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My first build Need some advice

Brob1969

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Feb 23, 2022
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I have been studying up on lithium batteries for awhile now and have been wanting to build my own 36v battery. I have a fair number of 18650 cells, but not enough yet to have the Ah I am shooting for.
Recently I was gifted three Renogy 12v SMART 100Ah LiFePO4 batteries that are less than a year old. They had stopped taking a charge, which is why I ended up with them. After disassembly, I found moisture inside the cases and some corrosion on the BMS boards; I'm guessing that is the issue. I spent (wasted) a couple hours on the phone with Renogy only to discover the tech to whom I was speaking, knows very little about the BMS; what I DID find out is the Renogy 12v batteries are not equipped to be connected in series.

SO...I'm hoping to get the proper BMS to connect the 3.2v polymer cells. Currently the 12v batteries consist of 16 individual cells, wired 4 to a series (4 series of 4 cells). I'm assuming I would need a 12 series 100a 36v BMS to create a 36v system.

I could definitely use a little guidance here as to the best "bang for the buck" 36v BMS and any tips on how to proceed are most welcome.

Thanks in advance for any assistance and I appreciate all the knowledge here! I hope this is just the first of many Lithium battery builds!
 

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Just out of curiosity, why are you so set on 36V? We've talked quite a few off that ledge already. There are surprisingly few products like BMSs for 36V.
48V and a buck converter to 36v?
 
Just out of curiosity, why are you so set on 36V? We've talked quite a few off that ledge already. There are surprisingly few products like BMSs for 36V.
48V and a buck converter to 36v?
Well, I have the cells from three 100Ah 12v batteries. I have a charger capable of charging 36v LiFePO4, the only purchase I really need is the BMS. If I did a step-down converter, then I'd need more cells and a different charger.

Bottom line answer to your question is economics. I have a future project that I want to do 48v, but this is what I have right now.
 
I've seen quite a few of the Daly 12s 100a BMS for reasonable prices, I just know nothing about the reliability.
 
I don't usually mention Daly and reliability in the same sentence, unless it is in a negative context.

If you really want a 36 volt battery then build a 36 volt battery with a single 36 volt BMS. But like MisterSandals said, good luck finding a BMS. They're out there, they just aren't mainstream.
 
I don't usually mention Daly and reliability in the same sentence, unless it is in a negative context.

If you really want a 36 volt battery then build a 36 volt battery with a single 36 volt BMS. But like MisterSandals said, good luck finding a BMS. They're out there, they just aren't mainstream.
I am planning on a single 36v BMS with 12s; my thought is using a continuous duty 36v contactor to handle the amperage draw.
 
I just received my new 12s 36v JBD BMS yesterday. I will be connecting it to the cells to get a sense of what it will do...
 
I have been studying up on lithium batteries for awhile now and have been wanting to build my own 36v battery. I have a fair number of 18650 cells, but not enough yet to have the Ah I am shooting for.
Recently I was gifted three Renogy 12v SMART 100Ah LiFePO4 batteries that are less than a year old. They had stopped taking a charge, which is why I ended up with them. After disassembly, I found moisture inside the cases and some corrosion on the BMS boards; I'm guessing that is the issue. I spent (wasted) a couple hours on the phone with Renogy only to discover the tech to whom I was speaking, knows very little about the BMS; what I DID find out is the Renogy 12v batteries are not equipped to be connected in series.

SO...I'm hoping to get the proper BMS to connect the 3.2v polymer cells. Currently the 12v batteries consist of 16 individual cells, wired 4 to a series (4 series of 4 cells). I'm assuming I would need a 12 series 100a 36v BMS to create a 36v system.

I could definitely use a little guidance here as to the best "bang for the buck" 36v BMS and any tips on how to proceed are most welcome.

Thanks in advance for any assistance and I appreciate all the knowledge here! I hope this is just the first of many Lithium battery builds!
The "3.2v" indicates more of a lithium iron phosphate cell in pouch form.
You need a BMS for LFP, not LiPo.

A relatively cheap and reliable BMS brand is JBD. I've used this, and found it to be very good.


I've also used this one, and it is very much rated to be used in series. It's my current favorite.

 
I've seen quite a few of the Daly 12s 100a BMS for reasonable prices, I just know nothing about the reliability.
I speak as the (not so) proud owner of 3 Daly BMS. Just say no.
JBD is a much more reliable product.
 
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