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High voltage BMS suggestion

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denmek

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May 1, 2021
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Hello guys,

I am planing a HV storage system with around 80-120S configuration.
The motivation to move to higher voltage than 48V is pure C-rate driven => optimize lifetime and overall efficiency.
But of course the BMS selection at this configuration is quite rare. can someone recommend any options for the prooven BMS options ?
max current will be around 50-100A


many thanks in advance.

rgds,Daniel
 
My pick would be to go with Batrium - The watchmon 4 and however many longmons you need (one for each cell). Its not going to be cheap but its a really good bms and for that many cells its important. I would stay away from smaller bms units linked together and go with one that can see all the cells like Batrium. I have put together a 96 cell powerwall using Nissan leaf cells and the Batrium bms and its been great. You will need to be very careful with that voltage. With the 96s build i did the voltage was just under 400v DC so you cant not touch it or really go near it. 10,000w at just under 400v was 25amps for our build btw. Given the high voltage of 80-120s as you said you really need a good BMS.
Hope that helps, and please remember anything over 100v DC can kill you, Your 80s will deff do that so I stress how safe you will need to be building it and then going near it when testing.
Michael
 
denmek said:
Hello guys,

I am planing a HV storage system with around 80-120S configuration.
The motivation to move to higher voltage than 48V is pure C-rate driven => optimize lifetime and overall efficiency.
But of course the BMS selection at this configuration is quite rare. can someone recommend any options for the prooven BMS options ?
max current will be around 50-100A


many thanks in advance.

rgds,Daniel
Click to expand...

You can arrange them in 48V packs, put them serial, and you can use any 48V BMS you like (one for every 48 pack).

BUT, please consider your choice !
256-384 Vdc is VERY dangerous !!!
Even the 3-400Vdc batteries sold for grid-tie inverters (like LG RESU) use inner 2-3x 48V battery.
They use a boost converter to make the 3-400Vdc from it.

I also do not understand your C rate problem. With 48V batteries you just have to parallel more.
Like with 16pcs 280Ah EVE cells (3,2V x 16pcs = 48V) recommended is 0,5C so you can charge and discharge it with 140A.
If not enough then parallel it with an another and you have 280A max charge and discharge current.
If not enough .... you can go up as you like
 
Thanks guys, Batrium is a nice
mikesdiypowerwall said:
My pick would be to go with Batrium - The watchmon 4 and however many longmons you need (one for each cell). Its not going to be cheap but its a really good bms and for that many cells its important. I would stay away from smaller bms units linked together and go with one that can see all the cells like Batrium. I have put together a 96 cell powerwall using Nissan leaf cells and the Batrium bms and its been great. You will need to be very careful with that voltage. With the 96s build i did the voltage was just under 400v DC so you cant not touch it or really go near it. 10,000w at just under 400v was 25amps for our build btw. Given the high voltage of 80-120s as you said you really need a good BMS.
Hope that helps, and please remember anything over 100v DC can kill you, Your 80s will deff do that so I stress how safe you will need to be building it and then going near it when testing.
Michael
Click to expand...
thanks Michael, batrium sounds really good. i will check them more in detail and compare the offers. Thanks for the hint regarding the HV danger :) . I did grow-up with HV , my farther was TV service technician, playing with sparkles over HV transformer (20kV) was my first met on teh real dangerous stuff :cool:
 
denmek said:
Thanks guys, Batrium is a nice

thanks Michael, batrium sounds really good. i will check them more in detail and compare the offers. Thanks for the hint regarding the HV danger :) . I did grow-up with HV , my farther was TV service technician, playing with sparkles over HV transformer (20kV) was my first met on teh real dangerous stuff :cool:
Click to expand...
transformer sparks can be fun to play with, Oh the good old days aye. With a build like your planning from memory Batrium can do just over 200S. One thing to also look at is a BMS that can handle/see all the cells together that way you can manage them. If you wanted something cheaper and more DIY then I think Stuart Pitta BMS will also work. If you google DiyBMS v4 you will find all the videos and details. Stuart has build videos and Adam.
 
Thank you , looks very interesting. I will share my build after first experience
 
mrzed001 said:
You can arrange them in 48V packs, put them serial, and you can use any 48V BMS you like (one for every 48 pack).

BUT, please consider your choice !
256-384 Vdc is VERY dangerous !!!
Even the 3-400Vdc batteries sold for grid-tie inverters (like LG RESU) use inner 2-3x 48V battery.
They use a boost converter to make the 3-400Vdc from it.

