# What is recommended BMS setup for 3P2S



## Ampster (Oct 6, 2012)

I just installed an Orion BMS and I beleive it can handle multiple packs in parallel with one BMS. Mine is a simple 16s2p setup but I am buddy pairing the cells so I only needed an Orion Junior. Orion technical support is very helpful or Evolve, where I purchased the BMS.
Hybrid Auto Center should is also an Orion dealer and has more experience with Volt or Leaf modules.


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## Yabert (Feb 7, 2010)

bonewibb said:


> In order to obtain 144 volts I am looking at a 2P3S configuration of the 48 volt 45 amp configuration.


You should call the things correctly. I think your 144v battery pack is in fact a 135v nominal and 90Ah. So, 36 cells in series and two 45Ah pack in parallel (36S 2P)
Then, you should use a BMS for 36 cells to protect your battery pack because the two 45Ah pack will be connected in parallel and act as one 90Ah cell.


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## frodus (Apr 12, 2008)

Yabert said:


> You should call the things correctly. I think your 144v battery pack is in fact a 135v nominal and 90Ah. So, 36 cells in series and two 45Ah pack in parallel (36S 2P)
> Then, you should use a BMS for 36 cells to protect your battery pack because the two 45Ah pack will be connected in parallel and act as one 90Ah cell.


I know you know this..... 

To clarify for the OP: in order to balance and monitor correctly, youre going to have to parallel at the cell level first, or run wires between each cell to the one it's in parallel with. Paralleling at the pack level doesn't do much good.


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## bonewibb (Aug 30, 2009)

The battery contains a BMS plug which exposes each of the 12 cells. So, I think just a matter of purchasing a socket with a 12 wire harness and connecting cells in the same position to the BMS if I am understanding correctly. For 2 packs, I would would end up monitoring both sets of cells for the entire 90 amp range.


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## frodus (Apr 12, 2008)

you could, but I'd avoid that. When discharging, parallel cells share current, so current may flow any which way in order to equalize between cells. A small wire could heat up, so I'd fuse them.

Its better to parallel the cells than it is to wire between cells to parallel them.


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## Ampster (Oct 6, 2012)

I almost bought a Volt pack for a stationary storage application but the complexity of monitoring drove me to using some prism cells and buddy pairing them. My inverter runs off 48v so my BMS costs for only 16 cells was reasonable. I was also able to find some used 160Ahr cells that had 90% of original capacity.


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## bonewibb (Aug 30, 2009)

Had a conversation with 1eyedcruiser concerning the chevy volt battery that he sells on ebay. He confirmed that a separate BMS is needed for each string. So now looking at two options: mini-BMS or Orion.

The mini-BMS would monitor all the cells. Cost for master mini-BMS is $650.00 plus $575.00 for each slave.
So three of the 48 volt 45 amp chevy volt batteries plus master BMS would be $2240.00. Each additional string of three would be $2165.00. Plus the cost of an Elcon charger of $1649.00. Looking at $6200.00 for a 3S2P setup or $8400.00 for 3P3S setup. 3S2P setup would give me 144 volts at 90 amps for the 69 vw bug convertible and 3S3P would give be 144 volts at 135 amps.

Going with Orion BMS would bump the cost a few hundred dollars for each string plus an additional $60.00 for the BMS wire harness from the Volt Li-Ion battery and would also add additional cost to the Elcon charger for CAN buss interface. According to 1eyedcruiser, the Orion BMS master/slave configuration can be a difficult wiring task. 




So some food for thought while working on the bug's body.


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## Ampster (Oct 6, 2012)

It would be more economical to have one charger. The multiple BMS's can be setup in a master slave configuration that would allow control over one charger.


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## Yabert (Feb 7, 2010)

bonewibb, I think you don't understand something... a BMS for 36S2P or 36S3P or 36S4P or 36S whatever P will only cost the price for 36 cells in series if you connect the other cells in parallel*.

So, mini BMS by example will cost you around 516$



*Each chevy Volt 48v 45Ah battery you are talking about is in fact build from 12S 3P.... yes, 36 cells 15Ah connected together. And Chevy only use a ''12S BMS'' to monitor this battery BECAUSE each package of three 15Ah cells are connected in parallel. Understand it right before buying anything and you will save money.


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## bonewibb (Aug 30, 2009)

I agree if I purchased the individual cells and wired them myself; however, take a look at the 48 volt 45 amp battery sold by 1eyedcruiser or hybridautoparts. Ebay item 18170700135. 

The item description is for a 36 cell battery constructed by 12 in series x 3 in parallel weighing 40 pounds with each cell being 15 amp, average voltage 3.8 vdc, maximum voltage 4.2 vdc, and minimum voltage 3.0 vdc. The optional BMS wire harness for the battery is pictured in Ebay item 181740519705. 

Without taking the battery apart (which I prefer NOT to do), there is no way to connect the cells of the multiple batteries in parallel and leave the battery intact.

According to 1eyedcruiser, the miniBMS for the nissan leaf chemistry is $15 per cell plus $75 for the master.


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## Ampster (Oct 6, 2012)

I think the point to understand is that this pack will be 45 Amp. Without tearing the modules apart to separate the individual cells there is only one way to get more amperage. That would be to parallel the modules(your term is battery)


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## Tesseract (Sep 27, 2008)

bonewibb said:


> ...According to 1eyedcruiser, the miniBMS for the nissan leaf chemistry is $15 per cell plus $75 for the master.


You should do some more research on "1eyedcruiser". Just search the forum for that name as a keyword. E.g. - here's one post by major.


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## bonewibb (Aug 30, 2009)

Thanks for the information.


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## Ampster (Oct 6, 2012)

I have been fortunate, my two transactions went smoothly and the used Elcon charger I bought from him several years ago is still working.


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