Noob to EVs looking for BMS recomendations LiFePO4 12S

[WalkerYYJ]

Hi all,
Building my first EV (Cargo BIke) and with the current plan being 12x 25AH Fortune cells (LiFePO4). I'm very new to this all and would love some insite into what the best option is re BMS for this setup.
I'm not super concerned about cost but I am trying to build something that will last a long time ideally with minmium needed tinkering (after its up and running.)

I live in a colder part of the world so low temp cut-off is needed, I would also like the ability to verify that cells are in good shape, so something with Bluetooth, or serial comms would be nice. I was looking at the ANT units and more recently the Neptune units (not sure if they have low temp cutoff).

For background, I'm happy to apply conformal coating (or even potting compund if that makes sense.). Also although I am a noob to EVs, I am not a noob to batteries, high amperage DC etc.

Planned config:
Grin all axel front hub motor (20" wheel) and GMAC geared motor (26") rear
with Twin Phaserunners for controllers.

Any and all suggestions would be greatly appreciated!

Thanks!

 

[agniusm]

Check out tinyBMS from energus. They are European brand and with that you get proper manual and support.

 

[WalkerYYJ]

Check out tinyBMS from energus. They are European brand and with that you get proper manual and support.

BOOM!

That looks like a winner to me! Thanks bud!

 

[Rassy]

I understand that you are looking for some special monitoring capabilities, but I have been sold on the Signalab BMS that Ping uses on his batteries. All his batteries are LiFePO4 so his 12s BMS should be perfect for your application. The main reason I like these is the 12 LEDs that all light up when the battery is fully charged and balanced. No other monitoring or checking required. The newest model, V5.0, draws the BMS needs from the full battery, not just a subset of the battery, and thus the BMS does not cause any inbalance within the battery.

I really responded here because I am curious why you want a cold temperature cut off. Do you want to be unable to charge the battery under a certain temperature, or do you want to be unable to use the battery under a certain temperature, or do I not understand at all?

 

[amberwolf]

In either of those cases, a simple thermal switch rated for the specific temperature would provide this ability, installed in the BMS's "enable" line, if it has one. If it doesn't, a bit of circuit tracing can be done to find the output of the enable lines of the monitoring chips to the FET gates, and the sensor(s) can be put in there to disable the FETs from turning on below (or above) whatever temperature the switches are for, and then bury the sensors inside the pack.

If you need multiple spots monitored, just put the switches in series, so they *all* have to be on to be able to be used.


Just remember that the more stuff you add, the more likely it is something with the extra stuff will go wrong and prevent you from using a perfectly good battery under perfectly fine conditions.

 

[john61ct]

I am curious why you want a cold temperature cut off. Do you want to be unable to charge the battery under a certain temperature, or do you want to be unable to use the battery under a certain temperature, or do I not understand at all?

Charge at too high a rate at too cold a temperature and you've instantly murdered the pack, rendered it to scrap, unrecoverable.

Other ways to protect them, and grey areas depending on chemistry, but a very valid concern in cold climates

 

[Rassy]

Charge at too high a rate at too cold a temperature and you've instantly murdered the pack, rendered it to scrap, unrecoverable.

Thanks John. Makes sense, if I have seen specifications for low temperature/charging limits I probably ignored it since weather here is not too extreme.

But that does bring up another point that many seem to ignore these days, including you. It was never forced by the forum, but the simple inclusion of your location in your profile, at least your country, often helps the reader understand the issue, and also can help when making recommendations about vendors, etc. Used to be a de facto standard and many early members wouldn't even respond to a post when new members didn't bother including their location.

 

[llile]

I'm looking at bmsbattery for a replacement BMS for a battery rebuild project right now, have use dthem before with good luck and they've been around a while.

https://bmsbattery.com/