DIYBMS v4

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 lcsc.com every day to see if they have the attiny in stock.

My kill rate was 4/10.

1 Like

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.

Man…
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.

2 Likes

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.

1 Like

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 ?

2 Likes

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:

1 Like

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.

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.

4 Likes

Very neat soldering!

2 Likes

Hi!
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.

6 posts were split to a new topic: Importance of short power cables to the modules

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.

1 Like

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.

1 Like