Need help with my 24V battery output

[SandboxWilderness]

I'm assembling a 24V battery pack using 16 280A cells. My pack is being used to power a big, 6,000W low frequency inverter (AIMS Power 24V 120hz UL-listed model). I'm trying to figure out the best (and safest) way to get the power to the inverter.

I was planning to use 24V 8S Daly BMSes on the two packs and then put them in parallel. I received one of the BMS' , and frankly, the wiring looks stupidly small (6 gauge, I think)... I really don't think they are going to cut it.

One option that came to mind was to make a single 2p8s pack with the Daly and just use it to control a Relay on the output side. Doesn't help me for input, but my charge controller has temp control, so I think I can live with that. If this seems like a good option, does anybody have a suggestion for a 500A 24V relay? (my inverter can run peak loads of up to 18,000W, but I can't see ever using more than 12,000W)

Another option is to abandon my Daly and go with a different BMS that can handle more power.

Would love some recommendations.

 

[Rednecktek]

Another option is to abandon my Daly and go with a different BMS that can handle more power.

This!

 

[Cajunwolf]

This!

LoL, good answer, short and to the point.

 

[Cajunwolf]

Do the 2p8s and get a 200 amp BMS. This way, all you need is one BMS. What are you trying to power with a 6kW inverter? You're going to need a lot more battery. I have 24.8v @ 400ah and have a Giandel 24.8v 4kW inverter; divide that out, and you get 162 amps wide open.

 

[SandboxWilderness]

Do the 2p8s and get a 200 amp BMS. This way, all you need is one BMS. What are you trying to power with a 6kW inverter? You're going to need a lot more battery. I have 24.8v @ 400ah and have a Giandel 24.8v 4kW inverter; divide that out, and you get 162 amps wide open.

I'm only likely to test the upper bounds off the inverter on the rare occasion I need a larger power tool.

 

[SandboxWilderness]

Should I just source a bigger Daly BMS, or would you recommend something different?

 

[Cajunwolf]

I'd re-phrase your question in the BMS Forum Section:

 

[Steve_S]

6000W @ 24VDC = 250A Pull Uncorrected for inefficiencies.
280AH Pack can output 280A Max for 1 Hour and take 140A Charge Rate max for 2 hours.
Two packs in parallel divide & share the Load & Charge.
IF Packs are Equal they will share equally BUT if not equal it will be proportionate to Capacity.
Packs in Parallel offer Fault Tolerance & Fall Back fail-over should any pack(s) be cutoff for any reason, the others will stay operational. In general, it is suggested to configure packs to be able to operate as "Last Man Standing" meaning that each pack can handle the full Charge/Discharge capacity of the system.

FET Based BMS need to be derated by at least 20% for safe margin. Therefore a 250A can safely handle 200A. MOST FET based BMS will only do 50% of the output handling for Charge Rate. Relay/Contactor BMS's depend on the Relay/Contactor for the Amperage Handling.

BMS Wires:
Sense Leads are always small from 24-18 gauge, even with Passive & Active Balancing (below 2A high Amps are a bit thicker)
Affixed Wires to BMS for Current are High Temp Fine Copper Silicone jacketed, it's not just regular ol copper wire with PVC jacket. It is not uncommon to have 2 or 3 wires per B- & P- on a High Amp FET BMS.

Current Popular BMS are: They are all carried by this vendor as well.

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[SandboxWilderness]

Thanks Steve_S - taking your advice to heart. I ordered two 250amp BMSes and will run two banks in parallel. Each can power most of my loads with ease on their own, and combined they can power just about anything I would throw at them at the extreme.