Wednesday, August 22, 2012


I am going to start right off saying that I am not an "expert" in vehicle or RV batteries. I do know what I have learned from others before and after we got the Roadtrek about the batteries that the Roadtrek uses. I also know how they work in our 2011 190 Popular.

First, the simple - there are either two or three batteries in your Roadtrek. One is the engine battery just like in your car. This is a wet cell (maintenance required or maintenance free) vehicle starter battery. It is different from the battery(ies) that you have in your coach - those that run everything 12 volts inside your Roadtrek. Current model Roadtreks have either one or two "coach" batteries. These one or two batteries have nothing to do with starting your engine and in most, if not all, Roadtreks there is what is called an Isolator in the engine that separates the vehicle battery from the coach batteries so that if one drains it will not pull power from the other. You would not want to not leave in the morning because you ran down the coach batteries the night before.

My 2011 Roadtrek 190 Popular has TWO coach batteries. When we were buying the Roadtrek every salesman we encountered told us that this is a feature of the 190. It turns out that the current Roadtrek models of 190 and 210 and the Sprinter models have two coach batteries. I have been told by owners that not all of the older models do and many have just one.

Coach batteries must be what are called "deep-cycle" batteries. This means that they are not designed for short burst starting like a vehicle battery does but that they are used much like the batteries in a flashlight that provides steady power over time. This is a very simple explanation - so the electric engineers who would like to comment with detailed and scientific explanations please do, but for the everyday Joe Roadtrek owner this is enough to understand. There are many types of "deep-cycle" batteries and when you look at battery displays to purchase these they are often labeled as Marine/RV batteries. In the 2011 models, Roadtrek started to use AGM deep cycle batteries. They use two six volt, AGM, deep-cycle batteries. The AGM batteries do not have "wet" cells". There is no water inside the battery cells. These batteries will not boil over because there is no water inside. If overcharged, a wet cell battery can boil - if there is not a special circuit to prevent this. The two AGM batteries that Roadtrek is using now have 220 amp hours. I will explain this more later.

Besides not boiling out, there are advantages to AGM batteries. They hold a charge longer. They deliver more amp hours. They do not need maintenance. And they do not need to be vented which means that they can be installed in an enclosed area without causing any problem. The wet-cell batteries do need to be vented which means that the compartment that they are stored in must have access to fresh air - and this should be outside the coach. Roadtrek still installs these batteries outside the coach. I will get to where the batteries are installed soon.

I said that I have two six volt AGM batteries - why not one 12 volt AGM battery or two 12 volt AGM batteries. I will share what I have been told. Two sixes give more amp-hours than one twelve or two twelves together. Don't ask me why. Again, this is for the engineers out there.

I have also learned that one cannot/should not - likely cannot - mix AGM batteries and wet-cell batteries in the same system. Now this does not include the engine and the coach but if one coach battery is AGM then any other coach battery or batteries added must be AGM.

I also know that you should not let your batteries go below half power without recharging them to full power. This is something to consider when looking at how long you can go just using your batteries.

Again - basics. No science. I leave that to the many engineers that know RVs and batteries.

In 2011, Roadtrek changed the storage of the coach batteries. The first time that I saw this was the day I took delivery of my Roadtrek. Every Roadtrek 190 that I saw before this - and I had never seen a 2011 model - had two battery compartments. One was above the back passenger wheel and accessed by a locked compartment door from the outside. The other was a large compartment with a locked door on the side of the van in front of the rear passenger wheel. That compartment has a sliding shelf inside that would pull out so that you could easily access the battery there and its connections. This made it easy to check the water in the battery and test the voltage with a meter if you wanted to. In 2011 - on the 190 - that rear over the wheel compartment was gone. The compartment in front of the wheel remained, BUT both batteries are now there and there is no longer any sliding shelf. The only way to access the batteries is to lean in to a very small and not really lean-into-able space. For the most part, I would need to reach in and unhook the connections on the batteries and pull them out. These batteries are EXTREMELY heavy. I know this because I saw an AGM battery display in a store and I tried to lift one and it did not move. (No, it was not held down in any way.) I can open the compartment door with the key and look inside and that is as far as I have ever gotten - and to me there is nothing to see that I can do anything about.

