to another poster, n900 is not likely to function on charger without battery. The charge circuit isn't able to regulate power that way.

f(x)

2009-10-04, 22:18

I second external battery packs. Lots of them available already, as previous links point!

I wouldn't use AA batteries, but rechargeable AA cells instead... Think of the environment! Put 4 or 5 of them (4.8V or 6.0V - someone prove me wrong, please!) together, add expensive, top-quality regulator, USB cable, some casing and you're done. First I laughed at chargeable chargers - out lout - but if they pack enough power, they just might save your week...

How about solar cells? Limited use cases, but hey, free power! Also widely available...

I mentioned AAA (AA is more bigger than AAA)
Check this: http://en.wikipedia.org/wiki/Battery_(electricity)#Battery_lifetime
Still, you are right about using battery cells.

By the way, I noticed that I didn't mention what I attended to in my previous post.
I was thinking of replacing Nokia original battery with 4 rechargeable AAA cells and connecting through a circuit where it also takes a power from a solar cells that is mounted on the battery cover (Or mounted in any better place?).

After all, I am sure people won't like to do this mod while their warranty remains unless someone made this in a good product and replaceable.

kamakazikev24

2009-10-05, 16:16

How about the cases with a battery built in like they make for the Iphone? As soon as the phone is put in the case the phone battery gets topped up.

ysss

2009-10-05, 16:40

@kamakazike: I think it'd be way too thick if they design it like the iphone's battery packs (the sleeve designs).

Dirty Harry

2009-10-07, 18:37

Nokia has a solution for this already (although not available with a USB pug yet)

http://www.mustaporssi.fi/files/middle/1209_middle_dc-8.jpg

shadowjk

2009-10-07, 22:16

according to nokia, the n900 sales package contains an adapter so you can use your old 2mm charger with n900 too. i imagine dc-8 has that?

DaKing

2009-10-10, 00:18

f(x)

2009-10-10, 01:13

how can u use the Nokia charger adaptor (CA-146C) i mean does it charge the battery when pluged ? and how can u charge that adaptor and how much power it contains ?
And is it true that when i get the device its better to charge it 12 hours before real usage ?
thanks
A- Is obvious I will pass it
B- Is same as A
C- Only if you are using Nickel (NiMH) batteries. You actually do it to try to get ride of time-effect on these Nickel based battries.
The good thing about Lithium battires is that they don't suffer of this and when its charged then you are ready to go.

shadowjk

2009-10-10, 07:06

how can u use the Nokia charger adaptor (CA-146C) i mean does it charge the battery when pluged ?

With it you can connect your old Nokia charger to the N900's new microusb port.

and how can u charge that adaptor and how much power it contains ?

The separate product Nokia DC-8 (http://europe.nokia.com/find-products/accessories/all-accessories/power/chargers/dc-8) is a portable charger device that takes a single AA and puts out voltage suitable for charging through Nokia 2mm charging plug. The power available depends on what batteries you use. From best to worst: Energizer Lithium AA, LSD type NiMH batteries (Sanyo Eneloop, GP Recyko, etc), regular nimh, alkalines, heavy duty.
Alkalines and heavy duty batteries are so weak they probably wont do anything useful at all.

Then there's the Nokia DC-11 (http://europe.nokia.com/find-products/accessories/all-accessories/power/chargers/nokia-extra-power-dc-11), which is essentially an external Lithium-Ion battery for your phone. It contains a 1500mAh LiPoly battery.

And is it true that when i get the device its better to charge it 12 hours before real usage ?
thanks

There's no need. You can use it right away. You can charge it whenever you want, you don't have to wait until you get battery low warning. You don't have to charge it full when you start charging, you can interrupt the charge whenever you want. Li-Ion batteries actually like it if you charge often. You can use the device while charging.

ossipena

2009-10-10, 07:40

I second external battery packs. Lots of them available already, as previous links point!

I wouldn't use AA batteries, but rechargeable AA cells instead... Think of the environment! Put 4 or 5 of them (4.8V or 6.0V - someone prove me wrong, please!) together, add expensive, top-quality regulator, USB cable, some casing and you're done. First I laughed at chargeable chargers - out lout - but if they pack enough power, they just might save your week...

