I would not be charging this pack any further without first checking the individual cell voltages.
Sitting this battery on the charger is not gonna help it balance any time this year. Most of our BMS work by using tiny little resistors to bleed off power from the high cells. Even if the BMS does try to balance that large a delta, its gonna take a hell of a long time.
Best bet in my opinion is to check the individual cell voltages, if all the cells are above 2.5v, i’d be individually bringing the low groups up to the same voltage as the high groups and carefully monitoring the pack over a couple of discharge cycles.
Most BMSs work with a balance current between 20-50mA. I agree that it’s going to take time. At 20mA it’s a day to discharge 0.5 Ah from a single P group. That should make enough of a difference already that it’s measurable. If instead of 36.8V it will be 37.6V the next day, that means that some extra time on the charger will rebalance the pack. Letting it sit on the charger is the easiest way to potentially fix the pack.
Opening it first would be preferable, I agree with you there.
That’s the best I agree. But it doesn’t seem like @Niklas is experienced with batteries, so I can understand being hesitant to opening it up and doing it manually, it’s a little daunting when doing it for the first time.
Good points. Gives me the heeby jeebies trying to charge such a wildcard pack. I would definitely wanna know what was happening in there before trying to charge it further.
Well I don’t think that it’s possible to spot undercharged cells (below 2.5V) anymore since it was already on the charger for a while. So I don’t think there is much going on that we would be able to see by opening it up. Unless the issue is broken wiring, which I doubt since Acido is a great builder, but nevertheless that can still be spotted if the pack starts balancing itself out on the charger but stops before finishing. So not reaching 41.5V or so ultimately.
EDIT: I also doubt that there are any overcharged cells in the pack, since the BMS did stop charging at 36.8V.
You can check connectivity between the same polarity cell terminals in the P group though, at least if the nickel that was used isn’t wide enough to cover up the terminal completely. If the connectivity is flawless everywhere (resistance is very low, unmeasurably low with cheap multimeters), all cells within the P group must be at the same voltage. The only way that a cell could be at a different voltage than the rest of the P group is if the nickel doesn’t make good contact.
So if there’s fully and less charged cells, the charger will stop charging because it detects full charged cells? And the BMS will register that the cells are not equally charged and level them out slow but steadily?
The charger is dumb, it can’t switch off. When you reach 4.2-4.25V in the highest voltage cell, the BMS disconnects the charger, and it knows that the highest voltage cell is a little overcharged, so it connects a tiny load to it. This a resistor inside the BMS. This very slowly discharges the high cell, until the voltage gets low enough - typically 0.05-0.1V below where the charger was disconnected. The BMS does this to all cells that are considered overcharged. At this point, the BMS connects the charger again, and charges all cells until the highest one reaches the cutoff point, 4.2-4.25V. The slowly discharges the higher voltage cells.
This cycle continues, until all cell voltages are very close to each other. When this process finishes, all cells should be fully charged, typically between 4.15-4.2V.
is there any way to “reverse” a ppm remote? with the case mod I’m using the old “backwards” is what I now want “forwards” to be and vice-versa. can I just invert it in software like with the motors? I could just use current bidirectional but I really want hyst reverse with the right throttle orientation.
This is a “medium” epoxy I’ve used for a long time. It’s hard but not as brittle as many. Silicone RTV (electronics grade) can work better for strain relief of wires.
[Later edit] But it can wick under and into things, perhaps into places you don’t want it to go, so it might not be a good choice.
Yup, I mentioned it is hard (80D).
I haven’t had any problems with it being too brittle. I use it for affixing heavier components to circuit boards (beepers, inductors, etc.) and have never had one crack off. With enough force though you can, of course, cause it to break.
I recommend going crazy with making sure you have a true 1:1 ratio when mixing as IMO most problems (not hard enough or too brittle) come from too little or too much hardener when mixing.
