Hot Ground???

OK, it's definitely the fridge, a two way Domestic Americana. I getting a reading of 9.55 amps when it's fuse is in and that drops to 0.223 amps when pulled. Any idea what might cause it to pull that many amps? I suppose at one point while we were gone it must have spiked above 15 amps to blow the fuse. Maybe I ought to start a new thread about it.

Tim Czarkowski
Totaltravelers.com

Chris Bryant wrote:
I often use a test light in series- the brighter the light, the more the draw.

X2 on the test light. Works for me all of the time. JMO

OK thanks. That seems to clear up some of my confusion. So if that's is the case then I have something drawing 10 amps, all the time, when it should just be the fridge and propane detector running. This seems to be confirmed since the batteries were run half way down this morning and they ought to be almost full.

I often use a test light in series- the brighter the light, the more the draw.
Just for fun, I would look closely at the breakaway switch, and double and triple check the polarity of the batteries. I do not think the refrigerator could cause a 10 amp draw, as it is fused at under 5 amps on the board.

buylow12 wrote:
This is from my batteries, the 12v DC system. With the ground wire off all my 12v equipment stopped working. From the negative terminal to the ground with all the fuses in I was getting 10 amps or so. From negative terminal to negative wire I was getting 0.75 amps. This seems clearly wrong from what I have read and sounds like a hot ground. However I'm confused, as I said above. I just want to be able to boondock without watching my batteries rapidly discharge.

Tim Czarkowski
Totaltravelers.com

Where does the negative wire go? Does it attach to the frame? If so, you do have a bad ground. That said, you can and probably did find the problem using your ammeter setting. Not the best way to find the problem. Very easy to damage your meter and/or equipment. A better method is using volt meter setting. In the 60 years I have been using VOMs I have toasted a few:B That bad ground may have limited the current to your fridge. I would check both the ground at the battery and the ground at the fridge.

beemerphile1 wrote:
I am confused as to why you are referring to negative and ground like it is two different things. In the 12vdc system the ground is the negative and the negative is the ground, same/same.

I believe they mean negative as in the negative terminal of the battery, and ground as in the connection on the frame of the RV. With the lead between the two disconnected at the battery, the OP is seeing a higher current flowing when measuring with an ammeter between the ground connection (on the frame) and the battery than when tested between the battery end of the ground connecting wire and the battery.

I would suggest measuring the voltage between the negative battery terminal and the ground connection on the frame with everything hooked up. It should be zero volts. If not, you clearly have a high resistance in the lead between the two, which indicates the wire is damaged or there's a bad connection on either end. That should be an easy fix. I think that would be more likely to be an accurate measurement than comparing current measurements (though both should be valid from a theoretical standpoint, assuming the load of the RV isn't varying).

A ground this poor would also result in obvious problems like having lights dim considerably as more lights are turned on when running from battery power.

I am confused as to why you are referring to negative and ground like it is two different things. In the 12vdc system the ground is the negative and the negative is the ground, same/same.

I hope your right. What started my concern was that it was not at 14.4 after 5+ hours of towing and the batteries were full the night before.

The sun is down now and the converter unplugged so I guess I'll see how it goes. The only 12v items on are the LP detector and fridge so I shouldn't see much draw down below 12.6(hopefully).

So what does measuring from negative terminal to negative wire measure? I was under the impression that would tell me how many amps were being drawn.

On the other hand what does the ground to negative measure? I was getting a reading of 10 amps which seemed like alot but honestly I don't really know what that would be measuring. This is what really confused me.

Any good books on RV electrical systems? Or articles for that matter? I want to have a fuller understanding, particularly the 12v.

Thanks,

Tim Czarkowski
Totaltravelers.com

buylow12 wrote:
I am using a panel from my solar controller. The 13.2 reading was at 2am after two weeks unplugged in a storage yard I assume the panels had brought it up to that point that day. Previously after a day of towing I'd get a reading of 14.4 which would then fall to a more normal 12.9 after being disconnected.


Tim Czarkowski
Totaltravelers.com

13.2 sounds right after a solar charge. The reason it wasn't 12.6 (full) is because they tend to hold a little extra for a little while after charging. Your charger was feeding it 13.2 volts before the sun went down and it stayed that way for a while. 14.4 would make sense after towing because that's what the alternator was sending it. This "extra" is called a surface charge.

The only way to get a true reading of the battery's charge level is get rid of the surface charge. Either wait 12-24 hours after fully charging or put it under a load of 20 amps for three minutes. Then you should see 12.6, which is considered full. It sounds to me like your battery is behaving normally.

As far as reading high amount of current between your negative battery terminal and ground. This also sounds normal. The negative post is where the elections come from. Electrons are negative, that's why that post is called negative. Negative and ground are not the same thing. The current is lower when you take a reading from the negative terminal to the negstive wire because there is now more resistance between the battery and ground (the chassis). MrWizard may be right, and the negative cable isn't connected properly to the chassis.

To sum it up, don't be alarmed if you test the battery after charging and it reads 13.2 or 14.4, and the next day it drops to 12.6.