If someone could enlighten me

Am picking out a bms for my lifepo4 battery banks and will probably go with JK BMS unless there are better options. There are 32 lifepo4 280 ah batteries in two banks hooked to a Solarc 12 k Inverter. Here is my confusion... The DC side of the Inverter says D.C. max of 190 Amps. So that would suggest that I need a bms of 200 Amps ?? However the AC pass through of this Inverter is 50 Amps.

So my confusion is that if the Inverter can only pass through 50 Amps AC why in the world does the D/C side need the ability to supply 200 amps? So how many amps does the bms need to be and why?

Thank you...

Suncatcher

SunCatcher said:

Am picking out a bms for my lifepo4 battery banks and will probably go with JK BMS unless there are better options. There are 32 lifepo4 280 ah batteries in two banks hooked to a Solarc 12 k Inverter. Here is my confusion... The DC side of the Inverter says D.C. max of 190 Amps. So that would suggest that I need a bms of 200 Amps ?? However the AC pass through of this Inverter is 50 Amps.

So my confusion is that if the Inverter can only pass through 50 Amps AC why in the world does the D/C side need the ability to supply 200 amps? So how many amps does the bms need to be and why?

Thank you...

Suncatcher

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Voltage matters.

DC amps is at DC voltage

AC amps is as AC voltage

SunCatcher said:

The DC side of the Inverter says D.C. max of 190 Amps.

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190A x 48V = 9120W

SunCatcher said:

only pass through 50 Amps AC

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50A x 120V (??) = 6000W

How many watts is your inverter rated for?

SunCatcher said:

Am picking out a bms for my lifepo4 battery banks and will probably go with JK BMS unless there are better options. There are 32 lifepo4 280 ah batteries in two banks hooked to a Solarc 12 k Inverter. Here is my confusion... The DC side of the Inverter says D.C. max of 190 Amps. So that would suggest that I need a bms of 200 Amps ?? However the AC pass through of this Inverter is 50 Amps.

So my confusion is that if the Inverter can only pass through 50 Amps AC why in the world does the D/C side need the ability to supply 200 amps? So how many amps does the bms need to be and why?

Thank you...

Suncatcher

Click to expand...

50A AC x 120V = 6000 watts

That of course is times 2 because it is 240V/120V split phase so 12000 watts

12000 watts divided by 48V DC = 250A

MisterSandals said:

190A x 48V = 9120W


50A x 120V (??) = 6000W

How many watts is your inverter rated for?

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It would be 12K with split phase with a 12K Solark.

As for BMS size, I'm not quite sure on what you have for battery bank, I doubt you have 32 batteries but rather 32 cells.

That makes a pair of 16S batteries. Batteries in parallel split the load, so 250A of load on a pair would be 125A on each battery.

Thanks everyone. Putting it into watts is what helped me understand this a bit. The inverter is the Solarc 12k and we are inputting 8k worth of panels. And correct... those are probably better called cells

Zwy said:

As for BMS size, I'm not quite sure on what you have for battery bank, I doubt you have 32 batteries but rather 32 cells.

That makes a pair of 16S batteries. Batteries in parallel split the load, so 250A of load on a pair would be 125A on each battery.

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At one site I looked at I see they have 100, 150 and 200 amp jk bms with three options for the 150 amp. So if I understand correctly I need two of the 150 amp? How do I determine which of the three. Here are the part numbers

JK-B1A20S15P
JK-B1A24S15P
JK-B2A24S15P

Mostly I want to be sure that I do not make a mistake here since this will be inspected and will need to pass. So thank you folks for your kindness in helping... Oh... and where can I get simple line drawings for my knife edge a/c kill switch that may even have it sitting near the meter since that is an important requirement to pass. Thanks again

Suncatcher

SunCatcher said:

At one site I looked at I see they have 100, 150 and 200 amp jk bms with three options for the 150 amp. So if I understand correctly I need two of the 150 amp? How do I determine which of the three. Here are the part numbers

JK-B1A20S15P

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1 amp active balancing, up to 20S

SunCatcher said:

JK-B1A24S15P

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1 amp active balancing, up to 24S

SunCatcher said:

JK-B2A24S15P

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2 amp active balancing, up to 24S

SunCatcher said:

Mostly I want to be sure that I do not make a mistake here since this will be inspected and will need to pass.

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You may need a labeled ESS if inspection is in order.

SunCatcher said:

So thank you folks for your kindness in helping... Oh... and where can I get simple line drawings for my knife edge a/c kill switch that may even have it sitting near the meter since that is an important requirement to pass. Thanks again

Suncatcher

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I ordered six of the 200A JK BMS without CAN and without inverter communication mentioned in this thread. https://diysolarforum.com/threads/jk-bms-deal-aliexpress.72147/ Inverter communication is not important to me.

I would go with 200a BMS as it complements your cells, that’s .7c discharge. Well within their capabilities.

Also if one battery needs to be isolated you won’t be that concerned with carrying loads on one battery.