Battery Voltage Drop

tjar

tjar

.
Aug 8, 2011
166
Hunter Legend 35.5 Tacoma, WA
I used to be able to run my refrigerator on the batteries for about a day and a half before I had to worry about recharging. But, lately I've noticed the voltage dropping below 12 volts with the refrigerator running. I chalked it up to my old mismatched batteries finally wearing out, so I sprung for a new set and installed them over the weekend. After charging overnight, we went for a sail and after a couple of hours the voltage was again reading below 12 volts (I don't recall the amps, but don't think they were excessive). Turning off the refrigerator brought the voltage back up to around 12.8 volts.
My assumption is that I must have some corroded connections in the system and I will chase them down this weekend. I've looked online for suggestions, but can't seem to find anything that addresses these symptoms. Am I on the right track to suspect corroded connections? How much of a voltage drop is normal when running loads like a refrigerator?
 
D

dlochner

.
Jan 11, 2014
12,945
Sabre 362 113 Fair Haven, NY
Checking the connections would be the first step, especially for the refrigeration. I would also be suspect of the refrigerator drawing too much current because something is failing. Do you have a clamp on multimeter that can measure the refrigerator's current draw?
 
Davidasailor26

Davidasailor26

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May 17, 2004
5,676
Beneteau Oceanis 37 Havre de Grace
Where are you taking your voltage measurements? If you're measuring somewhere other than the battery terminals then your readings will be affected by voltage drops in the wires, which will be worse if there are bad connections. If you're measuring directly on the terminals then any bad connections won't make a big difference.
 
J

JohnShannon

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Jan 4, 2010
1,037
Farr 30 San Francisco
could it be that the frig needs more AH then before? Like maybe it is low on freon or something?
 
tjar

tjar

.
Aug 8, 2011
166
Hunter Legend 35.5 Tacoma, WA
Thanks for the suggestions. I've just been reading the voltage from the onboard monitor, not sure where it's hooked up. I just notice that the voltage reading drops significantly when I turn on the fridge. I will take the multi-meter this weekend and perform voltage drop tests along the circuit.
It's also possible that the fridge is drawing more current then it used to. I will need to get a clamp on meter for that test.
 
bawlmer

bawlmer

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Sep 15, 2013
708
Catalina 270 Baltimore
Your connections between the batteries and the fridge are probably good. The fact that your fridge is able to draw more current then usual means a problem in the wiring did not develop. My guess is something in the fridge is causing it to draw excess current. I would definitely go with the current clamp and compare it against the factory specs. Best of luck!
 
D

dlochner

.
Jan 11, 2014
12,945
Sabre 362 113 Fair Haven, NY
Stu Jackson said:
You may not have a problem at all:

Breaking in New Wet Cell Batteries: http://c34.org/bbs/index.php/topic,6353.0.html
Click to expand
The link referenced in Stu's post on the C34 site leads to a primer on batteries and their care and feeding. However, it is on the Way Back machine because Ample Power is no more.

Here's a copy of that article in pdf form. After skimming it, it is now part of my boat manual.
 

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