Cor van de Water via EV wrote:
when I first installed my 312V pack... I wanted to give them some charge...
Apparently I got confused because when I decided to close the loop with my
multimeter
set to Amps to verify how fast it would charge, there was a flash and a loud
BANG...
from shorting it across 600+VDC.
I've had my share of "educational moments" as well. :-( This is an
effective way to separate the cheap meters from the good ones. A good
meter will have fuses and other protection to avoid just this sort of
"short circus" (another Bob Rice-ism). So I have several damaged cheap
meters... but my old Simpson 260 and Fluke 2010 have withstood
everything I've done to them.
On charging backwards: When a lead-acid battery is run totally dead, it
becomes almost an open circuit. The electrolyte has turned to water, and
the two plates are both lead sulfate. Connecting such a battery to its
charger backwards will simply charge it in the reverse direction! What
was the positive terminal becomes the negative terminal, and vice versa.
But the battery works poorly this way. The plates aren't optimized to be
used like this.
If the battery is *not* dead when you connect a charger in reverse, the
battery voltage and charger voltage fight it out. The charger says
"positive", but the battery shouts "NEGATIVE"! The battery is usually
stronger, and wins. It *forces* the chargers's output voltage to the
wrong polarity. This forward-biases all the rectifiers in the charger,
and some enormous current flows. If the charger doesn't have an output
fuse, then KABOOM goes your charger. This is why output fuses are pretty
much mandatory in battery chargers.
--
"Where's the kaboom? There was supposed to be an Earth-shattering
kaboom!" -- Marvin the Martian
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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