Power Inverter

[skybear4]

I am looking to add a power inverter to my teardrop to power a few items from time to time when
shore power is unavailable which would be a good bit of the time. I have a 12v deep cell battery
with a charger and a 7 pin connection to the vehicle. I'd like to power up a coffee pot, and occasionally
some kind of tv/dvd for viewing movies. I have cabin and galley lights as well as 110 & and 12v auxiliary
outlets too. Oh, and probably a low wattage ceramic heater from time to time. What wattage and
brand would one look for?

Thanks, Dave

[48Rob]

Dave,

The best way to determine what size inverter you need is to add up the wattage(s) of all the items you intend to run at the same time, and or the highest wattage item, and then size the inverter 25% or more higher.
Unless you have sensitive equipment that needs a very expensive inverter, there are a ton of cheap ones to choose from, brand wise.

Rob

[Vedette]

I carry a cheap inverter that we have yet to use.
But my understanding is that they will kill your 12 Volt Deep Cycle Battery very quickly??
Good Roads
Brian

[working on it]

I have a 410 watt Schumacher inverter for use in my trailer, to convert battery power to 110vac, only if necessary when externally sourced power is not available (I also have an onboard 2500 watt generator-noisy-as another alternative). I've used inverters rated at 400-410 watts in all my vehicles for years, for small item usage like a work light (prior to LEDs, an incandescent shop light worked best) or even a 3/8" drill. I still use one in my HHR Panel to power a small heater (200 watts Lasko) and to charge power tool batteries occasionally. In the trailer, I have the 410 w inverter to power the same small heater, or LED lighting, or even the 10" 110vac fan. But since the inverter only is about 85-90% efficient, and the drain on the battery is so great using the fan or heater (over a long period of time), I only will use them in moderation. If you choose a larger inverter (needed for a coffeemaker or electric cooking device), then the 12v battery will be drained even faster. Here are a couple of charts to give you an idea of wattage drain and battery life:

inverter_chart.jpg (77.92 KiB) Viewed 702 times

12vbatterychart.jpg (230.87 KiB) Viewed 702 times

Tailor your inverter size and length of appliance use to fit somewhere in the ranges given. Also, make sure your inverter isn't always on-line (either disconnect manually or by a switch) to your battery (whether turned on or not, the inverter draws power anyway); I didn't know that, and had mine drain my Optima to an almost dead state.

[Shadow Catcher]

To put it simply anything using resistance heat is a no no. When relying on battery we use a French press for coffee and any type of ceramic heater is a power killer. You might be able to use a coffeemaker but be aware how much it consumes.

[skybear4]

Thanks for all the good info. I am concerned about the battery drain. I'm seeing more solar usage. Would that
provide adequate an adequate power source normally? I would guess costs vary considerably.

[MtnDon]

Shadow Catcher beat me to it. But I'll say it anyways to reinforce the point. Resistance heating is a poor use of battery power. We do use some resistance heating in our off grid cabin, but only enough to make the odd slice of toast. We have over 15,000 watt hours of storage capacity though, compared to maybe 1200 - 1500 watt hours with a ordinary 12 volt battery.

If the sun was shining nice and bright and you had PV panels producing some refill power then it might work for a few slices of toast. A small one cup coffee maker that is done in three minutes or so might work. Figure out the power consumption of the coffee maker... amps, watts, whatever hen see what % of the battery capacity that would consume. 50% is a max draw down on the capcity of a battery. Less is best to make the battery longer lived.

[48Rob]

I am concerned about the battery drain. I'm seeing more solar usage. Would that
provide adequate an adequate power source normally? I would guess costs vary considerably.

Adequate power source is what most of us on battery and solar systems are always trying to achieve...

Just like sizing an inverter, sizing a "system" that you find adequate for your needs, depends on how "much" you need to get back out of it.
And yes, costs do vary a lot.
Someone that only runs a few light bulbs a couple hours a day can get by with a small, fairly inexpensive system.
Others, like me...need huge solar arrays and battery banks because of "need"

Rob

[bobhenry]

If you are trying to heat anything try and use propane or charcoal where possible. A 12 volt or 120v (converter powered) coffee pot can easily be replaced with a on the burner perk type. I have gone to simply boiling the water and using the coffee singles. Yep the little tea bag type coffee bags. The toaster oven is easily replaced with a good camp oven, some charcoal ,and a bit of patience. I am about to venture off grid full time and my only major concern is refrigeration and the drain that a small freezer and seperate fridge will need.

[48Rob]

I am about to venture off grid full time and my only major concern is refrigeration and the drain that a small freezer and seperate fridge will need.

Bob,

...Propane fridge/freezer...

Rob

[mikeschn]

Check out Norcold.

You won't like the price... but if you could find one on ebay.... maybe...

Also check out the engel models...

https://www.engel-usa.com/products/frid ... ing-models

Mike...

[MtnDon]

I am about to venture off grid full time and my only major concern is refrigeration and the drain that a small freezer and separate fridge will need.

Bob,

...Propane fridge/freezer...
Rob

We use a Servel 400 propane fridge in our cabin. At 8 cu ft it would be too small for our full time use. A friend has a CrystalCold that is something like 15 - 17 cu ft IIRC. They are happy with it. We have both had them for several years. Both are expensive compared to standard electric models. However if I was doing the refrigerator thing all over again I would try for a electric system. We are blessed with great solar here in NM. PV panel prices are half what they were in 2009. Unfortunately the storage still costs the same. But an electric fridge can cost a lot less than a propane one. I think it could be done today. I would want to have an autostart propane fueled generator though just in case of a winter storm reducing solar output.

IF you can live with a chest type refrigerator SunDanzer has some DC models that are pretty good on being power misers.

[bdosborn]

We run two electric fridges when we camp, and we have a kuerig coffee maker. It all works but we've got lots of panels:



No way we could use a ceramic heater though, it's just too big a draw...

Bruce

[bobhenry]

I am about to venture off grid full time and my only major concern is refrigeration and the drain that a small freezer and seperate fridge will need.

Bob,

...Propane fridge/freezer...

Rob

DUH ! I still have this propane/electric one out of the donor carcus for the caboose.

[Shadow Catcher]

We use a WAECO refrigerator freezer which is 12V or 120AC and like Bruce it is part of our solar system. With proper planning we managed 8 days out of a cooler and the refrigerator. The propane refrigerators designed for RV's are notoriously unreliable and in some cases fire hasards.