Possible battery short

[Padgett]

Just a thought but the 12v heater in the fridge is seperate from the other two systems. If the heater was pulling excess current the the fuse might blow shortly after changing from 120v to 12v on the fridge.

Really need to measure the draws to determine what is happening.

[Bill]

Assuming Norcold, the refrigerator has a built-in 20-amp fuse for the 12-volt circuit.

Bill

[tentcamper]

Thinking about it a little more?

Do you blow the fuse: 1) if you run the 12V fridge and are not hooked up to and the TV? 2) do you blow the fuse when traveling and are not running the 12 fridge?

[davlin]

Here's the latest update:

Found the problem with the propane side of the refrigerator. See attached photo.

The electric side is going to be a real puzzle. Everybody can play. Charged the battery. Set Norcold on 12 vdc, turned the thermostat to maximum (5) and turned on the refer fan. Inside fridge temp at start up was 85, ambient was 88 with a humidity of 85% (you may have heard: we're getting a bit of rain in Texas). After 3 hours on battery, no blown fuse and inside fridge temp was 72, freezer was 60. Since I've never before "timed" my fridges in either of my TM's (I always start them the day before), I have no idea whether that's "good" or "bad" performance.

After 3 hours, battery showed 12.4 vdc, and amperage drain was consistent at about 3.3 amps. Don't think it's a battery problem.

Now for the puzzle: during this testing the TV was not connected, so eliminate that as a variable for now. While shifting the mode of the refrigerator back and forth from battery to shore power to propane, etc. the battery fuse blew. I replaced the fuse and spend over an hour rotating the switch through all the positions in an attempt to re-create the failure, to no avail. I can be no more specific, because I didn't hear a pop and didn't know that the fuse had blown until I went back to 12 volts without shore power mode. Watching the current draw on battery is very boring, but I never got a fluctuation on that above 3.5 amps. I've left the refrigerator on 12 vdc with shore power connected. I'll let you know it's doing.

Dave

[Bill]

I know this isn't directly helpful - I'm puzzling over it - but assuming that the battery is the only power source, a battery draw of 3.3 amps to run the refrig is not nearly enough. It should be 10+ amps.

Or was shore power connected when you made the measurement? In that case, the battery draw should be zero - the converter should be supplying everything needed to power the refrig. In that case, a battery draw of 3 amps is way too much.

As a quick sanity check, can you measure the voltage and current at the input to the refrigerator, rather than at the battery, with shore power connected? And then do it again with shore power disconnected? We have to figure out what role the converter is playing here.

Something isn't making sense.

Bill

[Padgett]

Norcold says the current draw at 12v should be 12A. It also says that if the wire is too small (0-20ft should be 12 awg) or connections are bad, the voltage/current at the heater could drop and cooling performace could suffer.

Also a common failure mode of electic heating elements is erosion/higher resistance/lower heating.

If I can get access since mine is open and the GC2's are fully charged, I'll take some baseline measurements tomorrow.

Can say that mine seems to work best on propane.

ps: you said the battery was fully charged and after 3 hours it was 12.4v. Without knowing the size of the battery (grp size) or the starting voltage (say 5 minutes after turnon) that does not tell us very much but in general 12.4 would indicate about 65-70% remaining charge. 30% discharge of a 100 AH bbattery in 3 hours would take a more like 10A than 3A.

Bill: does that sound right ? See here.

[davlin]

Aren't electrical puzzles fun?

After running the Norcold for 20+ hours on 12 vdc with thermostat on 5 (max), with shore power connected (power supplied by converter), ambient air temp at 70 degrees and humidity at about the same, the freezer temp is 0 degrees, and the fridge is 38 degrees. Seems about right to me.

My Mastech digital VOM died, and new batteries and fuse will not revive it. Using my ancient, but rugged, Simpson 260, with shore power off and fridge and fridge fan on, I can only tell you that I am pulling in excess of 10 amps, because that's as high as the Simpson will read. So the 3.3 amp thing yesterday was most likely caused by a failing VOM.

I have played with the mode switch on the fridge again today, with variations of shore power on and off, to see if I could get the battery fuse to blow. No luck.

Additional thoughts: At no time have I ever blown the 20 amp fuse in the converter panel for the refrigerator. If the Norcold was at fault for the short/excess amperage, wouldn't you expect that fuse to blow first? I have not moved the trailer or connected the TV to the trailer, because the fuse blew yesterday without either of these variables. I don't want to increase the complexity of this problem needlessly.

Dave

P.S. Battery info for Padgett. It was installed one year ago.

[tentcamper]

Davlin,

So you can re-create it and no other fuse it blowing other than the battery? Is it the fuse in the converter or the fuse at the battery?


How many batteries do you have? Do you have anything attached to the battery other than the battery pos wire, such as power jack, solar controller, monitor, etc...?

since you are not blowing any other fuse? It sound like it's one of the following?
- battery wire
- the battery charge wire running up to the 7 pin connector
- something you have attached to the battery, or battery
- if you have 2 batteries maybe you are discharging to far and when you go to charge it you are pulling more than 30 anps
- Not sure about it on a TM, but many times the breakaway brake is not fused.

It would be interesting to see how many amp you pull on the battery charge line when charging with a full battery. Also when charging the battery when you have dropped the battery down to something like 12.1 V.

[oldstick]

Originally Posted by davlin

Aren't electrical puzzles fun?

Additional thoughts: At no time have I ever blown the 20 amp fuse in the converter panel for the refrigerator. If the Norcold was at fault for the short/excess amperage, wouldn't you expect that fuse to blow first? .

That makes sense to me as well. Makes me wonder if the problem is something between the 120V converter and the battery itself, like a surge of too much charging current back into the battery when the converter is plugged in.

I could see this happening in a bad battery with a shorted cell(s), but sounds like that one is not very old.

[davlin]

Originally Posted by tentcamper

Davlin,

So you can re-create it and no other fuse it blowing other than the battery?I SOOOO wish I could re-create it on command. It would make diagnosing much easier. And yes, only the fuse at the battery. Is it the fuse in the converter or the fuse at the battery?


How many batteries do you have? 1Do you have anything attached to the battery other than the battery pos wire, such as power jack, solar controller, monitor, etc...?Nope.

since you are not blowing any other fuse? It sound like it's one of the following?
- battery wire
- the battery charge wire running up to the 7 pin connector
- something you have attached to the battery, or battery
- if you have 2 batteries maybe you are discharging to far and when you go to charge it you are pulling more than 30 anps
- Not sure about it on a TM, but many times the breakaway brake is not fused.

It would be interesting to see how many amp you pull on the battery charge line when charging with a full battery. Also when charging the battery when you have dropped the battery down to something like 12.1 V.

I guess the first thing I need to do is buy a new VOM that will allow me easier measurement of amperage. My fear is that I'm going to sit and stare at the meter in a "normal" sort of range, hoping to catch it spike.

Keep coming with the ideas, though, I'm going to solve this one way or the other.