How about solar cells? Limited use cases, but hey, free power! Also widely available...

this is good point. i am thinking about putting 2 spare batteries into case (if device doesn't stay on when switching, no need to have 4 batteries, one is enough i think)

casing + solar panels in cover + usb out. so it will basically be improved version of the nokia's charging block. as long as the rechargeable charger isn't needed, it could be charged in sun. if i end up doing this for real, i could publish drawings for the case (so one could ask from machining shop how much is it to make one case from PO for example). because i need drawings for myself if i make it. and it means i have to make 3d-models to minimize design flaws and to be sure that all fits in.

ossipena

2009-10-10, 08:11

started allready sketching. and then one big question came to my mind.

battery loading with solar cells. there would be 5.5v 33mA modules with good size and voltage. and sensible prize tag. what would one need between the modules and battery to be 100% safe against li-ion overloading?
http://www.youtube.com/watch?v=jjAtBiTSsKY though that shouldn't be problem with low current solar cells, i'd rather be 110% certain there are no risks. 5.5v would be great so one could charge the unit via usb too from same wires. (electronics would be easier?!?)

shadowjk

2009-10-10, 08:20

Li-Ion does not tolerate trickle-charging, so even small solar panels connected directly to a Li-Ion battery sounds like a bad idea. It might not explode or catch fire if you're lucky, but if it trickle charges after the battery is full, it will most certainly damage the battery, reducing its capacity.

rcull

2009-10-10, 08:56

RevdKathy

2009-10-10, 09:44

I've been using this 3400mAh Lithium-Ion usb battery pack ( ~£20 + ~£1 for tip ) its the best I've seen yet.

http://www.portablepowersupplies.co.uk/usbliionbatterypack.htm

Both in and out are usb and tips are cheap.

Allnameswerout
I dont know about other laptops/netbooks but I can certainly charge from usb ( eee ubuntu ) while in 'suspend' mode.

Rick

Errr You what?

Short words please! (I'm a bear of very little brain!) You charge it up from your computer via the usb, in about 5 hours. Then you plug it into your device and charge that from it - fast enough not to trickle the Li-ion battery. And being a li-ion battery itself, you can top it up after you've used it, rather than wait till it's drained. Yes?? (Or did I misread?)

And this works for a nokia tablet? Sweet!

eiffel

2009-10-10, 11:15

Li-Ion does not tolerate trickle-charging, so even small solar panels connected directly to a Li-Ion battery sounds like a bad idea.

Let's rephrase that and say "Li-ion does not tolerate trickle-charging when it is fully-charged". I know that's what you meant, but it might not be clear to others that you can happily use a trickle-charger to charge a discharged Li-ion battery, provided you disconnect the charger when the battery is fully-charged.

Also, if you connect an external charger to the micro-USB port on the N900, it's not being connected directly to the battery but is going through the N900's charging circuitry, which should take care of isolating the battery at the proper time.

The N810's charger had full specs published, which you could use to homebrew a compatible charging device. I guess a similar document will exist for the N900's charger.

It does seem that the best way to use solar power is to use the solar panel to charge an external battery (like the Freeloader (http://www.solartechnology.co.uk/shop/freeloader-pro.htm) does), then when that external battery is charged up to use it to recharge the N900's battery "all in one go".

More details here: "Charging lithium-ion batteries (http://www.batteryuniversity.com/partone-12.htm)"

Regards,
Roger

shadowjk

2009-10-10, 11:25

ossipena

2009-10-10, 11:44

It does seem that the best way to use solar power is to use the solar panel to charge an external battery (like the Freeloader (http://www.solartechnology.co.uk/shop/freeloader-pro.htm) does), then when that external battery is charged up to use it to recharge the N900's battery "all in one go".

More details here: "Charging lithium-ion batteries (http://www.batteryuniversity.com/partone-12.htm)"

Regards,
Roger

this is what i ment.

i have 3 spare batteries for n900. i thought that i put 2 together into casing serial and make them output to usb port +5v DC with regulator. then with almost same amount of work, one could integrate a couple of solar panels within the package. making the battery box open like a wallet (then it protects panels when not used and so on..). so now i need to figure out how to handle loading those two batteries via 1) usb and 2) solar power. so i think i must put some electronics between power input and batteries.

so the casing would have
a) usb port for loading the battery pack
b) solar panels for loading the battery pack
c) usb port for loading external devices with battery pack

c) is taken care of, a) and b) is problem atleast for now.

solar panels have 5,5v 33mA nominal values so 4pcs would be smallest reasonable amount of those... glad those are only 2-3mm thick!. but at the same those can be put parallel to gain 5,5v 132mA nominal values.

that means that i must load one battery at time. then when it's full switch to another and when both are full, switch power output to a resistor. is this ok?

and the concept once more:
-put the casing to the sun and forget it (unless it starts to rain!)
-surf the internet until device's battery is about to die.
-connect those 2 things above
-surf more.

