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Old 07-27-2005, 03:01 PM   #1
Rivet Master
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1975 Argosy 26
1963 24' Tradewind
Seattle , Washington
Join Date: Aug 2002
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voltage at battery?

Just wondering if what I'm seeing is "normal."
Converter - Intellipower with charge wizard

Battery disconnected, 0 volts at battery cables with generator on or with tow vehicle connected.

New battery - 12.4 volts, with or without generator on (doesn't matter if in boost mode on charge wizard or not)

12 volt circut (measure at fuseblock and at chassis negative) shows a jump to 14.4 or so volts with generator on and boost mode on.

I'd suspect bad cables, but lights and stuff work with just the battery on.
(sorry for the duplicate type of post, but I don't think I have a feed line problem now)

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Old 07-27-2005, 04:25 PM   #2
Rivet Master
1975 29' Ambassador
Reno , Nevada
Join Date: May 2003
Posts: 1,351
You should never get 0 volts _at the battery terminals_

But you can get 0 volts if you are measuring the house side of a battery switch that has disconnected the batteries.

14.4 is a proper voltage for a bulk charge. This should drop down to 13.6 or so after a while. The Intellipower with charge wizard should drop down to 13.2 after completely charged and no battery drain activity.

The generator bit is a distraction. Whether you use a generator or some other 120 VAC supply to feed the intellipower makes no difference.

When you have the intellipower disconnected (no AC supply) and the battery is not being charged, the battery voltage will drop to under 13 volts. If your battery has more that 13 volts, it is connected to some external power source.

There are two primary indicators of 'bad' cables. One is that the voltage on the load side is quite a bit less than the voltage at the battery side of the cable (dim lights with good battery). The other is that a connection or something gets warm to hot. Switches and connections are where most battery cable problems (voltage loss) occur.

Battery voltage measurements for problems are often relative - battery terminal voltage to load terminal voltage comparisons. You can use Ohm's law to determine power loss to determine if you have a problem needing fixing.

To measure battery voltage to determine battery charge state, you need to drain off surface charges. 12.6 is usually considered a full charge and 12.2 at half charge.
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