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Discussion Starter · #1 ·
Saturday afternoon, I had about 100 trip miles on the car and decided
to take it on down to measure the pack capacity again. The first ~100
miles was normal 40-65 mph driving; the last ~50 miles was around a ~8
mile loop of rural roads, speeds generally less than 30mph. Previously,
I had "measured" 300 ah and 280 ah.

This time, it was 281 ah, distance traveled was 147 miles. Recently
installed new tires are about 6.5% larger than OEM, so the trip was
more like 156 miles. This time, I used "empty" to be the point where
the low single cell voltage alarm went off at less than 100 amps.
Static pack voltage after the test was 138 (138/45=3.07 average cell
voltage); low voltage alarm goes off when pack voltage is 122-124v
(~2.73 average). In warm weather with the pack charged, the low
voltage alarm doesn't go off with normal peak draws of 500+ amps. In
cool weather (pack around 30-35 deg F), the alarm goes off as low as
300 amps.

The TBS meter history functions tell me:
average discharge 121.5 ah
deepest discharge 301 ah
total ah removed 31.3K ah
total ah charged 31.5K ah

Trips are clustered at 20 miles (~40 ah), 60 miles (~120 ah), and
90-100 miles (~200 ah). I've done more than 120 miles only to test
battery capacity.

1) I'm almost 1/3 (3 years) into the 10 year life of the battery.
2) I'm about 4% into the supposed 4000 cycle life (260 x .7 x 4000 ah)
of the battery.
3) Barring disaster, I hope for about 70K more miles in the remaining
life of the battery. That would be about 24% of the expected 4,000
cycles. The most service I could hope for (60 miles every working day)
is about 130K miles or about 36% of 4,000 cycles.

I've replaced about three of the cells. This seems to be come from
malfunctioning EVPower cell modules that allowed the cells to over
charge (and swell). The EVPower modules probably failed due to getting
zapped with high voltage on installation. That is, improper
installation. I've replaced perhaps 10 EVPower modules; they quit
suppling modules for 260 ah cells and I've started using miniBMS
modules as replacements. I've detected two EVPower cell module failure
modes: high voltage fails to trigger charger shutdown and shunting
continues at low voltage.

Willie, ONWARD! Through the fog! Linux registered user #228836 since 1995
Debian3.1/GNU/Linux system uptime 140 days 5 hours 56 minutes

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