Can I use packs with different cells for more power?

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Jul 4, 2021
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2-6KW Triple chainwheel kit, 80/60A 48-72V BT programable controller/ LCD , top speed 125km/h waterproof connector, Silence, 500Nm torque, no over heat Square tape/ISIS BB

I bought this kit from cyclone but cant seem to get a response to my emails. I bought 60 of what I hope are genuine samsung 30Q cells and plan to use them in a 17s configuration to get 69.7 volts. I can make 3 packs like this but will only have 9ah if I am doing the math correctly. I have 39 other cells I salvaged from a damaged scooter pack, not sure what make. If they were very different in C rating, peak amps, and all other areas, can they be safely used in addition to what I have already to add to the overall range? Can i connect them in parallel or would i need to use them as a separate battery once the first one is depleted? I would like to be able to just buy more 30Q cells, but I am already $300 over budget. I also still need to source a charger for this setup and bms.
 
Anything can be paralleled NP

so long as voltage matches, get within a volt or so when connecting.

Of course one bigger pack all cells identical is the ideal.

Keep on top of testing / monitoring so a failing cell / group / pack does not threaten the health of the better pack.

Proactively recycle & replace in advance of problems manifesting.

This requires more knowledge / skills / gear than working with only new / healthy packs.

Don't parallel more than three, unless all the balance leads are cross-connected in parallel too

This also allows one BMS to handle all the sub-packs as one.
 
Say the 30q cells have a higher discharge rate than my mystery cells and , would this only cause the bms to stop all battery packs from being used, leaving the mystery cells with partial charge? Then I'm assuming i would need to charge separately due to the voltage differnce.
My initial battery is 3 in parallel, 17s 3p, amounting to 69.7v 9ah. Adding another 17s 2p, maintainig the 69.7v and adding an unknown ah hopefully giving me somewhere areound 15ah total. Could I safely cross conect this as you say, and how is that done?
I also will not be able to monitor the cells as it is beign builit for someone else who I don't imagine would want to or care to do the extra maintenance. So i dont expect this pack to last very long. perhaps i should jsut let them know to disconnect these packs if they run unto problems.

Thankyou for your input/feedback!
 
Brandon122603 said:
...I also will not be able to monitor the cells as it is beign builit for someone else who I don't imagine would want to or care to do the extra maintenance...

My advice in that case is don't parallel two different cells. Even if you build two separate packs and then joined them in parallel it still requires each pack to be within 0.1V of each other before connecting; and it must be checked every time. It only takes one time to forget and both packs could be destroyed or worse.

I ran parallel packs for a couple of years and it worked fine but that was only until I built one large pack and it made things alot easier.
 
Yes do not do this for another user that will not be willing and able to test/monitor proactively.

New high quality cells only.

Which of course all eventually start approaching EoL eventually, but at least all the cells around the same time makes things safer, or at least less complicated to maintain

Just buy a new pack when the old gets worn

rather than continually atomising / rebuilding.
 
I suppose you both are right. Better to be safe than sorry. I'll just let the customer know they need to upgrade the battery beyond budget if they want more out of their bike.

Thank you for your input.
 
my first battery had recaimed cells of the same brand, poor / failed connections resulted in cell string death, fitting a BMS showed just how soon strings where under voltage, my next build will have Cheap BMS, multi channel voltage monitor/alarm, active cell balancing, at a cost of £100, hopefully this kit can be reused when the cells are done, not a lot for a battery that can protect, active balance and is east to moniter
 
Yes, only the cells are consumables

the rest of your infrastructure should last much longer.

This is the promised advantage of solderless no-weld pack building systems

Just recycle the EoL cells, and pop in replacement ones, everything else can remain in place.
 
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