Thursday, March 30, 2023


RVelectricity – Winter battery maintenance

By Mike Sokol

There’s a lot more to winterizing your RV than simply draining out the water and putting pink stuff in your pipes. In fact, if you forget one really important item it can cost you many hundreds of dollars in the spring. And that thing is properly maintaining your RV batteries over the winter.

First things first…

The first thing to decide is do you bring your batteries into your garage, or do you leave them inside of the RV. There are advantages to each, but I personally think that most RV owners should not be disconnecting and reconnecting batteries. That’s because there are many hundreds of amperes of current available if you accidentally short a wrench across the battery terminals (or even a positive wire to the frame).

Don’t get burned

That’s bad enough as it is since those huge currents and sparks can cause a battery explosion, spraying sulfuric acid everywhere (including your face). However, if you get your wedding ring or metal bracelet in the middle of the connection, it can heat up above 1,000 degrees in seconds. Read my story about how this happened to one of my Facebook members last month. Read more HERE, but be aware the pictures get much worse.

And remember that if you do plan on removing your batteries, you’ll want to carefully mark the wires and take good pictures. I get emails from readers every spring detailing how they accidentally reversed the polarity and burned up their inverter. So if you don’t have to remove them, don’t do it.

However, you’ll still need to use some sort of float charger to keep the batteries healthy over the winter months. Now, if you already have a 3-stage charger/inverter with a float or maintenance mode, then all should be well. Just remember that you probably need to leave your battery switch in the ON position so the float charging current gets to the battery. But under no circumstances should you use a 2-stage charger with a trickle mode as it may boil out the acid of your batteries, killing them and rotting out any metal in the battery compartment.

Pick the proper charger

So, if you have an earlier charger or just don’t feel comfortable leaving your entire RV electrical system energized, you should consider a dedicated float charger such as one from Battery Tender. This one not only provides monitored float/maintenance current, it’s also a 10-, 6- or 2-amp charger that handles all battery chemistries.


To use a Battery Tender (float charger) you simply turn off your main battery switch in the RV and connect the Battery Tender clips to your battery terminals. Even if you do make a mistake and get the polarity reversed, these modern units are smart enough to warn you about it and not blow up your battery.

Don’t worry if you have 6-volt batteries in series – you just connect from the negative terminal of the grounded battery to the positive terminal of the battery feeding the inverter or power center.

Of course, Battery Tender, as well as other manufacturers, make smaller versions as well as solar panel versions that include a float charger mode. But I like having a 10-amp charger built-in just in case I drain my batteries and need an overnight recharge from an outlet.

But no matter what, don’t ignore your batteries this winter or you’ll likely have an expensive replacement bill come next spring.

Let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at For more info on Mike’s qualifications as an electrical expert, click here.

Email me at mike (at) with your questions.

For information on how to support RVelectricity and No~Shock~Zone articles, seminars and videos, please click the I Like Mike Campaign.



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1 year ago

I don’t want to sound stupid, but since the Battery Tender has to be plugged in anyway, why not just leave the RV plugged into house current? What are the downsides? Where I currently keep my RV in winter would require about 150′ of extension cord to keep it, or a Battery Tender, plugged in; plus we get lots of below freezing temperatures, so I bring the battery in for the winter.

Last edited 1 year ago by Irene
Mike Sokol
1 year ago
Reply to  Irene

If it’s easier to bring the batteries inside, then that’s your best plan.

2 years ago

I have used battery maintainers with a desulfation mode for years. My camper battery was new in 2007, still passes a load test and worked well this summer. Sulfate on battery plates is a major problem for batteries in storage shortening battery life and performance. Whenever my unit is not in use it is plugged into the maintainer. The brand I use is BatteryMINDer. I get them from Northern Tool.

2 years ago

I use the same equipment with the same results. Great product. I have used desulfators for 20 years and they always double normal battery life. My current favorite is Amazon’s or Northern Tool’s model 12117TC often available for 29.95 on sale.

Larry W.
2 years ago

I live in western Colorado. It gets below freezing virtually every night in the winter months and occasionally to zero or below. I would like to leave the battery in our Class C during the winter but I’m afraid it will freeze. Can I insulate the battery compartment to keep the battery from freezing?

Ed I.
2 years ago

Don’t forget you will need two chargers for a Motor Home, one for the Chassis and one for the House. You could connect the two systems together with a Fused wire between the positive terminals I guess, I just would feel safer with two chargers.

Michael Hayes
2 years ago

I have four batteries that I winterize inside my basement, 2 from camper, a motorcycle and a lawn mower. All are 12v but obviously different sizes and ratings. I put a float charger on one battery and switch it every week, so all batteries are “floated” for one week a month. Is this adequate?

2 years ago
Reply to  Michael Hayes

I used that method for several years on mowers, motorcycles, and Jet Skis, using the name brand Battery Tender for maintenance, cycling one from battery to battery. At about $35 a pop it would have been costly to use 7 of them. Then I discovered that Harbor Freight had their own brand that ran about $6 each, so I got a couple of them. That was a little easier, but still not as easy as it could be. Then Harbor Freight came out with solar powered battery maintainers to stick in the garage windows. Now, everything has it’s own maintainer either plugged into the wall, or stuck in a window. The Harbor Freight brand puts out about .5 amp compared to the Battery Tender’s 1.25 amp. The solar units are .5 amp or less while the sun is shining. They’ve all been working great for years. Love me some Harbor Freight. PS – Dont forget the fuel stabilizer.

2 years ago
Reply to  Michael Hayes

I bring mine in to the basement and just let them rest. I charge them before putting back on the tongue in the spring. My batteries have lasted 9 years so far.

2 years ago
Reply to  Michael Hayes

yes that is fine assuming low parasitic drain.

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