Educate me on BMS

[Mike from Texas]

I scored on a pair of 3P7S Leaf Gen 3 modules recently. Now I’m looking at what BMS to put on it.

My main question is, how do I know what “size” BMS to buy? Do you buy one rated slightly higher than the constant current you think your cart needs? For example looking at a Daly BMS a 14S 48v rated @ 250A gives 250A continuous and 5-600a peak (for very short bursts I’m sure).

I’ve see people using the Zeva BMS that doesn’t look very robust probably because it uses a shunt to monitor current. So I’m guessing you have to use external relays triggered by the BMS to open the circuit in an alarm situation?

Just trying to learn and make sure I do this right because as of now I already have more $$ invested in rebuilding this cart than when I originally purchased it 8 years ago. [emoji33]


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[mccainc]

What kind of cart do you have? Any modifications- big tires, upgraded controller, etc? All those will affect total current. I think most people would recommend NOT to run discharge current through a FET BMS like the Daly. They simply won’t last very long because of heat buildup. Much better to have the BMS control a separate high current relay. They can be made to work well if you’re ok just controlling the high voltage cutoff by routing only charge current through the BMS and using something else for low voltage alerting or cutoff. The Zeva uses external relays for both high and low voltage cutoff. Sergio’s “Basic Nissan Leaf...generic Chinese BMS” thread on the lithium club car forum is an excellent read if you’re looking to use something like the Daly.

[Mike from Texas]

Originally Posted by mccainc

What kind of cart do you have? Any modifications- big tires, upgraded controller, etc? All those will affect total current. I think most people would recommend NOT to run discharge current through a FET BMS like the Daly. They simply won’t last very long because of heat buildup. Much better to have the BMS control a separate high current relay. They can be made to work well if you’re ok just controlling the high voltage cutoff by routing only charge current through the BMS and using something else for low voltage alerting or cutoff. The Zeva uses external relays for both high and low voltage cutoff. Sergio’s “Basic Nissan Leaf...generic Chinese BMS” thread on the lithium club car forum is an excellent read if you’re looking to use something like the Daly.

98 Club Car DS series cart
700A Logisystems controller
D&D torque motor
1/0 cables
400A solenoid
400A F/R contactors
6” All Sports lift
22” tires (soon to be upgraded to 24”)
Nissan Leaf Gen 3 batteries (14S).

I know this cart draws high current from time to time. I’ve burned up (2) 200A solenoids previously.

After reading more on the subject I agree with not using the Daly style BMS.

Currently I’m looking at the choice BMS from electric car parts company with a 600a relay for the discharge side and a 200a relay (I know way overkill) for the charge side. I may never see 600A on the discharge side but the cost difference between 400A & 600A is minimal. I still would prefer to have Bluetooth capability but the choice BMS looks to be pretty comprehensive and customizable but I’m open to other options.


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[mccainc]

Interesting. That looks like a rebranded Chargery BMS, which is a good system. I’d suggest googling the Chargery store as I believe it costs less directly from them. The creator, Jason Wang, is very responsive to inquiries and requests for updates. There’s also a lot of good information on diysolarforum.com as those guys are setting up similar systems to us just for a different purpose.

[Pat911]

Sergio’s system in the above thread is the way to go. No high current relay is required. A cart electrical system already has high current switching capabilities, Just use the BMS to disable the KSI (key switch) line. That will disable the cart if required. The BMS then only has to be sized to handle the charge current, 30A will be fine.

Cheers
Pat.

[Mike from Texas]

Originally Posted by mccainc

Interesting. That looks like a rebranded Chargery BMS, which is a good system. I’d suggest googling the Chargery store as I believe it costs less directly from them. The creator, Jason Wang, is very responsive to inquiries and requests for updates. There’s also a lot of good information on diysolarforum.com as those guys are setting up similar systems to us just for a different purpose.

Looks like you are correct, and a LOT cheaper to boot.

https://www.chargerystore.com/index....&product_id=42



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[Mike from Texas]

Originally Posted by Pat911

Sergio’s system in the above thread is the way to go. No high current relay is required. A cart electrical system already has high current switching capabilities, Just use the BMS to disable the KSI (key switch) line. That will disable the cart if required. The BMS then only has to be sized to handle the charge current, 30A will be fine.



Cheers

Pat.

Hmmmm good point. I’ll have to go back and see what he did for charger management.


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