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[Shop-talk] battery tender

Subject: [Shop-talk] battery tender
From: racertod at racertodd.com (Todd Walke)
Date: Sat, 09 Jul 2011 14:56:20 -0700
References: <1b4b3f31.18fae9.1310eea95e8.Webtop.47@charter.net> <1b4b3f31.18fae9.1310eea95e8.Webtop.47@charter.net>
Bob wrote:

>Overcharging--charging at too high voltage--will cause a lead-acid battery 
>to vent hydrogen gas

         I have personal experience with this.

         15 years ago I bought a used Chevy van for work.  The previous 
owner must be a hunter or fisherman who camped in the vehicle 
regularly.  He had installed a 2nd battery in the far left rear corner of 
the cargo area for 12v accessories with the vehicle off.  There was a 
battery isolator up front with a wire running from it back to this 
auxiliary battery.

         So three days after buying the van, I'm driving around when I 
smell an odd smell.  I've been wrenching on cars for years and I knew all 
the usual car smells - burnt electrics, melted v-belts, hot fluids, 
overcooked brakes, etc.  This was none of them.
         I pull over to investigate.  I get out of the van and pop the 
hood.  Can't smell the odor outside the van at all.  I get back inside and 
I can smell it.
         I then notice that with the engine now off I can hear a soft noise 
in the back of the van.
         I exit the van and open the rear door.
         The auxiliary battery is boiling.  I mean BOILING.  It had a 
semi-translucent case and I could see bubbles in the acid.  The noise was 
the sound of boiling battery acid.  So I was driving around with a van full 
of hydrogen gas.  One spark and I'd have been a rolling mushroom cloud on 
the freeway.
         You never saw someone grab a wrench and disconnect a battery so fast.
         Don't know if it was the alternator or isolator that was the 
cause.  I disconnected the whole isolator system but the alternator died 
two days later anyway.

         Bottom line: overcharging really does cause out-gassing.  And I'm 
here to tell the tale...

Todd
Seattle,WA
'86 GTI, Red of course. (exciting racey car) 273,000 miles
'01 Golf TDI, silver.   (new work car)       292,000 miles
'87 Golf, Polar Silver. (retired work car)   654,000 miles <- Gone to a new 
home :(
http://www.pureluckdesign.com <-Ferrari & VW stuff

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