I'm no battery expert but I'm an electrical Engineer.
What you saw I think is capacitance.
Did you have the positives both hooked up to any sort of battery switch or
some other device?
Were the negatives still disconnected?
That could explain that.

Typically, when I'm working with electronics boards, a voltage measurement
that starts high then drops is due to a discharge of a capacitor. A volt
meter has a resistance to it (usually pretty high for a digital meter).
Likewise, if you are measuring resistance, the meter is putting out a
voltage, so capacitance will affect any resistance measurement.

Thats my 2cents worth.

David

"Charles T. Low" wrote in message
...
I am taking the "bold" (for me) step of leaving my two batteries in the
boat
over the long, cold Canadian winter, a common practice, based on the
theory
that a good, well-charged battery won't freeze, and if it does, it wasn't
good and should have been replaced anyway. Furthermore, keeping it cold
should prevent it from self-discharging as quickly as it would in a warm
place.

So, I disconnected the negative leads (which sounds backwards, but that's
what many pros do), turned the switch OFF, and tested the voltages with a
digital multimeter. This was after an hour or so off the trickle charger,
which has been on for weeks. The water levels are fine.

One battery, my new-this-season deep cycle, read 13.45V. The older one,
the
starter battery, said 13.33V. These, of course are resting voltages, and I
realize not as valuable as voltage under load, and I didn't test the
sg's -
I may still do that. (Although my deep cycle batterry which failed
mid-season had had good sg's until it died, then they went way south in a
hurry.)

However, the thing which really puzzles me is that when (for some reason)
I
tested the voltage between the positive and negative posts of the opposite
batteries, i.e. neg on battery one and pos on battery two, and vice versa,
there was a momentary reading in the 5V range, which within a split second
dropped to 1.5V, and from there plummeted. I watched it down to about
0.6V,
but it was still dropping rapidly.

If I let them rest for a minute, the same sequence would repeat. So, I
disconnected the positive leads too, and wiped off any dust and grime from
the battery surfaces, but the same thing kept happening.

Any explanation? I doubt very much that it indicates any kind of a
problem.
But I'm not sure. Mainly, however, I'm curious and puzzled. Thanks in
advance.

Charles

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Charles T. Low
- remove "UN"
www.boatdocking.com
www.ctlow.ca/Trojan26 - my boat

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