48v residential total off grid system

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
8,409
4 strings x 50V x 280 Ah = 58,000 Ah (gross)
Maybe you use 80% to 90% of capacity, 45 kW to 50 kW

Sounds like 3 strings would do it. Or 4, a bit extra, if you want.
Then you have to chose between 3p16s and 16s3p (how many BMS, max current, etc.)
 

bushi12

Solar Enthusiast
Joined
Sep 19, 2021
Messages
94
4 strings x 50V x 280 Ah = 58,000 Ah (gross)
Maybe you use 80% to 90% of capacity, 45 kW to 50 kW

Sounds like 3 strings would do it. Or 4, a bit extra, if you want.
Then you have to chose between 3p16s and 16s3p (how many BMS, max current, etc.)
Wont I need a BMS for each string? I'll probably do the 3p16s.
 

Pyrofx

Flux capacitor builder
Joined
Jul 27, 2020
Messages
525
Location
Oatman Az
Yes . Bms each string. Then to common busbar. Out from there to inverter.
I've got 6 strings of 16. Each with a rec bns.
Slightly pricey. But then with 12k in batteries, I sleep well at night.
 

bushi12

Solar Enthusiast
Joined
Sep 19, 2021
Messages
94
Yes . Bms each string. Then to common busbar. Out from there to inverter.
I've got 6 strings of 16. Each with a rec bns.
Slightly pricey. But then with 12k in batteries, I sleep well at night.
That's exactly what I'll do. What's the rec bns? Even with 6k in batteries it'll help me sleep!
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
8,409
Wont I need a BMS for each string? I'll probably do the 3p16s.

BMS for each string is better. That would be 16s3p

If you paralleled 3 cells, did that 16 times then connected in series that would be 3p16s. Only one BMS.

16s3p is better for several reasons. Current handling is approximately 3x (except for imbalance in current draw.) If one BMS fails you can run on two strings. There is some concern with one cell failing and the other two dumping current into it, with no way for BMS to disconnect.

Which brand/model BMS may depend on your inverter. REC makes one which would communicate with my Sunny Island. Better control and time to balance with communication.
 

bushi12

Solar Enthusiast
Joined
Sep 19, 2021
Messages
94
I'm running 2 LV6548 6.5KW - 120v Solar inverter 8kW -2 x 4kW 250V MPPT UL1741 compliant - built in Wifi for this system. Will rec work with these.
 

bushi12

Solar Enthusiast
Joined
Sep 19, 2021
Messages
94
Can anyone tell me what BMS communicates with LV6548. The manual says it uses a RJ45 type phone jack. I just ordered 32 3.2volt 280ah batteries.
 
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