Battery Power for Boondocking
Perhaps 50% of full time RV boondockers have two 12 volt batteries or two 6 volt batteries to power their DC accessories and appliances.
Another 25% have four or more batteries.
The other 25% have just a single 12 volt battery.
Some Things Don’t Run on Battery Power
Appliances that run on AC current (110V or 120V) don’t run on battery power. Hence, you don’t need to count them when determining how much battery power for boondocking you’ll need…
- Your air conditioner unit runs on AC.
- Microwave oven runs on AC
- Hair dryer, curling iron, electric shaver,
- Food processor, Instant Pot, blender, coffee maker
- Television
- Electric heater, portable fan
However, many boondockers have added an “inverter” which converts battery power (DC current) into AC current. Then they add an aditional AC outlet to a wall and connect it to the inverter. Or, the plug appliances directly into the inverter. If you don’t have an inverter, you’ll need a generator to produce AC current.
What Runs On Battery Power
Your RV will use battery power for overhead lights, vent fans, water pump, tongue jack, awning, Happi-Jac bed, in-sink garbage disposal, outdoor lighting, slide motors, propane leak detector, breakaway brake (on trailers).
There are also appliances that run on two of three different sources of energy:
- RV refrigerators use battery power for the control panel, but either propane or AC power for the cooling
- The furnace uses battery power to run its internal fan and igniter, but propane for the heater
- Your water heater uses battery for its internal controls, but either propane or AC power for heating
- If you have built-in generator (Onan) it needs battery to prime the pump and to start the engine.
The item you’ll depend upon the most is the water pump, because you won’t get any water from your water tank without it. You won’t be able to shower without it, and you can’t even flush the toilet without it. Your furnace will be next most important, to keep you warm at night. Furnaces can be big battery hogs. A single 12 volt battery won’t last for more than a couple hours trying to run a furnace.
How Many Amp Hours (AH) Do I Need for Boondocking?
How much battery power for boondocking you will need is measured in Amp Hours (AH). This is a measurement of how much amperage a set of batteries can hold and deliver, expressed in terms of hours of use. Generally, the larger in physical size the battery, the more AH.
A typical car battery used for starting an engine has about 87AH. But most boondockers are using deep cycle marine batteries or RV batteries that deliver 100-150 AH each.
50% of the RV boondockers mentioned above, with either two 12 volt batteries, or two 6 volt batteries, typically have about 200-250 AH at their disposal. That’s still plenty of battery power to run a propane furnace all night long, keep the lights on in the evening, run the vent fans during the day, charge electronic devices, and keep the water pump ready for use.
The 25% with four or more batteries, typically are running four 6 volt batteries, and usually have about 400-600 AH available. These boondockers often have a 2,000 to 3,000 watt inverter to convert DC power to AC, so that they can plug popular appliances (blender, food processor, television, coffee maker, hair dryer, vacuum cleaner, et al) into a familiar wall socket. These boondockers are looking to have all the conveniences of a brick-n-mortar home in a camper.
The other 25% of boondockers with just a single 12 volt battery, have only enough power to run their lights, fans, and water pump most of the day. A single battery won’t run a furnace all night long, and generally won’t even run it for more than a couple of hours. Hence, most boondockers in this category use a portable propane heater and lots of blankets.
You Can Only Use Half of Your Battery
Keep in mind that Lead Acid batteries, in either the Flooded Cell or AGM type, can only be used until it reaches 50% state of charge. If you continue to draw down a battery below 50%, it starts to suffer permanent damage. At that point, it loses its ability to recharge. Hence, a battery rated as having 100 AH, technically only provides 50 AH under proper use. When a battery is fully charged, it generally delivers as much as 14.0 volts. By the time it reaches 50% state of charge, that voltage will drop down to about 12.0 volts. Any lower the state of charge, that voltage will continue to drop and generally becomes too weak to power even simple lights and fans.
Lithium batteries are advantageous because they can be discharged all the way down to 0% state of charge without suffering damage, and without suffering voltage loss.
The Cheapest & Easiest Way To Go
Buy two 12 volt batteries, with at least 100 AH each, and a couple of thick (0, 1, 2, 3, or 4 gauge wire) and wire them together in parallel (see diagram). And that’s it, you’ve joined the 50% category of boondockers. It’s about as plug-and-play as you can get, without taking on too much cost…
- Technically, wiring two batteries requires four wires, but your RV should already have two wires there.
- It’s important that you are using two batteries of the same age, brand, type and size. Even though your RV may already have a single 12 volt battery in it, don’t buy just one additional battery, buy two and set your RV’s battery aside, and either use it elsewhere or take it to the store where you bought your others for the core fee refund.
Four batteries requires wiring two in parallel and another two in series, to get 12 volts. It’s a little more complicated, and the cost is quite a bit more due to the four batteries and cables. Four batteries also adds a lot of weight to your RV. It’s better to start out with two batteries, and determine later if four batteries is necessary.
For More Reading
- For a more technical analysis of how much battery power for boondocking you’ll need, the Boondoctor has an excellent article, “How Many Batteries Do I Need For My RV?“
- Thinking of going solar? Read our other article, “How Many Solar Panels do I Need for Boondocking?”