How to run fridge/freezer off extra battery

[mauisanna]

Aloha! I don’t have an RV but I do have a 1972 VW bus converted to be a coffee bus and have a question. My first thought was an RV forum because it is similar to how RVs operate!
I would like to be able to run my fridge and freezer off of an extra battery while in transit and parked (but not necessarily operating).
Right now I run the fridge and freezer off of a 2000w generator while operating (I park in one spot only, and the bus plugs directly into generator and everything is powered by an inverter ). I also power an electric kettle and coffee grinder with the generator. When I’m not operating (in transit) the fridge and freezer remain unpowered. When the bus is parked at my house it is plugged in (power from the house plugs directly into the exterior of the bus (1972 VW) and everything is powered through the inverter).
What I would like to be able to do is charge an extra battery while it is plugged in to the house so that it is possible to have the fridge and freezer running (off the extra battery) while I am parked/in transit for a little while. My husband could do it if I can get step by step instructions on what to do! Thank you so much for your help!

[glennts]

Several Coleman cooler ice blocks, frozen while plugged in overnight and put in the fridge section during your travel time, may be an inexpensive solution to try first.

[Almot]

mauisanna wrote:
not sure any of the info for the inverter as it was installed by the previous owner. I just know that if it is off then nothing electrical in the bus works when the bus is plugged in!

This sounds more like "Converter" to me. Not Inverter. It makes 12V out of 120V, and charges the battery. If lights and other small electrical things inside the bus don't work when it's off, then your battery is dead. Or you're accidentally switching both the battery and Converter off.

Running electric kettle without generator on a single battery, you'll kill the battery in no time.

Use propane for kettle. Fridge is possible to run with 2 batteries, solar and alternator.

[burningman]

I don't think you are accurately understanding whats happening. Regardless of what you're plugging your power through in your bus, you are not running on an inverter.
An inverter is a device that converts 12 volt DC battery power to 120 volt AC power.
You are running directly off 120 volt AC, either from your home or your generator.

I'll keep this in simple terms.

To do what you want will require a rather powerful inverter and a lot of large batteries.
The things you want to run use a lot of power. It can be done but you'll need at least four, probably six large deep-cycle batteries to reliably hold that much energy. It'll be big and heavy and expensive.

If I were you I'd just figure out a rack to hold your generator on the roof or front or rear bumper and run it while in transit. That will be way cheaper, simpler, and lighter.

[Almot]

Australians run 7-9 cu.ft 12V fridges in vans, using nothing but alternator and solar. No generator. Usually 180-240W solar - it's difficult to fit more wattage on the roof. Those are 12V fridges that need no inverter, they are expensive and a little more energy-efficient than fridge with inverter.

Your energy appetite is bigger because of electric kettle and grinder, both of them used frequently when in operation. Still, I would definitely add solar, in your location. Even if you're on the North shore. Solar will ease the burden on generator and alternator, and prolong the life of your batteries. 240W solar will cost under $500, in parts cost. Will probably pay for itself in one year, considering saved fuel.

[wa8yxm]

Some math: First some battery math. Batteries come in 3 basic flavors for this part of this discussion, plus a few more divided differently later on.

Starting: High current, low capacity (relative to peak current) Need to be around 80% full or more for best life
MARINE/Deep cycle.. Basically starting, you can go a little lower on SOC, perhaps 75% (But please do not quote me on that floor, may be higher)

DEEP CYCLE (Like the GC-2 Golf Car battery) You can go to 50% SOC safely (WOW, over 2x the avabial power!!!! and they cost less too if you go with GC-2)

Then we get into how much does each size store.. But I'l cover that later as well.

On your fridge. You have a wattage. Likely 100-300 watts. This is what it needs to run (note there are options if you don't need a lot of capacity I can get you an all electric RV fridge that draws less than 50 watts and Runs on 12 volts!!!!! Bit pricey, but then so are the Home type as well)

Let's assume 200 watts.. ok, that is 20 amps at 12 volts. So you want to run at least 8-12 hours so figure you need at least 200 amp hours of USABLE POWER, that is two pair of GC-2 six volt golf car batteries in a series/parallel arrangement like this..

-{6v}+-{6v}+12 volt

-{6v}+-{6v}+12 volt

both left - signs are connected together and both 12 volts are as well.

And a 1,000 watt Pure Sine Wave Inverter to power the fridge.
And a converter (Progressive Industries 9280) to recharge overnight at home.

If you recharge with the generator you can make that a 9260 or even a 9245 and only use one pair of GC-2's.

Now the other division on batteries

The GC-2 (most common) is a flooded wet cell, it should be mounted in a well vented to the outside compartment (either mount on a wall, sealed the compartment and install a loovered outside vent you can open and slide the batteries out for maintenance, Under a step or other location outside) and you should also mount that big inverter AS CLOSE AS POSSIBLE.

AGM batteries are a very well regulated (Valve Regulated Lead Acid) low venting and many mount them INSIDE which is NOT recommended for Flooded wet.

