I just purchased six 13s 48v 37ah li-ion packs which are 5c discharge. I am looking for advice concerning how best to set them up in parallel as a 222ah pack. Should I put a BMS on each pack and then parallel those, or use one large BMS and parallel the sense wires? And if I use individual BMSs, do I fuse each pack also? I will rarely draw more than 300 amps and the mathmatical max draw woiuld be 580 amps, but only for short periods of time. All help appreciated.
Li-Ion packs in Parallel ??
- Thread starter marklynch
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sunshine_eggo
Happy Breffast!
IMHO, With that kind of potential draw and 5C cell performance 6 13S batteries in parallel each with its own BMS makes the most sense, but it will be a bit spendy..
Any recomendation for BMSs? I'm tentatively looking at six Daly 80a smarts for 480 amp continuous and 720 amp burst.
sunshine_eggo
Happy Breffast!
Being the post whore that I am, I swear to God that DALY is the most problematic BMS on this forum. MANY accounts of folks experiencing multiple failures, DOA, etc. Sure, all BMS have problems, but DALY seems to have the lion's share. JBD and JK are my personal preference for "low end" BMS.
JK has active balancing, and they are "smart" in that they can be used for different cell counts within a certain range, e.g., they sell one unit that can be used for any cell combination from 8S-20S - no need to find a 13S specifically.
GXMnow
Solar Wizard
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I have a JK smart BMS on my older pack and it has been working great for 3 years now. The only issue I had was a sense lead failure which made it shut down as it read 2 cells as zero volts. Once I repaired the sense lead it has been rock solid. Sinc I added my DC solar charge controller, it also does not reset the full charge to 100% SoC. Not really an issue as I am using all voltage control. I know 4.1 volts per cell is my full (about 90%).
I am running 2 parallel strings on the JK BMS as it was $255 when I got it and they go for $300+ now. To safely run the two strings in parallel, I did put a 10 amp fuse on every balance wire to each cell in each pack. I am at 14S so that was 30 fuses and holders. The 2 amp active balancing in the JK BMS works great. I intentionally connected my 12 volt inverter to just 3 cells and pulled them down a chunk. The JK balancing got the ells all back in balance in just an hour. I have it set to only balance if a cell is off more than 0.008 volts. It has not triggered any balance current in over a year. All of my cells are staying within 0.003 almost every time I check on them. I opened the bluetooth app just now, and the lowest cell is at 4.082 volts and the highest cell is at 4.085 volts. That is the typical 0.003 difference. And it moves around from cell to cell as they are all so close.
I also have each string fused separately at 125 amps. And then the two strings feed into a 250 amp Class T fuse and a 400 amp disconnect switch to the inverter.
I later added 2 more strings of the same basic cells for more capacity, not to get any more current as I never exceed about 120 amps anyways. For the 2 additional strings I bought dumb Daly 100 amp 14S units. They just seem to work. Since they are dumb, there is no blue tooth and no way to really see what they are doing. But if I disconnect any single balance lead, it does shut off, so I know it sort of works. These have been running for nearly 2 years now. I have now taken out my Fluke meter and measured all of the cell voltages 3 times just for my own curiosity. My cells are all very well matched and balanced and the cell voltages have always been within 0.008 volts every time I measured them. The small 0.060 amp passive balance current seems to be good enough to keep these cells in check. Sine the cells in the older packs seem to hold balance so well, I figured this would be fine and so far it has been good. I will admit, I do miss being able to just open an app and see all the cell voltages and the pack temp. I might change out the BMS units for the Smart Daly version just for the bluetooth. Amazon had the 100 amp smart version on sale for less than I paid for the dumb ones. It looks like it will bolt up to the same screw holes and the balance lead plugs look the same too. They have a new version intended for parallel operation with multiple packs. If the pack voltages are different and it triggers an over current charge condition, it will still open the Mosfets, but it will then charge the lower voltage pack at 1 amp until the voltages are close enough for it to safely turn the Mosfets back on. That is actually a good feature to have. One of my worries is if a string does disconnect, if it tries to reconnect at a different state of charge, the current between the two batteries could be huge. The 100 amp string fuses in my system have never popped, but that is my safety if this every happens.
I also have a pair of 60 amp dumb Daly BMS units on e-bike batteries. They have also been rock solid for about 2 years of use. I know I am a small sample size, but 4 out of 4 Daly dumb BMS units here are all working just fine.
