Libre Solar BMS Development

Hello everyone,

we have started to develop the Battery Management System as proposed in Open Source Flexible Battery Management System for off-grid energy storage.

We are currently collecting requirements and invite everyone from the community to provide feedback, so that we can develop the BMS such that it suits the needs of as many future users as possible.

This is the GitHub repository where the hardware development will take place: LibreSolar/bms-16s100-sc

The firmware will be developed in a separate repository: LibreSolar/bms-firmware

In the hardware repo you can find a draft technical specification document (direct link). Please have a look and leave your feedback in the GitHub issues (@prithvirajnarendra has already started :grinning:) or here in this thread.

Martin

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Hi Martin

Can you please share the development on BMS hardware and firmware development so far ? when can we get access to some of the hardware unit for testing in the field ?
How are you handling the supply chain disruptions in development of prototype of your hardware design?
I am prompting on behalf of some of the companies waiting to hear more on the development?
Thanks.
Aarti

Sure, happy to share some more insights about the ongoing BMS project work.

We have just finished the first design iteration, which is currently under review. It looks like this:

We got some very valuable community feedback already, which I am now implementing as much as possible before we finally place the order for the first boards for lab testing and validation in a few days. The trial with a second batch of boards is planned for the middle of the year. The review process is public, so if you have any additional ideas or concerns, join the discussions in the
GitHub issues.

The part supply shortages were indeed a challenge during the design phase. We had to follow a design-for-availability approach. Before finalizing the board layout, I ordered all key parts from several different suppliers (mainly in China) which had some stock left. Now we’ve got enough parts for the prototyping phase, but we have to hope for an improved situation later this year to be able to deliver larger production runs.
We had to make some compromises regarding parts selection. For example there was no switch-mode power supply in stock anywhere which fulfilled both the high input voltage (80V) and the low idle-current requirements. We decided to go ahead with a part for max. 60V and replace it with a more suitable one as soon as it is available again. This limits the number of cells for NMC type to 14 cells in series.

If anyone has further questions, just let me know either here or directly on GitHub. I’m happy to answer every question.

Martin

Hi Martin

Interesting feedback on BMS development progress, especially PCB board in GITHUB library.
Can you tell us what all feedback points you have incorporated in your final PCB design and how its coming out ? any new challenges in manufacturing of these PCB’s ?

Hi Aarti,

the issues related to the hardware are tracked here. I have closed the issues which were already solved before oredering the PCBs. They were mainly related to some layout improvments. Some issues are kept open as enhancements and may be addressed in the next iteration.

During the build-up of the boards some small new issues arised (e.g. because of wrong footprints for a part). These are marked as bugs and will be solved in the next design revision as well. So far there are simple workarounds for all these issues for the prototype hardware.

One major difficulty we encountered was the soldering of the high-power terminals, which consist of a large copper bus bar with a press-fit bolt (see image above). At least for the prototype it was not possible to solder these in the small reflow oven we have available. We are currently looking into alternatives to this design.

If anyone from the community has experience with proven (and cheap!) solutions for high-current connections between a 25 to 35 mm² wire and a PCB, suitable for 100A continuous current, let me know your ideas!

I’m now commissioning the boards and will post some photos as soon as it works in the test battery pack :slight_smile:

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Hi All,

We are launching BMS Challenge. A fully customizable Open Source BMS hardware design is ready to release. We believe this Open Source BMS solution has the potential to help companies like yours and many others to increase battery life and provide a second life to used batteries, all while saving the trouble of developing your own BMS. We invite you to participate in the challenge to test 2 BMS PCBA boards by incorporating them into your own product.

We are sharing this challenge with you before sharing it with the public in order to give you exclusive early access – and only the first 5 successful applicants will receive the BMS PCBA boards.

Here’s how you can get your BMS PCBA boards:

  1. Fill in this form to apply for the challenge → https://forms.gle/hUYJzcBxyX1eAgXD6
  2. If your application is successful and among the first 5, then EnAccess will reach out to you to send you 2 BMS PCBA boards.
  3. You test the boards in your battery-based products/solutions.
  4. EnAccess checks in with you to hear your feedback about the boards.
  5. That’s all! You’ve gained free BMS PCBA boards by helping us test them & providing feedback.

Let me know if you have any questions!

We look forward to receiving your applications!