Sunday, October 13, 2013

Finishing battery box lids

I finished the battery box lids this weekend.  First, I found that the epoxy I used just did not have enough shear strength - the shear force I put on the hold-downs while I used a router to cut grooves for interconnects to pass under was enough to pop some of the hold-downs off the acrylic top.  So, it's nuts and screws for the hold-downs to augment the epoxy.  All of the screws and nuts are countersunk so that they don't have any chance of interfering with anything:

Next, I applied 3/16"-thick foam weatherstripping to the acrylic lids.  This is to provide some vibration resistance, as well as some resilience so that everything stays nice and tight under compression.  Here is the lower rear cover (you can see some of the gaps that I routed out in this picture as well):

Finally, I also applied the 3/16"-thick foam to the metal box tops.  Again, to reduce vibration and to keep everything tight when compressed with the nuts/bolts that hold this all together:

One last step before battery interconnecting - I need to add material to keep the cells in-place horizontally (they don't quite fill up the space that the former AGM-1280T batteries occupied).

Sunday, October 6, 2013

Battery Box Covers

Although a vacation interrupted progress on the ElectroJeep in September, it is getting very close to energizing the main HV circuits.  However, before that happens, I want non-conductive covers in place to protect against mishaps.  Since orange is the new black, I went with orange acrylic covers, with 3/4" by 7/8" clear acrylic blocks to hold the cells down by their edges.  Here are the hold-downs epoxied to the covers, resting in their respective racks:

The front rack is simplest - just 4 parallel blocks:

The upper rear rack is also fairly simple - 9 parallel blocks:

The lower rear rack is more complicated due to the different cell orientations.  There are 7 parallel blocks, and two additional blocks at 90 degrees to hold down the 7 cells at the front of the rack:

The final step will be to add self-adhesive foam between the blocks and the cells, and between the rack-tops and the covers - this is all to reduce vibration and to keep everything in compression.

The under-seat cells will reuse the polypropylene covers - there is not room on top of the cells for the BMS boards, so a simpler hold-down will work well.  However, I need BMS modules.  So, I reused two of the boxes I built for the old AGM BMS, and mounted 3 BMS boards in each one:

The bolts that the BMS is attached to do not go all the way through the box - there is an inner floor that they are bolted to.  The inner floor is then bolted to the outer floor to keep everything in place.

So - I think I can start interconnecting cells safely now.  And then to re-energize the controller, the DC-DC converter, the voltmeter, and the new charger...