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Mondo · Dec 8, 2020

Just finally pulled the trigger on 8x 280ah 3.7v cells. Then I realized I need a BMS, and maybe some other bits. Need some recommendation on what I should get along with them

curreny I have:
- 4x 105ah sealed lead acid, in series
- WZRELB RBP300012 3000W 12V... https://www.amazon.com/dp/B07XRP1GTF
- EPEVER 40A MPPT Charge Controller... https://www.amazon.com/dp/B077HHYYHT
- 2x HQST 100 Watt 12 Volt... https://www.amazon.com/dp/B07L7ZGGVT

anything needing an upgrade?
Which should I get to replace? Am in LA this week, and hoping to have everything installed by weekend, so can’t do shipping from China.

Steve_S · Dec 8, 2020

Right off the top, you will need a LOT more panel to charge that you know.
Assume you hit 0 SOC. 280AH @ 1C is 280A at 1 hour to charge to full, 140A (recommended 0.5C) is 2 hours from 0-100. Well it's a bit longer but that's the basic math. Temp and other things play into it.
I can push between 75A to 150A to my packs. Yesterday just charging 2x 280's from 10%, 5 hours @ 75A got the two to just under 75% ( I was also running stuff, it's my live system).

? Battery Fuse ? remember to get a Fuse on there. (3000W ÷ 12V = 250A)

The EPEver's are good little controllers, a fair bang per buck. If possible a bigger one capable of 75 to 100A charge would certainly help BUT you need the # of panels to support that capacity. But this brings you into a slightly different territory of gear and possibilities.

Overkill Solar is selling the JBD or JDB (ruddy alphabet soup) which are quite good Fet Based BMS' and he's in the southern side of the States. 12v BMS – Overkill Solar
ECPC may have something in stock and readily available: Lithium Battery Management Systems BMS | Electric Car Parts Company
and of course, there are eBay / Amazon vendors but I can't suggest any particular vendor as I don't know any personally for such equipment.

Hope it helps a bit, Good Luck.
Steve

Dzl · Dec 8, 2020

You have a few typos in there:

8x 280ah ~~3.7v~~ [3.2V] cells

- 4x 105ah sealed lead acid, in series
- WZRELB RBP300012 3000W 12V...

4 in series would be either 48V if they are 12V batteries or 24v if they are 6V batteries. Or if they are all in parallel they are 12V.

In terms of major components, If you plan to stick to the same voltage (8 cells can either be 12 or 24 Volts) you don't necessarily need to upgrade anything immediately.

Though the first thing that jumps out at me is how undersized your PV array is relative to the battery bank capacity 7kWh Battery, 0.2kW PV array so that would be a good place to start.

Both 'WZRELB "Reliable"' and EPEVER are budget options but well liked budget options from what I've heard. You are right you need a BMS, most come from China, if you can't Int'l shipping, Overkill Solar is the first option that comes to mind, or SBMS (but that is more advanced and sold out right now I think). If you go the overkill route, he gets his from China too so make sure he has US stock available before ordering. A big 'ole fuse (Class T, ANL, or MRBF) for the battery is important as well.

Mondo · Dec 8, 2020

Steve_S said:
Right off the top, you will need a LOT more panel to charge that you know.
Assume you hit 0 SOC. 280AH @ 1C is 280A at 1 hour to charge to full, 140A (recommended 0.5C) is 2 hours from 0-100. Well it's a bit longer but that's the basic math. Temp and other things play into it.
I can push between 75A to 150A to my packs. Yesterday just charging 2x 280's from 10%, 5 hours @ 75A got the two to just under 75% ( I was also running stuff, it's my live system).

? Battery Fuse ? remember to get a Fuse on there. (3000W ÷ 12V = 250A)

The EPEver's are good little controllers, a fair bang per buck. If possible a bigger one capable of 75 to 100A charge would certainly help BUT you need the # of panels to support that capacity. But this brings you into a slightly different territory of gear and possibilities.