shadowjk

2009-10-10, 12:10

You also need a chip to balance the two spare batteries if you connect them in series, and it's probably a bad idea to not use a protection circuit for preventing overdischarge/overcharge. If the N900 has "special charger" mode like N810, it will eat power down to 4.2V input, at which point your two series batteries will ideally be 2.1V each, which is too low for Li-Ion. Recharging them again after draining them that low could be dangerous or at the very least cause excessive wear&tear on the batteries. In worst case, if one of your spare batteries is older or has seen different use and thus aged differently, the two batteries will have different charge states, pushing one of them way below 2 or even 1V (when one of them gets empty before the other), which basically is "too dangerous to use again"-territory...

Protection Circuits can be found at batteryspace, for example: http://www.batteryspace.com/pcmwithequilibriumfunctionfor74vli-ionbatterypack20amplimitpcm-l02s20-265.aspx

Instead of having the batteries in series and dropping voltage with a linear regulator to 5V, I would have the batteries connected in parallell, and use a boost converter to bring up the voltage to 5V. This thing looks useable: http://www.dimensionengineering.com/lvboost.htm

This would do away with the balancing requirement, for connecting them in parallell you just need to make sure they're both at same level of charge before you connect them together. This would enable you to use a simpler and cheaper protection circuit, such as: http://www.batteryspace.com/pcbfor37vli-ion1865018500cellbattery3a-1alimit.aspx

Now you just need a charge regulator to make it perfect! The circuit above will cut off charge at 4.35V (or 4.275V if you believe the scan). Maybe a bit too high when considering wear&tear on the battery, but probably safe enough to avoid explosions and/or battery swelling :)

But a device like the one you've just designed already exists anyway, here's an example http://www.amazon.com/dp/B00152OCAQ/, both cheaper and more expensive models available..

rcull

2009-10-10, 12:12

Errr You what?

Short words please! (I'm a bear of very little brain!) You charge it up from your computer via the usb, in about 5 hours. Then you plug it into your device and charge that from it - fast enough not to trickle the Li-ion battery. And being a li-ion battery itself, you can top it up after you've used it, rather than wait till it's drained. Yes?? (Or did I misread?)

And this works for a nokia tablet? Sweet!

Thats exactly what you do ( although not from a eee on standby obviously :) )

From the Specifications

Size: 100x62x15mm (similar to a cassette tape)
Weight: 105g
Capacity: 3400mAh (12.58Wh)
Charging efficiency > 95%
Charges in 4-5 hours
Can be recharged approx 500 times
60% pre-charged and ready to use
upto 700mA Current output

I have charged my N800 twice without flattening it.

Rick

RevdKathy

2009-10-10, 12:17

Thanks! I feel like I'm learning a foreign language by going straight to a new country and having to communicate there! I'm not completely dumb (well, not quite completely) but much of what is said here is going clean over my furry head. I can usually work out when something is said that might be useful to me, but often need to check I heard right!

pycage

2009-10-10, 12:55

bugelrex

2009-10-10, 13:26

Heat is the biggest enemy of a battery. Unlike notebooks, the N900 doesn't get hot, so this shouldn't matter.

I'd suggest to just use the device without worrying about the battery too much. There's already fancy electronics and software installed to keep care of the battery for you.

Just use the device and be happy. I usually charge my N900 every night and then can use it the whole day without worrying.

Can you give us an idea of your daily usage. Eg.
9am to 1am. How many bars left
- set to 3G
- surf web for X mins
- watch video for X mins, listen to X music
- how often does it connect to internet?
- minutes of voice calls
- ever connected to wifi

ogahyellow

2009-10-10, 16:01

Instead of having the batteries in series and dropping voltage with a linear regulator to 5V, I would have the batteries connected in parallell, and use a boost converter to bring up the voltage to 5V. This thing looks useable: http://www.dimensionengineering.com/lvboost.htm

X2

AFAIK, A standard linear regulator usually needs a forward voltage 2-3V higher than its output to function correctly. Therefore as the batteries discharge, there is the potential a linear regulator might not be able to correctly control voltage.

pycage

2009-10-10, 16:09

Can you give us an idea of your daily usage. Eg.
9am to 1am. How many bars left

I'd say, about 2h of playing music in the car using FM transmitter (you'd suppose this to drain the battery a lot, but it doesn't),
about in total 15 minutes web surfing on 3G spread over the day, about 15 to 30 minutes voice calls,
sometimes taking photos.
The device is always online. WiFi at home, 2G or 3G elsewhere. I set it to connect automatically.

