Reuse of Old Batteries

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BigAl61

Member
Joined
Jun 3, 2020
Messages
5
Hi Folks, I have just upgraded my 2012 ZEO MK1 Leaf to 40kWhr. I'm very pleased so far with the outcome of that.
The old battery was dismantled and returned to me as 48 individual cells plus the ancillary parts.
I want to use this battery as part of a hybrid solar/battery/inverter/grid home system.
Does anyone have any advice on the best way to go about this? I am still at the stage of selecting a BMS and inverter combination.
The main issue seems to be to find a BMS that will seemlessly communicate with the inverter. The inverters I have looked at so far all have a list of batteries with which they are compatible, and a home made one from Leaf cells is not one of them.
I am looking at a 48V DC inverter, 230VAC 50Hz on the grid side. Probably 7 cells in series, (=14s as each pack has 4 cells 2s2p). Meaning I will use 42 of the packs on 6 x 7s pack modules
I am hoping to do this on just one BMS.
Any advice would be appreciated. Specifically, is there a recommended BMS/inverter combo? If not, can I just use a BMS with an inverter that does not need to communicate with the BMS?
 
can I just use a BMS with an inverter that does not need to communicate with the BMS?

Only if you are absolutely sure a) the inverter/charger wont go above 57.4 and below 43.4 volts, b) and if if does, the BMS will protect the 14s pack from those voltages, and c) the BMS will also keep the cells in good balance. The chemistry of the early Leaf cells is less likely to catch fire, but its not impossible. Certainly, this set up needs to be safely away from inhabited buildings. If you are looking for a system that would be in use daily, then meeting the above conditions will be difficult. The retail systems out there verify battery health continuously, and will shut down if something is out of spec. If you were using relatively safe chemistry like LiFeP or LTO cells, then there is less concern about safety.

There are BMSs which will talk with inverter/chargers. Try this thread: SMA - Sunny Island
 
I think I read one post which said they kept the charging voltage constant and allowed the BMS to vary the voltage/current dependent on SOC. And protect the unit if anything goes out of spec. Are these not standard BMS functions? Most of the units I have looked at also include balancing.

The other question is around how many cells can be connected in parallel. Eg, on a 14s configuration, can I parallel all the rest of the units and end up with 2 x 6 = 12 cells in parallel, or do I need either a BMS that can handle all 96 x 2p cells or 6 x BMSs?

The batteries will be in a safe spot away from any residential areas.

Thanks for the tip. I'll look it up. Certainly first prize will be a system where the inverter and BMS can communicate.
 
My recommendation is to use the battery as is
Yes, Dala's and your solution is elegant, but the OP stipulated that the cells were loose.

Are these not standard BMS functions? Most of the units I have looked at also include balancing.
Yes, they do balancing, but do they do it reliably and well? The only way to know this is to actively monitor cell voltages with a microcontroller; the microcontroller makes the decision about whether the pack is healthy enough to operate. Since you would be integrating the BMS with the cells, you should want to be able to see this active monitoring of each cell (or cells in parallel) and verify that the BMS knows what is going on and can shut down the system when needed. This is more sophisticated than most of the 14s BMS out there you can buy.
how many cells can be connected in parallel
You are working with used cells. A poorly cell that is paralleled with healthy cells can be a bad situation. You should do capacity testing on each cell and verify normal amounts of capacity loss before assembling anything.

Sorry if this sounds negative.
 
My recommendation is to use the battery as is, this is the safest way. Get a High Voltage Smart Hybrid inverter. See my setup below:
This is a really impressive setup...and good use of an (old) Leaf battery pack.
I was going to ask the OP if he still had the option to "reassemble" his pack, but it seems that ship has sailed. I used Dala's CAN-bridge in my 40 kWh pack upgrade, and was lucky enough to sell my (old) pack "whole" (as is).
 
My recommendation is to use the battery as is, this is the safest way. Get a High Voltage Smart Hybrid inverter. See my setup below:

View attachment 2876
This uses my homegrown can bridge a couple of years back, but now Dala has the same:
https://github.com/dalathegreat/BYD-Battery-Emulator-For-Gen24
Yes, I do like this solution. I decided to have the battery dismantled as I understood the HV inverters were prohibitively expensive. Perhaps I should have looked more closely into it. I may still be able to reassemble it, but I did leave the casings with the service provider.
My recommendation is to use the battery as is, this is the safest way. Get a High Voltage Smart Hybrid inverter. See my setup below:

View attachment 2876
This uses my homegrown can bridge a couple of years back, but now Dala has the same:
https://github.com/dalathegreat/BYD-Battery-Emulator-For-Gen24
Yes, I do like this solution. I decided to have the battery dismantled as I understood the HV inverters were prohibitively expensive. Perhaps I should have looked more closely into it. I may still be able to reassemble it, but I did leave the casings with the service provider.
 
What I have is EH10000TL, it is not listed on their website anymore, but very close to:

https://www.thinkpower.com.cn/hybrid-three-phase4-12kw.html
The App is very informative and their engineering team (through the local agent) was very helpful in doing the battery integration.

The best part is the fanless design, even when it is generating over 12kW for over one hour, it remains quite cool, I mean below 45C, I could comfortably touch it... Normally it just gets warm.

Another important feature is asymmetric three-phase output, where it will be almost impossible to balance your house loads across all three phases. The inverter handles my house loads with a charm, multiple A/Cs, electric cookers, oven, iron, water pumps, and all sorts of loads on different phases, I even don't know what load is at what phase.
 
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