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Old 11-08-2011, 03:37 PM   #1
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Reversed polarity damage

I had the misfortune of visiting two campgrounds in a row with reversed polarity 30 amp service. This was partly my fault for second guessing my EMS unit. I lost a refrigerator circuit board and all my food. Upon arriving home I found my batteries cooked! Notice the burnt strap. This looks dangerous! Also notice the positive battery post on the front four batteries. They are one year old and were shiny. I don't know how deep into the battery the damage is. Could someone help explain how this occurred? Should I replace the batteries? What else should I check for damage?
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Old 11-08-2011, 04:23 PM   #2
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1. Properly fill and charge the batteries. Use a known good charger, not the one in your MH as it *may* be damaged. Then have the batteries propery load tested.

2. After you have found the actual cause of the problem and made any necessary repairs, check the operation of all electrical components.

3. Re the "Reversed polariy". On a 120 volt AC system, reversed connections between hot, neutral, and ground should only cause no current to flow, or possibly a circuit breaker trip. It is with 240 Volt 50 amp service that an open neutral can cause excessive voltage.

4. What you describe sounds like a failure of your converter/charger, since that can give you excessive DC voltage to the batteries and the logic board.

What indication did your EMS give you?

Do you have an AC & DC voltmater available to test voltages?
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Old 11-08-2011, 08:04 PM   #3
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Richard,

Assuming you don't have a surge protector!? Once you get your current situation resolved, I highly recommend installing a surge protector between the Transfer Switch & the cable reel. The Surge Guard unit from Camping World is easy to install and provides led indicators when something is wrong with the source. It's well worth the money!
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Old 11-09-2011, 07:33 AM   #4
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I do have an Electrical Management System on board. I have also been wondering if the burnt batteries and hold down strap were caused by a big lightning strike near the coach a few weeks ago. It seems like the batteries arched over to the strap somehow.
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Old 11-09-2011, 09:39 AM   #5
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From what I can see in the photo, the only damage to the battery hold down strap is corrosion.
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Old 11-09-2011, 09:54 AM   #6
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Like Dale said it is hard to see the damage on the battery hold down. I also think it looks more like corrosion. Lightning strikes can do some amazing things so that is a good possibilty. Do you do a lot of "dry camping"? If not why not get rid of some of the house batteries or change to 6 volt batteries. Just a thought. I would do what bluepill has suggested and go from there. Let us know what you find.
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Old 11-09-2011, 12:08 PM   #7
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You can click on the photo to enlarge it two times. I am pretty convinced it is burnt as it was like the other strap a few weeks ago and the paint is disintegrated. Also the positive posts are discolored and black. I am replacing the strap with wood so as not to have metal so close to the positive posts.
I do a lot of dry camping and these are six volt batteries.
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Old 11-09-2011, 12:35 PM   #8
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FWIW - There was some discussion as well as "show & tell" among several owners at the recent ACA Heritage Rally (Albq) concerning batteries. Some owners have even left the hold down brackets off entirely after replacing old batteries. The comment I heard was "if there's a problem from not having those batteries strapped down, then you have bigger problems than the straps". I don't know that I would agree 100% with that position but after our batteries exploded and burned the entire compartment, the straps can be a REAL problem (cable laid on and shorted to a strap!?).

One solution I've seen and will implement next time my batteries are replaced is to use ratching straps across each set of batteries. You can avoid possible shorts by eliminating the hold down bars and yet feel relatively assured that the batteries aren't moving. There are probably other ideas but that's the best one I've seen this far.
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Old 11-09-2011, 12:47 PM   #9
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Alternating current does not have polarity, period.

I have always wondered how a single individual can have a camp ground hook up problem. The CG ground would be over whelmed with the corresponding report of problems with the CG wiring.