I am running 2 parallel strings on the JK BMS as it was $255 when I got it and they go for $300+ now. To safely run the two strings in parallel, I did put a 10 amp fuse on every balance wire to each cell in each pack. I am at 14S so that was 30 fuses and holders. The 2 amp active balancing in the JK BMS works great. I intentionally connected my 12 volt inverter to just 3 cells and pulled them down a chunk. The JK balancing got the ells all back in balance in just an hour. I have it set to only balance if a cell is off more than 0.008 volts. It has not triggered any balance current in over a year. All of my cells are staying within 0.003 almost every time I check on them. I opened the bluetooth app just now, and the lowest cell is at 4.082 volts and the highest cell is at 4.085 volts. That is the typical 0.003 difference. And it moves around from cell to cell as they are all so close.
I also have each string fused separately at 125 amps. And then the two strings feed into a 250 amp Class T fuse and a 400 amp disconnect switch to the inverter.
I later added 2 more strings of the same basic cells for more capacity, not to get any more current as I never exceed about 120 amps anyways. For the 2 additional strings I bought dumb Daly 100 amp 14S units. They just seem to work. Since they are dumb, there is no blue tooth and no way to really see what they are doing. But if I disconnect any single balance lead, it does shut off, so I know it sort of works. These have been running for nearly 2 years now. I have now taken out my Fluke meter and measured all of the cell voltages 3 times just for my own curiosity. My cells are all very well matched and balanced and the cell voltages have always been within 0.008 volts every time I measured them. The small 0.060 amp passive balance current seems to be good enough to keep these cells in check. Sine the cells in the older packs seem to hold balance so well, I figured this would be fine and so far it has been good. I will admit, I do miss being able to just open an app and see all the cell voltages and the pack temp. I might change out the BMS units for the Smart Daly version just for the bluetooth. Amazon had the 100 amp smart version on sale for less than I paid for the dumb ones. It looks like it will bolt up to the same screw holes and the balance lead plugs look the same too. They have a new version intended for parallel operation with multiple packs. If the pack voltages are different and it triggers an over current charge condition, it will still open the Mosfets, but it will then charge the lower voltage pack at 1 amp until the voltages are close enough for it to safely turn the Mosfets back on. That is actually a good feature to have. One of my worries is if a string does disconnect, if it tries to reconnect at a different state of charge, the current between the two batteries could be huge. The 100 amp string fuses in my system have never popped, but that is my safety if this every happens.
I also have a pair of 60 amp dumb Daly BMS units on e-bike batteries. They have also been rock solid for about 2 years of use. I know I am a small sample size, but 4 out of 4 Daly dumb BMS units here are all working just fine.
Where do you buy the JK BMS? I found it on Aliexpress.us from "JKBMS Store"for $52.87 each and free shipping from US warehouse. I'm thinking that's the best price I'm going to find. But it doesn't give me any specs on the BMS beyond being 80A and having acive balancing.
sunshine_eggo
Happy Breffast!
I bought a JBD from them, and they seem to be a reputable outfit:
srikobatteries.com
If the JKBMS Store is their legit outlet, that may be the one; however, Aliexpress is often regarded as one of the best places on line to get scammed.
SRIKO Batteries | Jk bluetooth bms US| Jk bms battery board US | Jk bms 17sUS
Are you looking for the best Jk bluetooth bms stores in the US?SRIKO Batteries provides the best jk bms battery board in the US.We are the best lithium ion battery pack suppliers in the US. Wehave the best online store for electronics.
srikobatteries.com
If the JKBMS Store is their legit outlet, that may be the one; however, Aliexpress is often regarded as one of the best places on line to get scammed.
Rednecktek
Solar Wizard
Sriko batteries has always done well by me so call this another vote in their favor.
Definitely do separate packs and just wire each pack to a bus bar and call it a day. Better redundancy, better load performance (you're not limited to a single BMS's max current), and not that expensive in the grand scheme of things when you're talking about multiple batteries.
Definitely do separate packs and just wire each pack to a bus bar and call it a day. Better redundancy, better load performance (you're not limited to a single BMS's max current), and not that expensive in the grand scheme of things when you're talking about multiple batteries.
Ironically AliExpress keeps declining my purchase. I did the online chat and they say I show up as a security risk, although they won't/can't tell me why.I bought a JBD from them, and they seem to be a reputable outfit:
SRIKO Batteries | Jk bluetooth bms US| Jk bms battery board US | Jk bms 17sUS
Are you looking for the best Jk bluetooth bms stores in the US?SRIKO Batteries provides the best jk bms battery board in the US.We are the best lithium ion battery pack suppliers in the US. Wehave the best online store for electronics.
If the JKBMS Store is their legit outlet, that may be the one; however, Aliexpress is often regarded as one of the best places on line to get scammed.