As I have said, older models and model to model things change. You may have one battery or you may have two. If you have a 170 you have one battery - that I am sure of. I know a 2005 190 owner who has one battery. With Roadtrek things change from year to year and model to model - and sometimes even mid-way through the same year. Roadtrek does have two model years per year - for example, there is a 2011 on a 2010 Chevy chassis and there is a 2011 on a 2011 Chevy chassis. I have a 2011 on a 2011 chassis.

Now, you have battery basics. What do these batteries run? Inside your Roadtrek you have overhead lighting fixtures -large and small lighting fixtures spread all over the coach. These are 12 volts and run on the batteries. The water pump runs on 12 volts. The 3-way stock refrigerator has a mode to run on 12 volts. The hot water heater runs on 12 volts. The fan for the furnace runs on 12 volts. The ceiling exhaust fan runs on 12 volts. The macerator in the newer Roadtreks runs on 12 volts. Older Roadtreks have 12 volt outlets in the coach that you can plug 12 volt things into - just like the cigarette lighter outlet on your dashboard. My Roadtrek has NO 12 volt outlets. To install one, it would be necessary to tap into 12 volt wiring going to a light fixture. Older Roadtreks may have a 12 volt TV set - they do exist.

Now, I am going to explain amp hours. As I said, my coach batteries provide a total of 220 amp hours. Every appliance or light or whatever electric uses X number of amps per hour. Many appliances will have this labeled on them somewhere. You can also test how many amps something draws with an amp meter. The Kill-A-Watt meter found at home stores has this function along with many other functions. I will talk about this more with other parts of the electric system. With the batteries - if something draws one amp that means it needs one amp to run for an hour. You have 220 hours of power. Run two things that each need one amp and you have 110 hours. Somethings use a fraction of an amp - somethings use a lot of amps. Some things like motors - fans, etc. draw a lot of amps quickly and these will run your batteries down fast. I understand that the furnace fan drains the batteries quickly. So if you want to know how long you can go without having to charge the batteries, you need to add up the amps in each thing you have on and compare that to what the capacity of the batteries is - and remember not to let them discharge to less than half. Again, this is a simple and basic explanation of detail electrical principles. When we get to the section on 110 volt power, I will talk more about this and share with you the Green Acres TV show (from the 1960's) method of understanding how much is too much.

Alright - this is your battery system. Your batteries will recharge when you drive your Roadtrek. Your batteries will recharge when you are plugged into 110/120 volt shore power. Your batteries will recharge when you run your generator. Your batteries will DISCHARGE when you run your inverter. Roadtrek says that it takes 12 hours for the batteries to fully charge. I have been told that driving the van will charge the batteries faster.

I am now going to share with you the most important thing to understand about the battery system and this applies to the entire Roadtrek electric system and I will repeat this in each article.


The battery disconnect switch is located on the bottom right of the monitor panel. Here is a photo of mine.

See the rocker switch on the right. It says "BATTERY" next to it. See the little LED light to the left of it that says "ON" under it. That is the light that tells you the Battery Disconnect Switch is on. Yes, it is called a Battery "Disconnect" Switch and this is the same for all RVs and trailers. It is the most mis-named thing. It CONNECTS your batteries - turns them ON. Shut it off and it disconnects your batteries. If you want to use your batteries- IN FACT - if you want to use ANY electricity in your Roadtrek (except vehicle electricity coming from the engine battery) this switch MUST be ON. There is a sticker in my Roadtrek on the wall adjacent to this panel that says this. The sticker may not be on all Roadtreks. Make yourself a label if you need reminding. This switch is key to all your power. If you go to the simulator that I linked in the first article about the Electric System in general, turn off this switch with all other combinations and watch what happens.

