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Discussion Starter #1
Hi Everyone:

About a year ago, I replaced my 2 lead-acid house batteries, and 1 lead-acid starting battery with 3 AGM house batteries, and 1 AGM starting battery and a new battery charger. The refrigeration unit used to work fine when sitting at the dock, and when underway either sailing or when the engine was running.

Now, when at the dock, the refrigeration compressor keeps cutting out with a under voltage LED flashing, and the ice box doesn't stay cold. When motoring out of the marina, the refrigeration unit works fine. When at the dock, the house battery bank registers in the 12+ volts range, and the voltage meter monitoring the engine alternator shows about 14 volts when the engine is running.

The battery charger is also supposed to act as a Power supply when at the dock, so it appears to me I have a voltage setting issue or excessive line loss somewhere, or the guy who wired up the new batteries missed something. Any suggestions on where to start looking?
 

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Where to start? Get a good digital voltmeter, and put the +/- probes as close as you can get to the compressor, to check the voltage at the actual connections in to the compressor.

Make the same check across the terminals of your house bank. Notice I said TERMINALS. The actual plug things sticking out of the batteries. Not the battery cable clamps.

If there's a substantial difference between the measure at the compressor and at the batteries (more than about 0.4 Volt UNDER LOAD), you've got a voltage drop which is probably due to undersized wiring or corrosion in the connectors (bet on the corrosion). There's often a big voltage drop from the terminal to the clamp. Check for that.

If there's not a substantial drop, suspect that your (new) batteries are somehow bad. Assuming there was no load on the house bank, "12+" volts is not very good for a fully charged battery bank "at rest".

Good luck.
 

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the pointy end is the bow
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Larry gave good advice. AGM batteries require a different charging voltage from deep cycle lead acid batteries and the newer fancy three stage chargers should have a setting to tell the charger what kind of batteries you have. Is that the way it is in your case? Wonder if the batteries got toasted?
 

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Discussion Starter #4
When I had the new batteries added, I had the charger changed out as well, and it is programmable and is set to AGM according to the LED indicators. All the battery bus wiring to the selector switch in the cabin was replaced as well. I wonder if the battery charger's "Charge voltage" could be set too low, even though it is set up for AGMs. I have a digital multimeter and know how to use it, so I guess I will just follow the voltage path and see what is up.
 
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