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House battery boiled over

On a recent trip, my House Batteries 2 -6 volts in series over charged and boiled over. This is on a 1987 grand villa ored oshkosh chassis. Checked fuses on dash and a 20 amp fuse had blown. Got home on chassis battery.  Added. 2 - new 6 volt battieries and the fuse continues to blow even with the house battery switch off and chassis battery on. Can't tell what the 20 amp fuse goes to but is in the bank listed as Inst lights

Re: House battery boiled over

Reply #1 –
There must be a dead short in something that's on that circuit. Could be your battery isolator. 
The isolator went bad on my 1981 Foretravel and it fried the alternator.
1993 U225 Build #: 4285
500 Watts Solar
Honda CRV AWD
Former 1981 Foretravel Travco
Retired, Full Time Off Grid Snowbird

Re: House battery boiled over

Reply #2 –
Thanks for the reply. Battery isolator. Is that the switch that connects the house battery?. The problem has to be related to when the house batteries over charged and blew the 2 am fuse because the prob remains the same with new batteries. Of it is only the isolator that might be an easy fix. My alternator works fine so I am lucky there.

Re: House battery boiled over

Reply #3 –
Quote from: Rkcox2 –
Thanks for the reply. Battery isolator. Is that the switch that connects the house battery?. The problem has to be related to when the house batteries over charged and blew the 2 am fuse because the prob remains the same with new batteries. Of it is only the isolator that might be an easy fix. My alternator works fine so I am lucky there.
Here's a photo of a battery isolator. They are usually located in the rear wheel well.
"A battery isolator can eliminate the problem of battery drain all together. The isolator's role is to allow the alternator to assist with charging the primary battery, while at the same time not allowing other loads in the charging system to drain the primary battery."
Search the forum for "battery isolator". I'm sure there is a lot of info about them and the problems they can create.
1993 U225 Build #: 4285
500 Watts Solar
Honda CRV AWD
Former 1981 Foretravel Travco
Retired, Full Time Off Grid Snowbird

Re: House battery boiled over

Reply #4 –
I attached a picture where the 20 amp fuse is missing. This fuse keeps burning out. It is in the instrument bundle but I can't determine what it feeds. Nothing on my house  is getting current. I am hoping someone can enlighten me so I can get to the bottom of this. I hate to take it in for repair when it maybe minor. Thanks for any help

Re: House battery boiled over

Reply #5 –
There may be 2 fuse boxes under the dash . One is hot key on , the other is always hot . 
 Key on box runs the driving systems, running lights, turns sig, ect .    Key off box runs a lot of dash stuff also . The little  fans above the driver seat, get hot and could  blow fuses. Look for stuff that doesnt work and go from there.

  A place that has shorted on my bus is  at the dock lights' wires as they go across the bottom of the doors.  I crash car parts or jacks on the wires.   
  Another  area is under the water tank. The tank settles through the floor and cuts the harness at the edge of the frame . 
  I mounted my tank on  painted 3/4 ply over  square tubing that sits on  the frame as cross members.

Re: House battery boiled over

Reply #6 –
Quote from: Rkcox2 –
I attached a picture where the 20 amp fuse is missing. This fuse keeps burning out. It is in the instrument bundle but I can't determine what it feeds. Nothing on my house  is getting current. I am hoping someone can enlighten me so I can get to the bottom of this. I hate to take it in for repair when it maybe minor. Thanks for any help
If your isolator is shorted out, it could do all kinds of things like blow fuses, cut off power from the house batteries, ruin your batteries and possibly start a fire. 
1993 U225 Build #: 4285
500 Watts Solar
Honda CRV AWD
Former 1981 Foretravel Travco
Retired, Full Time Off Grid Snowbird

Re: House battery boiled over

Reply #7 –
I appreciate all the comments. All my fuses look good.. This should be simple from the fact that my house batteries over charged , boiled over while I was driving... I replaced the batterieb and the new fuse still blows. The over charging and boiling  over is what started the whole process and it would seem that there would not be all these other interviening factors. Possible but. not logical. So all I have to do is determine what caused the 20 amp fuse to blow and what other reactions may have occurred during that failure. I will work through the suggestions. but nothing stands out.

Re: House battery boiled over

Reply #8 –
My battery boiled when it died and the on board charger kept charging it .
    The alternator should not be able to over charge it to extreme.  The engine bat will also gets charged and the volt meter will read over 15 volts.    Sounds like that part works fine.  I would find out why the fuse is a hard short and go from there.   
Your battery connector should be right  inside the engine side door , on the rear bulkhead.  Disconnect the end cables.  Try th fuse box again.
 If fails. 

Disconnect the battery/s.    Hook up a solo battery , jumper cable through a 50 amp breaker to the system.  Plug in fuses and see what doesnt work or what fuse blows .

Re: House battery boiled over

Reply #9 –
If you have can get a tone tracer you might be able to fined where the wires go and find out
what it does.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: House battery boiled over

Reply #10 –
Quote from: Rkcox2 –
I attached a picture where the 20 amp fuse is missing. This fuse keeps burning out. It is in the instrument bundle but I can't determine what it feeds.
Captain Obvious here, but you need to find everything that 20A fuse is protecting oh so well.  Physically trace the wire until it disappears, and with help from the electrical schematics and cartoons find out where it re-appears.  Once you know what is connected to that 20A fuse, then you'll know what is causing the problem.  Keep track of your time spent and once you're finished write a check to yourself @$25/HR.  You'll have earned it.  And saved money.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: House battery boiled over

Reply #11 –
Took out isolater, it had shorted out. Replacing in a couple of days. This may correct my prob. If it had not been for this website I would not have been aware of the isolater. Thanks to all

Re: House battery boiled over

Reply #12 –
Good idea to take a smart phone and take a shot of the isolator before you remove the cables so you get everything back in the same spot. The PO replaced ours and got it all wrong so both banks were always connected. The cables have ID labels wrapped around them a couple of inches from the end but time and exposure to the elements may make it hard to read.

Other, more modern alternatives to the isolator that may be a possibility when it comes to replacement time.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)
 

Re: House battery boiled over

Reply #13 –
Taking a pic I did. Very good idea esp for the novice. I will be putting it in soon and will give update. Thanks again for responses.