How To Lipo #2 - Battery Configs, Charging, Capacity Testing

[@frostytf2]

I still don't understand how you only have 27k subs. Does the algorithm hate you? Are there this little people interested in actually learning about electronics / repair? I'm so confused.

[@FourInTehMorning]

Almost 35k now, algorithm is doing it's magic.

[@krisd1000]

No voltage change is happening. These cells are 3.6v nominal. Some are 3.6, 3.65, 3.7 and 3.8v

[@bardigan1]

How does a controller change voltage without using a transformer?

[@jimmatrix7244]

Is that LIPO or Lithium Ion cells? Can we use Lipo cells for laptop batteries?

[@Adamant_IT]

You can, yes. If you have a BMS compatible with the laptop, and you make it all to spec. I don't think it's worth doing, personally, unless you can't get pre-made laptop batteries in your country.

[@danman32]

Here's the problem with the equation: In order to determine mAH, you have to calculate current draw over unit time. However during the charge/discharge, the battery voltage does not remain constant so that 3.7V is meaningless. Typically when a lipo is fully charged, it is anywhere from 4.0v to 4.4v depending on its specific chemistry and configuration. As you use the battery, the voltage starts dropping. The question becomes, what do you determine to be the end voltage of a discharged battery as it approaches its rated capacity? Some say 3.5v, others say 3.2v, still others say 3.0v or even 2.7v. This is important since if you're trying to determine the actual usable capacity of your smartphone battery, you need to know the voltage that the smartphone reads as 0% remaining charge, or when it cuts out. I just replaced my HTC battery that has a rated capacity of 3000mAH, howevery I am suspicious that I'm not getting the rated capacity. Unless i use it down to the last % displayed, I don't get anywhere near the rating according to AccuBattery. Drawing down from 100% to 2%, AccuBattery claims I used 1955mAH with voltage at 3.6V when drawing 278mA. Voltage drops if more current is drawn. I read as low as 3.551v when 726mA is drawn. So with those numbers, is my battery providing the rated capacity or am I ripped off, or is my HTC phone ripping me off showing lower % charge left than actual? As I mentioned, that really depends on what HTC calls 0% capacity and shutdown. Incidentally, I don't think Accubattery showed anywhere near 1500mAH used when the charge percent was 50%.

[@Adamant_IT]

You're correct, the 3.7 is an estimate. On a typical discharge curve, the cell should be at 3.7 for most of the discharge, and then the 4.2 high and 3.2 low roughly cancel each other out. But yes, it's a rough estimate. The only real way to know is to use a digital load with a battery test function that actually monitors all this for you. With regards to your replacement battery, what was the rating of the stock battery? It's incredibly unlikely that a replacement will be more than the stock. You can also measure the size of the cell and compare it to other cells to see if they're likely fibbing or not.

[@danman32]

@@Adamant_IT The HTC 10 battery is rated 3000mAH. Assuming that AccuBattery is given the voltage readings with almost no resistance from the internal meter to the battery, I estimated the internal resistance to be 0.12 when calculated at 30% displayed remaining capacity and 0.13 ohms when around 2%. Internal resistance determined by taking the delta current divided by the delta voltage, change in current manipulated by changing screen intensity. As long as the delta is taken at a reasonably close interval, the internal voltage shouldn't have changed much to influence the Ri calculation. The calculated internal resistance seems a bit high to me, though that could be resistance between the battery terminals and where HTC measures the voltage. At 30% I calculate the internal voltage to be about 3.7v (readings were 3704mV at 136mA and 3657mV at 525mA) according to AccuBattery. I forget what my mV/mA readings were at 2%. The phone seems to cut out at somewhere between 3.4-3.5v but hard to say. My last discharge to end went down as low as 3.2v depending on current draw, staying at 1% for a really long time compared to previous 1% drops. This last time it stayed at 2% for a long time, but not very long at 1%, never showing to be near 3.2v like before. Last charge from 1% to 100% mostly in screen off yielded a calculated charge of 1769mAH in 1h 49m The time before that it calculated 2610mAH charged in 1h 51m, again with little screen off time. So the question still remains, is my lower than rated capacity the fault of the battery, HTC battery management, or the AccuBattery measurements? By the way, the voltage displayed when fully charged is 4.4v.

[@danman32]

@@Adamant_IT PS. The main reason I had to replace the battery was because the phone would shut off or reboot when i took pictures (with or without flash) or woke it up from sleep. This would happen when % charge remaining showed about 30%, but has occurred as high as 60%. When the phone abruptly shut off, I could only complete power on if i put it on a charger for a bit during reboot. I had to replace the original stock battery last year for the same reason. Accubattery estimated battery health and capacity of the previous battery (the one I just replaced) at about 1600mAH or 58% rated capacity/health. With the replacement battery, it hasn't cut out on me prematurely.

[@Adamant_IT]

Yea, I'm not sure to be honest. It sounds like the replacement battery just isn't very good - however it's better than a failed battery. You might have more luck replacing it again. I get bad batteries when replacing laptop batts now and then, they work, just not very well.

[@patrikpavlik3540]

WHERES THE LIPO? ONLY LITHIUM WTF

[@phasehalide]

Your trying to revive a very damaged cell that has been irreparably discharged and lost most of its life to oxidation at the cathode. No point unless you are very desperate. if you find the cell below 3.0v consider it seriously damaged and not good to actually use in a pack or standalone. Same for pouch or cylindrical cells. Any heat during normal charging or discharging within C Rated conditions is also a red flag. Build a proper precise discharger with an Arduino and a 16x2 display or buy a single cell dedicated discharger. Don't use inaccurate USB meters, there are losses on the USB connectors and not too accurate. You do voice very many good points and cautions though. Also if you leave cells sit for two days and then disscharge them you will see true numbers cause bad cells self discharge and their voltage drops!