The problem with the 50 amp 2 phase power having a defective common circuit is a real possiblity. I would think that the 30 amp hook up could be subject to this type of problem. A common volt meter would show this problem.
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Old 11-09-2011, 12:58 PM   #10
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If shorting from the straps buy some split loom and cover them. I do not think from the photos that is a short. If it was a short, there would be a burned and melted section of wire and of the clamp. It looks like corrosion from battery acid. Lightning, as said before, can do some strange things but generally not with the 12 volt system. Almost always with the AC 120 volt portion of the electrical. The only common shared link between the two are the frame of the coach. Wash everything down with baking soda and water to neutralize the acid and charge all batteries with a known good charger. Buy split loom (Red and black) for 5$ and cover all those leads and buy some red and black electrical tape and insulate the connectors ends. I'm guessing that maybe your batteries will be ok.
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Old 11-09-2011, 01:15 PM   #11
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I see one potential big problem here. The cables that are run UNDER the plexiglass stand a great chance of chafing and shorting out on the edge of the metal tray.
The third cable from the left has its own cut-out, which greatly reduces that chance. I would give each of those cables its own cutout, and even (at the very least) wrap the portion that comes near the edge of the tray with several layers of electrical tape as an added precaution.
I can't see enough to inspect them from here, but I would certainly pull those cables and check them on the underside.
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Old 11-09-2011, 06:37 PM   #12
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Enlarging the photo in post#1 above, its easy to trace the edge of the battery acid stain on the top of the front left battery.
With your voltmeter, put the black lead on a neg post, and touch the positive lead to various parts of the plastic battery tops. I believe you'll find varying voltage, perhaps ranging up to a few volts. Worse case I've found probing this problem of voltage leak was ~4.5V, which is a helluvalotta leakage. I'd guess corrosion is battery acid bublling out to form a film on battery tops.

I suggest same as above for proper water fill (not overfill which will exacerbate bubbling out problem), followed by proper charge then battery load test.

As to battery hold down, running w/nothing isn't bright. If you have larger problems, why add to them? Guaranteed you won't like the result. And if I was an extended warranty writer looking for a handy exclusion, lack of battery hold downs causing an arc strike would sure look tasty, because its a stupid problem to have.
When I went to AGMs, I strapped the new batt's down with 175# zip ties (I buy 3 footers which have zip the whole length; longer ones have sip for ~36" and the rest smooth, so a small-loop tie won't grab). Had to strap in 3 directions, used maybe a dozen 3' ties total. Neat, no metal, not bulky so not in the way. Used (E) OEM holes in base of the tray to strap around under; strapped pkg of 4 batt's together on tray, strapped batt's in pairs for extra safety factor. Shouldn't take much to hold the batteries down, but w/the # of ties I used, probably would hold if I rolled the coach. And (extra bonus of AGM) AGM's won't spill, so when I do roll the coach- no battery acid mess!!! Of course, no mess any other time either; I haven't even washed out the battery compartment since installing AGMs 18 months ago.
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Old 11-09-2011, 07:36 PM   #13
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From the picture it appears to be a corrosion problem due to hydrogen gas emitted from charging batteries. Positive battery terminals appear to be discolored due to heat generated from a high current draw on battery bank. There does not appear to be any fault tracking between hold down bar & battery terminals. I suppose an internal fault in one of the batteries could have caused the high current draw but same could be said about a fault on load side of battery bank. Low electrolyte or overcharging the batteries due to inverter/charger fault could have initiated this event. Would not trust any battery that has the discolored terminals. Take hold down bar to a local dealer and have it Rhino lined to insulate it if worried it could cause a short.
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Old 11-09-2011, 08:44 PM   #14
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I agree with Tom, the cables pressed against the metal edge is just asking for trouble. Especially those red positive cables against that negative grounded plate. It isn't likely to be the cause of this problem, but it might be the next one. The cutouts are an improvement, but still not the right way to do it.

I also think the tie down strap is corroded from battery acid fumes, not arcing. Mine were the same way, due to damaged caps leaking. I went with AGM's, and much happier now.
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