Thank you. I’ll try

2 posts were split to a new topic: NiMH cell/packs

Can you track down where the CRC error is being introduced is it in the modules or the comms back to the controller?

What does the configuration web page show, are there high error counts on the modules?

53 posts were split to a new topic: Alternative balancing ideas and charging from solar

A post was split to a new topic: Module v4.2 swapping R19 and R20

4 posts were split to a new topic: Programming ATTINY841 - error “target doesn’t answer”

So the chip used by JLPCB was different and ended with a “T” instead of a “P” I had to change the code to correct the error.

Just a note to say thanks mainly to Stuart and also others on here for all the work that has been put in over the last few years. I’m glad I hung in there as the v3 BMS nearly drove me nuts when it just wouldn’t communicate. V4 is so much better and improving all the time with the updates.
I started my battery storage project almost exactly 2 years ago when I collected my first cells from the local tip and started processing them. I now have just over 10kWh of storage in a 14s100p configuration though I’m only cycling about 40% of the capacity to prolong the life of the cells (all 1600mAh+ and 80%+ of original capacity still).
In the last 24hrs I’ve only imported about 0.25kWh hrs from the grid, roll on next summer!
My project is still a work in progress as I’ve not got current control of the Flatpack power supply implemented yet. This is also only a temporary location.
Hang in there everyone still working on their own build it is well worth it in the end.


@Keith great powerwall. Really interested to see you using 1600mAh cells. I’ve been looking at 1500mAh for my own powerwall, working with multiple 7s18p banks.


Some findings on our packs.

Don‘t use shared wires, even 5cm longs for the cell modules,

Always use 2 extra wires from each cell module to the battery tap/pole.

If we use - from first cell and + from first cell for the first module, but the same + wire from cell 1 as - for module 2 the meassured voltage on module 2 will rise when balancing starts on module 1.

The reason is that the minus voltage is dropping with the cable resistance on 800mA balance power but the + voltage stays where it was, because module 2 is not balancing yet.

Then we had a chain reaction up to the last cell, even if they were balanced first, all 16 modules start to burn energy

After cabling every cell module directly to the battery this „feature“ has gone.

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I just looked at the price for the mouse bites PCB here at Open energy monitor…
21.18 pounds or 25 euro / 28 dollar

18 august I ordered 30 x cell pcb at JLC all parts assembled (include attiny841, not pin headers) 85 usd.
85: 30 = $2.83
28:4 = $ 7.00
That is a lot extra for connector and pin headers.

Obviously I like to sponsor @stuart, that is not the question.
My idea for the mouse bites was to reduce the costs, not triple it!!!

If you need sponsoring for the great work at the DIYPCB please provide your PayPal.
Abusing my suggestion for mouse bites this way make me feel really bad for even giving this idea.

Its cheaper to buy 30 pre-assembled from JLCPCB then 3 sets of mouse bites (=12)
and you don’t even need to solder the attiny841.

Not that it is a big problem, but I did manage to kill 7 during my last hand solder set of 30 pcb…
You really should provide 6x attiny841 in the set for this price as there can easy be a few mishaps.

Perhaps I was misreading, and the kit is 16 cell modules for 27 dollar??

(in case people wondering, I have 80 cell setupS16, total 1016Ah, and like to provide each module with a cell PCB.
that will use the 5x controller boards I have :slight_smile: )

I accidentally ordered a set from JLCPCB that did not have the attiny. I think someone claimed the qty between when I checked and when I pulled the trigger. I wasted a ton of time learning how to solder those mini pins. It was so difficult to find the #1 pin indicator. On some of the chips, the dent was invisible. I thought I correctly figured out what orientation the writing was, and I was able to see the writing if I held the chip at the right angle with the right light. I soldered 4 before realizing I should test it. I was wrong. Of the remaining 6, one crapped out. I bought the desolder stuff and was able to get the chips off. I resoldered one, but it didn’t work. The second one worked. The cats were hiding in terror. I vowed never to buy any board that requires surface mount soldering, even though I am now somewhat competent at it.

The time cost is ludicrous.

The experts have no clue how much they know, and how many ways a novice can screw things up.

I will run my 8s pack with just one module before I buy another module where I have to solder the attiny. I check every day to see if they have the attiny in stock.

My kill rate was 4/10.

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Novice to novice…
I suddenly feel expert by just frying 7 out of 30 :slight_smile:

Thanks @John_Taves for backing me up here.

It’s not that easy and really takes hours to do, or in my case, 3 weeks as the thermistor (R19) was out of stock and I needed to do that one by hand also.

