Battery isolator question

[BioTex]

Recently purchased a 2020 Forester class C RV with less than 4000 miles on it. Upon my first dry camping experience, I found that my engine would not start after having run down the coach battery. I did not realize the 12 V fridge pulled so much power and will not do that again. But not being able to start the engine or the generator got me to thinking that I might have a bad isolator. It is my understanding from previous class C motorhomes that the two batteries should be isolated so you are always able to drive away.

It would appear that I do not have a way to jump both batteries together so that I can start the generator to charge the chassis battery. That kind of surprised me also as I thought that was standard on all class c’s. Is my thinking correct and I might have a bad isolator or is it common for both batteries to be allowed to drain while dry camping?

 

[Aussieguy]

chassis and house should not be connected unless there is a charge voltage

you will have to confirm what system was installed in your model
AND if the previous owner had "Played around" with any of the system

If the batteries are in parrallel... use a jumper cable to get the generator going.
or plug into shore power (generator) so converter will charge up battery

May take a few days to work out your electrical system ... have shorepower or a generator handy while you work it out.

 

[bikendan]

Moved thread from the Tech and Repair section to the Motorhome section's Forester and Sunseeker sub-forum for better help from other Forester owners and possible factory support.

 

[Reverse_snowbird]

It's not common for both batteries to go dead while dry camping.
Those batteries should not be connected unless you press the button to connect them. (It's usually located on the left side of the seat or on the dash.)
If you're driving down the street, the engine alternator will charge the house battery as you drive.
However, it is possible that the batteries are connected somehow.

The simplest way to preserve that chassis battery when dry camping or storing would be to disconnect the negative cable on the chassis battery.

You could pack a jump starter to jump the engine battery and use the chassis engine to charge the house battery enough to start the generator. The problem would be charging the house battery if it's been drawn down to the point that it's dead.
Those 12v refrigerators do draw a lot of power. You could get something like a Jackery power station with portable solar panels that attaches to the battery and helps keep your house batteries charged.

Welcome to the forum!

 

[ppine]

So if you have a travel trailer with lithium batteries, and no battery isolator, disconnect your 7 pin when the TV is parked.

 

[Aussieguy]

So if you have a travel trailer with lithium batteries, and no battery isolator, disconnect your 7 pin when the TV is parked.

Trucks usually disconnect the 7 pin aux power..... when parked and engine off
measure with a multimeter your power OUT from the truck to confirm how yours is setup


If in doubt unplug 7 pin while stopped for long time .... for ANY type of battery

no reason to have the house and starter battery connected for normal usage

 

[Reverse_snowbird]

This is NOT a travel trailer.

It's a Motorhome which has both a 'chassis' battery and house batteries.

 

[BarabooBob]

The only difference between an RV and TT is that the motor is in the RV. All of the other stuff is the same. You have a battery isolator, water system, heat, stove and refrigerator.

My guess is that your isolator is not working properly. I have had to trouble shoot electrical problems on multiple rec vehicles for myself and other people. Almost every problem was traced to the isolator or very small gauge wires. My current truck has 6 ga wires run from an added isolator at the battery to the travel trailer with an Anderson power pole connector.

 

[Twinboat]

The only difference between an RV and TT is that the motor is in the RV. All of the other stuff is the same. You have a battery isolator, water system, heat, stove and refrigerator.

My guess is that your isolator is not working properly. I have had to trouble shoot electrical problems on multiple rec vehicles for myself and other people. Almost every problem was traced to the isolator or very small gauge wires. My current truck has 6 ga wires run from an added isolator at the battery to the travel trailer with an Anderson power pole connector.

Motorhomes use a 200 amp solenoid and 2 gauge or thicker cables between the batteries. They do that so it can double as a boost start circuit. They also use a voltage sensing device to close or open the solenoid, depending if a charging source is available on either battery.
If you don't know, don't guess.

 

[Bob K4TAX]

Multiple batteries, ugh! I never cared for connecting batteries in parallel on a permanant basis. I prefer using a battery selector switch, and that being one that I operate. Likewise, I never cared for connecting the house batteries to the coach battery. And I never cared for any automatic switching between the systems.

Too many things to go wrong and worst of all too many different ways to handle the situation and the all famous one, "I FORGOT". Worse is, I DIDN'T KNOW".

Dead batteries anywhere for any application are a royal PITA.

Bob

 

[Twinboat]

Multiple batteries, ugh! I never cared for connecting batteries in parallel on a permanant basis. I prefer using a battery selector switch, and that being one that I operate. Likewise, I never cared for connecting the house batteries to the coach battery. And I never cared for any automatic switching between the systems.

Too many things to go wrong and worst of all too many different ways to handle the situation and the all famous one, "I FORGOT". Worse is, I DIDN'T KNOW".

Dead batteries anywhere for any application are a royal PITA.

Bob

You can forget manual switchs , you can't forget automatic switching, its a much better way to go.
Drawing down one battery and letting it sit discharged, while drawing down the other, shortens both of their lives, along with having a heavier discharge on each battery. In parallel, the current draw is 1/2 on each battery.

 

[Outbackwack]

What part of the country are you in? When we lived in Phoenix, batteries had a life expectancy of 2 years or less. My used 2020 came from California and replacing the batteries was one of the first things I did before we went full-time. I also installed 3 lithiums in the coach, a new lithium BIM plus 800w solar. Even with 3 lithiums, I can only go 3-4 days without sun before needing to charge the batteries...

 

[wschneid]

I have a 2000 FR Sunseeker 23.5 with E-450 engine. I have the booster switch on my driver's seat so I assume I have the Battery Isolator Solenoid. It is not working, no click on the switch and no charging of my house batteries while driving. My problem is I cannot locate the solenoid. Does anyone have a similar year and model that can tell me where to look for it?
Bill Schneider

 

[Reverse_snowbird]

Might not be the solenoid. We had a fuse near the chassis battery that failed and shut off the connection between batteries.

 

[wschneid]

Might not be the solenoid. We had a fuse near the chassis battery that failed and shut off the connection between batteries.

I'll check it.
Thanks

 

[Aussieguy]

It's a used rig........ which means anything may have been modified
work out what you got in there and how to test it

worse case disconnect the ability of the chassis battery being depleted by the house
by disconnecting the BIM or DC-DC or Bird Solenoid

If you are unable to figure it our............ an auto electrician can do it in less than 30minutes
maybe worth you spend a few $$ to get someone to look
then advise you on best approach to stopping an re-occurrence

 

[Twinboat]

My 2000 Gulfstream class C had a solenoid next to the brake master cylinder that connected chassis to house battery when the ignition key was on.

Look for a silver solenoid with battery cable size wires on it.