First BMS board works!!

​I'm starting to get real excited now.   All the major parts have been obtained or ordered.  The new BMS boards came back and they work.  The new coupler slice is good enough to order a full size version.   There are places to mount the 2/3rds of the batteries. The largest pack is soldered up and awaiting final assembly.   There is still lots of work to do with two smaller packs to assemble and the charger & dc-dc converter to figure out.  Also a 1.8L NB engine to get rid of and an adapter plate to make and mount.   All these issues can be taken care of, one at a time.

The eMiata is back in my driveway with a noticeable change in the back. Check out the battery boxes,  firmly mounted in location.

The trunk will still be quite usable.  Thanks Bruce and Eric for a fantastic job, welding, cutting, fitting and making dreams come true!  Now I have a place to put all those parts that have accumulated in my office, which will make Teresa very happy too!  Batteries can't really be installed without the BMS components and Joe is making fantastic progress there too.

Joe received our first set of 30 partially assembled BMS boards. He finished assembly on one board, installed our firmware and ran the acceptance tests.   All Tests Passed!   Joe gave me one board to use for physical mounting measurements. With 110 of these boards needed, Joe is giving some thought to producing an automated firmware install and test fixture using a Raspberry Pi computer.  I also have the new serial isolator boards so I'll have less of a mess on my desk writing the BMS software.  Thanks Joe! Battery boxes - check, BMS boards - check, on to the batteries.

The most tedious and time consuming phase is completed on the big battery.  Doing the happy dance!  In its discharged state, the largest pack now measures 115.4 volts.  I'll set this pack to the side until I work out the details of how I'm going to mount the BMS boards in our battery packs.  With the batteries taken care of, it's time to turn our attention to the drive system, specifically the coupler.


The new coupler slice arrived on time.  I really liked using sendcutsend. They did exactly what they promised, kept me up to date and didn't cost a ton.  I'd definitely recommend them for your thin metal cutting needs. The perfectionist in me is not sassified with the coupler fit, but it is better than the previous version.

It will be good enough for our prototype and much better than the Fiat clutch disk I tried. The real coupler ordered has been ordered and is due to be shipped on Sept 8th.   Scott and I will continue on designing a better coupler by modeling the Leaf shaft using dental putty. Thanks to everyone who worked on the coupler.   By working together and not giving up, we solved a tough problem for the home hobbyist.

My neighbors are helping us too!  William Lemke, who runs Cedar Park Bicycle Repair, had donated several bicycle inner-tubes. These are used to cover the high voltage wires so we can avoid un-intended arc welding using batteries as well as re-use and recycle. Thanks William! Also, Andy Bruner knows the guys who can remove the refrigerant from the AC compressor in the Miata before I pull everything out.

Next week we'll work on assembling the small batteries (264 cells, vs the 704 cells of the large battery).  I'm sure we'll make more progress on the BMS automation as well.  The next milestone is to use our two small eMiata battery packs in our go-kart and test the batteries performance as a pack, complete with BMS.  Thanks for reading!  Wishing you all health and fun.   Please comment!