Where to invest on improving electricity in your RV for winter use

My journey. What I thought was ideal and what I am planning to do.

The idea is to operate out of an RV in Ski Area parking lots for days or weeks at a time. To give up little, aside from square footage and luxurious long hot showers. To plug in all my electronics to any outlet whenever I want. To do it without being plugged into electricity which is not available in most ski area parking lots. Imagine being in the far corner of the parking lot or in a remote trailhead parking lot. Your cabin in the mountains that can move to different mountains and ski areas.

This article is not a deep dive into amps, watts and all things technical. I will try to stay big picture. Give you a basic understanding of the factors without getting lost in the weeds. Like many things, the more you know the more complex it gets. There are many good resources on line that dive deep into RV electronics. One of the best sources I have found is https://allaboutrvsinfo.com/rv-electrical/. Jared Gilles is a guru of all things RV, especially so on the electrical side. Often times the information goes very deep. My intent is to stay big picture and give you bottom line advice specific to this world of Skiing out of your RV.

Let’s get after it.

Batteries

First, let’s remember that this is about staying in an RV in the dead of winter in a ski area parking lot. Not plugged into power. Not getting much sunlight to shine on your solar panel(s).

There are four types of batteries:

12 volt lead acid (Typical car battery type)

6 volt (Golf cart battery)

AGM (No maintenance)

Lithium (No maintenance, complete discharge & much faster charging)

12 volt lead acid (Typical car battery type)

This is the standard and is basically a car battery. If you almost always stay in camp grounds and plug into electricity this will be fine. They are easy to get and cost about $100 per so you might as well get two.

Each battery will give you about 75 to 100 amp hours. Buy two and they are are wired in parallel which means you add the amp hours to achieve 150 to 200 amp hours. (Exactly how many hours of use you get out of an amp hour is complicated. For our purposes, we will just use amp hours to compare the different battery types.)

One other critical factor is the depth of discharge. How low can you discharge the battery before you do damage? The standard here is 50%. Which means you can only discharge the battery 50% before re-charging. So that means each battery can really only provide 37. 5 to 50 amp hours. Total amp hours with two batteries is then 75 to 100.

It does require maintenance. My initial reaction is no big deal. Just add some distilled water when needed. But it also involves cleaning the battery terminals as they corrode with heavy use. Not a show stopper but certainly a hassle.

All lead acid batteries need venting. No big deal. Install them outside or in a compartment that is vented.

If you are an RV skier it is not what you want. Spend a little more money and get much better performance. Move on.

6 volt (Golf cart battery)

These are bought in 6 volt pairs and wired together in series (versus parallel) to create one 12 volt battery. RV’s operate on a 12 volt system. Typical amp hours is 215 to 230 per battery pair. When wired in series one does not add together the amp hours. So if you have four of these 12 volt batteries the total amp hours will be 430 to 460. More than double 12 volt lead acid. Note these are taller than lead acid batteries so they will take up more space. Each 6 volt battery is close to the cost of a 12 volt lead acid so they are roughly double the price. Well worth it in my opinion.

These have the same discharge characteristic, no more than 50%. So the real capacity of this 4 battery configuration is 215 to 230. More than double the standard 12 volt configuration.

Maintenance and venting is the same as 12 volt lead acid.

AGM (No maintenance)

Each battery will give you about 100 amp hours. Buy two and they are are wired in parallel which means you add the amp hours. So you get 200 amp hours.

AGM has better properties on discharge rate. Meaning you can drain them below 50% unlike 12 volt lead Acid or 6 Volt golf cart type. Some people say you can take it all the way down to 20% charge. Others say when you do that it reduces the life of the battery. For comparison purposes lets use 35% as the discharge maximum.

Using 35% as the discharge maximum, that means two AGM batteries will give you 65% use of the battery before they need to be charged. 200 X .65 = 130 amp hours.

They do not discharge as quickly when not being used. Again, no big deal for most. Just make a note to plug your RV in for a day every month or two when not being used in between ski trips.

AGM can charge100% faster than Lead Acid IF you change out the converter/charger to a model that can accommodate AGM and charge at a higher rate.

They are about the same foot print as Lead Acid so they take up less room than Golf Cart batteries.

