Okay, I know JLC is cheaper than the shop - it always will be!

However it stocks the boards and has them ready to ship, no delays due to manufacturing or components being out of stock or Chinese holidays etc.

10 USD for a completed cell module is still higher than the shop sells them for (I know you mention complete, which isn’t possible as JLC cannot assemble the ATTINY).

A complete novice here. Before this year I never soldered more than a few wires together. I knew soldering the Attiny841 was going to be a challenge, however using a combination of techniques (solder paste, ceramic tweezers and a ‘good’ soldering iron) I managed to solder them with no hassle. I had to switch R19 and R20 which proved to be much more of a challenge as the solder on the board is not compatible with the paste I use. Attached are a few pics of one of the 8 boards that I populated and uploaded the image to so far. Hope this encourages anyone with no experience but a bit of will to learn to take this on as well.


Very neat soldering!


Can you help me. Why errors grow only on 1 module?

Errors like that normally mean the module Before it in the chain has a problem. Try swapping those two modules over and see if the problem moves.

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Hello, just an update on the OEM Shop, due to changes in underlying costs, I’m please to announce that the price has DROPPED for the 4 module kit - this includes all the parts needed to assemble 4 diyBMS modules.

Which equates to £5.52 per module, or about $7 USD. You do still need to complete the assembly by soldering the ATTINY (SMD) and some sockets & headers on (through hole).

You will still need the controller board, this will be available in the shop soon.

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It may be advisable to mention ‘Solder Paste & Hot Air’ when referring to soldering SMD parts.
I wouldn’t even think of trying to hand solder SMD’s when I can barely see them as it is. :smile:

Nice work - I also handsoldered mine as well, with my soldering station. They’re fiddly, but not impossible.

The way I did it was to pin the PCB to the workbench with some tape, that left the only moving part the IC. I put flux from a flux pen onto the pads, gave pad 16 the slighest amount of solder, and while still melted, I pushed the chip into position with tweezers.

Then it was just a matter of drag soldering the rest, and finally touching up pin 16.

Works really well, and the flux prevents solder bridges.

The attiny isn’t that small, the pins are quite a close pitch though.

I’ve just soldered a chip to the shunt circuit I’m working on, it was only 3x3mm could barely see it, and it cost £7 each!

I can see that being a costly mistake if you get it wrong :slight_smile: Good skillz.

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I doubt that chip will make it to the final product, it works fine but just too difficult to assemble.

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For DIY projects, ease of assembly is up there on the must have list and £7 is expensive. I just got some SAB Mosfets to experiment with and they were just under $5 each.

Wouldn’t it make sense to have diffent chats for “support” and “ideas / developement”?

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We are discussing how best to do that. When the thread started there was just one post. There is now a DIYBMS category that new threads can be started in. I anticipate this thread will get locked to force the use of new, specific threads.


Click on diyBMS and create a new topic.

To continue discussion from a specific post, click on reply in that post then click on the little arrow in the top left and select Reply as Linked Topic - remember to select the diyBMS category :grin:.



Possibly one for @stuart to comment on, but is it worth putting some of the other diyBMS related discussions into the same category ?

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Good day,
I have to write here my negative experience with
Ordered, among other things, two ESPController + boards equipped with STM.
Price 20USD. Unfortunately, even though it was ordered and paid for, the U3 (PCF8574T) was not mounted on the board.
The support offered 2USD compensation and then even 4USD for the next order. It’s a sad experience.
Otherwise, this project is excellent and I will be a big fan of it.

I finally received the ATTINY chips from LCSC backorder and will be soldering them on later tonight. I had some questions for the others on this forum that have successfully used these BMS modules.

If I am making a 13s2p pack, how many modules do I need? Are the POWER1 connections the leads that go to each cell? Where does the pack power connections go out?

Is there anyone here willing to do a quick video call to explain how this module/controller works in a system?