168 Cell BMS anyone?

mjsfbay

New Member
It's funny how complex things seem as a beginner. I hope I can look back at this post 1 or 2 years from now and laugh at how clueless I was when writing.

I was over-eager. I couldn't see past the $0.13/kWh pricetag.... and now I have 16.5 kW of LiFePO4 power. You'd think I'd be happy, right? Wrong!

Each pack has 56 cells at 3.7V and 10AH. I checked the voltage prior to purchase and 6 were 12.28V, one was 16.09V and the last consisted of 56 cells and no busbar to check.

However, this is the least of my problems it seems. I'm in the market for a Sol-Ark 12k and need these batteries to flow at 48V...

I'm of the understanding that I can charge these batteries up and reach their rated 16V which means it'll take 3 to reach 48V... which means I'm looking at 168 cells to strap to a BMS and top balance... Am I right? If not, I'm looking at 4 packs and a 224 cell BMS... I just hope I'm wrong.

Questions:
1) I took for granted that the Voltage should increase once the battery is recharged... is this true?

2) I don't think even an Orion BMS can manage 168 cells right? Even if it could, they're going for $400 plus. Not really a reasonable option from my point of view. So... is it possible to purchase multiple cheap BMSs to accomplish this goal?

I'm just a tad over my head, I'd be grateful if one of ya'll can lend me your brain for a few to sort this out.

Thanks!

Pic below:

IMG_5143.jpeg
 

A.Justice

Swears he didn't start that fire.
You will not need 168 cell BMS to monitor that battery pack.

You only need one balance wire for each "block" of cells in parallel. If each 3.7v "block" is made up of 7 individual cells in parallel, and then you would only need one balance wire for every 7 cells. Each block of 7 cells would then be connected in series to get your 16 volts.
 

mjsfbay

New Member
You will not need 168 cell BMS to monitor that battery pack.

You only need one balance wire for each "block" of cells in parallel. If each 3.7v "block" is made up of 7 individual cells in parallel, and then you would only need one balance wire for every 7 cells. Each block of 7 cells would then be connected in series to get your 16 volts.
Thanks for your reply @ A.Justice. Best news I’ve heard today.

Either I misinterpreted the DIY Battery Handbook or the information stating that top- balancing needs to be done on cell-by cell basis.

While prepping the battery banks last night it hit me…. These cells are already wired and ready for some BMS action. Would be great if I could find a molex connection to snap in and get going.

By the way, check out how these cells are connected… the whole top of the battery is a giant terminal… an accident waiting to happen.

What’s the gold standard to protect the bus bar in a situation like this?
 

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A.Justice

Swears he didn't start that fire.
Thanks for your reply @ A.Justice. Best news I’ve heard today.

Either I misinterpreted the DIY Battery Handbook or the information stating that top- balancing needs to be done on cell-by cell basis.

While prepping the battery banks last night it hit me…. These cells are already wired and ready for some BMS action. Would be great if I could find a molex connection to snap in and get going.

By the way, check out how these cells are connected… the whole top of the battery is a giant terminal… an accident waiting to happen.

What’s the gold standard to protect the bus bar in a situation like this?
Top balancing is done on a cell by cell basis, but all the cells should be in parallel while top balancing, so there's no need for a BMS. If you need some top balancing advice, I can refer you to a great thread.

I would say that plexiglass, or other non-conductive plastic is probably the best way to protect those cells terminals. I have some 3.5 inch wide electrical tape that I used to cover my cell terminals while I'm working on them as a pack, you could probably get an even wider strip to cover yours until you can get a more permanent solution in place.
 

mjsfbay

New Member
Top balancing is done on a cell by cell basis, but all the cells should be in parallel while top balancing, so there's no need for a BMS. If you need some top balancing advice, I can refer you to a great thread.

I would say that plexiglass, or other non-conductive plastic is probably the best way to protect those cells terminals. I have some 3.5 inch wide electrical tape that I used to cover my cell terminals while I'm working on them as a pack, you could probably get an even wider strip to cover yours until you can get a more permanent solution in place.
@ A_Justice. Thanks for clarification and advice. Yes, please share the thread you’re referring.
 

A.Justice

Swears he didn't start that fire.
@ A_Justice. Thanks for clarification and advice. Yes, please share the thread you’re referring.
 

mjsfbay

New Member
Question. With the batteries pictured above, is it safe to use that thin of wire for BMS connection?

I just received Will’s recommended DC charger, and a 48V Overkill BMS will be in tomorrow… so I’m getting close to having what I think I’ll need to get started.

These batteries aren’t the standard 2 terminal units that I’m used to seeing here… so I’m a bit lost on where to begin with choosing and separating 16v 140AH, 56 cell units.

Any help appreciated!
 

mjsfbay

New Member
Question, in the picture below, how would you go about testing whether or not you can use these wires (red box in the picture below) for an initial Top Balancing?

Each pack has 56 cells and there are 6 bundles of 4 strand wires coming from each pack.

I just want to be cautious so that I don't ruin these batteries or burn down my home.

Thanks for any insight!


IMG_5187.jpg
 

mjsfbay

New Member
Confirmed today by seller. These are Lithium Ion batteries. Not Lithium Iron Phosphate.

This was a $2k+ mistake if I can’t find another use for them.

Does anyone have suggestions?

Note: I expect the temptation to want to flame me for this blunder. Just keep in mind, it’s a mistake I recognize and have paid for. Help would be appreciated.

Thanks.
 
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