[RE-wrenches] Hidden corrosion caused catastrophic battery system failure
Ray Walters
ray at solarray.com
Sat Jan 21 17:29:54 PST 2017
When I'm evaluating an old system, one thing I do is really yank on all
the battery connections. If it turns, tighten it down, and in several
cases, the cable just pulls loose from the connector. They are time
consuming to do right. Cable has to be stripped long enough, the
crimper needs to be set correctly, and be the right crimper for the
particular lug.
Below is an example of:
the wrong cable (THHN, not X Flex)
Not enough cable stripped
Wrong Size Lug
Not Crimped Properly
Not Vaselined
Now let's put 150 amps continuous through that garbage and see if we
have some long term issues......
R.Ray Walters
CTO, Solarray, Inc
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 1/21/2017 3:16 PM, Dan Fink wrote:
> Last weekend. 3-year old, 24v battery bank, series/parallel.
> 6v Trojan L-16 in an 8-battery bank, one battery on one string showing
> 4v. Negative end of string. Replaced the one upstream of it last
> summer, same problem. Aha! I say, and folks here on the Wrenches list
> (including me) complaining about Trojan cell failures, factory defects
> (I've had one too) and that the battery on the negative end fails
> first. Darn you Trojan. Up your game.
>
> 3yr - 3yr - 3yr - 3yr
> 4v - new - bubbling - 3yr
>
> So as I am disconnecting this string so the homeowner has at least
> half a battery bank, I can hear the next battery upstream of the NEW
> one bubbling, with no power in or out, system shut down. Didn't need
> the thermal imager this time, we could feel it was hot.
>
> And, as we are doing this disconnect and pulling off interconnects,
> the cable between the 4v battery and the new one pulled right out of
> the ring terminal lug. Bad crimp. Cause of problem now known. These
> were factory interconnects purchased from AltEDirect.com.
>
> Never again...I have the tools to make up interconnects and do it on
> small projects, it's just they are so time consuming to do right
> (crimper, glue-melt heat shrink, etc) that it costs me more in labor
> (unless I have student interns working for free) than buying them from
> AltE.
>
> That crappy crimp cost my customer 3 Trojan L-16s. I have notified
> AltE. They should be ashamed.
>
> I believe it was Mr. Tom Duffy, SolarBiz, on this list who pointed out
> during the Trojan thread that cell failures were rare, most failures
> are due bad connections. I've had a real cell failure (Trojan J185)
> but in this case, Mr. Duffy was spot-on.
>
> Best regards;
>
>
>
> Dan Fink
> Adjunct Professor of Solar Energy Technology, Ecotech Institute
> IREC Certified Instructor™ for:
> ~ PV Installation Professional
> ~ Small Wind Installer
> Executive Director, Buckville Energy
> NABCEP Registered Continuing Education Providers™
> 970.672.4342 <tel:970.672.4342>
>
>
> On Sat, Jan 21, 2017 at 7:54 AM, cwarfel
> <cwarfel at entech-engineering.com
> <mailto:cwarfel at entech-engineering.com>> wrote:
>
> 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 <tel:%28802%29%20371-8678> cell
>>
>> 802-888-4917 <tel:%28802%29%20888-4917> home
>>
>>
>>
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> --
> Christopher Warfel, PE
> Entech Engineering, Inc.
> 401-466-8978 <tel:%28401%29%20466-8978>
>
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