Did I mention no maintenance? No corroding terminals. No need to carry distilled water and dealing with it freezing if you keep it in your truck.

The batteries are about double the cost again from a 6 volt golf battery set up. More if you need to change out the converter/charger.

AGM does not need venting. So more flexibility in where you can install them.

Lithium (No maintenance, complete discharge & much faster charging)

Best performance by far because they can be discharged completely before recharging. Meaning a typical 100 amp hours Lithium is actually twice the capacity of a 100 amp hour lead acid/6 volt golf cart because of the 50% discharge limit of lead acid batteries.

Two 100 amp hour Lithium batteries deliver up to 200 amp hours.

About the same foot print of 12 volt lead acid but much lighter.

No maintenance and no venting required, just like AGM.

They require a different kind of converter/charger. For Lithium, they charge at a MUCH higher rate and actually vary the charge as the battery nears capacity. Charges about 5 times faster than lead acid. This is especially huge in the winter when solar panels will not be very effective. (The sun does not shine when it is snowing!)

Lithium batteries are way more expensive up front, approximately 10 times the cost of 12 volt Lead Acid. ($1,000 versus $100.) However, the other 3 types of batteries will last about 1,000 charging cycles. Lithium supports about 3,000 so it should last about 3 times as long. Actually, even longer since the batteries will have 75-80% of their original capacity after the 3,000 cycles.

Temperature is a big deal to Lithium. They don’t like to be too hot or too cold. They will not discharge (produce power) when the temperature is below -4 F. They cannot charge when the temperature is below 32 F. On the surface that seems to knock them out for winter use. But there a couple options that make them viable for winter use.

• Some Lithium manufactures make a battery that has an optional heating component. Push a button to turn on the heater. It uses a minor amount of power when the heating function is on. In theory you could install Lithium batteries outside in an insulated box of some type if your setup has enough room. Certainly seems workable but it makes me nervous. Imagine a connection coming lose and it is -10 F. Now your battery will not discharge to start the built in generator. You have no heat, you are screwed.

• Install the Lithium batteries inside the RV. This pretty much eliminates the potential problem of the batteries getting too cold to discharge or charge. (As long as you don’t drain the batteries to nothing and therefore your heater stops working.) The downside of this is you must find a location for the batteries and pay extra labor for a custom location that will typically be in some storage space that can no longer be used. It could easy be a full day of labor for all the cable and carpentry work required.

Battery summary

Here is a chart comparing the different battery types. Of course not all battery manufacturers and chargers have the same specs so these numbers represent an average. The math and science behind these numbers is a bit complicated so I elected not to not try and explain how these numbers are calculated. I did validate these numbers with several experts.

Note the column in red above. Running your generator 10 hours every day to replace 100 Amp hours does not seem practical. This leaves AGM and Lithium.

AGM advantages

• Can be installed outside where the existing batteries are likely already installed. This can save a full days labor compared to Lithium installed on the inside.

• Assume $1,000 additional labor and $1,200 cheaper batteries for a total cost savings of $2,200.

AGM disadvantages

• Lower capacity than Lithium. 130 hours versus 200. This means you will have to run the generator more often with AGM.

• Slower charging time than Lithium. 5 hours versus 2 hours to charge 100 Amps.

Lithium advantages

• More capacity. 200 Amp hours versus 130 Amp hours.

• Faster charge time. 2 hours to charge 100 Amps versus 5 hours for AGM

Lithium disadvantages

• More expensive. Assuming an extra $1,000 to install inside, a total of $$2,200 more. Install cost could vary, may be even higher.

• Sacrifice some storage space where the batteries are installed.

• Lithium is new technology. Some are still leery of it and don’t like the idea of batteries installed where they live. (Remember they are sealed so no vapors.)

I made the decision to go with Lithium and will install on the inside of the RV and pay the extra install costs and give up one storage drawer. After our first ski trip I will post an update on our experience with pictures and battery performance data.

Battery Monitor

All RV’s have some kind of limited battery monitor capability. Typically it is the simple “idiot light” variety. Full, Medium, Low. This isn’t going to cut it for RV skiing. It would be like driving across the country not knowing how much farther you can drive before running out of gas.

