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Ground cable smoking & Boiling battery


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I received a call from one of our Granddaughters two nights ago about a battery problem in their 2007 Keystone/Montana 3000RK 5th. They are in the Pacific NW (20* nights) and at first I thought they were just trying to use to much juice. They are newly married, in their mid 20's, hard working, and trying to get ahead, so trying to use as much park power as they can. Started blowing a 15 amp 120V breaker first, then at about 3 AM night before last woke with a burning smell, and called my son(her father), and he 1st told them to GET OUT, and unplug shore power!!! Things cooled down, so told them to unhook + battery cable, as the battery had been boiling over, and the ground cable was fried. Soo, unhook the positive cable, then restart shore power, making sure cable isn't touching anything. Turn off 1500W heater, electric hot water, dehumidifier, etc. All was well, THANKYOU LORD, no fire. Had battery checked yesterday, BAD, replaced it, and also the ground cable. Everything was fine until 5 AM this morning, then same thing. Battery boiling over! Could this be as simple as a bad converter? Why the ground cable? All of our family has been warned about a camper fire, and me and my son both are 1,200 miles away, so I fell so helpless. Don't want to keep tempting fate. Any Ideas? Does anyone know where the converter is on a unit like this? Could the converter overcharge a battery that quick to the boiling point, and if so, would it be the ground that would be getting so hot along with the battery? They are in a kinda' remote area, so I'm not sure if a local repair is available. Thanks, Dick T

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Hard to say over the internet, but I agree with the above I SURE SUSPECT THE CONVERTER or its wiring, sounds like the battery could be receiving max full current or heck maybe even 120 VAC (versus the rectified and reduced 12/14 VDC) if there's some kind of a rare short in it or the wiring associated with it. Its 120 VAC IN and supposed to be around 13 to 14+ VDC OUT, may be (If a stand alone converter only type of unit) located in the vicinity of where the shore power cord enters the unit or close to the battery storage area or where the AC Circuit Breakers and DC Fuses are. Look for a big metal box looking thing (lots of 120 volt romex wiring plus red and black DC wires in and out) and many are a combination Converter,,, and AC (Breakers),,, and DC (Fuses) Power Distribution Panel IE located behind where the AC breakers and DC Fuses are like under a bed or inside a closet or ???????? NOTE on some such combination units there is one AC 120 volt 15 or so amp circuit breaker labeled converter or charger etc that cuts off 120 volt AC input power to the converter/charger yet would allow all the other AC circuits to operate plus the DC distribution from battery to DC loads to operate. On my old system one 15 amp 120 VAC breaker shuts my converter/charger off yet all else AC and DC can operate.


Cable heat is due to current passing through a resistance so any carboned or burned or corroded faulty part of a cable or a too small cable itself can heat up due to excess current PLUS excess current can fry a battery in short order.


Id check the Converters output voltage (easy simple test with any cheap Voltmeter) which should be big red and black cables that exit the unit and connect to the battery + and - terminals BEFORE re wiring any new battery to it. There should be two fairly big cables (Red and Black or + and -) leading from it to the battery. Id except it to read 13 to 14+ Volts DC. If its much higher I SUSPECT A BAD CONVERTER and remember it may be a stand alone unit or part of a combination Converter with the AC and DC Distribution as described above.




John T

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Most likely a bad converter. Turn breaker off to converter or unplug it is the best. Also disconnect the converter from the batteries. Test battery for voltage. If it is not above 14 .0 volts and still has water in it then power it with a 10 amp or higher battery charger. It will take 10 amps to charge the battery and be able to use the furnace to heat with.

Test the voltage with meter and test often to see how things are working.


Another version of what to do



Safe. Travels, Vern

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A 750/1500 watt heater runs about $20 buy 2 of them but shut one off if you plan to run microwave. and leave that propane , 12V sucking furnace off and then what makes all the difference is an elect blanket.

