Odd Electrical Issue (Converter)

[Dan_Frisbie]

My rig has the 25 amp reverse polarity fuses on the converter, 3 of them. Occasionally, for no reasonable or apparent reason, they will blow. I am not operating or working on anything.
I use a Bulldog power monitor and have very little running inside the rig (it’s in my yard).
Since it’s at home, I am in the MH once or twice a week and occasionally will find the batteries drained and when I do, the fuses are blown.
This has been happening since I bought the MH nearly two years ago.

Any ideas?

For the latest solution to keep from depleting my batteries, I have the battery switch “Off” and an external charger/maintainer on the batteries.

 

[Ex-Calif]

Do you use any other power sources besides shore power like an on-board generator?

Something giving a voltage spike while you are not watching?

 

[Gary RV_Wizard]

Something is momentarily reversing the direction of current flow from the charger - it only takes a second to blow those fuses. Something obvious like a lightning bolt would surely have been noticed, but maybe some smaller "surge" in the 120vac power could do it. For example, I've read where a faulty neutral on 50A shore power can sometimes cause a reverse surge through the charger.

Not really relevant here, but an interesting anecdote... One of my electrical engineer co-workers back in the day came from a family who owned a small lumber mill in a little New England town. They had to be extremely careful about shutting down the huge rotary saw because it's big electric motor sometimes pushed power back into the village power system, popping fuses and even light bulbs in local homes. One of his projects while earning his EE degree was to figure out how to improve the saw's power connection & switching to prevent that back-surge.

 

[Dan_Frisbie]

Something is momentarily reversing the direction of current flow from the charger - it only takes a second to blow those fuses. Something obvious like a lightning bolt would surely have been noticed, but maybe some smaller "surge" in the 120vac power could do it. For example, I've read where a faulty neutral on 50A shore power can sometimes cause a reverse surge through the charger.

Gary, this seems plausible. WE live in a 70 year old house that has been retired, but still, 70 year old house…
I am trying to remember if this has happened anywhere except home and cannot ever remember having this problem while camping. We keep the Bulldog plugged in even at home And it has never shown red or indicated a fault.
If a lightning bolt or flash surge does this, why does no one seem to think that it’s normal or happens all the time?
Do you think that I should put an additional ground rod on the RV when it’s parked at home?

 

[SuwanneeDave]

Is it possible that one or more of the batteries has an internal short?

 

[Kirk]

Do you think that I should put an additional ground rod on the RV when it’s parked at home?

You could do that if it makes you feel better, but it won't do anything for you. If you have a 50A cord with a floating neutral that will not change it. Do all 3 fuses open, or just 1 of them? Anything that would cause the current to exceed the 25A rating of a fuse will cause it to open, so it may not be a reverse polarity issue. If you have a floating neutral on your 50A power supply the converter may occasionally see far more than the expected 120V as it would be possible(although not probable) for it to get as high as 240V.

 

[L-M-L]

Gary doesn't the fuses protect the 12 volt side of the converter to protect it if the battery cables are hooked up in reverse? If that is the case wouldn't it have to be something to do with the batteries or the wiring going to the batteries?

 

[Kirk]

If that is the case wouldn't it have to be something to do with the batteries or the wiring going to the batteries?

Fuses open due to excessive current. The fuse and connections are not all the same and depend on what converter you have. For the polarity to actually be reversing intermittently would be something really unusual that I have never seen happen.

 

[Dan_Frisbie]

Is it possible that one or more of the batteries has an internal short?

I doubt it. I have replaced the batteries in the last year.

 

[Dan_Frisbie]

I appreciate all the ideas and theories.
Hopefully, one of them will be a solution…

 

[John From Detroit]

Gary doesn't the fuses protect the 12 volt side of the converter to protect it if the battery cables are hooked up in reverse? If that is the case wouldn't it have to be something to do with the batteries or the wiring going to the batteries?

yes they are supposed to but in one of the books Murphy's law and other reasons why things go wrong (Not sure if book 1 or 2) "A $25.00 Transistor will blow to protect a $0.25 Fuse"
They are both more expensive now days.
Someone ask about grounding. an RV in storage.
Won't hurt. Wont help Won't do anything other than take time and perhapd money. No difference.
If it were a tall tower (Say 50 or 100 feet) taller than anything right close by.. Might help with static discharge.. Might not won't affect a lightening strike.
Grounding on house systems is a safety precaution.. To preent you from becomming the "neutral Wire" back to the transformer.. If it's plugged in the ground wire in the plug/cord should provide. If it's not plugged in . there is no path FROM the transformer so the path back does not count.