Thanks Dave, This is all helpful. We do90% battery systems, and I need
to emphasize periodic maintenance. This will help. Chris
On 1/21/2017 10:52 AM, Dave Palumbo wrote:
Hi Chris,
I don't have any pictures myself, the Backwoods email included a photo
of a corroded bolt and a clean assembly which I've snipped and attached.
Off the Wrenches list I have had a conversation with another wrench
who shared his successful methods which I will share here.
<< The issue I remember from before on this thread was do you put the
material between the lug and post or outside of it?
And I’m not sure from the article if it was put on between or outside?
Personally I’ve done between and never had a problem. Yes I’ve seen
corrosion around the lug, but take the lug off and its clean.
Outside seals the corrosion in, inside prevents it from forming IMO.
However, if the bolt got lose, it would generate heat, which would
melt out any and all material, creating oxidation, more heat and away
you go to failure mode.
Also the photo doesn’t show split/lock washer. I think its really
important as the lead does flow over time, so no matter how tight you
make it, it will loosen up over time especially with higher
currents/heat.
The lock washer will buy you some time before needing to retorque the
fasteners.
I’m curious about the damage mode to the inverter and all that. I
don’t understand how a short on the battery would destroy all the
electronics?
I’ve gone to a battery angle grinder with flappy wheel to prep the
terminal posts. - fast. >>
My response to him.
I wondered about the failure of those big expensive components too,
but I have never had a dead short for more than a split second at the
batteries (a few misplaced cables when working too quickly are easily
dealt with). I have been installing a catastrophic class T fuse
between the battery bank and the DC distribution center breaker also.
I would always buff the cable ends with a green scrubbie and file the
battery terminals to remove any corrosion and then lightly coat all
surfaces, including all the hardware thoroughly (incldng lock
washer), with petroleum jelly before assembling and tightening (very
tight - tight as I could without breaking the hardware, lead starts to
compress). I've been very happy with doing it this way for 30+ years.
Learned much of this from Peter Talmage and Rob Wills here back east
as well as from Richard Perez (RIP).
Dave
*From:*RE-wrenches [mailto:[email protected]]
*On Behalf Of *cwarfel
*Sent:* Saturday, January 21, 2017 9:54 AM
*To:* [email protected]
*Subject:* Re: [RE-wrenches] Hidden corrosion caused catastrophic
battery system failure
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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