Aneta Posted November 4, 2019 Share Posted November 4, 2019 (edited) I have an ewheels.com fast 5A charger, the one with voltage and current readouts, as well as switches for 80/90/100% charge and 1/2/3/4/5A. It's a 48V charger (54.6V max) I use to charge my e-scooter battery. I've encountered some strange behavior that I don't understand. I'm afraid it may lead to a misbalanced battery over time. Near the end of the CV phase, it stops charging at about 0.5A current, and voltage drops by 0.2V from 54.6 to 54.4V. This is different from how it used to work several months ago, when it was always finishing the charge at 54.6V. So, I suspected that the battery got out of balance. I used this and several other 54.6V chargers, leaving them on for hours, in attempt to balance the battery, but nothing worked - the battery never achieved full 54.6V. But I found that if I use a portable powerbank with a built-in inverter as the source of 110V AC, and plug the ewheels charger when battery is at 54.4V, it starts flowing small current (like 0.10-0.30A) that gradually diminishes over some minutes to hundredths of an amp, to 0.01A, then 0.00, and voila - the battery is fully charged and stays at 54.6V! Apparently, the inverter produces a square wave, not sine, and somehow this allows ewheels charger to continue CV charging down to 0.01A and below, for true 100% 4.2V per cell charge. Can someone explain what's going on? Are cells properly balanced in the second case? Or they are still misbalanced, but square wave "trick" makes some of them overcharged over 4.2V (but the average is 4.2)? Why does ewheels charger stop at 0.5A when using sine wave 110V AC? Edited November 4, 2019 by Aneta Quote Link to comment Share on other sites More sharing options...
xorbe Posted November 4, 2019 Share Posted November 4, 2019 (edited) The amount of energy stored between 54.4 and 54.6 is so minuscule, don't worry about it. Batteries age. The "problem" is that the tail charge stops at 500mA, so technically, the battery will never be "100.0% full". It is curious that the charger behaves differently with a square wave than sine wave mains. Be careful, some electronics malfunction on square wave. Edited November 4, 2019 by xorbe 1 Quote Link to comment Share on other sites More sharing options...
Aneta Posted November 5, 2019 Author Share Posted November 5, 2019 3 hours ago, xorbe said: The amount of energy stored between 54.4 and 54.6 is so minuscule, don't worry about it. I don't worry about energy, I'm worried about cells getting out of balance. Quote Link to comment Share on other sites More sharing options...
dmethvin Posted November 7, 2019 Share Posted November 7, 2019 Do you have another charger? You could always use that one every week or so to do a full balancing charge. Quote Link to comment Share on other sites More sharing options...
Aneta Posted November 7, 2019 Author Share Posted November 7, 2019 (edited) 2 hours ago, dmethvin said: Do you have another charger? You could always use that one every week or so to do a full balancing charge. I do. I have no way to tell if there was any balancing going on at all. With all chargers, the pack always stayed 0.2V below full charge voltage. But with the ewheels charger "trick" as described in OP, I was able to bring it to perfect 54.6V. It's a mystery. Edited November 7, 2019 by Aneta Quote Link to comment Share on other sites More sharing options...
xorbe Posted November 7, 2019 Share Posted November 7, 2019 (edited) If the charger stops before 0.00001A then the voltage tends to fall down under peak voltage. Also, when the battery cools slightly from being warm from charging. Pushing the pack to exactly peak charge only shortens its life span. Edited November 7, 2019 by xorbe Quote Link to comment Share on other sites More sharing options...
Aneta Posted November 7, 2019 Author Share Posted November 7, 2019 I don't like that batteries are "black boxes" - we don't know what's going on inside, we only have one piece of info: total voltage. So, for my custom 14s battery for my escooter, I bought this 16-pin connector: that will be connected to individual parallels, so I can measure voltage of each parallel at any time without disassembly, and balance manually, if needed. If this idea proves usefull, I'll install a similar connector (22-pin) on my EUC, too. Quote Link to comment Share on other sites More sharing options...
xorbe Posted November 7, 2019 Share Posted November 7, 2019 Photo of said connector on your escooter? Quote Link to comment Share on other sites More sharing options...
Aneta Posted November 7, 2019 Author Share Posted November 7, 2019 7 minutes ago, xorbe said: Photo of said connector on your escooter? It's just an idea so far. Quote Link to comment Share on other sites More sharing options...
dmethvin Posted November 7, 2019 Share Posted November 7, 2019 I agree that it's super frustrating we get so little data on the battery, when it is the most expensive part that the first to go in many cases. I think I have a bad cell on my KS14C that seems to have started when I rode the voltage down too far one time. The only way I will know for sure is to open up the wheel, slice open the blue shrink on the pack, and get access to the individual cells to measure them. Quote Link to comment Share on other sites More sharing options...
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