How to setup a dedicated battery for residential fridge?

[amauri]

I would like to install a dedicated battery to power the residential fridge.

What I'm not sure about is how to charge the two batteries independently using the converter while connected to shore power and via the alternator while towing.

Our 2017 3250RL has a PD9270C converter/charger and a Xantrex SW2000 inverter for the fridge.

I'm thinking that I can install a battery Isolator like the Victron https://www.victronenergy.com/batter...tery-isolators

But I'm not sure if that would work and would appreciate some tips.

Thanks

[TitanMike]

One way is kind of "old school with modern parts".

A simple continuous duty relay with high current rating with 120 volt AC coil.

Use contacts to connect positive terminals together when plugged into shore power and disconnected when shore power is disconnected.

If high current continuous duty (300 amp) relay with 120v ac coil not available use a $20 solenoid rated for continuous duty. Then find a simple 120v to 12v power supply that will supply the "coil current" for the solenoid. A 120vac to 12vdc @5 amp power supply to run led light strips etc is $10.

Plug powersupply into outlet that's only live when on shore power, 12v output to solenoid coil, and battery connect to high current terminals.

I recommend a high current solenoid as you are connecting batteries at different states of charge. The instantaneous current flow from ful to empty battery could cause premature failure of the contacts unless some form of current limiting was implemented.

The above is simple and relatively inexpensive.

The Argo FET isolator you linked sells for $100 plus.

[djousma]

I'm curious about why? What problem are you trying to solve? I run a pair of 6v golf cart batteries. They will maintain fridge for over a day? Rather than an isolated battery, just wire in more batteries into the bank and extend all 12v use?

[corn18]

Originally Posted by djousma

I'm curious about why? What problem are you trying to solve? I run a pair of 6v golf cart batteries. They will maintain fridge for over a day? Rather than an isolated battery, just wire in more batteries into the bank and extend all 12v use?

That's the same thing I did. I have a dedicated 1200W inverter for the residential fridge. I have another 2000W for everything else. I just swapped out my 2 group 24 lead acid batteries for two 206Ah LiFePO4 batteries (412Ah total). I have remote panels for the 2 inverters so I can pick and choose which one/both to run. Really nice for going down the road and just having the fridge inverter on. The other inverter draws energy for silly things like TV's and stereos that really never turn themselves off.

[amauri]

Originally Posted by djousma

I'm curious about why?

We just recently purchased the trailer, and maybe it is a simple matter of learning how to deal with the differences compared to our old trailer.

This is our first residential fridge w/inverter, hyd slides and hyd leveling system.

On our break-in outing this weekend I had issues with the GFIC on the inverter tripping and powering off the fridge when I closed the slides, retracted the auto levelers, and unplugged shore power.

Before heading off, I double checked the control panel in the trailer and noticed the green light on the inverter on/off switch was turned off.
I tried unsuccessfully to turn it back on but it would not until I discovered that the GFIC was tripped. After resetting it I was able to turn on the fridge and the fridge stayed on till we got home and operated the levelers again.

Could it be that the hyd pump is causing enough of a voltage drop on the single battery to trip the inverter GFIC ?
I suppose I should try the easiest option as you've suggested, add a second battery (2-GC2 in series or 2-12v in parallel).

[Jusfloors]

I was wondering if two 100 watt panels will keep house batteries charged with residential refrigerator?

[CHICKDOE]

what battery and how many of them do you have? we have two 6 year old group 27 batteries and have the same converter and inverter for the refrigerator and seem to do just fine. running the slides and levelers from just the battery does put as load on the batteries. when we arrive at a site i hook up the shore power cord first thing before i use the levelers / slides. and the shore power cord is the last thing i disconnect before we leave. we really only use the inverter while we are towing the trailer. no occurances of the gfci in the inverter tripping.

[amauri]

Originally Posted by CHICKDOE

what battery and how many of them do you have?

A single group 27 that is 3 years old.
My thought was to get a second and isolate it for the inverter/fridge only.

But I'm beginning to think that getting two fresh batteries in parallel is a better and simpler way to go.

[FollowTheSun]

Originally Posted by amauri

I would like to install a dedicated battery to power the residential fridge.
...
... .

Your plan to use a battery isolator for setting up a dedicated battery should work fine with two or more batteries. The isolator essentially divides your 12-volt loads into two systems: One system for your refrigerator, and other system for everything else. The isolated portion of the system will deplete without discharging the other part of the system, and both portion of the system can be charged together.

However, it may not be the best method for completing the task you wish to accomplish. For the same cost, (excluding the isolator) you could add two more 12-volt batteries, which would substantially increase the available power to the 12-volt system. Additionally, including an energy management system will help you monitor power usage, and adding a solar charge system (200-watt or greater) will greatly facilitate the 12-volt system health.

[CHICKDOE]

i don't know the layout of your cardinal. but ours is limited in the space to install batteries. there are two battery boxes in the front compartment. they are individual boxes with vented covers. they are in the same compartment up front with all the electronic devices like the inverter, leveling system, etc. as such it is very important that the batteries be in the vented boxes so that they do not vent into the compartment and corrode the electronic devices. this limits the number of batteries that you can install.

we have two maintenance free group 27 batteries in these boxes. the have worked just fine for us for 6 years now. an upgrade would be agm batteries or even lithium if you can afford them. lithium is to the point now where they are not much more expensive than agm. one caution though. if you have an internal generator make sure the lithium can start it!

you are not going to be boondocking with a residential refrigerator and a couple of group 27 batteries. but they have worked just fine for us for years to keep the refrigerator running while we tow for a day and then hook up. you could also install a battery monitor like the victron smart shunt to monitor the batteries.

i don't see the benefit of trying to isolate the refrigerator batteries. to me it would just make things more complicated.