Opinions on connectors
Henry Palonen
I just uploaded my latest revision of master-shield to my OpenBMS-fork at [1]. I did put those 3 SSR's there, they are optically isolated and can handle 60V / 4A each. But at least daughter-boards SPI needs an connector and I would also very much like to change that current-sensor connector too. I'm thinking that so far the most easy EV-connectors I have had to work with are just simple screw-terminals. I used those for SSR's and perhaps smaller ones could be used for other connections too. That would also allow us to make an case that houses everything and get those connection wires through cable-seals even after board is in case. If we have some kind of connector in the wire, then it's harder to get it through cable-seals (at least seals that have only small holes).
What do you think about master-board connectors in this phase ? Later perhaps connector and PCB form-factor can be same as is used in daughter-board. But for now, when using Arduino+Can shield+BMS shield - approach, going with simple screw-terminals sounds like a good way to move forward.
Best regards,
Henkka
Ricky Gu
I haven't reviewed your circuit yet, I will do so soon. Maybe tomorrow. It's 1am here in Vancouver.
I just want to make a quick reply because you mentioned screw terminal. I don't think screw terminals are very appropriate for long term reliability specially in automotive environments. With months and years of road vibration, screw terminals are bound to get loose. Thats why in cars they use thread lock. But you don't have thread lock on screw terminals.
My initial motivation to redesign this openBMS from the original design in the UBC Ebeetle is to make it super reliable, and up to automotive standards. Where you can install it, set it up, then forget about it without worrying things would go wrong. This means all connections should be automotive grade.
A good source for automotive grade connectors is mouser. They have more than 18,000 automotive connectors listed and over 3400 different ones in stock ready to ship.
http://ca.mouser.com/Interconnects/Automotive-Connectors/_/N-1ehb5Zscv7/
What do you think?
Best Regards,
Ricky
Henry Palonen
I thought about using high-quality screw terminals and some component to fix it (eg. glue or lacquer) after final assembly to make sure screws don't come loose. I have seen that even complex combined small-aeroplane instruments use screw terminals as you can see from [1] (I just fixed similar unit). Also fairly new high power DC-controller, Evnetics Soliton-family (1 and Jr) [2] use only screw terminals as their low-voltage connection method.
But you are also correct that a proper connector would add reliability if that is combined with a proper single master-board. I think that an decision needs to be made if we first make an Arduino + CAN-shield + BMS-shield combination or should we go directly to single-board master, including functionality of Arduino + CAN-shield + BMS-shield in one single board. That would add reliability, not only with proper connector but also there would be no connectors inside of the board (versus many connectors needed to connect those Arduino-shields together). Those Cinch-connectors and case could be used and physical form-factor can be exactly (?) the same as in daughter boards.
I originally thought about finishing a drawing of that BMS-shield solution and get one or two shields manufactured (for example at BatchPCB). And then test the software and get BMS initially working with those shields and then move on to single-board solution. So that BMS-shield would be an intermediate step towards single-board solution. I don't even have batteries for my next EV yet so that shield-solution will not necessarily go in the car at all. But as I think about it after your post, this 2-step approach adds desing-time and cost since it involves both shield-design and single-board design.
And if your team already has an working solution for your EV-Beetle, then perhaps you would like to go "directly" towards single-board solution ? That would also be ok for me. Then we must look closely to Arduino & CAN-shield designs to see what we need to draw an Arduino-compatible master-board with CAN-bus integrated. I am not after all in great hurry with this, how about you ?
With very best regards,
Henkka
[1] http://www.mglavionics.co.za/Images/Odyssey%20rear.jpg
[2] http://www.evnetics.com/products.php#
Ricky Gu
I can totally see your point. Maybe for now just make something simple to test things out. then later improve it with heavier duty components if you are ready to go commercial.
Best Regards,
Ricky