500,000 bottles of sparkling wine mature in this section of the underground cellars at Cricova Winery just north of Chisinau, Moldova. Photo taken December 3, 2016.
Where are Kevin and Ruth right now? Chisinau, Republic of Moldova.

Where are they going next? Transnistria. The country that doesn't exist!

Sunday, August 7, 2016

We didn't understand 12 volt batteries!...Part 3

In part 1, we talked about the basics of the 12 volt electrical system in your RV. In part 2, we talked about the different types of RV batteries. Today in part 3, we are going to talk about how to keep those batteries charged and maintained.

There are four common ways of charging your RV batteries.

The first is by driving. In a motorhome, your house batteries will always charge by driving. If your batteries are down to the 50% level, it will take about three hours worth of driving to bring them back up to full charge. In travel trailers and fifth wheel trailers, your house batteries will charge if  your trailer wiring connector is wired to provide that charge. But the charge will often be slow and not complete due to the smaller wire sizes provided by the connector.

Second, you can simply plug in your RV at a campground. Every RV has a built in converter/charger unit to convert 120 volt household electricity into 12 volt power. The converter side of the box provides 12 volt power to the 12 volt circuit in the RV, and the charger side of the unit provides power to recharge the house batteries. Usually, your batteries will be fully charged by morning.

Third, a generator. Most motorhomes have a 120 volt generator on board. Using the generator is exactly the same as plugging in at a campground. The power from the generator goes to the converter/charger box and the batteries charge exactly the same way as if you were plugged in at a campground. Except that you get to listen to the annoying drone of the generator. Many people with travel trailers or fifth wheel trailer also carry around a portable generator.

Fourth, solar panels. I could write an entire blog post just on solar panels, but again we're trying to stick to the  basics here.

Let me tell you a story. Our first time in Mexico with our motorhome, we had cheap Walmart marine batteries and we did not yet have any solar panels. I had been relying strictly on driving to charge the batteries. I was also occasionally running our built in generator, but we can't stand the noise from a generator. We were parked up in one place for about four days in a row and the batteries were very low. I drove into town, about 15 minutes each way expecting that to charge up the batteries. Well it did. I think it brought them from 30% charged up to maybe 40% charged. It was then, that we learned how important it was to our style of RV'ing to invest in solar panels!

Of course the drawback with solar panels is that they will only charge your batteries when the sun is shining.

Speaking of weather, this is very important. The usable power in your batteries goes down the colder the temperature is. They say that 80F is the optimal temperature for your RV batteries. For every 15F drop in temperature, the usable capacity of your batteries drops by 10%. So when it goes down to 35F overnight, you have to remember not to draw your batteries to low by using your RV furnace very much. The fan blower motor in a typical RV furnace sucks a lot of 12 volt power!

Battery maintenance. Two very important things here. Keep the battery connections clean, and keep the fluid in the batteries at the proper level.

Most cheap marine batteries are sealed. These batteries will typically expire just after the warranty does! Nothing that you can do to change that short of making sure you don't use them very much. Of course you still have to keep the terminals clean. Still, these batteries are fine for those of you who move from campground to campground and are plugged in all the time at those campgrounds.

Deep cycle wet cell batteries have caps on the top. You have to pop the cap off, and check the fluid level in each cell. When they are new, most deep cycle wet cell batteries don't lose very much fluid, but as years and use go on, they require more frequent inspection. You need to "water" your batteries with distilled water, never letting the fluid level go below the plates.

AGM batteries are completely maintenance free. It's one of the benefits of the price that you paid for these high end batteries!

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Last year, I bought one of these little battery system monitors that simply plugs in to your cigarette lighter. On our motorhome, the cigarette lighter is supplied by the house batteries, so it gives me a live reading of the battery at any given time. And, it's on sale right now. For the money, you can't go wrong!

Battery and Charging System Monitor



21 comments:

  1. I bought the Renogy 100W solar panel and charge controller you recommended a couple of months back - thanks for the recommendation!

    To get more visibility into what the system is doing, I bought a digital meter that displays voltage, instantaneous current, instantaneous watts, and cumulative watt-hours drawn from the house battery since reset. It's a bit tricky to hook up and not as easy to interpret data, but cost only $18.75 vs what is probably the gold standard (Trimetric) at about $160. Hopefully the link below works. BTW, some cigarette lighter sockets are connected to the starter battery, not the house batteries!

