Please help me choose a 21700 battery pack...

[marjoriefinnigan]

Hi guys
Running a cyc stealth 1500w motor.
Don't usually do more than 20-30mile ride with pas not throttle.
No time to build my own pack at the moment so these are the two choices which are both in shark type cases...
Would ideally have liked a smaller battery like a 'Bicycle motor works pocket rocket' but not much choice in the uk at the moment, so trying to be practical about it.

52v 80A 655Watts Molicell P42A 21700 (14s3p) 80amp bms
https://www.electroncycles.co.uk/product/52v-14s6p-80a-18ah-936-watts-ultra-high-performance-downtube-battery-sony-vtc6-charger/

52V 19.2AH, LG-4800mAH Cells (21700 Cells) with 40a bms
This is an eBay battery from a seller with 100% feedback

If you've got any better ideas of be delighted to hear them.
Thanks in advance!

 

[pwd]

What is the peak battery current that your motor controller will draw? A bigger, better performing battery will last longer in the long run than one that is used close to it's limits.

 

[marjoriefinnigan]

65a peak I think.

 

[pwd]

For 65A, neither of those packs seem ideal unless you can live with a lot of voltage sag and short life of the battery pack. I'd shoot for a pack with at least 4x P42A or 5x LG M48T (4800mah) in parallel to help deliver that current.

Alternatively; you could lower the max battery current to around 40A if the controller is programmable.

 

[marjoriefinnigan]

Thanks.
The batteries above are cyc's own and what they suggest for the motors.


The other option Electron does is...
14S4P 52v 19.5Ah Panasonic Tesla 21700 (4850 mAh per cell and). 50Amp Nominal BMS. 4p x 10A cells

Thanks again for the guidance.

 

[The Battery Doctor]

No reention battery cases are rated for use over 1000W according to producer in germany we work with. Sure it can handle more but it will be a lot of wera and tear, like running a 250W motor on 400W. And to claim 80A is bold! Building good quality high amp batteries and HARD and most batteries you will find online is built in china. I would not trust electroncycles unless they built it themselves and have images of the build. The only one in china you should trust is em3ev. They are experters on high amp ebike batteries.

 

[slaphappygamer]

I didn’t know cases have limits. I have a Reention Rhino IR-5. Its 13s4p (18650 Samsung 35E) and the discharge port seems to be rated at 20a max(?). The BMS is 25 amps (I believe). Looking at other batteries of this same model, I also see other packs with 21700 cells and a 30AMP BMS. I’m wondering now if there are different amp rated discharge ports for this same battery case. Is there even a way to get around this limit?

 

[amberwolf]

I wouldn't worry about what TBD says about things like that; it might be a language barrier or a misinformation problem, but a case (or it's mounting hardware) wouldn't be be watt-limited (even if a seller "rates" them that way).

It could be *current* limited, in that the connectors in the case and any mounting hardware it might have connectors to plug into, as well as any wiring, switches, or fuse-holders, will only be able to handle so much current.

It could be *voltage* limited in that the switches or included fuses might only be able to handle so much voltage and still guarantee disconnect.



If you need higher current out of a pack that's in a case like that, you can change all the lower-rated stuff in it out for parts that are rated as you need (cells, interconnects, wiring, fuses, switches, connectors, etc--anything that's in the current path).