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.

6 posts were split to a new topic: Platform IO V5 “Upload file system image” option moved

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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(post withdrawn by author, will be automatically deleted in 24 hours unless flagged)

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?

The wires will be a few inches long at most. The balancers will be mounted to the side of the cells, with a small air gap to allow natural convection to cool the back of the board when the resistors heat up, and prevent that heat from transferring to the cells (although my cells are massive, 180Ah LFP’s)

Thank you Stuart.

I understand that ordering directly from JLCPCB will be cheaper, but one needs to go in the process of ordering at JLCPCB, perhaps need to switch components (different brand resistor, same value) if something is out of stock, and order attiny 841 from different sources.

All that work needs to be compensated + stock and tax things.

You think it’s possible to share the mouse bite on GitHub?
(I did not check if you already did)

For me needing more then 10 additional, it would be a great help.

That is sad.

The PCF8574T is not expensive, but (!)
Buy separate from mouser (expensive but fast) or AliExpress (cheap but take long time) the $2 does not compensate the real costs.

You probably paid with PayPal.
Good reason for full refund and order 5 new boards


S13 is 13 modules.

Solder the Attiny841 is a pain.
If you can get your hands on some solder paste, it is much more easy.
Otherwise I hope you bought a few spare Attiny841…

If you read about 20-30 post back [post no. 2570: DIYBMS v4 - #2570 by stuart], Stuart shared a video link on how to do with frying pan if you have no heat gun.

With soldering iron it is difficult.
Really difficult.

Solder paste and hot air works just fine.

[edited to add link - Moderator (RW)]

I managed to use solder paste and flow it with a soldering iron, see my post above for the result. Solder paste was ordered from AliExpress, costs just a few bucks. Use a tiny tiny amount. Working under a magnifier helps as well.

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Sorry to hear about the problems at JLC @UTima

I’ve not had any problems so far, but with the volume of boards they generate I expect they also get a fair share of failures.

Did you not order the board with the resistors populated?

If you need to purchase a single fully populated controller, the OEM shop now sells them - this saves you ordering 5 boards and waiting for shipping from China. [DIYBMS Controller V4 (PCB ONLY) - Shop | OpenEnergyMonitor]

Just in time, ordered, any recommendations for WeMos D1 mini Pro ?