    Links not working for me, but search Amazon Automotive for "Bayite LCD Meter With Shunt"

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    1. So glad you are enjoying your solar panel and charge controller, now that you have the one panel and can see what it does for you, you may be like us and want to increase your solar output with additional panels. The the nice thing about solar, you can add to as you see fit. :-)

      That is possible, I guess with our unit they are all connected to the house batteries so maybe Kevin was not aware of that fact.

      Kevin is very much a numbers kind of guy so he may just be interested in that digital meter display that you have. He will definitely have a look at it that is for sure. Thanks, for the suggestion.

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  2. This is definitely the best set of articles on basic 12v for the RVer. Thank you for writing it.

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    1. Thank you Barney, that is good to hear. :-)

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  3. All very good advise and works wonderfully, we too have been doing about the same as you, but still when hit a few cloudy days might need use our generator a bit, mind 4 batteries instead of two would give us more storage.

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    1. Remember that it takes much longer to charge four batteries than it does two. This applies whether you are counting on driving or solar. I am not sure we drive enough hours in an average day to completely recharge four 6V batteries from a 50% discharge condition.

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    2. Yes, 4 batteries certainly give you more storage. We are very happy having the 4, Kevin has even mentioned the odd time of getting 2 more but by doing that it would be giving up more of our motorhome basement storage which we don't have too much of to begin with.

      Yes Croft, it does take a little longer to charge but we normally find with a nice sunny day that all four batteries are totally charged by lunch time and that is with us using some of the battery power during those morning hours. We find it nice to have that bit of extra battery power for a rainy day. :-)

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  4. Thanks for sharing all your research Kevin. It has spurred me into dedicating myself to be more conscious of what is going on with my batteries. I ordered one of those cigarette lighter battery monitors. Thanks for the link.

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    1. You are welcome Croft! Hope you like it too. :-)

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  5. On our first MH we had two 12 volt batteries hooked in parallel. I never had good luck with them. I doubt if they lasted more than two years for each set. One would typically go bad and drag the other one down with it. On our new MH we have two 6 volt batteries in series, a 100 watt solar panel, and charge regulator. I have had the batteries for 7 years and they are going strong. I check the water level periodically. I would love to get two 6 volt AGM batteries to replace the current house batteries but I can't kill them. The starter battery did go bad a couple of years ago and was replaced with an AGM.

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    1. Yep, it takes a look to kill the 6 volt batteries, especially when they are maintained properly. We would never go back to the 12 volt and like you, we may even go with the AGM ones as well if our current Tojans ever die.

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  6. Another advantage of AGMs are that you don't need to vent them. They can be kept inside the rv. For us it would be a good option since we have a travel trailer and it has little to no outside storage. They would fit neatly under the sofa which is next to the converter.

    I can't imagine traveling without solar. Even in a campground it's once less thing to hookup and worry about whether you have a secure connection.

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    1. Yes, there are certainly many advantages to having the AGM batteries. I guess the main thing would just be getting over the cost of them. Then again, better products are more money but can be worth it in the long run. It is a matter of whether it is worth that extra cost to you or not.

      We can't imagine traveling without solar as well. We love being independent! :-)

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  7. Great posts!

    rocmoc n AZ/Fld/Baja

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  8. Thanks Kevin right now we are in NS using the solar all the way, right now supper is almost ready in the crock pot, it's been cooking for 6 hrs at no cost other than the sun. I'm so glad you showed us what to buy. Now do you know where we can get a toaster oven 800 wts. Then we would be all set thanks for all the info on batteries

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    1. So glad you are enjoying your new solar set up Wendy! Doesn't it feel so liberating? :-)

      Normally, anything that requires heat usually has a higher wattage. Just google "toaster oven under 800 watts", it looks like there might be a few available but not sure how good they are.

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  9. Replacing my two 12v batteries with four 6 volt batteries appeals to me but I see a potential problem. My 12v batteries fit into a sliding tray. It might hold two 6v batteries but I can't see where I could put the other two without long, heavy gauge connecting cables.

    How did you fit four batteries into Sherman?

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    1. Kevin had to do a slight modification to the set up for our 2 main batteries that are under our entry step. As you said the 6 volt batteries are a slightly different size. The other 2 he put in the basement compartment right beside the steps. Here is the post of when he installed them, it also shows a picture of where they are situated. www.travelwithkevinandruth.com/2010/03/cedar-key.html

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