Over 1C charge, pulsed


SLS BATTERY AUCTIONS are now live at www.batteryhookup.com EV, Lithium, LifePo4, Inverters & More

harrisonpatm

Member
Joined
Jan 5, 2022
Messages
169
My motorcycle uses 32650 LiFePO4s from BatteryHookup, 6000mAh rated. They are rated for a continuous charge current of 1C. At 12p24s, that means continuous charge current of 72 amps. Continuous being the key word to my inquiry here.

I'm setting up regenerative braking. I want a decent amount to extend range. I realized that I should keep an eye on the max amperage that's coming in (my ammeter for driving is analog, so I can see amps leaving, but the needle stops at 0 and I can't accurately read amps going in), so I pulled out my phone to read current while braking off my bms's bluetooth. At 30mph, regen engages and I saw around 70 amps max, did it a few times. Charge current decreases as you slow, obviously.

So here's my question. If I was going faster, 60mph, and engaged regen, I am likely to see a pulse charge of around 150-ish amps, which will immediately decrease as I start to slow. It will last only seconds, especially the faster I am going, because if I'm going 60mph, I will also be using my good ol analog brakes in addition to regen, slowing myself faster than regen alone would. This will exceed the recommended "continuous" charge current, but only for a few seconds. Is this a bad idea in the long run? Is it likely to decrease my battery's lifespan? If more info helps, they are rated for 3C discharge continuous, 10C discharge pulsed 10 seconds (216amps and 720 amps, respectively).

Edit: https://iopscience.iop.org/article/10.1149/2.0801713jes
After wading through the internet for awhile , finally found something resembling research. Seems to suggest that short pulses of high C charging during regen don't strongly contribute to lithium plating, as long as they're short. One takeaway from the paper is that they suggest it even increases the battery's lifespan.
 
Last edited:

Redpacket

Active member
Joined
Feb 28, 2018
Messages
1,457
they are rated for 3C discharge continuous, 10C discharge pulsed 10 seconds (216amps and 720 amps, respectively).
Since they are rated for short high discharge current bursts which are well above the 150ish amps, they are very likely to be OK with this.
 

harrisonpatm

Member
Joined
Jan 5, 2022
Messages
169
Since they are rated for short high discharge current bursts which are well above the 150ish amps, they are very likely to be OK with this.
Just want to confirm, you are saying that because they are rated for 10C discharge pulses, they should be fine with 2C or 3C charge pulses? Because that is my thinking as well, I just can't find hard data to back it up.

Wondering if this is a problem across the board with all EV's and all regen. It's pretty standard to have cells capable of much higher discharge than charge rates, and yet all regen is essentially high-C pulse charging. Widespread EV use is limited to about the last 10 years or so, which is probably why the research paper I added in my original post is one of the only ones I could find, so I'd be curious to see more hard data on how regen affects battery longevity.
 

Redpacket

Active member
Joined
Feb 28, 2018
Messages
1,457
because they are rated for 10C discharge pulses, they should be fine with 2C or 3C charge pulses?
Yes, that's my gut feeling. On batteries I've read up on, I recall seeing the specs for discharge related to charging, so more or less the higher the discharge rating, the higher the charge current rating. Maybe not equal, but related.

When thinking of the risks, I'm thinking factors could include:
a) heating - covered by the high discharge current design/spec, I doubt that would be a problem.

b) "stressing" the chemistry possibly resulting in gassing or localised electrolyte/anode/cathode changes.
Question would these short, relatively irregular events/pulses really have enough energy to cause such issues & I'm strongly doubting they would.

Overall, I'd say that other factors like vibration, water ingress, accident/impact/drop damage are far more likely to be the determining factors in the batteries life on a motorbike.
 

harrisonpatm

Member
Joined
Jan 5, 2022
Messages
169
Yes, that's my gut feeling. On batteries I've read up on, I recall seeing the specs for discharge related to charging, so more or less the higher the discharge rating, the higher the charge current rating. Maybe not equal, but related.

When thinking of the risks, I'm thinking factors could include:
a) heating - covered by the high discharge current design/spec, I doubt that would be a problem.

b) "stressing" the chemistry possibly resulting in gassing or localised electrolyte/anode/cathode changes.
Question would these short, relatively irregular events/pulses really have enough energy to cause such issues & I'm strongly doubting they would.

Overall, I'd say that other factors like vibration, water ingress, accident/impact/drop damage are far more likely to be the determining factors in the batteries life on a motorbike.
Thanks, in any case, I turned regen down just a bit, for smoothness of riding anyway, so all around I don't really expect any issues. Just wanted to throw it out there.
 
Top