OpenEnergyMonitor Community


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no problem, did you see my part about using 2 of these modules per cell to see if it would run 2a discharge if used in parallel?

also seem to be having a problem with the module controller reverting back to 4100mv and 70c, i change it to 4000 and 75c click save and then a few hours later its gone back to 70c and 4100mv

anyone else having this issue?

My first post, though I’ve been following for a long time. I’m about to order 30 of the 4.2 boards and I’ve not done anything with JLCPCB before. Am I correct in understanding from the quote above that if I upload the Gerber files and select the SMT Assembly option that JLCPCB will mount all the components on the boards for me (except for the ATTINY chip and the JST sockets)? Do I have to upload some kind of component list for them to do this or is it somehow included in the Gerber file?

OK, I see you have to add the two files for the components in the next step. Do the boards come ready cut individually or do they come as a board of several boards that you have to cut up yourself (if you see what I mean)?

they come seperatly and stuck together in a line with masking tape

Great thanks for that. I can’t seem to find a BOM and CPL file for the controller board, are there any? Also, I’ve been looking through farnell to order the JST connectors but there are so many to pick from I’m not sure which to get. Order code 9491902 seems to look right but I don’t want to order the wrong bits, can someone (who has ordered from farnell) confirm? Thanks.

I ordered the wrong pcf8574at. I ordered pcf8574t. I know Stuart said you can change address in code. Can someone point me in right direction ? Or should I order the correct one. Thanks

Finally got my test pack (7S30P) all finished! Everything seems to be working correctly… now its time to do some testing


Line 88 of main.cpp of the controller code.

//PCF8574P has an i2c address of 0x38 instead of the normal 0x20
PCF857x pcf8574(0x38, &Wire);

Thanks Tyson I found . Works great !

Your packs look well balanced


in the “ESPControllerCircuit” folder there is a “ESPControllerCircuit.csv” which I believe is the BOM, but I also can not find the CPL file

Hasn’t anyone in the UK ordered the JST connectors from Farnell? Also are all the JST connectors (on the controller board and cell board) the same? So for 28 cell boards and 2 controller boards 100 connectors should be enough.

100 connectors will be enough, they are all the same, the connector you selected from Farnell will work fine, I switched mine to a 2.54mm pitch (vs 2mm pitch) and they fit fine also.

Are you reading this on the web page or on the module configuration? The web page doesn’t store the new values it just sends whatever you specify to all the modules to do a bulk configuration.

Click on a module to see what it has stored as the config.

Yes thats correct, but bloody expensive - £6.35 for 100, I’ve just brought 300 from AliExpress for less than £2 delivered!

Like these? (curved 2mm, PH2.0 2mm),searchweb201602_9,searchweb201603_55
First post … sorry if I cant link to stuff.


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Curious why the JST sockets are also not part of the BOM and CPL files as it seems as though they could be?

Also to make up the cables what are you all using? I found these on AliExpress, are they the right sort? Seems like a good price.

Before I go ahead and order version 4.2, have you tested the new prototype version? Are they good to go or would I be better ordering version 4?

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Yes the verson on github in the 4.2 branch works fine

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Charging / Discharging Problem on higher currents:

Hi, I have also trouble with higher currents in the charging / discharging state (15A and above) -> the DIYBMSv4 controller lose connection. I’ve shorten all cables (crimped on my own), but it doesn’t help. Now, I twisted the longer cables (RX/TX form/to the controller) and it works (not testet with higher currents like 120A and above). Maybe you can see it in this photo: