Parallel yes or no

[Pierre R]

This forum is a wealth of knowledge and I have studied it at length. Many things would be easy for me to answer but my problem is one of maybe's and possible range bias.

I would to know the answer to paralleling two batteries. The reason is for voltage sag and ultimately pulling a bit more watts because of higher voltage drop. That may be where my bias is clouding the issue as that may not balance out in the overall picture like I hope it will.

I have two batteries. Both batteries are about the same age and both are GA 3,500mah cells. Not positive they are the same manufacturer (both red cells) Both batteries have 30 + amp bms

Battery one is a 14s4p with about 270 charges total and can be charged to 58.5 volts. I recently pulled 501 watt hours out of this battery (10.8 ah) at 300-550 watt draws before the battery reached 43 volts. Upon sitting the battery returned to 46.6 volts after an hour. The BMS did not cut the battery out and I was still asking for 300 watts out of the battery right up till that point. I got 32.5 miles from the battery.

Battery number two is a 14s2p battery with about 55 cycles on it. I have not run this battery on my bike with a watt meter. Its been on my wife's bike.

Ultimate question is I would like to take a few rides with longer range and the possibility of charging some during the ride. Am I better off running these batteries separate or paralleling them. In my head the answers are gray. Maybe someone else can give a less biased opinion.

 

[BVH]

I added a second, identical battery to my Prodecotech Oasis for longer range with the added benefit of reduced Voltage drop at a given current flow. They are separately key-switched, BMS'd and I charge them separately. After charge, i allow them to reach a differential of about .2 to .3 Volts before I "parallel" them by turning on both key switches. You can do the same with your two packs despite the capacity difference. They will discharge evenly Voltage-wise, more from the 4P pack. I never run one at a time. There's no benefit for me in doing that.

 

[goatman]

parallel them, I do it all the time. I wouldn't want to pull 12amps from 2p of ga. its easier on the cells to parallel and increase the p/ah.
I parallel batteries all the time. ive got one battery that's 3p that id never run by itself, its just paralleled as a range extender. luna makes a wolf pup, grin makes Ligo. same thing.

 

[john61ct]

The only mainstream requirements are

pretty closely matched chemistry and S-count, so the voltage vs SoC% are at least similar, and

similar voltage before connecting (Safety issue!)

my guideline is delta under 0.1V per S-count, but apparently many advise closer

Age, brand etc does not matter if only paralleling at the bulk-lead, pack voltage level.

But there may be BMS issues, hopefully someone will help clarify.

Ideally, each cell-group gets paralleled, so one BMS can protect as one pack, but then more closely matched would be better.

 

[hemo]

I also parallel batteries and do so using different celled packs and capacity with no issue, just make sure SOC is as close as possible before connecting I aim for less then 0.2v. A simple led £2 volt metre wired to each pack allows me to keep an eye on the voltage every now and then.

 

[Pierre R]

I want to thank everyone. I finally did parallel the batteries. Everything worked perfectly without so much as a spark when I paralleled the two.