Also flooded wet need to be distilled watered ONLY DISTILLED from time to time.
(Took just shy fo 4 years before I had to wate my Deka's)

There are some other battery types but I do NOT recommend. Either very poor for this type of use or VERY EXPENSIVE.

Now.. I mentioned the RV size electric only units.

Both Domethic and Norcold offer or offered a High Effiency (Danfoss class) Refrigerator that drew liek 40 watts on either 120 or 12 volt I have an ENGLE Chest freezer. That is also of this class (36 watts I run it on battery only it cost like 800 bucks when I got it. The unit I have can be either a freezer or Refrigerator. Will see if I can find a link for you I think this might be ideal for your use.

https://www.thecoolerzone.com/engel/

This is not a sales site, this is a "Review" site. that tells you more abou them, You will see photos of htem, They are not large, but they work great

Since for a "Coffee Wagon" you do not need but a fairly small amount of refrigerated storage. They should work, I'd guess 2 of 'em.

[time2roll]

mauisanna wrote:
The generator is a 2000 watt generator (mostly to run hot water kettle) not sure any of the info for the inverter as it was installed by the previous owner. I just know that if it is off then nothing electrical in the bus works when the bus is plugged in!

So to recap, would like to charge extra battery while plugged in at my house, and probably need a switch to be able to run off of that battery while i'm at my 2nd job. Thank you again!!!

The inverter is already connected to a battery. You need to open something up and post for us the brand and model number of that inverter.

You may need new equipment or maybe just the existing battery is shot. You probably need 2 to 4 batteries. Keeping them charged is the easy part. Hard to recommend much until we know what you have.

If this electric stuff is beyond you, consider contacting a mobile RV repair to evaluate what you need.

[Matt_Colie]

Mauisanna,

Where I in your position, I would try leaving the reefer and freezer unpowered for that 20+ minute drive. When our original RV reefer died, we could not afford to repair or replace it. So, I stuffed a "dorm" reefer in the hole. I was initially worried, but when the ice cubes didn't melt in a 4 hour drive on a hot (for Michigan) day. I stopped worrying.

So, try that before you spend money.

Matt

[Bill_Satellite]

If you do have an inverter then when you are not plugged in at home or running the generator you would still be able to get 120V power with the inverter turned on. We would need to know what kind of inverter and the capabilities (400 Watt, 1000 W, 2000W, etc.) and what battery/batteries you have. You may only need to add a converter and add an additional which will charge your batteries when plugged in and on generator. Your engine alternator "should" already be wired to charge this battery when driving.

[2112]

We need to know how much power your fridge/freezer consumes. There should be a data plate on it somewhere that states 120V xxA or xxW. What are the xx's? You could buy a Kill-A-Watt meter from Home Depot and measure it. They cost about $20 here on the mainland.

Is this a single fridge/freezer unit or a separate fridge and a freezer?

You might be able to do this with 2 6V AGM batteries and a charger but we won't know until we know how much it/they consume.

[mauisanna]

Thanks everybody!
sorry i couldn't reply sooner, was having trouble posting in forum from my phone.
I'm in transit for 40 min a day (20 min each way), not very long. I would like to figure out how to charge the extra battery while parked at my house (16 hours). i only operate (generate) for 4 hours in the morning. I'm looking to be able to run the fridge/freezer for five hours while parked at my other job, maybe 2 days out of the week. (the fridge/freezer would not be opening at all during that time). The generator is a 2000 watt generator (mostly to run hot water kettle) not sure any of the info for the inverter as it was installed by the previous owner. I just know that if it is off then nothing electrical in the bus works when the bus is plugged in!

So to recap, would like to charge extra battery while plugged in at my house, and probably need a switch to be able to run off of that battery while i'm at my 2nd job. Thank you again!!!

[Dusty_R]

Maybe what your calling an inverter in a converter.
A converter changes 120 volts AC to 12 voltes DC.
An inverter changes 12 volt DC to 120 volts AC.

[time2roll]

I don't follow if the generator or an inverter is powering these items? Or is this an inverter/generator like a Honda 2000?

Otherwise you need 2 to 4 batteries to really run a 2000 watt inverter. You also need a method to keep the battery charged. And you will need a transfer switch to integrate into the electric system... or you will be swapping plugs.

[coolmom42]

Given that you are in Maui, solar would be a good option

You will have to do some calculations to figure out how much battery and solar you need.

THIS IS A GREAT SITE to figure out your solar needs and explains it very well. I highly recommend you do your reading on this page and the linked pages, for some good education on how to use and manage a 12V system.

You want to avoid repeatedly depleting the battery bank below about 50%--that is death to deep cycle batteries. They also need to be totally recharged often, don't keep running them at about 80%.

[Bill_Satellite]

Your engine alternator will be the only thing available to charge your batteries while driving unless you consider adding some solar power to the roof as well.
A couple of good 6V golf cart batteries will likely keep your fridge and freezer going for 1/2 day if the doors are never opened and the battery if fully charged. The alternator will add some time to this formula and solar could make it pretty much unlimited depending upon the setup. Opening the doors puts a whole different twist to the story so what you have and how you plan to use it will make all of the difference in the World!