Thanks for the update. Let me know when you need a beta tester.
Can you estimate the final price for getting such a bms? Can you estimate a date for a beta test?
@JTAG when can you shut up and take my money? lol
iām itching for a compact high powered 12S, as well as a 10S variant. These monstrosities iāve been using are great but they take up a lot of room and prevent any sort of super-stealth build.
Sorry man, there is just loads of trash talk towards you guys te keep me structured 
.
Also motivation raised to a new level:
- Got a decent laptop now (T440P) that lasts long enough to make long train rides productive again.
- I have a functional but hacky personal electric longboard with no BMS that forces me to walk sometimes because I suck at charging it in time -> no state of charge indication XD.
- I extended my student Altium licence with one year, I am at the latest version now hopefully getting rid of some annoying bugs.
- SUMMER HAS COME.
Cost A cost estimate calculation is boring to make and might be a little confronting, let me first build a prototype and judge on what components to go the cheap route. Some current / voltage monitoring stuff might be simplified in the final design to reduce cost.
Firmware
Some of the never ending developments like feature adding will be realized in firmware and companion software, at some point I hope that others will jump into the SW development boat and help make the BMS even cooler. Because of the more luxurious (lazy) BMS hardware route the software development becomes doable for everyone (even for a hardware engineer like me) and add lots of features that in some regard might dazzle commercial boards. I hope that when(if) more of you end up with this BMS software development will make a jump and utilize all hardware features 
(and mature into something as cool as the VESC).
Progress The latest progress is mainly focused on the circuit that controls when the power is enabled and the microcontroller can take control. There are many things to take into consideration and I might have overlooked some (that what makes the prototype stage fun^^). The main problem lies in the fact that when the BMS is disabled the current draw from the battery pack should be as low as possible demanding the powerstate control electronics to be low power but still be āintelligentā (else a device that is made to protect and control the pack will end up breaking it when in storage mode for a long time). I also want many thing to trigger the enable state and even more challenging that once the power is enabled the microcontroller can detect āwhatā made the BMS to turn on.
I want that the following items to enable the BMS:
- Power button This will be a āsoftā power button, so only push( being a momentary switch) opening possibilities for integrated rubber (boosted like) and small waterproof switches + making it possible to serve other roles/tasks ->. This will not only function as a power button but also to control the menu structure on the OLED/eINK display (when either of them is installed*).
-
Microcontroller
Since the power button is only a momentary switch the controller should also be able to keep the power (and therefore itself) enabled
. - Power applied to CAN bus connector In some applications where I fancy this BMS the usage will be on a remote location. In these applications a 3G modem will be present to relay telemetry data to the manager of the system. This 3G modem will have its own power supply ( something like the particle electron ), the modem could trigger on request or at a set interval applying power to the CAN bus enabling the BMS and request SOC / cell voltage data (notifying the administrator in case of failures / low battery).
- Power being applied on charge input (detect that a charger is connected) In order to track the state of charge, state of health and most importantly keep the cell voltages between set limits the BMS should detect when a charger is connected and act accordingly. One can also choose to keep the rest of the skateboard in power down (applying no power to the VESCs) during charging.
- A computer being connected trough the USB connector In case of firmware upgrade or configuration the BMS should remain on.
*In the future I would like to get rid of the whole display and communicate all the data trough the CAN interface to the VESC which in his turn relays is to a phone or smart remote (evolve like). Because of the VESC versatility and the communities effort this is a REAL big and sensible option.
In the current design all of this should be possible. If it all works as intended the display could give very useful information:
- How many hours left to charge to battery to full.
- How much of the capacity is used ( in total / trip) and available in mAh and/or percentage.
- All measured data (max current / average current / cut off reasons / cell voltages and all the other stuff controlled by the already available button).
In case you omit the display I opted to support a digital WS2811 style LED to indicate the power states.
I updated the latest progress to Github and will update the PDF shortly (done).
11 Likes
Thank you, Danny!! You are really contributing a lot here! Big respect, bro!
Did you think about a remote power switch? It would be a great idea to start the engine (BMS) with a button on a remote!
Wouldnāt the receiver constantly be using power? Not sure I want this on my battery.
Yeah, thats true. Another idea died 
Unfortunately the receiver would need continuous power indeed, that is not that big of a deal since there is a freaking huge battery connected and transceivers nowadays can operate with extremely low power. However the power management needs significant extending (add a power supply to make constant 3.3V ). So sure its possible and would indeed be cool, maybe if many like or want it we could add it (maybe as an optional board or something).
It might also become a little scary when a kid grabs the remote and a 3kw+ beast awakens :P.
With the current setup an auto power off function when the remote is inactive or turned off is easy to realize.
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Well if you put your board into a corner of your room and do not use it for a long time your battery will be drainedā¦ It does not happen that often but is annoying. A better idea is that everything is shut down and when you pull the transmitter out of a holder from the eboard it could power the receiveron and wait until the transmitter is on starting the main power. When you put it back into the holder the BMS detects it and will power off the receiver. That would be a freaking cool idea. But somehow the BMS has to detect if the transmitter is in the holder of the eboard.
Well that you can simply do yourself with a switch - just modify the momentary switch @JTAG wants to add to the BMS anyway.
Just keep attention that you do not set the āauto shut off timerā too low. If a transmitter fails and needs to be restarted the board should not turn off 
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It took a bit of fiddling around but finally all components are on board! The rough placement is done .
Now the routing starts, the part I love the most ^^.
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Awesome! I wish I could contribute anything to your project, but thatās another level of building stuff. Keep up the good work and make this masterpiece available for the community.
Incredible! I really like the direction you are heading with this! 
Thanks for the support! It helps me to keep motivated ^^!
Had a couple or routing hours:
Got a lot of work done, still quite a bit to do trough, we are getting there :D.
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Nice idea. Looking good as far as I can tell. 
But what are the dimensions? Looks like something around 5,5cm x 12,5cm now. And what charging voltage do you plan to use?
Iād like to contribute too, but this seems out of my league. I guess I could offer sutures if things get out hand 
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@JTAG Iād love to test a couple of these out.
For science!
You are raising the bar on what can be done DIY. I just want to support what you do!!
2 Likes