BMS Per-Cell Cost?

[boom]

What are people generally paying, per-cell, for a system which includes:

• Charging
• Protections (overcurrent, under-voltage, etc)
• Active balancing

I'm curious about off-the-shelf systems vs DIY.

For systems based on 18650's or 26650's.

Not counting the cost of the cells, cell enclosures, wiring, etc. Just the circuitry.

 

[DaLanMan]

Are you asking what people are paying for a bms?

The ones I use come in 3 flavors:
1) the crap ones trhat come with my 12v kits, they provide basic protections and are installed because they literally come with the rest of the kit (box, plastic batt clips, the BMS all for about 6 bucks FOB My local warehouse)

2) Mid grade BMS, does not include Bluetooth reporting, but does have a reporting function: IIRC I get them for like 15 bucks in bulk or 20ish singular These are for the battery packs I put on kiddy bikes, unless said kiddy wants to actually be able to communicate with the unit, then I talk to the parental units,

3) Just like 2 above, but includes bluetooth, they run like 17/25 ballpark

I have not seen a true DIY BMS system, generally you are talking a fairly complicated circuit, I imagine I could stagger my way into building one from scratch but it would start with getting a board cut (10-20 dollars) Components (5-400 dollars) and then you have to figure out what kind of logic you are gonna have on the board. That could represent a *LOT* of time to develop. I imagine one of the EE's I know could approach this with confidence, but honestly they for the most part use off-the shelf with modification more than true ground up design.

As for the "circuitry" I imagine you could get away with a single diode, couple of fusible links and then the inter-tie connections (nickel/copper or solid Nickle stips) and you could literally do the whole things for a couple bucks. But if you do, please annotate your battery in vivid glowing colours that it has no circuitry protection besides what you ginned up in your garage, I want to know to park a ways down the row.

 

[boom]

Great answer. How many cells are the various costs you estimated?

 

[DaLanMan]

Oh, generally I am between a 7s3p and a 13s7p the pricing I laid out is kind of an estimation based on what I have built, the up side, all my builds are recent, I have not been doing this for very long.

The down side, I chose units based on *my* preferences, which often times are not all that deeply entrenched with knowledge.
Also, my ability to source materials is extremely good, I actually have a couple people in China that regularly will locally source merch for me and toss it on the next out-bound pallet to my old company. So the prices I get sometimes reflect those old connections.

So there ya go, from 21 to 91 cels, I buy all the dribs and drabs in fairly large volume (I just ordered a few kilo's of battery inter-connect material, If I hit a point where I don't need it, I am fairly certain someone on these forums would have a use for it and would be willing to take it off my hands. Again, not even sure what the pricing points would be if I was buying to make a single battery pack.

 

[boom]

Oh, generally I am between a 7s3p and a 13s7p the pricing I laid out is kind of an estimation based on what I have built, the up side, all my builds are recent, I have not been doing this for very long.

The down side, I chose units based on *my* preferences, which often times are not all that deeply entrenched with knowledge.
Also, my ability to source materials is extremely good, I actually have a couple people in China that regularly will locally source merch for me and toss it on the next out-bound pallet to my old company. So the prices I get sometimes reflect those old connections.

So there ya go, from 21 to 91 cels, I buy all the dribs and drabs in fairly large volume (I just ordered a few kilo's of battery inter-connect material, If I hit a point where I don't need it, I am fairly certain someone on these forums would have a use for it and would be willing to take it off my hands. Again, not even sure what the pricing points would be if I was buying to make a single battery pack.

I don't mean designing your own circuit-boards. I assume you're using off-the-shelf modules, right?

Also, i'm not asking for "What's the cheapest it can be done?', but rather, "What would you pay for quality components that do a good job of charging, protection, and balancing?"

Let's assume you're buying in bulk, at the good Chinese prices you get. Say you're building a 13S*P pack for an ebike or adult scooter or electric motorcycle, using 18650's or 26650's. Could you ballpark the boards? (not counting all the wiring and connector and housing, just the charging, protection, and balancing electronics.

I appreciate it!

 

[DaLanMan]

The ones I have heard the most about and found to be personally appealing (I can't say it is from great knowledge) were the
jbd with bluetooth

Daly BMS no BT

Daly with BT

Amazon has benefits to the buyer (massive buyer protection) however can obviously be pricey. I have purchased both of these units elsewhere for significantly less (aliexpress and ShioWeng (not sure if that has an english side to it)

That is my ,02, you may want change...

 

[boom]

The ones I have heard the most about and found to be personally appealing (I can't say it is from great knowledge) were the
jbd with bluetooth

Daly BMS no BT

Daly with BT

Amazon has benefits to the buyer (massive buyer protection) however can obviously be pricey. I have purchased both of these units elsewhere for significantly less (aliexpress and ShioWeng (not sure if that has an english side to it)

That is my ,02, you may want change...

It seems those are just protection boards, correct? They don't include a power-supply, they don't provide CC-CV charging, and the don't do balancing (active or passive), correct?

thx!

 

[DaLanMan]

correct, just the BMS.

 

[E-HP]

It seems those are just protection boards, correct? They don't include a power-supply, they don't provide CC-CV charging, and the don't do balancing (active or passive), correct?

thx!

The descriptions show balancing, just not active.

 

[DaLanMan]

I have buit a few of each, they do not do the kind of balancing you are thinking of.. I think the higher end versions do, but the ones I have installed do basic charge management