[RE-wrenches] Hidden corrosion caused catastrophic battery system failure

[cwarfel]

Hi David, do you have any pictures of this that could be shared?  Chris


On 1/20/2017 12:52 PM, Dave Palumbo wrote:
>
> Following is an entry from a Backwoods Solar email that I received 
> today. I would like to share this as a teachable point for RE techs 
> not familiar enough with proper battery bank care and as a reminder 
> for those of us with years of storage battery experience.
>
> I have underlined the two issues in the Backwoods email copied below 
> my bullet points to highlight the teachable issues.
>
> ·Checking wiring connections: Check not only for tightness but also 
> for temperature. There are two simple methods that work well: #1) Use 
> an IR Thermometer to ensure all connections are of a similar moderate 
> temperature. #2)  Use your fingers to check temperatures. I'm 
> practiced at this second method because inexpensive IR thermometers 
> were not available when I began to care for storage batteries. I 
> simply use my bare fingers (with a light coating of petroleum jelly) 
> to wiggle test each battery cable at the battery terminal. Fingers are 
> sensitive enough to gauge proper temperature. I have easily found 
> several warm or hot connection points over the years caused by loose 
> or corroded hardware. Do this as preventive maintenance every time you 
> water the batteries or bi-monthly with sealed cells. Corrective 
> measures (tightening, or taking apart and cleaning, or replacing, and 
> reinstalling) are taken immediately when a warmer than usual 
> connection is identified.
>
> ·It is not recommended by most veteran wrenches to use any 
> "anti-corrosion paste" on the terminal connections. This has been 
> discussed a few times over the years on the Wrenches list. Most of us 
> have found that a thin coating of petroleum jelly (Vaseline is one 
> brand) does the best job of protecting against corrosion while still 
> allowing some visual inspection.
>
> from Backwoods Solar 1/20/17.  << This past summer Backwoods had a 
> visit from one of our retired co-workers, xxxxx.  While it is always 
> good to have friends visit, the circumstances for his dropping by were 
> less than ideal.
>
> A small, catastrophic failure had led to the loss of a battery bank, 
> two inverters, and a voltage converter.  Ultimately, the failure was 
> traced back to a single nut and bolt in the battery bank cable 
> connections, that had developed hidden corrosion over time. Corrosion 
> causes resistance to the flow of electricity, which in turn generates 
> heat.  With enough corrosion, and enough current flow, the amount of 
> heat generated can be sufficient to melt battery terminal connections; 
> which is exactly what happened in xxxxx’s case.  The melted metal 
> flowed between the negative and positive terminals of his industrial 
> battery, causing a high power short that was beyond the capabilities 
> of any of the circuit protection, resulting in the damage to the 
> equipment.
>
> Now keep in mind, xxxxx is one of the more detail-oriented people 
> we’ve had here at Backwoods.  The discipline of a military background, 
> along with critical thinking of an engineer, were still not enough to 
> overlook one very tiny detail.  xxxxx does his mechanical maintenance 
> on a routine schedule; _checking for tightness in wiring connections_, 
> cleaning accumulated spray off battery tops, cleaning out dust and 
> spider webs, _and keeping his battery terminal posts coated with 
> anti-corrosion paste._  This is not the type of person you’d expect to 
> see such a failure.
>
> So what happened?  It all boiled down to the battery terminal 
> connections.  What xxxxx had NOT done, was dissembled the nut and 
> bolts from the battery terminals and cables to check for internal, 
> hidden corrosion.  It had been about 6 years since he had done that 
> level of inspection.  When previously reviewed, the hardware had been 
> thoroughly inspected, cleaned, and re-assembled, and then coated with 
> _anti-corrosion paste on the exterior_.  In one of the 16 nut/bolt 
> pairs, a small bit of contamination or moisture must have been left 
> trapped inside.  Over the course of the next six years, the corrosion 
> grew, contaminating the entire connection; but was NOT visible 
> externally at all! >>
>
> Best regards,
>
> Dave
>
> David Palumbo
>
> Independent Power LLC
>
> 462 Solar Way Drive
>
> Hyde Park, VT 05655
>
> 802-371-8678 cell
>
> 802-888-4917 home
>
>
>
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-- 
Christopher Warfel, PE
Entech Engineering, Inc.
401-466-8978

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