insanelysexy | # 1 | 2017-02-27, 13:08 | Report

I have attached a 4000mah battery on Intex Aqua Fish. There are some issues that I am facing.

1. Reported voltage is not matching the measured one. Right now: reported: 3.84 V
measured: 3.96V.

2. 2500mah original battery and 4000mah extra one always some voltage difference.

3. Original one gets charged a lot quicker than 4000mah one. Can i use a charger + - to directly connect 4000mah battery's + - to charge it ?

pichlo | # 2 | 2017-02-27, 13:15 | Report

This is merely a speculation but could it be explained by some circuitry between the battery terminals and the point where the voltage is measured? If the difference stays contact at different charge levels, that would be a good indicator.

That would also point in the same direction.

Of course the bigger battery charges slower, it is double the capacity! A twice as large bucket will also take twice as long to fill up from the same tap.

I am not sure what you mean by charger+-. The phone is charged through the USB port, right? Do you mean cutting the USB wires and connecting them directly to the battery terminals? That would be a sure way of killing the battery (and maybe losing an eye in the process, if the battery explodes in your face).

insanelysexy | # 3 | 2017-02-27, 13:32 | Report

Voltage is measured at the terminal of the battery, just before connecting it to the phone. And "Btry" shows fluctuating voltage. Like batterymeter for N900. But seems to work okay.




Yes, thats what I meant and now feeling stupid about it.

elros34 | # 4 | 2017-02-27, 13:45 | Report

Measuring voltage without load is pointless as it will drop. The higher current the higher voltage drop.
Btry use power supply kernel interface.

juiceme | # 5 | 2017-02-27, 13:49 | Report

Ahh, so you measure the battery separately before connecting to phone!?

Of course the unloaded voltage is different from loaded voltage, those will really have nothing in common!
Same thing explains what you call fluctuation; the current that the device draws any given moment changes all the time, hence the internal resistance and current sourcing capacity of the battery defines what is the terminal voltage at that time...

lal | # 6 | 2017-02-27, 15:22 | Report

oh well, and the accuracy of meter matters too.

On a different note, wouldn't the meter be more accurate (assuming it's not a cheap Chinese one and measured under similar condition that it is loaded). How accurately could a phone measure?

juiceme | # 7 | 2017-02-27, 15:34 | Report

Metering accuracy is not really a concern in voltage measurement; there are quite a few other things to consider. Perhaps having a good stability long-time reference is the most important thing.

Measurement is pretty rarely just "direct D/A conversion, at least when there is any sense in the system as that is about the most inaccurate way to do it (albeit it is a fast measurement, and now we are talking Msamples/s even on cheap systems)
The right way to do it is to have an integrating measurement, where a capacitor is repeatedly charged and discharged through a resistance and the cycle time is measured. Just about all DMM's use this method.

pichlo | # 8 | 2017-02-27, 16:01 | Report

THAT seems to be the right question. I had not even considered that possibility, knowing that it would obviously give different results.

I always considered the integrating method a fudge, to replace an expensive 12 or 16 bit ADC with a cheap comparator and a counter. But now you mention it, it does have some advantages too

insanelysexy | # 9 | 2017-02-27, 17:31 | Report

Yes I measured the voltage BOTH times. Once before connecting the battery and then on different intervals, with phone on and working. Results are the same.

insanelysexy | # 10 | 2017-02-27, 17:34 | Report

Both before connecting the battery and then while using the phone.