[RE-wrenches] Hidden corrosion caused catastrophic battery system failure
cwarfel
cwarfel at entech-engineering.com
Sat Jan 21 07:58:17 PST 2017
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:re-wrenches-bounces at lists.re-wrenches.org]
> *On Behalf Of *cwarfel
> *Sent:* Saturday, January 21, 2017 9:54 AM
> *To:* re-wrenches at lists.re-wrenches.org
> *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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> --
> Christopher Warfel, PE
> Entech Engineering, Inc.
> 401-466-8978
>
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Christopher Warfel, PE
Entech Engineering, Inc.
401-466-8978
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