How many output terminals on the main PCB v2?

Hello there, I am happy to have stumbled upon this open source project and love the idea :slight_smile:

I noticed the 4 metal posts on the main PCB and was wondering if these are B(in) +/- and B(out) +/-? Or can the terminals be configured to have different potentials above ground state, such as a 110/220v option? Given in my case, I am hoping to have a ground and 12-14V but would also like to have half of that potential on another (+) lead, but with the same resistance.

My Goal is to possibly trick a hybrid vehicle into believing there are more cells then there actually is. To Use 14x (possibly lead-acid) 14V modules instead of 28x 7v?

Let me know your thoughts! Or if I’d be better off using many more smaller battery modules and just adjust the minimum SOC to improve the longevity of the lithium pack.

Dear Kyij,
First of all, welcome to our community. It’s great to have you here.
As you didn’t specify which project you are talking about, I’m just guessing from your message that it is on the Libre Solar BMS C1, right?
@martinj, can you answer this question easily?

Hello there VivienB! Yes, I am referring to the BMS-C1. I had misread somewhere about development on the 2nd or maybe just the rename that was done. I am not sure if I can still edit my title to help confusion?

I was able to get KiCAD installed to open the schematic and export it as a gerber for a quote to see how much it would cost to get ~60 made. It is not clear to me why the wiki mentions Autodesk Fusion, as it could not read the Kicad files?

I will try to attach the schematic image - courtesy of Martin Jäger’s work

  1. To verify, the Pack +/- is where the load is supposed to go?
  2. Does Battery 1 +/- actually wire to the pack rails? Or is this only needed for high amperage loads? Versus just using the wires connecting in-between each cell?
  3. Is the Pack 2+ and Pack 4- used to connect the boards together, or something else?

Thanks for any help!

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Hi @Kyij ,

Yes, the PCB is indeed made with KiCad. Not sure where you read Autodesk. We are not using any Autodesk products at Libre Solar because of their licensing.

Not sure I really understood what you want to do with the lead-acid batteries. But the BMS is meant to be used with Li-ion batteries and max. 60V.

Regarding your above questions:

  1. Yes, BAT+/- is where the cells are, PACK +/- where the loads or chargers are (e.g. MPPT solar charger or AC inverter). Did you find the BMS C1 manual?
  2. Not sure I understand your question. BAT +/- must be wired to the last cell’s + and the first cell’s - terminal.
  3. Please ignore the numbers. Those just identify the pads of that particular component (bus precharge resistor and shunt resistor in your case). There is only one PACK+ screw terminal and one PACK- screw terminal.

Hope I could answer your questions.

Best regards,


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