[Public-List] Bizzare electrical problem

Tue Apr 9 20:55:05 PDT 2013

As followup to my weird electrical problem, today I inspected the batteries and starter system. Interestingly both batteries were wet on the outside of their cases, and they were sitting In some small pool of water in their battery cases.   Assume this is due to condensation somehow working its way up from the bilge, although the rest of the FG'd areas in the battery compartment were not wet with condensation.  (I built new battery boxes under the cockpit floor two years ago when I rebuilt the cockpit.  There is no way rain water could have dripped in through the cockpit floor or hatch above.)

Q: So, thinking about last weeks earlier comments on the list,  can wet batteries sitting  in smallish pools of water (>1/4 cup) somehow cause sufficient impedance in the electrical system to semi melt coax cable attached to the backof a VHF radio, when the engine is started ???  This seems beyond bizarre! 

As FYI, my battery ground and positive cables and connections are in good visual shape, some slight corrosion on the engine ground, (such as one would expect from one year of service); look  like new on the battery terminals.  The batteries are new AGM deep cycle I installed last spring.

The  battery ground, on the engine, had two or three years normal corrosion on the grounding bolt, not bad looking.

 I started the engine once with each battery with no ill effect on any wiring in the general area of the engine, including the radio antenna, so again could not duplicate the overheated wire condition.

Verified that The pushpit is not shorted or grounded to any electrical circuit, but is grounded to the emergency VHF antenna via clamps that attach the antenna to the structure.  I am going to find some insulated clamps to,replace the hose clamps I presently use to attach the antenna to the stanchion.

I guess my next step will be to remove batteries and starter and go have them bench checked.  Also will remove the engine ground, clean and reinstall.  

A lot of trouble to do this as the starter is mounted on the lower back (port) side of the engine, behind the alternator.  doable, but a major pain  unless performed under nice 80 degree sunny weather conditions and preemptively fortified with some high grade of chocolate and dorito rancho cheese  snacks to a-swage the usual bursts of rage and doom which broach forth when the alternator bolt or the one usable  wrench  slips out and tumbles into the bilge.

Gpb

Sent from my iPad

On Apr 7, 2013, at 6:16 PM, n4lbl <alan.schulman at gmail.com> wrote:

> I'd be really interested in the quality of the starter battery ground.
> On Apr 7, 2013 2:09 PM, "Glennb" <brooks.glenn at comcast.net> wrote:
> 
>> Yep, thats kind of what I though.  So far as I know, the hull was dry,
>> except for sitting in the water at the slip.  iam going to go check for a
>> short or ground to,the pushpit tomorrow. Still amazed a heavy gauge
>> shielded coax cable would heat up three feet away from the radio as well as
>> the back side of the radio, with no damage to any of the much smaller
>> ground or positive wires leading to the  radio, or nearby parts of the
>> wiring system...
>> 
>> Maybe iam thinking along the wrong lines.  Perhaps the impedance ran up
>> the radio ground wire from the negative bus to the back of the radio,
>> thence started to cook the coax? The radio,itself still works and only the
>> heat sink on the back and rear part of the frame was hot.  Maybe had
>> nothing to do with the pushpit - which i still believe is isolated from the
>> electrical system, except for the emergency antenna clamps.
>> 
>> Still Weird!
>> 
>> Glenn
>> Dolce 318
>> 
>> Sent from my iPad
>> 
>> On Apr 7, 2013, at 12:23 PM, Gordon Laco <mainstay at csolve.net> wrote:
>> 
>>> The glass in the hull can't carry a current, but moisture on it
>> certainly can.
>>> 
>>> On 2013-04-07, at 1:53 PM, Glennb <brooks.glenn at comcast.net> wrote:
>>> 
>>>> I can see stray electrical currents, but can fiberglass hulls conduct
>> enough electrical energy to heat coax antenna cable to the melting point???
>> Never thought that was possible.
>>>> 
>>>> Btw,  i havent looked into the battery compartment yet - under the
>> cockpit behind the engine- but everything is new back there this past year.
>> Plus I did hose off the engine last spring as part of a serious cleanup
>> following a lot of FG and wood sanding .
>>>> 
>>>> Gpb
>>>> 
>>>> Sent from my iPad
>>>> 
>>>> On Apr 7, 2013, at 8:54 AM, n4lbl <alan.schulman at gmail.com> wrote:
>>>> 
>>>>> That was true, but,,,,
>>>>> 
>>>>> http://www.thebatteryterminal.com/TechTalk_Batteries_on_Concrete.htm
>>>>> 
>>>>> http://www.snopes.com/autos/techno/battery.asp
>>>>> 
>>>>> 
>> http://www.cartalk.com/content/business-batteries-and-concrete-floors-needs-be
>>>>> 
>>>>> 
>>>>> On Sun, Apr 7, 2013 at 9:19 AM, Don Campbell <dk.campbell at xplornet.ca
>>> wrote:
>>>>> 
>>>>>> That is the quickest way to drain a battery that sits without being
>>>>>> recharged,  and if you set a battery onto concrete,  this is the way
>> charge
>>>>>> is lost to ground, i.e. through condensation between the battery and
>> the
>>>>>> concrete. By setting the battery onto a piece of wood,  that breaks
>> the
>>>>>> continuity of the water film and so maintains the charge in the
>> battery.
>>>>>> 
>>>>>> Don
>>>>>> On 4/6/2013 2:31 PM, Gordon Laco wrote:
>>>>>> 
>>>>>>> That's good advice.   I once had a shock (pun intended) when I
>> casually
>>>>>>> touched the probe of a multimeter to the inside skin of my boat
>> while the
>>>>>>> other probe was touching the SIDE of one of my batteries.    There
>> was a
>>>>>>> slight current.    I noticed everything was damp with condensation.
>>  I
>>>>>>> dried everything I could reach and was able to kill the stray
>> current, at
>>>>>>> least so far as my meter could detect.   If ever there was a good
>> reason
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