LiFePO4 and Regen

[Gibles]

Is regen possible for LiFePO4 batteries with a BMS? I've searched everywhere on these forums with no result.

 

[ZapPat]

Is regen possible for LiFePO4 batteries with a BMS? I've searched everywhere on these forums with no result.

It would have the same limits to regular recharging, so it really depends on what lifepo4's you are using. A123's would be great to accept fast recharging, but no-name packs only capable of 0.5C charge rates would limit your regen capability quite a bit.
Also, any battery will accept more recharge current the more it is in a discharged state (like at least under 60-70% or so, depending on the battery).

 

[Jozzer]

My LifeBatt pack on the motorcycle will happily take 2 or 3C regen charging rates, even at 95% full charge. In practice, a regen current this strong will slow the bike pretty damn quickly, so it will not maintain high current for long.

Steve

 

[Gibles]

My LifeBatt pack on the motorcycle will happily take 2 or 3C regen charging rates, even at 95% full charge. In practice, a regen current this strong will slow the bike pretty damn quickly, so it will not maintain high current for long.

Steve

If the battery doesn't hook up to the controller through the BMS, how can you ensure a proper regen? Or if it will at all?

 

[Jozzer]

The Kelly controllers have a high voltage regulator on the regen, settable via software. Regen current is controlled via a halls throttle on the lefthand bar.
The Kelly starts limiting regen to maintain the haigh voltage you set (ie, mine is allowed to regen to 88v, and starts limiting at 82v.)
In practice, once the surface charge is gone, you can regen effectivly. Unless you live up a mountain you wont have problems. Bearing in mind you are lucky to get 10-15% back of the outgoing current there should not be a problem!

 

[Gibles]

The Kelly controllers have a high voltage regulator on the regen, settable via software. Regen current is controlled via a halls throttle on the lefthand bar.
The Kelly starts limiting regen to maintain the haigh voltage you set (ie, mine is allowed to regen to 88v, and starts limiting at 82v.)
In practice, once the surface charge is gone, you can regen effectivly. Unless you live up a mountain you wont have problems. Bearing in mind you are lucky to get 10-15% back of the outgoing current there should not be a problem!

Maybe I'm doing a horrible job at explaining myself. The tech I talked to about the pack said I must plug a 30amp current into the BMS/charger to charge the pack and that it doesn't charge otherwise.

 

[ZapPat]

The Kelly controllers have a high voltage regulator on the regen, settable via software. Regen current is controlled via a halls throttle on the lefthand bar.
The Kelly starts limiting regen to maintain the haigh voltage you set (ie, mine is allowed to regen to 88v, and starts limiting at 82v.)
In practice, once the surface charge is gone, you can regen effectivly. Unless you live up a mountain you wont have problems. Bearing in mind you are lucky to get 10-15% back of the outgoing current there should not be a problem!

Maybe I'm doing a horrible job at explaining myself. The tech I talked to about the pack said I must plug a 30amp current into the BMS/charger to charge the pack and that it doesn't charge otherwise.

Any chance of a battery brand, model, web links to tech info about the BMS/charger/battery pack? This might help us help you. :wink:

 

[Gibles]

http://www.electricwheelsinc.com/batteries.shtml

It would be a 36V 100Ah setup. He isn't very specific on the BMS or charger except it'd be coming from the manufacturer whom he doesn't name.

 

[ZapPat]

http://www.electricwheelsinc.com/batteries.shtml

It would be a 36V 100Ah setup. He isn't very specific on the BMS or charger except it'd be coming from the manufacturer whom he doesn't name.

Ask him about it before buying anything, because the info on that web page is not enough to know much.

One thing we can see is that these batteries will accept up up to 200A charge current...

 

[Jozzer]

I'm not sure the BMS charge circuit is even relevant, if for instance it has a seperate 30A input for charging..
The regen power would flow throught the discharge circuit which may allow current back to max discharge rate rather than max charging rate.

You would have to experiment to be sure.

 

[sharkmobil]

Has anybody put together a supercapacitor - Lifepo4 combo? Seems like a match made in heaven.