12.5 V but no amperage?

[Wolfe10]

Absolutely check voltage at the refrigerator.


And, the usual symptom of bad battery(s) is that voltage drops rapidly with any load. No voltage drop and 12.5VDC suggests that the load is not well-connected to the batteries.

[Bill O]

If the batts are low on water, only add distilled water to bring them up. (also don't overfill)

[Shanachie]

You don't mention whether other electrical appliances are working.


If the lights turn on and the engine starts (presuming an inboard), the problem is limited to the refrigerator.



Commonly, problems such as this arise when the ground connection is bad. I once had my electrical system randomly flicker on and off because the main cable between the battery and and the negative buss came loose.


Another question: Is the refrigerator connected to the load connection on the solar panels? That would allow it to bypass the batteries and run directly off the panels.

[Zanshin]

@squaw999 - I'm in a similar scenario with my 4-year old 1200Ah bank. It's got voltage after charging but as soon as I've got a drain it drops down. I can keep the fridge going during the day with my 700W solar bank, but once the sun sets it drops below my pre-set fridge low-voltage cutout. I have a cheap battery tester from a car shop and this is probably your easiest test option. I'm about 700Km from a cheap battery source, but once I get to St. Martin I'll be replacing my bank.

If the system worked before, and you didn't change anything then Occam's Razor will point you to the batteries. Unfortunately, those are also the most expen$ive to replace.

Do you have a clamp ammeter on your multimeter? If you measure the amperage coming out of the battery bank when you turn on your fridge and it matches the published start-up figures, and the voltage at the bank drops and doesn't recover then that is another pointer to the battery bank.

[squaw999]

Originally Posted by noelex 77

You need to measure the voltage at the fridge itself as well.



The most likely cause of your problems is a poor connection between the battery and the fridge. If the voltage is low at the fridge (when the fridge is trying to start), but normal at the batteries it will confirm this hypothesis.

I will do that. I notices, when contact is poor, ventilator started but compressor not.

[MarkSF]

Do the batteries start the engine OK? If so, that would eliminate any internal problems.

It is possible for batteries to fail in a way where they will produce normal voltage without much load, but completely collapse when large current is demanded. But as I say, if they start the engine, they are fine.

Then you must have either a bad connection in the cabling, or a fault with the fridge compressor itself.

A bad connection, again could be Ok with small currents but cause a large voltage drop with a large current.

These kinds of problems led to my eventually replacing all the large gauge cabling betwixt the batteries and the loads.

[SV__Grace]

I might have missed it but how did you test your batteries?

If you test while they are connected to your solar panels they will show higher voltage than actual.

So first disconnect or turn off any charging sources, test their normal resting state, then do a load test by turning on anything that has a significant draw.

Then disconnect the batteries at their terminals then put a meter on each one the batteries. Are they the same? You might find one that is significantly lower and creating a problem for the bank.

Then, if you can, disconnect one or all and let sit overnight and test in the morning- a good battery won't change just sitting overnight.

This is how I diagnosed a bad battery in my 1200ah battery bank of AGMs. Since the batteries have to be matched I couldn't just replace it, so functioned with 800ah until replacing the whole bank with lithium.

[fireant]

First check your batteries, a fully charged battery should be at 12.68 volts.
A12.5v battery is at 50% charge. Check to Make sure your charging voltage is good, min 13.8v. if you have bad connection, you might find that the battery is not being charged.
if you don't have the proper load tester, follow SV Grace test it will work.
Repair anything that is not up to specs. When you mentioned battery at 12.5v it shows a problem right there. just need to find a cause.

after you make sure batter and charging system up to specs. Test your electrical again. If problem is gone great if not use a voltage drop test.

https://www.youtube.com/watch?v=APLic9F7ZsA

Its great knowledge to have to find. For practice is you are bored nothing to do just take a section of a wiring and test it. You might find future electrical problems.

Make sure you have a good voltmeter. You can get good ones for the boat for around $50.

[MVDarlin]

Test each battery with a load tester. Disconnect each battery first. It will quickly let you know if a battery is bad. It only takes one bad cell to drop voltage to 10.5 when a load is applied. $30 for tester on Amazon.

[beirutsailor]

Agree with all who say check battery connection, wire size, and voltage at the fridge connections. Compressors are very very sensitive to any poor connections, as the start up causes a surge in consumption which triggers a shut-off.
I was once told to change my "broken" compressor. The new one did not work either. Half a turn on the battery clamp, and all was fine. In the menatime, I had thrown my "broken" compressor in the dump. Still hurts today.

[Goodxcharly]

A new battery could do it and you aren’t out anything if it doesn’t work, new battery.

I had the same problem when purchasing my recent sailboat. Just enough amperage to start the motor but not enough to run the windlass.
So I replaced all 4 - 6 volt batteries and everything works great.
The 6 bolts were 5 years old so it was time.

[cr180]

Agree with others. All indications are that you have excessive voltage drop from batteries to fridge and low voltage cutout on fridge taking you out, or fan will start but not compressor. Have had both conditions occur on a Danfoss ( Secop) compressor.

Solved by running a dedicated #10 circuit off battery, with in line fuse and on off switch directly to fridge bypassing main panel.

[wholybee]

I think there are a few things going on, and some testing is in order. First, 12.5V is not a fully charged battery, and 12.3V is pretty low. So there might be some battery issues. Possibly a shorted cell, low water, or sulfated.

The fridge is going to typically need at least 11.5V to run. Maybe more depending on settings. So, the difference in wire size/voltage drop could very well be a factor. It could be that with good batteries (12.7V) it would run fine. But also, that with larger wires it might run fine with damaged/worn batteries.

10AWG wires should be a minimum. I ran 8AWG. I have found that with a higher voltage to the compressor, not only does it cool better, but it uses less power to do so.

So, I would address both those issues, performing a thorough load and capacity test of the batteries, and increasing wire size. Even if addressing one seems to fix the issue, you might be setting yourself up for future issues if you don't address the other as well.

[Disailor]

12v measured at appliance but no amperage has always been the result of a corroded connection in my expsriences.