Battery isolator charge vehicle battery on shore power

[jjrbus]

I have a new to me 02 Roadtrek on a Chevy chassis.
There is what looks to be a newer 4 post isolator,
I see no name brand or specs on it.
I have been RV'ing long time and never had an isolator before
and assumed they charged the vehicle battery when on shore power.

I am plugged in for a couple weeks
and everything is functioning properly.
My house battery is showing 13+ volts at the isolator terminal
and the vehicle battery is reading 12.25 volts at the isolator terminal.

Should this be charging the vehicle battery on shore power??

[jjrbus]

I checked and I do not have a Aux/combiner switch. Seems I have some choices add a solar charger, small 120 volt trickle charger, switch, solenoid. Is there a simple easy way to make this automatic??

[MrWizard]

Gjac wrote:

jjrbus wrote:
I do not understand why I would add a solenoid? Wouldn't I add a wire between the 2 battery terminals on the isolator with an inline 12 volt
switch??

This is one way that is simple, another way that you probably have built into your chassis already, is to turn your key to ACC and that should combine both batteries. While plugged into shore power check both batteries to see if you get 13 plus volts.

Turning the key to acc is not going to change the way the Diode Isolator functions,
Turning key would only work if activating a combiner relay/solenoid
Is used instead of diode isolator

[MrWizard]

Yes this is correct for what you are describing use a toggle switch, you can run a wire from the positive aux battery terminal (at the battery or at the solenoid) to the switch then from the switch back to the control terminal on the solenoid,
Most Motorhomes, come with an Aux/Emergency start button , which activates a momentary duty solenoid/relay , to connect the two battery systems for a built in jump start.
It Might be possible to replace that one with the new continues duty solenoid, then add the extra switch to turn it on , that would eliminate attaching more wires at the Diode isolator,

[jjrbus]

Am I looking at this right?? If I add a solenoid where do I get the 12 volt power from to activate the solenoid when on shore power?

[MrWizard]

Diode based isolation is a one way device, it lets the alternator Charge the camper while the engine on, but keeps the camper from draining engine battery while camping, it does not charge the engine battery from the converter, too do that automatically requires a battery combiner system, its a two way charging control for charging house and engine batteries, from engine or generator/shore power, yet keeps them separated if there is no charging source available, the last thing most people want is to be boon docking someplace and have dead engine batteries ,

[jjrbus]

Again thanks for the input always greatly appreciated. Using the s
olenoid for an automatic disconnect did not sink in. Now I need to sort through normally open/closed solenoids. I do have a battery switch from another project so may use that.

[pianotuna]

wolfe10,

The wire size depends on what is wanted,

I added a voltage sensitive relay @13.5 volts (suggested by BFL13) from the house bank to the generator battery and deliberately used #20 wire to limit the amperage. It trickle charges the SiO2 that I used for the generator while in storage, and will power the remote electric start from Pinella's when the RV is in use. Since the battery is never "deep discharged" there is no risk of the wire becoming a fuse.

[Grit_dog]

jjrbus wrote:
I do not understand why I would add a solenoid? Wouldn't I add a wire between the 2 battery terminals on the isolator with an inline 12 volt
switch??

You still need to understand what the existing isolator is doing and if it’s working. Although it’s 99% likely its supposed to isolate the house bank when the vehicle is not running.
You haven’t posted enough info to show that you understand what’s wired how, currently.
Once you figure that out, you can work to achieve charging the start battery off of the converter in the most efficient way.
IMO adding more aftermarket switches that no one will understand except you as long as you actually remember is silly. But he’s a simple solenoid switched to whatever you want it to be switched to is an option and not a bad option. It’s also not dummy proof like an ACR.

Take the advice here carefully as there’s some bad intel in other posts.

[Grit_dog]

pianotuna wrote:
Hi,

I added an addition solenoid rated at 200 amps continuous. For the starter battery I added a Trik-L-Start. Today I'd chose a dc to DC charger.

You’re completely backwards on this. And misleading the OP. You’d never add a DCDC charger fed off of the converter, charging the start battery when shore power is plugged in…

[Gjac]

jjrbus wrote:
I do not understand why I would add a solenoid? Wouldn't I add a wire between the 2 battery terminals on the isolator with an inline 12 volt
switch??

This is one way that is simple, another way that you probably have built into your chassis already, is to turn your key to ACC and that should combine both batteries. While plugged into shore power check both batteries to see if you get 13 plus volts.

[wolfe10]

Yes, of course you can just run a large-gauge wire from battery bank #1 to battery bank #2 with a switch in it. Can be at the batteries or any place you have large-gauge wires from both banks in close proximity. And, this is the KISS way of doing it. Wire size and switch amp rating should be high so if one battery is deeply discharged, you won't over heat the "connection" with high-amp transfer.

But, it is not automatic and that is what most people value over KISS.

[jjrbus]

I can run wires and do pretty impressive terminals and it has been a long time since I let the smoke out of anything. But I am not understanding why an added solenoid is needed and where to put it?

In my class A with a bit of instruction I added a battery selector switch, which worked well for the years I had it. In my Toyota a simple battery switch bypassing the solenoid served my purpose. My concern here is the van electronics, will adding a switch damage anything?

I did replace the OE converter with a Progressive Dynamics 9245 if that makes any difference.

[pianotuna]

jjrbus wrote:
I do not understand why I would add a solenoid? Wouldn't I add a wire between the 2 battery terminals on the isolator with an inline 12 volt
switch??

Diode based isolators tend to introduce voltage drop. Solenoid's do not, if the wire is sufficiently large.

A dc to DC charger may be best.

[jjrbus]

I do not understand why I would add a solenoid? Wouldn't I add a wire between the 2 battery terminals on the isolator with an inline 12 volt
switch??

[pianotuna]

Hi,

I added an addition solenoid rated at 200 amps continuous. For the starter battery I added a Trik-L-Start. Today I'd chose a dc to DC charger.