Prepping an RV for Cold Weather
Most people don’t RV camp in freezing temperatures, but sometimes it’s unavoidable.
Maybe you needed to stay up north an extra month, or you need some temporary housing for a job in a cold area.
There can even be random freezes that hit the warm southern states that normally have temperatures that stay well above freezing year round.
Related Product: Indoor propane heaters like the Mr. Heater Buddy (click to view on Amazon) are a great way to keep your RV warm without using electricity.
Whatever the reason, it’s a good idea to be prepared for freezing temperatures if you are going to be using your RV in the winter, early spring, or late fall.
It’s easy to keep the inside of your RV warm with the RV furnace, space heaters (if you have electricity), or propane heaters.
But the outside of the RV is a different story.
Some RVs have the freshwater tank inside, but many have them mounted underneath the RV. All RVs have the black and grey tanks mounted underneath as well.
Being mounted outside the RV saves space inside but it leaves the RV tanks exposed to the cold.
There’s a chance of them freezing, which could result in a break or crack. Broken RV holding tanks can be a time consuming and costly repair.
What Are RV Tank Heater Pads?
One easy way RVers can help keep the RV holding tanks from freezing is to install RV tank heater pads.
These pads have heat cables running through them. They adhere to the bottom of the tanks so the heat can transfer upwards and stop freezing.
Most RV heating pads are 12 volt powered. That means you can hook them up to your RV battery and power them even if you aren’t connected to 120 volt power.
There is a 120 volt option in this article, make sure you double check the voltage before purchase so you get the right one.
They are great for any kind of camper and are a simple upgrade that can help give you peace of mind when camping during the colder months.
In this article, I’m going to go over the power usage of some of the most popular RV tank heater pads sold by Facon and RecPro
I’ll give the amp and watts usage of the different sizes and also give you the information you need to calculate how much battery power the heater pads will use.
I’ve also included some of the smaller RV heater pads that are used for RV drain pipes and gate valves.
RecPro (Facon) RV Tank Heat Pads Power Usage
Last update on 2023-09-29 / Affiliate links / Images from Amazon Product Advertising API
On the table, there’s a row called “Temp Control.”
The temp control feature is a built in thermostat that will turn on the RV tank heat pads when the temperature drops below 45°F.
It helps save power and makes it so you don’t have to switch them on and off every time you want to use them.
This feature isn’t built into the smaller drain pipe heaters, they will need to be turned on and off manually.
One thing to note if you’re boondocking is the thermostat draws a little power all of the time, you may want to turn off the pads completely when not in use so your battery doesn’t slowly drain.
RV Tank Heat Pad Installation
In general, installing heating pads on RV holding tanks and drain pipes is really easy.
All of the ones in this article have adhesive on one side, just peel and stick.
If your RV is covered underneath it might be a little harder to access the tanks, but that shouldn’t stop you from installing heating pads.
You can cut into the underside cover to expose the tanks and install the pads.
When you’re done you can use my zip tie method to put the cover back in place.
Most of the time RVs with a closed underside are also insulated, but if there’s no insulation you can add some when you are installing the RV tank heater.
The electrical is the most difficult part of installing RV tank heater pads.
If you have multiple pads you can connect them together in parallel and connect them all to one rocker switch and your 12V power source of choice.
Or if you have a switch plate like this (click to view on Amazon) that has a switch for each tank, you will need to run wires from each pad to the switches.
You can connect the main power cable either directly to the RV battery or to the 12 volt part of the RV power center.
The wire gauge you should use depends a lot on the number of tank heater pads you are going to be using.
Use the table to find the amp usage of each heating pad, add all of them together, and get a gauge of wire that can supply power to all of them.
RV Battery Run Time Calculations
I’ve written out each step of the calculations in detail below for those who are new to the world of RV batteries.
If you already understand battery capacity I’ll give a short version quickly so you don’t have to read through the detailed explanation.
Battery Capacity (in Wh) / Total Watts Used by Heat Pads = Number of Hours Battery Can Power Heat Pads
Remember for lead acid batteries you only want to use 50% of the capacity. For lithium 80% of the capacity.
Also, cold temperatures can reduce the storage capacity of batteries.
This estimate is also based purely on the power draw by the RV tank heat pads, there are also lots of other things that draw power from an RV battery.
Remember to take those things into account when calculating.
Figuring Out the Battery Storage Capacity in Amp Hours (Ah)
To get a general idea of how long your RV battery could potentially power one or multiple RV tank heater pads you need to know the capacity of your RV battery or batteries.
Most batteries are sold with the capacity listed in amp hours right on the battery.
If you have a marine/RV battery that is both a starting and a deep cycle battery it is going to be a little harder to calculate the storage capacity.
They discharge power a little differently than regular deep cycle batteries and don’t always have the total Ah listed.
That’s why we recommend getting a standard RV deep cycle battery over the marine/RV combos.
If your battery gives you the Reserve Capacity in minutes, instead of the capacity in amp hours, you can use this formula to figure out the amp hours.
Reserve Capacity (in minutes) / 60 = Reserve Capacity (in hours)
Reserve Capacity (in hours) X 25 = Amp Hours
Example: The NAPA Marine/RV DP27 Dual Purpose 12 volt battery has the Reserve Capacity listed as 150 minutes.