Overkill Solar is selling the JBD or JDB (ruddy alphabet soup) which are quite good Fet Based BMS' and he's in the southern side of the States. 12v BMS – Overkill Solar
ECPC may have something in stock and readily available: Lithium Battery Management Systems BMS | Electric Car Parts Company
and of course, there are eBay / Amazon vendors but I can't suggest any particular vendor as I don't know any personally for such equipment.

Hope it helps a bit, Good Luck.
Steve

Brilliant. Thanks.

I was afraid I’d need to update a bit. I was going to add another panel. Nice thing about California is I draw down my max 36A just about all day.

for the BMS. 2x BMS for a 2p4s pack? Or 1x BMS on 4p2s (I think I’m writing 4 sets of 2 correct)?

Mondo · Dec 8, 2020

Dzl said:
You have a few typos in there:

4 in series would be either 48V if they are 12V batteries or 24v if they are 6V batteries. Or if they are all in parallel they are 12V.

In terms of major components, If you plan to stick to the same voltage (8 cells can either be 12 or 24 Volts) you don't necessarily need to upgrade anything immediately.

Though the first thing that jumps out at me is how undersized your PV array is relative to the battery bank capacity 7kWh Battery, 0.2kW PV array so that would be a good place to start.

Both 'WZRELB "Reliable"' and EPEVER are budget options but well liked budget options from what I've heard. You are right you need a BMS, most come from China, if you can't Int'l shipping, Overkill Solar is the first option that comes to mind, or SBMS (but that is more advanced and sold out right now I think). If you go the overkill route, he gets his from China too so make sure he has US stock available before ordering. A big 'ole fuse (Class T, ANL, or MRBF) for the battery is important as well.

Yeah, for the life of me can never keep series/parallel straight.

Looks like I’ll definitely go the Overkill route. And of course a 3rd panel (if not replace the other two as well)

Dzl · Dec 8, 2020

Mondo said:
Brilliant. Thanks.

I was afraid I’d need to update a bit. I was going to add another panel. Nice thing about California is I draw down my max 36A just about all day.

for the BMS. 2x BMS for a 2p4s pack? Or 1x BMS on 4p2s (I think I’m writing 4 sets of 2 correct)?

Your options are 2P4S or 4S2P (the first means one 8 cell 12v battery with one BMS, the second means 2 x 4 cell 12v batteries each with its own BMS) you cannot do 4 sets of 2

When I first joined the forum the first option was the soup du jour but large unmatched cells were not common, these days it seems the overwhelmingly more popular option is the latter options (separate packs), there are tradeoffs to either approach the advantages of separate packs are less balancing workload for the BMS (which is important with these cells), redundancy, and actual individual cell monitoring (and you can potentially get away with a lower current BMS since you have two packs to share the work. The downsides are somewhat more complexity and somewhat more cost.

Steve_S · Dec 8, 2020

If Overkill does not have one on hand, BigBattery may have some in stock too. It's the timing, last minute (less than 5 days) limits your options. Being where you are, you can also get New Old Stock or used Panels quite cheaply too. Satansolar for example will ship to you but there are likely local supplies that could be found as well. You have the advantage of location.
Solar Panels Archives - SanTan Solar Store

HRTKD · Dec 8, 2020

I started down the path of 2p4s but finally came around to 4s2p. This is in an RV trailer so moving two batteries into the trailer was a lot easier than moving one big battery.

Steve_S · Dec 8, 2020

Weight seems to be an afterthought. Folks, please remember that the 280Cells and similar AH Capacity cells come at 5kg/11Lbs each. That adds up FAST and then you have to move it/ shift it and place it somewhere. Heck of a workout if your not ready for it.

Build confirmation

Mondo

New Member

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada

Dzl

Unofficial Forum Librarian & Perpetual Newbie

Mondo

New Member

Mondo

New Member

Dzl

Unofficial Forum Librarian & Perpetual Newbie

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada

HRTKD

Boondocker

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada

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