GXMnow
Solar Wizard
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This is the newer version of the model I have.
srikobatteries.com
Listed at $228 on that site, not too bad. When it was my only BMS I wanted the 200 amp continuous unit. With 2 battery cabinets, it now never sees over 70 amps. If I went with 4 separate strings, I would still use at least a 100 amp version. This one is 120 amps.
srikobatteries.com
Less than half the price, but it also drops from 2 amps of balance current to just 0.6 amps. That would be fine with my well matched cells though. It is 10 times the balance current of the Daly, but it can only work on 1 cell at a time, the Daly can pull 60 ma from all cells higher than the average voltage.
For just over $100 I might get one to monitor the cells in the second cabinet.
Just saw the post about the security risk pop up. That is an odd one.
JK Smart Active Balance BMS Board 7S-24S 200A 2A Balance Current | SRIKO Batteries | Online store for electronics | Online battery store
JK Smart Active Balance BMS Board 7S-24S 200A 2A Balance Current
srikobatteries.com
JK Smart Active Balance BMS Board 7S-24S 120A 0.6A Balance current | SRIKO Batteries | Online store for electronics | Online battery store
JK Smart Active Balance BMS Board 7S-24S 120A 0.6A Balance current
srikobatteries.com
For just over $100 I might get one to monitor the cells in the second cabinet.
Just saw the post about the security risk pop up. That is an odd one.
OK. I ordered 6 of the JK 80 BMSs. They have 150A max burst amps. Now I'm wondering if I need a fuse on each one or 1 fuse after all 6 come together?
calsolarcat
New Member
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I would recommend fusing at each battery for some peace of mind especially while you are assembling each pack. I recently built 8-50Ah 48V batteries out of LiFePO pouch cells from jag35.com. Each 48v battery has a 300A Blue Sea Systems terminal fuse on it for just-in-case short protection.
Then, I parallel 2 of the 50Ah batteries together for a 100Ah battery and use 1 JBD 48V BMS for each 2-pack making a total of 4 100 Ah batteries. The balance leads from the BMS are connected to a DIN-mount wire board and each battery's individual cell leads are screwed and paralleled to the wire board. Then the positive 48v from each battery pair are jumpered together and goes to a 63A DIN type solar DC rated breaker and the output from that breaker to a large postive battery bus bar. Even though the BMS's are rated for 100A, I only had the 63A breakers lying around from another project and never felt I needed to upsize them since testing. Then, each negative from a battery pair goes to another 63A breaker and then to the BMS Battery negative terminal so I can isolate the BMS from the battery for service. Depending on which battery pair, I might have the negative load BMS output going to another 63A breaker to isolate the BMS from the negative bus bar.
So each 100Ah pack being about 5kWh, I have about 20kWh total in capacity. I still have them on a bench in daily operation from the past 6 months, but am about to re-assemble them into a rolling cart so it can be closer to my Schneider XW Pro 6848 inverter and I can finally reclaim the workbench. I've run about 600kWh through the whole system so far for evening/nighttime TOU house consumption using the zero sell feature of the Schneider.
Then, I parallel 2 of the 50Ah batteries together for a 100Ah battery and use 1 JBD 48V BMS for each 2-pack making a total of 4 100 Ah batteries. The balance leads from the BMS are connected to a DIN-mount wire board and each battery's individual cell leads are screwed and paralleled to the wire board. Then the positive 48v from each battery pair are jumpered together and goes to a 63A DIN type solar DC rated breaker and the output from that breaker to a large postive battery bus bar. Even though the BMS's are rated for 100A, I only had the 63A breakers lying around from another project and never felt I needed to upsize them since testing. Then, each negative from a battery pair goes to another 63A breaker and then to the BMS Battery negative terminal so I can isolate the BMS from the battery for service. Depending on which battery pair, I might have the negative load BMS output going to another 63A breaker to isolate the BMS from the negative bus bar.
So each 100Ah pack being about 5kWh, I have about 20kWh total in capacity. I still have them on a bench in daily operation from the past 6 months, but am about to re-assemble them into a rolling cart so it can be closer to my Schneider XW Pro 6848 inverter and I can finally reclaim the workbench. I've run about 600kWh through the whole system so far for evening/nighttime TOU house consumption using the zero sell feature of the Schneider.
GXMnow
Solar Wizard
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I agree on the fusing, but they should be sized to protect the wiring. I have each of my 4 strings going through a 100 amps fuse. That will keep the #2 AWG battery cables safe. After the join, I then have a 225 amp Class T fuel and 2/0 cable to the inverter.
calsolarcat
New Member
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Totally agree Gary. When I reassemble my packs into the cart, I plan change out the wiring and include T Class on the main bus.
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