Using the equation above you can divide the 150 minutes by 60 and get 2.5. The 2.5 is the Reserve Capacity in hours.
Then take the 2.5 and multiply it by 25, which equals 62.5.
Based on the calculation, your Marine/RV battery has around 62.5 amp hours of storage capacity.
How to Find RV Battery Capacity in Watt Hours (Wh)
You can calculate how long your RV battery can power an RV tank heating pad using the amps if you want, but sometimes it’s easier if you calculate using watt hours instead.
To find the storage capacity of your RV battery in watt hours all you have to do is multiply the amp hours by the voltage of the battery or battery bank.
Amp Hours X Voltage = Watt Hours
Example: A 12 volt battery with a 100 amp hour storage capacity has 1,200 watt hours. (100 x 12 = 1,200)
For Multiple 12V Batteries Connected in Parallel
If you have multiple 12 volt batteries connected in parallel (which they should be for RVs since they only use 12 volt appliances) you can find the capacity of each battery and add them together or multiply the Wh by the number of batteries.
Example: If you have four 12 volt batteries wired in parallel and each battery has a capacity of 100Ah (1,200Wh) and you want to find out how many watt hours you have in total.
All you have to do is multiply the Wh of one battery by the total number of batteries. 1,200 x 4 = 4,800
Your four 12 volt batteries have a combined storage capacity of 4,800Wh.
For Multiple 6V Batteries Connected in Series
For those of you who have RV battery banks made up of 6 volt batteries, the storage capacity is calculated a little differently.
Because you are wiring them to increase the voltage the capacity actually stays the same.
Example 1: If you have two 6 volt batteries with 200Ah each wired in series so they output 12 volt power the amp hours stay the same at 200dAh.
You still multiply the final amp hours by the final voltage to get the total watt hours. In this case, 200Ah x 12V = 2,400Wh.
Example 2: If you have 4 6 volt batteries in your RV, they should be wired in both parallel and series.
Two pairs are wired in series to make 12 volts, then the pairs are wired together in parallel to combine the 12 volt pairs.
So if each 6 volt battery has 200Ah you get two 12 volt pairs with 2,400Wh. When those get combined you end up with a final of 400Ah capacity or 4,800Wh.
Estimating How Long Your RV Battery Can Power RV Tank Heat Pads.
Take the capacity of your RV battery in watt hours (Wh).
If the batteries are lead acid divide the total Wh capacity of the battery by 2.
This is because most deep cycle lead acid batteries will start to get damaged and lose capacity when discharged past 50%.
Some higher quality lead acid batteries like AGM and some Gel can be discharged more than 50% before getting damaged but in general, it’s 50%.
If your RV batteries are lithium, multiply the total Wh capacity by 0.8.
This is because most deep cycle lithium batteries can be discharged 80% before they start to get damaged.
Using the table above calculate how many watts each RV tank heating pad will use by taking the watts used by each one and adding them together.
Example: If you have 3 of the largest RV tank heating pads that use 78 watts every hour each they will in total be using 234 watt hours.
Take the battery capacity in Wh and divide that by the total number of watts the RV tank heat pads will be using.
The number you are left with is an estimate of the number of hours your RV battery or batteries can run just the RV tank heat pads.
Example: A lead acid RV battery bank with a total capacity of 2,400Wh can discharge up to 1,200Wh before getting damaged.
If you have 3 RV tank heating pads that use 78 watts each, 234 watts in total, you will divide 1,200 by 234.
You end up with 5.13. That means your RV battery bank could run all three heat pads for 5.13 hours.
That is if nothing else is connected to the RV batteries. Which there most likely will be.
A lot of 12 volt appliances use power from the RV battery, especially the RV furnace.
Once you start adding up all the watts used by other appliances your RV tank heating pad run time is going to go down a lot.
If you are boondocking with a limited power supply I recommend only turning on the RV tank heating pads for a few of the coldest hours.
Otherwise, you might end up with a dead battery.
You can run things for longer if you use a generator or a portable power station when boondocking.
Frequently Asked Questions About RV Tank Heater Pads
Can the RecPro Facon RV heat pads be daisy chained together?
Yes, the RV tank heating pads sold by RecPro and Facon can be connected together in parallel.
That way you will only need one main power cable coming from the RV battery or RV power center.
You will also only need one switch if you don’t want a different switch for each heat pad.
My RV heater pad says it’s for 13.5 volt power, is it ok to use with my 12 volt RV battery?
Yes, you can use the RecPro and Facon RV tank and drain pipe heating pads with a 12 volt battery.
Even though it says 13.5 volt on the heating pad, both companies have stated that it’s ok to use them with 12 volt batteries.
What wires are positive and negative on the RecPro & Facon RV tank heating pads?
The 12 volt wiring for RV tank heating pads is very simple.
The red wire is positive and the white wire is negative.
Will the RV tank heating pads damage the tank if it’s empty?
These heating pads shouldn’t get hot enough to damage any of your RV holding tanks or freshwater tank if they are empty when the heat is turned on.
You shouldn’t need to have the heating pads on if the tanks are empty, but if it accidentally happens it shouldn’t damage them in any way.
Have any more questions about the power usage of RecPro & Facon RV Tank Heating Pads? Leave a comment below.