Working out max regen current.

I have a 20S14P Panasonic NCR18650GA battery that I would like to find out the maximum regen current that I can put though it. I use it with a 8000w motor and I keep warping my disc rotors so I would like to use regen to slow me down.

Regen is charging, so max regen current is the same as max charge current.

I found a datasheet that said NCR18650GA recommended charge current is 1.45A. You're using 14p, so your pack's max charge current is 20.3 amps. You could possibly push that to 25, but really not more than that is recommended. So, 25 amps regen current.

What are you riding that's so heavy you need an 8000w motor and you keep warping discs?

harrisonpatm said:

Regen is charging, so max regen current is the same as max charge current.

I found a datasheet that said NCR18650GA recommended charge current is 1.45A. You're using 14p, so your pack's max charge current is 20.3 amps. You could possibly push that to 25, but really not more than that is recommended. So, 25 amps regen current.

What are you riding that's so heavy you need an 8000w motor and you keep warping discs?

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Thanks for the response. I'm also guessing that regen charging has nothing to do with the charger input charging because regen current will go through the discharge side of the BMS? I'm asking because my BMS can only handle up to 15A charging but since regen uses discharge side, this should not matter?

I also ride an eletric enduro bike. I do a lot of riding on technical courses where you're always either full throttle or locking up your brakes with very little breaks for the rotors and pads to cool off but regen braking will probably save my brake pads and rotors when I'm on the street.

Discharge side vs charge side... sounds like you have a split port BMS, as opposed to a common port. Not all of them support charging through discharge side. Meaning regen might not work on your setup. Got any info on your BMS?

I haven't done it myself, but other people on the forum might have more info on enabling regen through this kind of bms

Regen would "always" work on the discharge side...but there are two potential problems with it, caused by the thing that allows it:

--There is an intrinsic diode in every FET that will let current flow backwards even though the FET is turned off. If the BMS tries to turn off for any reason, the diode keeps the current flowing, but the diode has a voltage drop across it, and can create heating inside the FET much greater than it's normal heating from the FET's RDSon resistance.

(if the FET is on, it shorts across this diode, reducing the voltage drop and internal heating of the FET)

--Because the FETs can't turn that diode off (it's always there), the BMS cannot stop this current flow, even if there is a problem with the pack, such as it detecting a cell over HVC, or an overcurrent event, etc.

Adrian_ said:

I also ride an eletric enduro bike. I do a lot of riding on technical courses where you're always either full throttle or locking up your brakes with very little breaks for the rotors and pads to cool off but regen braking will probably save my brake pads and rotors when I'm on the street.

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Question:

How much torque will the same amount of current you expect from regen be able to generate in the motor?

Meaning, if you use say, 25A regen current, how much motor torque do you get from that same 25A current as discharge current from the battery?

This should be about the same as the braking torque you can expect from the system for that current.