Can I charge my ebike in parallel...

So currently me ebike has 2 of these a123 lifepo4 packs... See one on each side of the bike...

I basically take each battery out of the bike and chargew them individually... They pop off easily...

Currently, I've been hookiing the balance leads to each of the 12 terminals basically with alligator clips. On my balance leads, ive crimbed on alligator clips to go to the terminals and to run to the BMS... In the second image, ive removed those wires, but it shows the terminals...

Can't I just alligator clip my batteries in parallel and charge them both at the same time... right?

Am i missing something here... I dont think so... I would only need to hook my bms balance leads to one of the batteries then, correct?

Thanks!!!

Quite an original setup you have going on there.

The answer to your parallel question is yes. Provided each battery is at the same voltage when you start charging. Otherwise the two batteries will try to self balance the voltages causing an inrush of current from one battery pack to the other. That could result in unwanted problems.

Properly wired you could parallel both side of your bike for charging and balancing. However it is critical that you get the wiring properly done. Also, it won't charge or balance any faster unless you add more charging current, but you wouldn't need to change the wires all around every time you want to charge and balance.

I have an unrelated question...
Where do your legs go when you sit on the bike?

Keep in mind that depending on how much current your charger can supply it may not be any faster than charging one after the other. The amount of current drawn by the battery is given by the voltage divided by the resistance of the battery. Like one of the other posters mentioned, connecting the two batteries at a different voltage may not be wise.

e-beach said:

Quite an original setup you have going on there.

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BDamari said:

Where do your legs go when you sit on the bike?

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serious_sam said:

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Never got a response, I hope I wasn't a bearer of bad news...

What's the size of that battery series and parallel did you buy that battery packs from battery hookup ? Looks like a science test project.

I have seen people charge in parallel, but I've always been wary. But.... what happens if one cell goes bad? Instead of the BMS watching just one cell, it is watching the paralleled cells. Will the good cell mask issues of the bad cell and cause an issue? Are you willing to risk it? Maybe I'm over cautious.

Instead of rigging up parallel charging, I'd concentrate on some proper connectors to make charging safer and more convenient. Alligator clips and exposed electronics are just asking for trouble. But I'm not an expert - just wary of high power cells.

Colin

ColinB said:

one cell goes bad? Instead of the BMS watching just one cell, it is watching the paralleled cells. Will the good cell mask issues of the bad cell and cause an issue?

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Yes and no. Upon charging, the BMS might think the good/bad sell group is fine and balance for the given voltage. But, upon discharge the good/bad cell group will reach a low voltage cutoff faster then the good/good cell groups causing you to inexplicably have reduced range. Then, you will need to test each cell group separately to see if one is lower then the others. What I would do is parallel them proper connectors, charge it over night (or long enough for all the cells to balance.)Test all the cell groups for voltage, write the voltages down and tape it on the wall for reference. Then, ride about 1/2 of there expected distance and then go up a steep hill. At the top feel the battery to see if any of the cells are really hot. Then, go home and test all the cell groups for voltages before charging. Write down all the numbers and date it and tape it to the wall for reference.