I agree about the converter being shot. Being newlyweds maybe forget the blanket :huh:

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John T has given you some solid advice, but I'll address some of your concerns that nobody has made comment on. The first is the use of 120V-ac power.


Started blowing a 15 amp 120V breaker first,

There is no relationship between the 12V system and your use of 120V heaters, even though the circuit breaker for those may have been tripped. The first question to address there is, which circuit breaker was it that tripped? If could have been the one supplying the converter or it may have been the one supplying the heater or it may have been supplying the converter that appears to be the problem. While I do agree with your son's advice to get out first to be sure that there was no fire, now that we know you need to find out if the same 15a breaker is supplying both the inside outlets and the converter. It really should have a separate circuit breaker for the converter, but some of the less well designed RVs have been known to supply the converter with the outlets.


As to what they can use on 120V at the same time, that depends upon what size power cord they have as well as the configuration of the distribution panel. If they have only a 30A cord, they were clearly pushing things to the limit with so many loads and need to adjust. A 1500 watt heater will draw about 12.5a, the water heater on electric perhaps 10a, an dehumidifier another 8-10a and the converter will depend upon the state of battery charge and what voltage it is supplying. You clearly would have exceeded the ability of a 30a supply if all of these were to be operating at the same time. If they have a 50a cord then all of those at one time would be no big problem and they also most likely have two circuits for outlets and a separate one for the converter.


On the 12v problems, it is my opinion that anyone who uses an RV very much should take the time to read "The 12V Side of Life" from Mark Nemeth, and I strongly suggest that you get the grandson to do so at his earliest available time. There is simply not nearly enough information here for anyone to trouble shoot the problems beyond some basics and guesses. Why the ground cable melted and not the positive is a guess, but more than likely there are several leads attached to the positive battery post and only a single cable to the ground, since that is pretty common in RV design. In such case all current has to return through the single ground cable, but that is only speculation.


I'll also agree with Vern's suggestion to supply 12V power if you take the converter out of the circuit. A good quality, 3 stage battery charger could be a good temporary replacement for the converter, but with the cable melted down again they probably also need batteries as well.

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  • 2 weeks later...

The suggestion that the converter is passing 110VAC is bogus. None of the lights or appliances that work off the 12 VDC system would tolerate that for more than a few seconds. Need someone that can use/read a multimeter and use it after all the connections mentioned above are cleaned and reconnected. Be sure the battery is not low on fluid (below the top of the plates) top off with distilled water if it is. I would NOT stay in that camper while the problem is not resolved. Unfortunately a very good chance of fire until it is fixed.


Check with others in the campground, RVers are usually very helpful IF you can find one that knows his way around a digital multimeter.


Stay safe, have fun.

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Yes. a very dangerous condition. leave the batteries disconnected until the problem is solved. i have seen batteries explode during those type of failures. also electrical fires are very common in RVs. like others, i long distance guess, converter is bad or adjusted poorly.

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My thinking on this is that in order to fry the ground cable. That there is a direct short on the 12V side thus the converter trying to keep power in the battery and cooking it. I would start by looking the big red wire from battery to the fuse panel for places it may have rubbed on metal and have a bare spot.

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Kirk, and ALL you other folks offering help.

Sorry for my lack of information, but we lost our internet service until today at about 5:00 PM. I finally got our new mobile dish up and running, and being in NE Kansas for Christmas with family it was not so great working on it with 20* out side.

More to the point about the kids camper. Thankfully, it is now in the shop for repair. Those crazy kids have stayed in the camper without much 120V AC or 12V DC electric working for the last 2-3 weeks. They decided to tuff it out until they came back for Christmas, and have it repaired while gone. I will be relieved that they had a professional check it all out, plus I will be interested to know what went wrong. I will post the results, but again it will be a while.

Again, thanks for all the comments, prayers, and concerns. BTW, MERRY CHRISTMAS!!!! Dick T

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