The battery is then usually still half full in the evening. My G1 was half full in the evening too, but only if I did not do much more than carry it around with me during the day, reading a little email.

The N900 battery only begins to drain more quickly when disabling WiFi power management for connecting to the device via ssh.
I currently don't watch lots of video on it.

bugelrex

2009-10-10, 17:50

I'd say, about 2h of playing music in the car using FM transmitter (you'd suppose this to drain the battery a lot, but it doesn't),
about in total 15 minutes web surfing on 3G spread over the day, about 15 to 30 minutes voice calls,
sometimes taking photos.
The device is always online. WiFi at home, 2G or 3G elsewhere. I set it to connect automatically.

The battery is then usually still half full in the evening. My G1 was half full in the evening too, but only if I did not do much more than carry it around with me during the day, reading a little email.

The N900 battery only begins to drain more quickly when disabling WiFi power management for connecting to the device via ssh.
I currently don't watch lots of video on it.

Thanks very much for the clarification. It does seem liveable for most light days

pycage

2009-10-10, 17:54

Yes, definitely. And not light days, well even the N810 didn't survive those with a single charge. :)

pycage

2009-10-10, 17:55

I have to add that I don't have the latest firmware currently. So in the end the battery life could be even better in the sales product.

ossipena

2009-10-12, 07:55

one more question:
can i supply +5v straight to battery if i put this somewhere between:
http://www.batteryspace.com/pcbfor37vli-ion1865018500cellbattery3a-1alimit.aspx
?

i think i'll start making 3d-model of the casing today after work. now i'm glad our company buys all electronics from one place. better chances to negotiate more reasonable prices to these small private projects.

twaelti

2009-10-12, 10:11

It was mentioned here before, but really: the Nokia DC-11 (http://europe.nokia.com/find-products/accessories/all-accessories/power/chargers/nokia-extra-power-dc-11/specifications)is the solution in terms of hardware. It is explicitly mentioned right on the first pages of the manual, in an advertisement (for this and the bluetooth speakers, to "share your experiences").

ossipena

2009-10-12, 10:23

i know.

this is only a hobby for me. nice to have a project sometimes. specially now when i got moved to another department @ work. it means i can use companys soldering irons, cnc & manual machining tools and other equipment for free at my spare time(and when those aren't used for work) as long i don't do business with things i create.

and this is an idea that is easiest to pull through from all my crazy ideas. (EN1.4404 enforced camera module for any backpack, ESLUT -loudspeakers, and stuff like that aren't so easy to do compared to this)

eiffel

2009-10-12, 10:39

can i supply +5v straight to battery if i put this somewhere between:
http://www.batteryspace.com/pcbfor37vli-ion1865018500cellbattery3a-1alimit.aspx
According to this link (http://www.batteryuniversity.com/partone-12.htm): "Most cells are charged to 4.20 volts with a tolerance of +/-0.05V/cell. Charging only to 4.10V reduced the capacity by 10% but provides a longer service life. Newer cell are capable of delivering a good cycle count with a charge to 4.20 volts per cell"

The PCB you mention seems to have a cutoff of 4.35 volts. So it's a protection circuit rather than a charging regulator.

You should use a protection circuit like this one, but you also need a regulator. Again, according to the above link, a good way to charge lithium-ion batteries is:

charge with a constant current (at the cell's rated charging current) until the cell is charged up to its voltage limit, then...
maintain that voltage until the charging current drops to 3% of rated current, then...
switch off the charger, i.e. don't keep trickle-charging

Regards,
Roger

ossipena

2010-03-09, 08:46

Finally got things moving. I found out that the batteries already have safety circuits. plus I realized that the bundled charger adapter is a miracle maker.
http://www.dealextreme.com/details.dx/sku.29208
(NOT ORIGINAL!! AT YOUR OWN RISK!!!)

I can charge n900 only by plugging a battery to the adapter.

then I finally ordered a device I can charge external batteries with:
http://www.dealextreme.com/details.dx/sku.31488

now I only need to figure out how am I going to get three batteries charged with the charger. (plus casing after that)

ossipena

2010-04-28, 17:45

finally I did it!

Just a spare CA-146C charger adapter, piece of wire plus plug from old nokia charger (big headed), 3x spare batteries and external charger from dealextreme.

http://www.dealextreme.com/details.dx/sku.31488

then I just soldered the wire into the charger and voila.

Now I can always charge external batteries with any nokia charger, and either use one external battery as spare power/minor loading or switch phone off and switch empty battery into full one.