Compared to a 0603 the attiny was easy.

I used to be proud to be able to solder the jumper connector!! (2.54 things)

This is a whole different ballpark that @stuart seems to find hard to understand that most people really don’t have the skills to solder attiny841.

@John_Taves, I think we should talk PM…

Quite possibly, until I started the diyBMS project I’d also never soldered SMD stuff. I’ve only recently got a hot air soldering station, before that I used solder paste and a frying pan!

Don’t try and solder the ATTINY841 with a soldering iron, you can do it but likely to bridge multiple pins. A little solder paste and an oven/hot air station or even a frying pan all work and the paste magically “sucks” to the pads and pins like magic.


Hi Frank, sorry if you feel this way, I was in discussion about stocking the parts with Glyn at Open Energy Monitor long before any mention of mouse bites cropped up, they seemed like an ideal format to put into the shop as most people buy the modules in multiples of 8.

Obviously the shop has overheads, there is also the issue of import duty and VAT which UK payers are subject to (for JLC orders).

You do realise that you can add multiple PCB orders to a single JLCPCB order? To avoid multiple shipping charges.

As you have seen JLCPCB rarely have ATTINY841 in stock, this is often cheaper to purchase from the main suppliers like Farnell/Digikey etc.

Pardon me for butting in, but we all had to learn at some time or other. It’s just that the experts have done their learning, but you’re doing it now.

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I have now been using the DiyBMS for a month and for the most part it has worked perfectly ony 7s80p bank, I only have 2 issues now

  1. when the controller reboots because it looses WiFi the relay activates and trips the shunt, I am hoping to resolve this by changing to D1 mini Pro and external antenna
  2. Lastest issue is I did some pack cell testing to get each packs capacity, when I was done I connected the back into a 24v pack and charge them up, one cell was slightly higher than the rest and once it got to full pack change this cell was 4.16v and the rest were 4.01, all should be 4.02, and my bypass is set to 4.04. the high cell pack is bypassing, but it’s been 2 days and we are not even halfway there. So this does bring up the discussion about dump capacity

I know we can add more modules, but this seems like a hack and work around, what would would be good if it were possible to add additional dump capacity to the modules, via an extension, not should exactly how this can be, maybe a dump board with its own power connection to the bank and the main module activates an tiny realy, MOSFET or something that can dump like 2A ?

I know Stuart might not be keen on this or most probably doesn’t have time maybe someone else can look into this ?


News flash: (or old news??)

JLCPCB factory has production problems.
Maximal order for assambled is 10 X PCB.

This will take atleast a month or longer to get back to the normal 30…

If there ever was a good time to share the Gerber etc. files for public use, it’s now.

It would save me the hassle of making it again (as @stuart already made)

I need to order more then 10.

For me I can make the time to learn EasyEda and make a file for 2, 4, 6 and 8 cell PCB’s.
(Or just 4/8, depending on the time it takes)
I will share after I created.

Or Stuart is kind enough to share it with us.

Both works for me, outcome is the same.
Probably the file from Stuart have the least change of failure :laughing:

The cost reduction of making 4 at the time should be enough to cover the overhead expenses.
It’s now tripple.
Not real problems, if it was finalized product.

People are willing to pay 10 USD per (finished) cell module.

(I did a poll on a few other forums how much people would be willing to pay for a per cell solution with one controller.
Most people do 10 USD, $12.50 is already pushing it.,$15 and higher is a no go)

Frying pan probably would work…
Not really good way to promote a product…

The confusion already start when it tells “soldering required”
And now I read that I should not solder but use pan or oven or hot air…

Would be nice to tell at the start solder paste and hot air station required.
Alternatively you can use a frying pan :yum:

The novices like me read soldering and will do soldering, with iron.
The result is known…

Please do share to safe me the time to make again what you have ready.

It also is a great Opportunity to lean to make PCB.

Perhaps add some features like active balancer using buck/boost.

I saw some schematic that can probably easy be add on for the cell module.

Just thinking out loud.
No idea yet about the costs of the components.

Add on would be as simple as 2 additional pins on the battery connection …
The rest is separate board.
It just saves the time of splitting the DC.

Or, if the components are cheap and easy to add, I make it on the PCB.

I never used the software.
It can be I’m way over my head even thinking I can make mouse bite PCB :laughing:

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Details of why capacity is restricted

As I said in my post earlier, you can solder the ATTINY chip, it depends on the experience and skill of the builder. It is much easier to use solder paste and hot air - I gave an example of “thinking outside the box” and using a hot pan instead.