First Faux Pas
Bill Dennis <ev1 <at> q.com>
2011-08-01 00:24:26 GMT
With the new battery pack in the MetroLectrical, I've been driving the car
to work this week to shake out the system. Until Friday, everything was
going splendidly. Then on Saturday, I was about half way to work and came
to a halt at a stop sign. When I stepped on the accelerator to start up
again, though: nothing. Car wouldn't budge. I took out the key, opened the
hood and looked around. Couldn't see anything amiss. So I got back in the
car, inserted the key, and would you believe it: the car took right off.
"Wow," I thought, "must have been nothing"...until the I came to the next
stop sign, that is. Stopped, stepped on the accelerator to take off again,
and nothing. No contactor clack. No Curtis squeal. There I sat, dead on
the street, waving other motorists to go around me, heart racing, trying to
figure out what was going on.
Finally, it dawned on me what was happening. Just to get the car running
last weekend, I haven't installed the DC/DC converter yet. Instead, I put
in a string of four old LCP 90Ah cells as the 12v battery. When I installed
them, they had 14V. On Saturday morning, they still read 14V, about 3.5V
per cell. Shouldn't be a problem right? Plenty of charge left.
These cells are so un-stiff that the smallest amount of current was dragging
them down to a low voltage--too low to pull in the main contactor. But
after the car had rested for a few minutes, the voltage had recovered to the
point where it would pull in the contactor. Of course, once the contactor
as engaged, only about 6V was required to keep it closed.
So, I let the car sit for a few more minutes, then inserted the key, started
off, and drove back home, making sure I never took my foot off the
accelerator. Ran a changing red light or two, but made the 1700 ft. climb