I also do not understand your C rate problem. With 48V batteries you just have to parallel more.
Like with 16pcs 280Ah EVE cells (3,2V x 16pcs = 48V) recommended is 0,5C so you can charge and discharge it with 140A.
If not enough then parallel it with an another and you have 280A max charge and discharge current.
If not enough .... you can go up as you like
Click to expand...
Hi

thanks for the suggestion. Do you have any technocal material for that ? I would be interesting how they daisy chain the BMS.
In praticle I also believe it is fine, the only limitation would be adiditonal software to hook up all serial BMS in the configuration.
How about the balancing, any suggustion for such solution?

thanks in advance
 
denmek said:
Hi

thanks for the suggestion. Do you have any technocal material for that ? I would be interesting how they daisy chain the BMS.
In praticle I also believe it is fine, the only limitation would be adiditonal software to hook up all serial BMS in the configuration.
How about the balancing, any suggustion for such solution?

thanks in advance
Click to expand...

I wrote a post about the LG RESU 10H 400Vdc battery pack with pics ... but I only translated and summarized it from Hungarian :)
I am not the author. But I think the 3 x 48V BMS does not sync or balance in the RESU. So there is no master BMS over the three small 48V BMS
diysolarforum.com

Any suggestions for adding capacity and backup power to my current SMA Sunny boy system

I am currently in the process of installing an SMA SunnyBoy 7.6 KW (Grid-Tie split phase 120/240v) system, with 30 Qcell 320 watt panels. I am awaiting my permit to finish install and to get the power company to reprogram my meter to read backwards. Right now I have 15 panels on my roof "testing...
diysolarforum.com diysolarforum.com

I was also thinking this problem when I saw the new Tesla Model 3 LFP battery disassembled:
diysolarforum.com

Munro: Peak into the Tesla Model 3 CATL LFP battery pack.

First I tough this are the 310Ah CATL cells we can buy from china. But it seems the height is lower and the length is bigger.
diysolarforum.com diysolarforum.com

That is like a 104s pack.

So if I would start this project (and I am not Tesla to make my own very expensive BMS) then I would start with
- a perfect top balance for all cells
- a BMS for every 48V pack like JK Heltec.
- serial connection from every BMS to RasPi
- main highVdc relay controlled by RasPi. So the RasPi is the master BMS that shuts down the pack if needed.

And lets see how long it takes for the big 48V pack's Volts to got unbalanced.
(and of course use battery only in the 10-90% SoC range, because there is no balancing between the 48V packs)


Another "stupid" idea : overlapping balancing.
The Heltec BMS is 24s (and 48V is 16s). So you connect
- 1st to 1-24 cells
- 2nd to 17-40 cells
... so you have 8 cells overlap.
This cells then transfer power between 48V packs.
 
REC can also do high voltage.
Don't think that will compete pricewise with that other one you found.

I think for many of these schemes, it will be up to you to select a suitable high-voltage contactor. The lower voltage BMS of a 48V can't be used to open-circuit themselves for self-protection, can't hold off voltage of the entire pack.
 
Here's a brand that raised my eyebrow (seeing it a couple years ago)...

123ELECTRIC BMS123 Smart Gen3 - Complete Set (4 Cells) With Bluetooth 4.0 | GWL Group

GWL/Power BMS123 Smart Gen 3 – a complete solution for LFP, LTO, NMC and Li-Ion cells to make battery with Bluetooth monitoring and management using your smart phone, iPad, tablet or other device.
shop.gwl.eu shop.gwl.eu


I've been checking these out for quite some time, as I would like to someday build a 56s LFP pack for my Prius... This brand allows to put up to 255 of these per-cell BMS into a string...

Just thought I'd throw it out there in case this system looked interesting for your needs. They also sell contactors to go with the kits, and whatnot...


Manual Reference:
 
I did stayed with 48V battery sofar. Some days i will re-investigate for a trial on HV.

Rgds Daniel
 
I have been looking at this for an existing 650v pack (200s LFP) to find an alternative to the closed source BMS in there.
But this gets expensive fast.

For a home installation, as this topic started, 48v keeps things safer and much cheaper. If the pack size a bit big, add an active 16s balancer in there.

Because of the modular build up to get to high amounts of cells, the prices increase quickly.
The Orion can go up to 180s in one unit, but then I need cell tap extension, of which I cannot find the price (or I am misunderstanding it)
 
Yes, that is my last state of my research. It will become quite expensive and complex. I did end up in 48V system with parallel inverter, that is scalla ble and min disadvantages .
 
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