1994 US Electricar Repair Blog by Mike

The UK boards arrived today. The parts will get ordered soon. The 3
Thundersky cells are installed and running in the pack.

So about 11 nicads were pulled and the 3 Thundersky 40ah cells were
installed with a temp monitor on the middle cell. So far it’s running
cool on neighborhood and highway drives.

The last of the bench testing of the 3 Thundersky cells took place
today. At a 40 amp and 55 amp load they are close to 100% of their
rating. This also implies a low Peukert factor.

The cells are grouped together from Thundersky with extrusions at each
end. The screw heads stick out enough that it would surely puncture a
nicad. So tonight I drew up a 1/4″ thick plastic panel that will fit
over the cells ends and cover the screw heads. Tomorrow I hope to
machine a couple of them. Then about 12 nicads have to come out of the
pack to make way for the group of 3 Thundersky cells. Then I have to
make up some thick spacers to make sure the Thundersky’s and the
nicads are packed in tight.

I plan to install the Thundersky’s discharged about 10% so it will be
hard to overcharge them for the first drive/charge test. Drives will
be with temperature monitoring while driving aornd the block, then
around the neighbrhood, then on the freeway.

The BMS boards are only bypassing .50 amps. I’m going to modify them
to bypass something like 1-2 amps for a margin of safety. I sent the
designer a note asking for a part number of the transistor. I’d prefer
a fet. But the trigger voltage available is only around 4.0 volts.
Maybe a logic level fet would work ok.

These cells will be a good test of the various BMS systems that are
here already and some others that are on their way.