charge packs in parallell ?

Is it a bad idea to charge batterypacks with built-in bms in parallell?
I have a lot of hoverboard-battery but only 3 hoverboard-chargers. I want to connect 2-3 packs to each charger.
Is this a good or bad idea ? I know it takes a long time but 9 packs a day is good enough for me.

Paralelling them at the discharge wires would not be the way to go. that would charge two of the packs backwards, through the out wires.

I can't say if you could parallel the packs at the charge input wires or not. Old posts by member Dnmun should have the answer, but it will be a long hunt for your specific question.

These 10S-2P packs have a common XT60 connector for both charge/power. When I do run two in parallel, I have been charging them together. Makes it less likely I'll forget to do one.

I'm not understanding your answer, Dogman, about the cells getting reverse voltage unless you were thinking he had two or more packs connected in series while trying to charge one pack by itself?

So is there only a single port for both charge and discharge?

Only one port. Two packs in parallel.

docw009 said:

I'm not understanding your answer, Dogman, about the cells getting reverse voltage

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Not reverse voltage, but current flowing into the battery thru it's discharge connector rather than it's charge connector (when those are separate), so the BMS would be incapable of shutting charge off if a cell reaches HVC.

If charge and discharge ports are the same, then it doesn't matter if you connect them in parallel or not, as each pack's BMS would cut it off of charging as needed. If there is no BMS on the packs then it also won't matter, as they're all going to charge to the voltage of the charger whether they're in parallel or independent.

Unless the charger is one designed to shut off when current drops below a certain level, and the packs can't handle a charger that keeps the voltage across them all the time, I don't see a reason they couldn't be parallel charged.

There is a danger, though, if there is no BMS, that if a cell in a pack does not charge correctly (stays at a low voltage) the other cells could become overcharged and cause a fire. The same could happen without paralleled packs, but the fire itself could be as many times larger and harder to contain with multiple packs as there are packs paralleled. (similarly even if they're not paralleled but are physically close enough to catch fire anyway).

Looks like it will be ok to parallel, and charge together, since the bms is designed so the output wire is also the input wire.

what I meant was don't charge through the output wire, if there is a separate input wire. That would be putting it in, through the out wire.

It will be fine as long as both packs are the same voltage when you connect them to each other. Once paralleled, it should charge fine and both packs would be protected by their BMS.

My two 36V chargers were slightly different in voltage. Only about .10 volt at full charge, but it did result in a small current flow when packs with that small difference in voltage were connected. Parallel charging bypasses that.

It would seem to me that if one had a BMS, any HVC cell circuits would work on the output port. They're already on the board.

Anyway, my packs do have a BMS. Whether they work is yet to be proven. I need to get to a connector and see how the cells stack up.

Im asking because I dont know if its the bms or charger that cuts of at 42 volt. I think this cheap BMS only drain each cell for balancing and the charger cuts of at 42v
Lets say that the first pack charge faster and reach fylly charged baut the second still need som juice so the charger doesnt shut of.
Will this ovarcharge then? Or when connecting several packs in parallell the current flows from one better battery to another and equals the voltage and let the charger cut of at 42 volts.
Should I maybe put a resistor in series (about 20 ohm, 20W) on each battery so there is no current rush?

When two packs are in parallel, their voltages will be exactly the same. Even if the packs were different capacity, as long as the cell count is equal, they will both reach full charge at the same time.

The BMS should normally never cut off. It is a safety backup if something fails. The charger controls the cutoff.

If you had a weak cell or grossly imbalanced pack, one might hit HVC and cause the BMS to cut off, but the other pack would continue charging.