Discussion of DIYBMS version 4

Source code and files

(GITHUB open once project is launched)


Here is the introduction video


Gracias por todo el trabajo que haces
Thanks for all the work you do

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Looks nice, any chance of this project in kit form?

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I’m having a chat with the OEM shop and also with some Chinese PCB builders to see what cost that would be.


I’ve just been working through a bill of materials list - its uploaded onto GITHUB named “CellModules_LCSC_BillOfMaterials.xlsx”

If I use LCSC.COM to order all the sundry items like LED’s, resistors and capacitors, the total is $17.73 USD for enough components to build at least 15 modules (and hundreds of components left over!)

Then use Digikey for the 2 parts I can’t get from LCSC - ATTINY841 (£0.82) and LM4040BIM3-2.0 (£0.90 in 10qty)

Total approx £39.80 GBP (+VAT) or around $50 USD for 15 modules

Which means each module is about £2.65 + VAT + the PCB cost.


Great, thanks for the LCSC BOM!
I see they can export a cart, but no import :confused: Let’s add they one by one…

How many ATTINY841 and LM4040BIM3-2.0 are needed, one per module?

Could you add/share the Digikey links for them?


There is a BOM import on LCSC! You have to create an account and login, then use the BOM tool link - Welcome to LCSC - LCSC.COM

PLEASE NOTE IF YOU USE THE BOM FILE YOU WILL HAVE A LOT OF SPARE PARTS! Although thats probably still cheaper than using a local supplier.

ATTINY841 - Octopart


100-ppm/°C precision micropower shunt voltage reference 3-SOT-23

Many thanks Stuart.

If anyone orders the PCBs from JLCPCB there is an 8$ discount on parts from LCSC at the moment. Not sure for how long. Also when you upload the BOM make sure quantity is one of the columns you select or you will get an order with just the minimum no. of parts they supply for each item. Nearly made that mistake. It was the fact that my total was less than Stuart’s alerted me to my error!

what was the cost through jlcpcb if you ordered the boards with the parts? (how many boards would you get)

does jlcpcb put the parts on too? or just ship you the parts?

You order the number of boards you require in multiples of 5.
If you create an account you can get a quote before placing the order.
I paid around $8.10 for 20 bms board and 5 controller boards. This was plus carriage which depend how quickly you want the boards. I paid $8 for post to UK which will be about 10 days. The parts cost pretty much as Stuart indicated for 15 bms but I ordered a lot of other items at the same time so my bill was higher.

I have just ordered boards and components. I don’t know if they assemble as well. You will have to enquire. They have always been very helpful.

I’ve got at least 50 spare module boards - send me a message if you are in Europe/UK and I can supply you some for cost price + postage.


As mentioned in previous messages - you will also have a LOT of spare parts left over, for instance you will only use 15 of the resistors (but you purchased 100 - minimum quantity) but don’t worry they will be useful for other projects !

Also please check that the list of parts makes sense - double check against the design !

If this is the first time anybody has tried soldering SMD devices (especially small 0805 size) please practice first - and use solder paste + flux !

See my previous video for soldering with a frying pan - it works, just be careful not to over heat!

If you are struggling to get hold of the LM4040 you can use the lower quality “C” rated version - LM4040CIM3-2.0/NOPB this has accuracy of 0.5% compared to 0.2%.

You can also use the “A” rated version, but that is more expensive.


He encontrado este, pero no se si sirve como remplazo
I found this, but I do not know if it serves as a replacement



I’ve published a new video on how the rules and relays work


Stuart , do you also have the BoM list for the controller board somewhere ?

The list is in the file

If you have ordered the BOM for the modules then you will already have most of the parts, like resistors and the JST connectors and also the optocoupler.

What you will need are:

R1 and R3 may be able to be swapped for similar sized values if you have spare ones.


I can use 21 boards pse. (Spain)

Looking forward to seeing pictures of V4 boards being built - let me know how you are getting on!