I came up with a simple solution that removed some unnecessary components and traces. On the LTC6803 GPIO and WDTB are connected together, with a pull-up. That connection is then passed to the Charge_FET control. If MCU hangs the WDTB is asserted and pulls the line low. Then when MCU controls the LTC6803 I can switch the GPIO pin to either pull the line down or let the pull-up pull it high.
Why not create a open source programmable charger instead? Why do we need all of this on board?
I imagine this: https://www.amazon.com/dp/B00B3C2Z52/ref=cm_sw_r_cp_api_vbyHAbFE6SG66 + A boost converter module with nice lcd interface would be perfect to charge anything from 4-12s maybe even higher!
Then your BMS only gas to do the basics, protect from ov/uv/oc & balance when charging if dv>100mv between highest cell and lowest cell. It could be really small. You could make it even more modular and separate the balancing into a different module. In this scenario, you could have the balancer within the charger too and you’re down to crucial protection components on board.
I am really looking forward to this project regardless of the approach
1 Like
Sorry for that
I’m meant… bigger ? not big 
Thank you guys for this electronics porn ! 
WDTB on Battman is not used (at least, that’s what I’m understanding).
Your safety feature is really smart JTAG !
Ok, key design choice time (Poll at the end). The module interconnector, AKA the connector that connects the Main- & Switch-modules together. I have two styles picked up and I’m going to explain the differences between them and then shortly go through the pros and cons with each approach. (Switch-module design hasn’t been started yet, so upcoming pictures are mock-ups)
Why aren’t these two styles compatible with each other? It’s because they flip the pin order in relation between them, as demonstrated below.
Let’s start with a closer look at Style B connector.
Male: (https://www.digikey.fi/product-detail/en/sullins-connector-solutions/SBH11-PBPC-D08-RA-BK/S9179-ND/1990072)
Female: (https://www.digikey.fi/product-detail/en/sullins-connector-solutions/SFH11-PBPC-D08-RA-BK/S9204-ND/1990097)
Pros:
- Simplest and easiest way to connect the modules together
Cons:
- Wasted space as the board edges can’t touch each other. Gap caused by the connector housing.
- No any kind of flexibility in positioning between the modules
Style A connection:
Board side: (https://www.digikey.fi/product-detail/en/sullins-connector-solutions/SBH11-PBPC-D08-ST-BK/S9171-ND/1990064)
Connector side: (https://www.digikey.fi/product-detail/en/sullins-connector-solutions/SFH210-PPPC-D08-ID-BK/S9288-ND/2095297) or (https://www.digikey.fi/product-detail/en/sullins-connector-solutions/SFH11-PBPC-D08-ST-BK/S9196-ND/1990089)
Pros:
- Allows modules to be touching each other with a bridging PCB that has female headers on it. Almost no wasted space. (error in picture text, bridge PCB has female connectors)
- Option to use ribbon cable with IDC-connectors at the end allowing flexibility in positioning and different mounting angles between the modules. (Ribbon cable has to carry only charging current, which is carried by 4 wires in each direction)
Cons:
- Needs extra parts to connect modules.
- Needs a bit more vertical room
There. Short explanation between the connector styles, why they aren’t cross-compatible and short pros & cons for both. I’ll discuss about this with you or answer questions and update the Pros & Cons list if good points are made. Other connector suggestions are also welcomed.
I’m naming this project from this point onward under the alias "FlexiBMS"
Poll below has it’s voting descriptions mixed-up in contradiction to the info above, which are correct. Options should be: Style A, Extra connector, allows for optimized space use, or more freedom on module positioning Style B, Simple and easy, with a bit of wasted space
- Style A, Simple and easy, with a bit of wasted space
- Style B, Extra connector, allows for optimized space use, or more freedom on module positioning
0 voters
OH CRAP! I just now noticed I have my poll options are mixed up. I’ll fix the descriptions, if I can and holla to the voters to check their vote. Sorry for the mix-up
Update. Board routing is done. I’m going to do some sanity checks to see if I have missed anything critical, but otherwise we’re starting to look good for the first iteration prototype.
I’m also adding one more useful feature, which allows the module to put itself into deep shutdown state, essentially cutting it’s power use almost completely for long term storage, so it doesn’t drain the battery pack empty. The amount of time before the module disables itself will be configurable, for example, “if nothing happens in 15 days” -> “shutdown”. Wake-up is done via a pushbutton. You will also have to wake-up the module when you connect the battery pack, but it will then run on the shutdown timer.
Sorry about this, but could following users check their voting choice on the post #64 poll, knowing that the connector descriptions were mixed-up @Freddiecook @rene @bevilacqua @b264 @louwii @riva_00 @GrecoMan @JonathanLau1983 @TarzanHBK @ShutterShock
5 Likes
I like the extra connector and voted what was stated in the vote option - not the intro.
I voted based on the image, not the text, for style A. I’m still not sure exactly where the mixup was. You should make a new poll so you can keep track of who voted again and who may not have understood
Is the schematic already published somewhere or should we wait 
?
Oh yeah I voted based on the picture too.
2 Likes
Schematic is not yet released, but I intend to make it public once I complete the sanity checks on it. Probably on this week though.
Also @ShutterShock Did you vote based on, if the connector was vertical or horizontal like in the pictures?
I was thinking vertical connector with a short ribbon cable, I think it is more flexible 
1 Like
Style A is meant to allow stacking both boards ? Erf, both stles have their pros and cons. What about “Style C” with vertical pin but not crossed ? Is the length between boards critical ?
Also I guess it’s more convenient to have the USB port vertically like VESC 6. Our enclosure are often messy, lot’s of components/wires everywhere so it’s not that easy to plug a USB cable on the side.
The connectors could always be unsoldered and changed if desired
Sure, but the PCB layout will changed between crossed and not crossed style, right ?
2 Likes
Yep, good call
This ^^
I’ll make a new poll shortly with new images to demonstrate the styles clearly.
3 Likes
Okay. New connector poll time. with hopefully better pictures this time.
Here are our mock-up boards.
Vertical connectors:
Boards can be right next to each other with a connector PCB, like so: Or you can use a reasonable length ribbon cable to have some distance and angle between the boards, like so: FYI, this is a ribbon cable:
Horizontal connectors:
Simpler with no additional parts needed to connect the boards. There will be a gap left between the boards, like so:
I would like to use:
- Vertical connectors
- Horizontal connectors
0 voters
3 Likes
@SimosMCmuffin I like where this is going, with the ribbon The flexibility increases a lot since you can cram the power board somewhere else
About the balance port, couldn’t it also be vertical? If reduces the footprint a bit but reduces the used space a lot since there are no wires going to the side