One last thing about the photo - see the panel above the switch. The last column of LEDs on the right will tell you approximately how much battery power your batteries have. The C on the top stands for charging. If that light is on when you push the TEST switch, the batteries are charging from one of the sources I listed earlier that charge the batteries. After a long charge, that light may stay on even when not charging (when you push the test button). It will not come on in a day or so - or less. The G is "good" - basically there is full battery power. The F is "Fair" and the "L" is Low. Charge the batteries before you get to the "L". This panel is not absolutely accurate but it is good enough as long as you stay on top of keeping your batteries charged.

When we leave on a trip we turn on the Battery Disconnect Switch and it is not turned off until we get home.

When your Roadtrek is at home and you are not using it, shut off the Battery Disconnect Switch. While it is on, it will drain your coach batteries as there are a few 12 volt devices that remain powered on when it is on such as the propane alarm and the carbon monoxide alarm. If you are not in the Roadtrek between trips there is no need to have these running. Another good thing to know is that while you are driving, with the Battery Disconnect Switch OFF - your Roadtrek batteries will still charge from the engine running.

The next article coming in the electric system series will be 110/120 volt shore power.


  1. the Roadtrek 190 and 210 Simplicity models have one 12V AGM coach battery and do not have inverters. When I bought my new 2012 RT this March, I was told by the RT service tech to only turn off the battery disconnect if my unit was to be idle for several weeks, otherwise to always leave it on.

    1. True - the Simplicity models only have one battery.

      If you leave your battery disc switch on when you have your RT just sitting between trips all you are doing is draining the battery. My dealer said the same thing as yours and then I asked the RT tech at the factory - and he told me exactly what I have wrtitten above - turn it off between trips.

    2. The simplicity has a converter charger but no inverter. The Simplicity has left out a lot of key features that in the past hadbeen standard to RTs and many RVs.

  2. This is very helpful. Thanks! My 2010 190 Popular has 2 6-volt batteries in the slide-out tray. They are Excide 3600s (I think). When they die, I look forward to a maintenance free battery set-up.

  3. I would worry about having agm coach batteries with a lead acid starter battery. The two chemistries have different charger needs and mixing them will result in one battery being over or under charged resulting in much reduced battery life.

    1. This is how Roadtrek makes all of their models now - Coach batteries are AGM and the engine battery is whatever the chassis manufacturer installs. The system has worked and is designed by the Roadtrek techs. I do know that one should not mix the two coach batteries - AGM and wet cell (in those models with two coach batteries). There is a battery separator between the engine battery and the rest of the electric system and Coach batteries in Roadtreks since 2005. 2004 models and earlier have a battery isolator - and the Coach AGMs only came in with the 2011 models.

    2. The problem is that when the batteries are charged they are connected together by either an isolator or separator. The Agm's can not accept charge at voltages above 14.2 volts, while the wet cell wants 14.4

      If you set things up for the Agm's you under charge the starter battery. If you set up for the starter battery you will cook the Agm's either will shorten the life of the battery. This is not going to cause the battery to fail this week, or this year, but it will shorten the life..

      I guess I need to join the roadtrek Facebook site and ask the president about this.

    3. The Tripp Lite Inverter/Converter/Charger manages charging of all of the batteries. I am not an RV technician nor an engineer. There are some things that we need to have faith that the people who design something like a Roadtrek know how to do it, especailly when they have a great reputation as Roadtrek does. As you suggest yourself, you should contact Roadtrek and ask them how they do it.

  4. We own a 2008 190 Popular. Our coach battery is a 12 volt deep-cycle lead acid battery. We are replacing it with a mainterance free AGM 12 volt battery. I was told by someone that you are required to change the settings (dip switches) on the inverter when you install an AGM batery. Do you have any information about this. /Bob

  5. Yes! There is a change of settings on the dip switches on the Tripp-Lite Inverter for different batteries. Take a look at my article on the inverter. There is a link to the manual there and there are illustrations and directions in the manual to do this.