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DIY Lithium Battery Balancer and monitoring (BMS)

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stuart, thank you for replying.

So it’s basically down to the i2c isolator not working at lower voltages and wanting the system to be comparable with other cell chemistries other than standard lithium. That makes since.

Is there any work being done on the ESP controller board to be able to cut power to the load of the entire pack if one of the cells reports under-voltage or some other error? (Either through a relay or power mosfets.) From my current understanding the ESP only collects and reports each cell’s status.

How has your setup been performing Stuart?

I’m in Portugal at the moment so will let you know when I’m home!

Enjoy :slight_smile:

Finished my first hand soldered board. Waitng for the programming adaptor to arrive…

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Looks good, I hand solders my first one too. I had mine installed for about a week. They initially started great but then I started getting more and more false figures till all but one wasn’t working. Going to look at the code modifications to see if I’ve broken anything. I need to double check the validation code as the rogue readings are getting through to grafana which shouldn’t be happening.

Hi everyone,

I’ve been following along for the past few weeks and have been working on a parts list this weekend. I have published my current working list here. I have found everyone on Mouser and Element14 and prices are in Australian dollars.

During my search for parts I noticed a slightly cheaper I2C isolator and wondered whether the Texas Instruments ISO154x-Q1 isolator (ISO1540QDRQ1) would work as alternative to the ADUM1250ARZ. From my very limited understanding they do look similar, and have the same pin layouts and dimensions. Thoughts?

Hi Jesse C, Your list is handy if you want it fast but …some items are expensive over there!!! Take a look at my list above on Aliexpress the Adums are 1/3th of the price!!

Which 50w resistors are you guys using?

I can’t say for definite these would work, but they do seem to be compatible - suggest trying one and finding out!

I will try one or two aswell, hope someone can check my order so i don’t order the wrong stuff (not familiar with smd components).

And i’ll order 4 adums and not 20 right away so i can still test the boards on my 4s pack!

Something like this work okay…

but you don’t really need 50W - 10W would be fine, they just get hotter.

Thats some nice and neat soldering, well done!

What resistance should i use? 1R?

Using Ohms law you can work it out -

3.5Ohm would be around 1Amp @ 3.5v (5 watt)
2Ohm would be around 2Amp @ 3.5v (8 watt)

I wouldn’t go any lower, 2 amp is plenty

Thanks. Im going to go with 3.3ohm. Not sure if i should use ceramic vs aluminum resistor though

After many hours of hand soldering…
Got them installed on my battery pack. I am occasionally seeing the bars shoot up to 64v but besides that it is working well.

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The voltage spikes are driving me insane. Any idea what is causing them?

Are you using my variant or Stuarts vanilla code?

Your variant