Battery overcharging

J

John R

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Oct 9, 2012
110
Catalina 36 Emeryville
Yesterday, I took my Catalina 36 out. (Yes, here in the SF Bay we sail year round.) When I started the engine, I found that the house batteries were low and I had to put the switch on "both" to start the engine. (I checked, and the shore power seemed to have been turned on.) There was no wind so we motored for about an hour and a half, and the batteries were charging, starting at about 45 amps, down to about 25 by the time we got back. When I hooked up the shore power, it showed charging at around 20 amps. I figured something had gone wrong and the batteries would charge up over time.

Today, I got a call from a boat neighbor - the CO alarm was going off. When I got to the boat, I smelled sulphur gas and after a minute I found that one of the two house batteries (glass mat batteries, about 5 years old) was hot and was off gassing. The second house battery (bought at the same time) seems to be fine. Whenever I turned on the power, it would show that it was charging at around 20 amps.

Any thoughts on what the problem could be?
 
Skipper

Skipper

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Oct 9, 2008
1,739
Bristol 29.9 Dana Point
It's almost certainly the charger.
It's either gone plooey, wrong setting, or has a wire crossed. Or was never good to begin with, and finally cooked a batt.
What brand/model/age is the charger?

-or you could have a grounded pos wire, but that would show up on your draw. Plus other indications, like smoke :-O
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
22,770
Catalina 34 224 Maple Bay, BC, Canada
Or you have a dead battery. Take a look at each individual battery. Any signs of cases bulging? Disconnect them and check each individual one for voltage. Check the output voltage of the charger, too, when connected to a good battery.
 
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Maine Sail

Maine Sail

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Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
Sounds like a classic case of a failed/shorted battery... Remove the suspect battery and see if your charger returns to float after charging the other one..

What charger - Brand & Model?
What AGM's - Brand and model?
What dockside loads do you leave running?
What are the absorption & float voltages set to on your charger?
Does your charger have temp compensation?
 
Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
6,473
Hunter 310 West Vancouver, B.C.
Stu Jackson said:
Or you have a dead battery.
Click to expand
Almost guaranteed.

But before you throw them over the side, check to see what your charging voltage is (using a voltmeter) for the first hour or so of charging. This will give you a better idea if your charger has gone rogue.
 
J

John R

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Oct 9, 2012
110
Catalina 36 Emeryville
Thanks for all the answers and questions. I'll check it tomorrow (Sunday) and get back to you.
 
J

John R

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Oct 9, 2012
110
Catalina 36 Emeryville
Maine Sail said:
Sounds like a classic case of a failed/shorted battery... Remove the suspect battery and see if your charger returns to float after charging the other one..

What charger - Brand & Model?
What AGM's - Brand and model?
What dockside loads do you leave running?
What are the absorption & float voltages set to on your charger?
Does your charger have temp compensation?
Click to expand
My charger is a Xantrex 20+. The batteries -- oops, I forget to check, I think they're West Marine brand and about 5 or 6 years old. The only dockside load I leave running is a dehumidifier. As far as the charger questions: Sorry, but that's above my pay grade. I don't know about absorption & float voltages nor about temp compensation.

Finally, I tried to check voltages out with my voltage meter, but - I'm embarrassed to say - I really don't know how to use it properly, Here's a picture of the meter. Maybe somebody could tell me what settings I use for what and which terminals (on bottom of meter) I use for what. (I'm assuming the center - black - one is for the black/negative wire and the ones on either side are for the pos. wire, but which side I use for what I don't know.)

thanks in advance for your patience.
 

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J

John R

.
Oct 9, 2012
110
Catalina 36 Emeryville
I should add that I doubt it's crossed wires or wrong setting since nothing has been changed in all of that.

Also, two other bits of info:
1) None of the batteries were bulging or misshapen.
2) It still makes sense to me that it's a bad battery for this reason: A little while back, I was on the boat about 3 weeks after one of my boat partners had used the boat. I found that the main breaker for the shore power was off, which means that for 3 weeks or longer the batteries were going uncharged. I'm assuming that that means that they had been run down and, in fact, when I ran the motor it was charging at a pretty high rate for about an hour or longer. I'm thinking that this might have damaged the batteries, no? (I can't really blame the partner for sure because I don't know for sure if he left the switch off or if something tripped the breaker.)
 
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Ron20324

Ron20324

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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
[QUOTE="John R,... I'm embarrassed to say - I really don't know how to use it properly, ...Maybe somebody could tell me what settings I use ....[/QUOTE]

You should consider helping yourself by Goggling the meter to get an owners manual.
 
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Likes: John R
J

John R

.
Oct 9, 2012
110
Catalina 36 Emeryville
Ron20324 said:
[QUOTE="John R,... I'm embarrassed to say - I really don't know how to use it properly, ...Maybe somebody could tell me what settings I use ....
Click to expand
You should consider helping yourself by Goggling the meter to get an owners manual.[/QUOTE]
Good point. Will do.
 
whatfiero

whatfiero

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Oct 30, 2011
542
klidescope 30t norfolk
If you got 5 to 6 years out of a marine battery you lucky sounds like time to buy a new one
 
BarryL

BarryL

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May 21, 2004
1,007
Jeanneau Sun Odyssey 409 Mt. Sinai, NY
Hey
To use your meter to measure voltage you set the center dial to the 20 in the yellow area. This is for measuring DC Volts, up to 20 volts (you boat has a 12volt DC electrical system). You plug the black probe into the center COM plug and the red probe into the the plug on the right. Note that it has the yellow, red, green and dark gray print above it. The left plug is to measure AMPS (it's the same gray as the DC10A on the dial). Be sure to connect the black prove to the negative and red to the positive.

Some other notes for you: To measure AC volts (like you have at home or when connected to shore power) set the dial to the red 200 setting. If you want to check a lightbulb or for a broken wire use the gray setting just to the left of the DC10A. This is to measure resistance and it will beep if the light bulb or wire is good (connect the probe to both ends of a wire or to the + and 0 of the lightbulb.

Good luck,
Barry
 
A

alexco38

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Sep 25, 2008
1,096
CS 30 Toronto
If you don't know how to use a meter, may be it's time to get professional help like Maine Sail.
 
J

John R

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Oct 9, 2012
110
Catalina 36 Emeryville
alexco38 said:
If you don't know how to use a meter, may be it's time to get professional help like Maine Sail.
Click to expand
Yeah, except he's in Maine (I assume) and I'm in California. But I have contacted a marine electrician out here.
 
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