How many Amps can my battery handle?

[maarten_almighty]

Hello all,
My battery pack is 10parallel, 20series (72v nominal) built with Sanyo NCR18650BL cells. They are rated for 7A max continuous discharge, but i could not find any info on temporarily discharging them at a higher rate (for example 10A per cell). Is it acceptable to discharge a cell (during a very short period of time for example 1 minute) at a higher peak amperage than the rated continuous max amperage? (provided the battery pack temperature is being monitored via the bms and as soon as temperature gets over for example 70 celcius the bms cuts the power or more likely limits the power to 7A per cell).
Or is it a bad idea and a no-go to discharge any cell (even temporarily) above rated continuous max amperage?

cell info: http://www.nkon.nl/sk/k/NCR18650BL-specification.pdf

Could you give me an indication of how bad the effect on cell life/capacity would be caused by this temporary higher discharge rate?

My bms can handle 200A but is adjustable (via bluetooth), can adjust max amperage adjusting to current temperature.

Thank you very much!

 

[goatman]

the resistance of the cell is less than 35. whatever that means

for cycle life, i wouldnt run that battery hotter than 40 celsius

i dont know where you live but in cooler climates you might want that high resistance cell to maintain pack temperatures between 25 and 40 celsius but in warmer climates the pack might get too hot at 3.75amp continuous. go ride and see what pack temperatures youre operating at

 

[Matador]

For this 7A cells, I would personally not exceed 5A max and 3.5A continuous. Would avoid 7A as the cells (I'm guessing the 35 mOhms is AC internal resistance/impedance, rather than DCIR) would likely get quite warm/hot. Sure you could do 10A burst, but don't expect the cells to last more than 50 cycles. Still in 10P config, 5A per cells is 50A total from the pack.

Matador

 

[Matador]

May I ask what motor and controller you want to use ? How many watts and amps your setup will be able to pull maximum ?

 

[maarten_almighty]

@Matador

Motor:
Suringmax 3000w (nominal) v3 motor; link:
https://www.aliexpress.com/item/4000212162738.html?spm=a2g0s.9042311.0.0.27424c4dn23KMk

BMS:
200A 20s adjustable BMS:
https://nl.aliexpress.com/item/4001297015223.html?spm=a2g0s.9042311.0.0.18864c4dOHGM33

Controller:
Sabvoton SVMC72150 (max power and many more things adjustable):
https://nl.aliexpress.com/item/32811537596.html?spm=a2g0s.9042311.0.0.18864c4dOHGM33

 

[pwd]

I think 10A per cell for one minute would be too much. If you did 8A per cell for say < 10 seconds; that would be better but would still be a lot for my taste on those cells. As other other mentioned; you will significantly reduce the usable cycles from the cells if you are heating them up frequently.

 

[999zip999]

Off topic how you like that motor what turn ?

 

[maarten_almighty]

Off topic how you like that motor what turn ?

Thus far I am quite happy with the motor. plenty of torque, doesn't get too hot (approx 80-100 celcius max temp so far using 3kw nominal 5kw peak) (but I don't know the exact temperature as I currently don't have a temperature sensor installed).
I am not sure how many turns I have, the 'standard version' of the motor is what i bought, will ask supplier how many turns it has.

I previously had a 500w nominal 800w peak motor which i overvolted (using 1200w controller) so perhaps that's not the best comparison material..

 

[999zip999]

The C.A. v3 has a temp reading plug and nice opinions.

 

[maarten_almighty]

The C.A. v3 has a temp reading plug and nice opinions.

Thank you for the suggestion. Do you know if it (C.A. v3 ) will work with my motor/controller combo? (controller is sabvoton SVMC72150). Temp sensor in motor currently is a 10Kohm NTC. Thank you once again

 

[999zip999]

Does it have a 6 pin just plug ?

 

[maarten_almighty]

Does it have a 6 pin just plug ?

Yes the motor has a plug with 6 pins + the three phase wires (1 wire for temp. sensor, 5 wires for hall sensor signals+power).

The controller also has a plug with 6 pins (1 wire for temp. sensor, 5 wires for hall sensor signals+power).

 

[Matador]

@Matador
Motor: Suringmax 3000w (nominal) v3 motor
Controller: Sabvoton SVMC72150

So basically your controller can do 150A and your 20S10P battery is 72V. Meaning the controller could ask each cells for 15A...

But the cells you have arr 7A max.

I only see a few options here.
Either turn down the max amp setting to 50-60A max if your contoller is adjustable.
Or get a new battery that can survive the 150A that the controller is capable of drawing.
You could monitor battery temps and pull more than 50-60A but it's almost certain that anything higher than 70A will damage the cells. Why ruin a perfectly good battery.

I would want to recommand bulding a 20S10P with sony VTC4 or LG HG2. Or even a 24S10P with A123 M1A LFP cells if you can afford it.

Running that 150A controller out of you current battery is like running a Hayabusa mototcycle engine off of a tiny scooter carburator.

 

[maarten_almighty]

@Matador
Motor: Suringmax 3000w (nominal) v3 motor
Controller: Sabvoton SVMC72150

So basically your controller can do 150A and your 20S10P battery is 72V. Meaning the controller could ask each cells for 15A...

Yes indeed. Luckily I can limit max current for this controller in the settings. I will most likely limit it to 70A (or lower if battery temp gets too high with 70A)

 

[Matador]

Wise choice. You can still enjoy your bike a 70A. And at 72V, it's still 5000W. But don't do it too often, stay at a more conservative 3000W most of the time and your battery will last much longer life.

The great thing about your controller is one day if you decide to get a higher power battery, you alteady have the option to increase you controller amps.

 

[ZeroEm]

Looks like a big motor for 142mm dropouts but all the advertised power is based on 30 amps or i'm I wrong?