Date: Fri, 03 May 1996 20:50:13 -0700
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: jwakefield@4dmg.net (john wakefield)
Subject: Re: 87 Vanagon: 3rd choice for gauge
Jim Davis said "A voltmeter doesn't give you quite the information of
the ammeter," and seemed to feel that it doesn't offer the wealth of
information that an amp meter does. I've changed my mind over the years
on that comparison. The one thing that an amp meter does better than a
volt meter is, clearly show just how "active" your battery(s) are/is. An
active battery (connected group of cells as recently well instructed) is
able to accept and deliver current at a high rate. Now if you have a
pint sized motor (eg. VW) spinning it with the starting motor requires so
little current compared with what's typically available with modern
batteries, that even a tired bat near the grim recycling center, can spin
it quite convincingly. But when the motor starts, an active battery will
briefly pull current like mad as it reestablishes it's ion balance. As
you watch an amp meter, the tired one accepts the recharge visibly
slower. So the amp meter's main claim to great utility lies in revealing
battery condition, not that of the charging system.
Now the volt meter offers a better pallet of information for the Westy
owner. First of all, the charging system's voltage is its best single
indicator as to it's condition. After a long cold cranking period or
hours of motor-off coach electrics load, if it can't pull 13.8 volts very
quickly against the load of a hungary active battery, you know it's not
able to deliver the current it should. So in this round about way, it
reveals current delivery. But there's more. After a long parked
motor-off coach electics drain period, you may have concerns as to having
enough power left to restart in the morning. Faced with killing the TV
late at night while absored in the plot just to save the battery,
restarting the motor to recharge for a bit while irritating your
neighbors, or taking a chance, the amp meter is as instructive as your
speedomenter. But the volt meter tells you EXACTLY what percentage
charge is left in your battery. I don't have the chart before me, but
it's often published. The better photo cell energy books always include
it. My books on that topic are at another place of mine over a thousand
miles away, so somebody please post this chart data showing voltage vs.
percentage charge.
I vote for the volt meter, no contest.
How many of you have elected to run a second "coach" battery, isolated
with the standard diode/heat sink package sold at RV centers? Three
potential locations are the two wells behind the front seats, and the
large cavity to the right of the motor compartment. I have an inverter
ready to pop in, but it's wave shape has nasy vertical walls. I didn't
know that when I bought it, and running electronics with it may be a
marginal case. Any inverter equiped Westys?
John
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