Fortunately these products are not that expensive (about $200) and they are independent of any other electrical system. It connects directly to your battery and measures very accurately things like:

• The current state of charge

• What the discharge rate is right now. (Is something plugged in that shouldn’t be?)

• What is the current charge rate. How much longer before they are fully charged.

To learn more check out this video.

Generators

Don’t even think about not having one, it is a requirement. When your battery type runs “out of gas” you must recharge them. Generators power up all your 110 volt outlets in the RV and charge your batteries. How it does that is a bit complicated so let’s not go there.

Like everything else…There are several different options:

• Built into the RV. Runs off propane that powers your furnace. Push a button inside the RV and it starts. This is the only way to go in my opinion. Who wants to go outside in the dark and cold to mess around with fueling and starting a generator. Keep your slippers on and push a button inside the warm RV. But if you don’t have this, you still need a generator so read on.

• External generators. They are moderately priced. Can run on propane or gasoline. (Some models can run on either.) Gas will run the generator at higher RPM’s but it is messy. You are going to spill it and need to worry about safety. Gasoline also gets old. After only 30 days is starts to go bad. Propane doesn’t get old and will never make a mess. Biggest issue might be whether it delivers enough Watts to power the start up demand of your Air Conditioner. Of course that isn’t a concern for RV Skiing or vacationing in mountains during the summer. But just in case you are interested, here are the numbers. A 13,500 BTU air conditioner pulls 2,750 watts on start up and then settles down to 1,250 when running. If you might run an air conditioner on your generator just be sure it exceeds those numbers a bit. Check the specs on your AC to see if it is different.

Inverters

Sometimes you don’t want to turn on the generator to do something simple or it is late and turning on a generator is not neighbor friendly. Things like watching TV for an hour, charging your laptop or running a dehumidifier.

The basic function of an inverter is to convert DC power (your battery) to AC power. Inverters can be inexpensive and simple, or very complex by integrating into your entire electrical system.

The most simple design is to connect an inverter to your battery and then plug a 110 volt AC device into the inverter. Best to have the invert located as close as possible to the battery. Simple and could work fine if there is just one or two devices you would plug in.

Turn it on, plug in your device, enjoy.

On the other extreme is a Hybrid Inverter. This a very complex device/set up that integrates into your entire electrical system. Depending on how thing are configured, it does things like:

• Integrates into your electrical system so that every outlet can be on and powered by the batteries when not connected to shore power and the generator is not on.

• When plugged into shore power of some type, it can pull power from your batteries if you are drawing more power than the shore power can deliver.

• Automatically detects what power source is on and automatically switches.

This is what I wanted. (Who wouldn’t want this?) If you are an electrician or a superman DIY type perhaps you could do this yourself. I am not, so I went to a higher end RV dealer to get a quote. RV dealers are now super busy in these COVID times. It took me months to get a quote and my jaw hit the floor when I saw it. Over $3,000 in labor. Total cost over $6,000! One of the challenges is that there are several components to this, lots of cabling and perhaps a new fuse box needed. Most RV’s (Vans and sub 30 trailers for sure) don’t have extra space for this stuff. So in addition to tons of cabling work there is also retro fit carpentry work involved. My lesson learned is that if you have a modest sized rig this should be implemented when initially built.

So as I contemplated and moped about not having my ideal electrical situation the solution came to me. I remembered the days when going on vacation driving across the country, I would plug a small electrical box thing into the cigarette lighter outlet and plug my laptop into it. This of course is an inverter. My trailer has a cigarette lighter (12 volt connector) and I suspect all vans, RV’s and most trailers do as well. I can simply plug one of these portable inverters into the 12 volt connector and now I have two 110 volt outlets! Perfect for running the dehumidifier 24/7 and perhaps watching a movie after dinner. The disadvantage of this on the cheap solution is that there is a limited amount of power that can be delivered to the 12 volt connector. I believe 150 amps. Should be good enough for a TV, computer….I will report back.

Solar

Who doesn’t like Solar. Get electricity from the sun “free”. Challenge is that there is not much sun when it is snowing. So a short section here folks. Great stuff when the sun is shining during your summer adventures. For RV skiing it is the generator that will charge your batteries.

Bottom Line

Upgrade your batteries to AGM or Lithium.

Buy a new converter/charger

Get a battery monitor.

Be sure you are 100% confident in your generator solution.