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Gotta be a short!

 
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DSigmond



Joined: 09 Apr 2016
Posts: 5
City/Region: Bainbridge Island
State or Province: WA
PostPosted: Tue Jul 09, 2019 12:00 pm    Post subject: Gotta be a short! Reply with quote

My 22 Curiser is fairly new to me, and I'm a really happy newbie.

The two year old batteries would go flat in 48 hours, so I plugged in the shore power, everything seems turned off, so I'll let the charger "float," and all is well.
Then the start batttery got really hot when I'm away for a week. I suspect a bad cell, refill the water, I can stall for a bit.
Came back to the boat, unplugged shore power, switched the Perko to All, 5 minutes pass, and smoke is roiling out the battery box. The Perko is deep on the far side of the battery -- inaccessible, but I got the lead on the battery unscrewed and off. Whew.
The Perko melted at both contacts. #2 wire to battery melted all the insulation, nothing else!. No char or melting or apparent heat anywhere else. Other battery is fine.
What happened? What's the circuit? What's the ground?
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bridma



Joined: 13 Sep 2011
Posts: 1050
City/Region: Comox
State or Province: BC
C-Dory Year: 2009
C-Dory Model: 22 Cruiser
Vessel Name: Nomad
Photos: Nomad
PostPosted: Tue Jul 09, 2019 12:54 pm    Post subject: Reply with quote

I do not attempt any fix that can endanger life or my boat unless I am 100% sure I know what I am doing.
Me personally, I would bring in a marine electrician, check the system and change both batteries. Then sleep assured that all is well as you start from day one with your new to you boat.

Martin.
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Sea Wolf



Joined: 01 Nov 2003
Posts: 8632
City/Region: Redding
State or Province: CA
C-Dory Year: 1987
C-Dory Model: 22 Cruiser
Vessel Name: Sea Wolf
Photos: Sea Wolf
PostPosted: Tue Jul 09, 2019 1:20 pm    Post subject: Reply with quote

As a Wild Ass Non Scientific Guess (WANSG), without further experimentation and testing, I'd guess you have one battery that is internally shorted out (bad cell with + & - lead plates touching) that is causing the other battery to discharge into it and boil the electrolyte in the shorted battery when you connect them in parallel with the Perko switch on "All".

Boiling / steaming sulfuric acid a is a foul, dangerous customer that can cause both severe chemical and heat burns. Avoid it at all costs.

I'd second bridma's advice above and be safe. Get not only two new matched batteries, but an electrician to check out your circuitry and replace any faulty elements after your experience, like the Perko switch and cable ends as needed.

Good Luck, circuits, and batteries!

Joe. Teeth Thumbs Up

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Lake Shasta, California

"Most of my money I spent on boats and women. The rest I squandered'. " -Annonymous
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thataway



Joined: 02 Nov 2003
Posts: 17248
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Tue Jul 09, 2019 2:29 pm    Post subject: Reply with quote

Definitely a short---but it is not clear where. Did you do any change in the wiring? Have you moved any wire? Generally a badly shorted battery will not take a charge.

Obviously one battery is destroyed--and will have to be replaced--as well as the Perko switch...and wiring. Also there should be a circuit breaker or fuse within 7" of each battery--the only exception is the lead to the starting motor. Do you have this fusing? (should be before the Perko Switch..

Were both batteries going flat in 24 hours with the Perko switch off? When you put in a new switch--make sure it is someplace you can get to it, without endangering your hand, arm, face, eyesight or life!

This can and should be a learning session. If you don't already own a volt meter, buy one now and learn how to use it. After the batteries running down was discovered, the first thing to do, would be to determine what the item was which was causing the batteries to drain rapidly--this may be a clue to what has happened, and it may be the cause of the ruined battery--rather than the other way around....

Batteries should be at about 12.6 to 12.7 volts at least fully charged. Generally you should not discharge a battery to less than 12.2 volts (steady state at rest; this means no current draw, at the time, and no charging or discharging for 30 minutes before the measurement. I prefer to monitor the batteries with a meter such as the Victron 702. It gives voltage for 2 batteries, and amps in and out state of charge for the house battery. That alone can help to solve issues before they begin.

The reason to DIY, at least diagnostics, is that you may be in an isolated area and have an electrical issue. Beside the volte meter (and I also have a clamp over the sample amp-meter which will read up to 400 amps on both AC and DC. resistance, as well as low amperage--the usual amp meter has to change the shunts (different plug in for the red lead) if over several hundred milli amps [0.200 amps], and the other shunt is only good for 10 amps. When testing current, I first use the clamp over the wire amp meter on 400 amps--and be sure it is less than 40 amps--then I switch the scale to 40 amps. If it suggests that the current is less than 10 amps, then I go to the leads, because it will be more accurate, and you can go way down of current draw, looking for instruments which have "phantom" or a constant draw, even when the instrument is off. This may be only 10ths of an amp.

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Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL
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