BMS Question

[weboughtabus]

So I think I may have come across a good deal on some 8v Lithium battery modules, which I would assemble in a 3s3p configuration for a 24vDC bank. I've seen lots of people making recommendations to use a BMS with Lithium, but I'm having trouble finding out much information on how this works with series/parallel strings. Would anyone be able to shed a little more light on how this should be set up? Obviously I want to try to ensure that I keep my batteries happy so they will return the favor and keep our lights on.

And if anyone has a recommendation on good and/or inexpensive BMS that they suggest, that would also be greatly appreciated.

Thank you!

[HazMatt]

What sort of deal..?

[john61ct]

"Lithium-Ion" is an umbrella term for dozens of chemistries, widely varying characteristics, LFP vs NMC vs LMO vs LCO

Then you have Lipo or not, cylindrical vs pouch vs prismatics

Depending on the specific chemistry involved, the nominal cell voltage can vary from 3.3V up to 3.7V.

In a mobile living situation, LFP prismatics are IMO the only way to go.

And there are no 8V cells in the LI world, 2S pairs maybe?

[weboughtabus]

Originally Posted by haz.matt.1960

What sort of deal..?

I have a friend working on a battery project that picked up a Nissan Leaf battery pack and has some modules that aren't required, so I can scoop them up real cheap!

Originally Posted by john61ct

"Lithium-Ion" is an umbrella term for dozens of chemistries, widely varying characteristics, LFP vs NMC vs LMO vs LCO

Then you have Lipo or not, cylindrical vs pouch vs prismatics

Depending on the specific chemistry involved, the nominal cell voltage can vary from 3.3V up to 3.7V.

In a mobile living situation, LFP prismatics are IMO the only way to go.

And there are no 8V cells in the LI world, 2S pairs maybe?

They're Nissan Leaf modules, which I believe are LMO. Each module is 2s2p

[semipro]

My understanding is that a BMS must work at the individual cell level to most effective. That is, each cell must have a connection to the BMS so that it is balanced individually, not in combination with other cells connected in series or parallel.

[john61ct]

Originally Posted by weboughtabus

They're Nissan Leaf modules, which I believe are LMO. Each module is 2s2p

NCO or NMC if 2014 or earlier, LMO after that.

play out in the back shed

I would not have them traveling on the bus with my kids.

[weboughtabus]

Originally Posted by semipro

My understanding is that a BMS must work at the individual cell level to most effective. That is, each cell must have a connection to the BMS so that it is balanced individually, not in combination with other cells connected in series or parallel.

Thank you for confirming. That's basically what I thought, but I wanted to be sure. I saw instructions from Orion BMS on how to connect to a 3s Nissan Leaf setup. Since each module is comprised of 2p2s, each of the internal series are treated as one cell by the BMS. In each of my 24v series I would then be monitoring 6 cells. Time to start shopping for some inexpensive BMS.

[weboughtabus]

For anyone who may be interested, I'm planning on using this smart BMS and accompanying Bluetooth modules. All told it's going to be $47~ per 24V Battery module, of which I'm planning three. These look to be very similar to the ones that were used by ComfortEagle for their Chevy Volt battery system.

[PassNthru]

Hey there from Arizona--im researching the Nissan leaf modules currently and your 2yr old post was the first to pop up- did you completed the project?can you offer any advice, suggestions?

Thank you!

[weboughtabus]

Originally Posted by PassNthru

Hey there from Arizona--im researching the Nissan leaf modules currently and your 2yr old post was the first to pop up- did you completed the project?can you offer any advice, suggestions?

Thank you!

Thanks for your interest in our build. We did end up going forward with our build and are living in it, currently. Most of the information about the Nissan Leaf batteries we got from someone on Instagram ezzydortoka. He even has a coupon code for a supplier of the modules and bus bars and such. I'm willing to answer any questions you have if you want to message us on Instagram charlotte_thebus since we use that more regularly, go right ahead!

[Bert06840]

I have very good experiences with BMSes from Overkill solar
https://overkillsolar.com/shop/

and

Battery Hookup
https://batteryhookup.com/collections/accessories

I also have bought one directly from Aliexpress, and it works equally well, but the software is NOT the same.

I'd buy it from a local distributor and eat the $50. It's worth it, but YMMV. I'd also go for a higher current rating that 60A. You gonna short it out sooner or later, or an inverter inrush current spike will trip you over that number.

One comment: I'd go for LiFePO4 chemistry, not LCO or NMC (Leaf packs). LiFePO4 ("LFP") fails safe in case of thermal runaway. I don't want to sleep on used cells that can fail catastrophically.