Wednesday, April 6, 2011

Green Stuff - a Cautionary Tale

2011 04 06
Too windy to paint, too cold to sit still.  Time for a movie

The Red  Top Optima Starting Battery was not the problem as it turned out.  
The board is our battery retaining system intended to stop the battery 
from crushing anyone sleeping in the quarterberth in a deep roll.

This is the post that I intended when I expressed my opinion on the "separate starting battery" issue.

Last December, before I had thought through the issue of whether keeping a separate starting battery was a good idea, we purchased and installed a new Red Top Optima starting battery.  Within a week of its purchase the battery appeared to quit working.

When the engine ignition key was turned to the first stop the fuel pump would run, the panel would light up, everything running in good order.  When the key was rotated to the starting position everything shut down.  Nothing happened.  The panel which had at the first stop exhibited such exuberant multihued life turned black and sat before me like a dead toad.

It seemed obvious the battery was defective.  It could provide the 3 or 4 amps needed to power the fuel pump and panel but when called on to supply the huge amount of current needed to drive the starting motor the battery could not do its job.

Having learned not to rely on the obvious we ran some simple tests before returning the Optima for replacement.

In running the tests we discovered the true source of our starting woes was deep set corrosion in the battery cable that led from the start battery to the start motor.

We found the problem by shorting out each element in the starting system.  First we shorted out the battery switch to see if were the contacts in that switch.  It was not the switch.  Next we shorted out the ACR - the charging relay that ensures both start battery and house bank are charged according to their needs and that ensures the two battery banks are kept isolated from one another - so the house bank cannot drain the start battery.

When the BC turned the key with the ACR shorted out the engine started easily.  AHA.

No.  Not AHA.  Rather HMMMM?  I removed the short from the ACR and had the BC turn the ignition key once more.

This time I saw sparks.  Many sparks.  The start motor did not turn but the huge battery cable that connected the starting battery to the ACR was shooting a shower of sparks.  This was not good.

The cable was totally sealed and had been "professionally made up" by a mechanic.

 With sparks issuing I had no compunction about cutting into the battery cable insulation and taking a look.  To the right is a somewhat blurry shot of what I first found.  The cable is reduced to less than half its original diameter because many of the individual strands of copper which are woven into the cable are severed.

The battery cable, size 2/0, costs $16 a foot at West Marine so cutting into it can be daunting.  Sparks trump daunt however.

You can see there is a very damaged end hiding under the shrinkwrap insulation.  Having opened up the cable at the connector a lot of green was visible on the copper strands.  Green is nice on a copper roof.  Nowhere else.  I started cutting back insulation.

Here is some of what I found.

The green was corrosion of course.  Despite its great size the cable was so corroded that it could not carry the current needed to run the start motor.  The problem is that when this happens the cable itself heats up.  This cable was so degraded that it was shooting sparks.  Fire was not too far behind.

The corrosion was so bad it fell off the woven strands of the cable in piles as you can see on the white paper.

I had to cut back almost 8 inches of insulation to find cable with no green corrosion and at that the strands were still black and suspect.  The cable was thrown out and new cable and connectors purchased at West Marine.

This time we did not use the professionals.  We did it ourselves.

Instead of a nice zero cost replacement of our starting battery we found ourselves spending a couple hundred dollars on new cables and connectors.

Cheap at the price.  How lucky for us.

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