BMS Relay 200A with 600A Peak Amp

[alvirtuoso]

Is my BMS 200A with Peak 600A(single Relay charging) is undersized?

My system plan:
12K Growatt Low Frequency Inverter
16s 48v LiFePo 302AH CATL
Max Daily Power Billed usage is 71KWH

Using this calculation:
12000 watts * 1.5 surge factor / 48 volts low cutoff = 375 dc amps

I was thinking if I should base my BMS 600a peak with 375a.

 

[Ai4px]

How long will you peak over 200amps? A brief surge is no problem for a gigavac, I think the specs have it good to 1000amps for a few mS. based on your 71kwh per day, that is an expected 3kw draw 100% of the time .... 63 amps at 48v.... that is absolutely no problem. The most difficult thing on a contactor is making and breaking under load. Simply running a load is easy, and 63 ams on a 200amp contactor is easy going.

 

[John Frum]

Is my BMS 200A with Peak 600A(single Relay charging) is undersized?

My system plan:
12K Growatt Low Frequency Inverter
16s 48v LiFePo 302AH CATL
Max Daily Power Billed usage is 71KWH

Using this calculation:
12000 watts * 1.5 surge factor / 48 volts low cutoff = 375 dc amps

I was thinking if I should base my BMS 600a peak with 375a.

Please provide a product link so that we can get more info on the bms.
12000 ac watts / .85 conversion factor / 48 volts low cutoff = 294.117647059 service amps.
Its my policy to design the system to cover the full inverter capacity.
If your batteries were full the inverter could run full bore for an hour until your batteries were empty.
Even longer if the pv panels are also providing power.

 

[alvirtuoso]

Please provide a product link so that we can get more info on the bms.
12000 ac watts / .85 conversion factor / 48 volts low cutoff = 294.117647059 service amps.
Its my policy to design the system to cover the full inverter capacity.
If your batteries were full the inverter could run full bore for an hour until your batteries were empty.
Even longer if the pv panels are also providing power.

QUCC BMS

175.0US $ |Qucc Smart Bms Relay Contactor 7s 8s 10s 12s 13s 14s 15s 16s 17s 20s 200a Li Ion Lifepo4 Bms 24v 36v 48v 60v 72v Bluetooth App - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Thanks in advance @smoothJoey

 

[MrM1]

why not double the size of the bank to a 16s 2p with a single BMS on each 16s pack. That way together each pack and BMS will only "see" half the amp / current draw of the entire system. I am designing a system with the Growatt 12kw with 32 cells in a 16s2p config. I will then put fuses between the series packs and the parallel busbars that will blow if either pack tries to exceed the average limits of either of the BMS units.

 

[John Frum]

QUCC BMS

175.0US $ |Qucc Smart Bms Relay Contactor 7s 8s 10s 12s 13s 14s 15s 16s 17s 20s 200a Li Ion Lifepo4 Bms 24v 36v 48v 60v 72v Bluetooth App - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Thanks in advance @smoothJoey

I can't tell anything specific about the contactor but this guy has been using a QUCC bms for a while now without any real issues.

https://www.youtube.com/channel/UCSv0QdWrddSghKQ9gXDT7pQ

Personally I would not push it past its continuous rating for more than a few seconds at a time.
If I ran a contactor based bms and it ever tripped under load I would want to know the cause and i would buy a new contactor.
Its my understanding that once they trip under load the contacts get pitted and once they are pitted the chance of them welding closed goes up significantly.

 

[John Frum]

Personally I would design my system so the whole current path including the bms is rated for greater than 300 amps continuous.

 

[alvirtuoso]

Personally I would design my system so the whole current path including the bms is rated for greater than 300 amps continuous.

Is it possible to double my bms on a single series battery bank? I bought 2 BMS 200A for backup spare.

 

[John Frum]

Is it possible to double my bms on a single series battery bank? I bought 2 BMS 200A for backup spare.

I don't see why not.
Disable balancing on one bms though.
Set you charge and discharge profiles conservatively so that you never trip the BMSs.

 

[Itohmamma]

why not double the size of the bank to a 16s 2p with a single BMS on each 16s pack. That way together each pack and BMS will only "see" half the amp / current draw of the entire system. I am designing a system with the Growatt 12kw with 32 cells in a 16s2p config. I will then put fuses between the series packs and the parallel busbars that will blow if either pack tries to exceed the average limits of either of the BMS units.

Sounds like what I’m doing, TWO DALY 200amp common port. however I’m still trying to figure out The best size DC circuit breaker for each of the battery banks. I will be using a 30 K inverter with dual post input, 2/0 welding cables ( one for each 16 S) suggested breakers? ??

 

[Itohmamma]

Is it possible to double my bms on a single series battery bank? I bought 2 BMS 200A for backup spare.

I’m really not sure why you would double up on the BMS’s? I think it should be a spare, should be a spare… to have a spare in case you need a spare!….and why confuse the electronics on either one of them? Am I missing something here?