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Monday, October 26, 2009

Battery Charging

I am a true RV beginner with a Chinook Class C motorhome. I've tried to take the time to become knowledgeable about my new vehicle, especially regarding the LP, plumbing and electrical systems. I'm reading as much RV literature as I can get my hands on. I've talked with many RV owners and have read every article on your website. As a new RV owner, I realize there is a lot to learn and so far it has been a good experience, except I am not an electrician and deep cycle batteries have never been too friendly with me. Converters, inverters, battery chargers, circuit breakers, voltage etc., where do I begin? As a new RV owner I just can't seem to keep my batteries charged when I use my RV. The problem with dead batteries seems to occur after using the unit at a regular 30-amp shoreline campsite for three or four days. During hookup all appliances, lights, etc., work great. When I get home to clean the unit without AC hookup, everything is dead. I can't start my generator. Monitors and lights don't work. Everything is dead. Fluids in the batteries are at proper level. All circuit breakers (that I can find) are okay and have not tripped. My unit has a converter. Attempts have been made to charge the batteries with the adapter for the shoreline connection at home without success. Only after the engine is running for about five minutes can I get power to the TV/VCR and lights and can start the generator. With the engine on, everything works great. When I rely only on my batteries (no shoreline or generator power source); DC life is dead. This unit is brand new - what am I or the unit doing wrong? How good is the "built in" converter for charging the batteries? Do I need to purchase a separate multi-stage battery charger? If so, what brand charger do you recommend?
Mark, (Philipsburg, PA)

Mark, battery problems seem to ever nag us. The first step in finding out why batteries seemingly discharge quickly is to analyze the battery itself. Sulfated batteries simply will not hold a charge. The degree of sulfation is proportionate to its ability to hold a charge. All batteries self-discharge, but sulfated plates quicken the rate. Find a shop in your area that has a carbon-pile battery load tester. This test will provide insight to the internal happenings of the battery.

Clean and tight electrical connections are also extremely important. Corrosive terminals and faulty butt splices and other connections all lead to early battery loss. Don't overlook the negative side of circuits as well. Also, determine if the battery has been fully charged. Chances are your battery has not been given a chance to become completely charged. Many RVs are notorious for employing mediocre or even inadequate charging systems. Some alternators and converter/chargers do not have the technical algorithms available today for proper and complete automatic battery charging. Rarely do the batteries ever reach full charge.

A fully charged battery is one that, during the charging process, maximizes the specific gravity reading and then plateaus, (the specific gravity refuses to rise any higher). After two hours in that state, the battery is then, fully charged. Tests should also be performed on the battery circuits to determine if any drains exist. Some small, parasitic drains are normal, but when current drains approach 700-800 milli-amps, something needs to be rectified. Obviously, a larger drain on a battery is even worse. Any professional technician can easily perform this test for you, but if you have a good, quality multi-meter, you can even do it yourself.

There is good news, however. Today there are aftermarket alternators and chargers that increase the RVers ability to extend the electrical life in the batteries. Also, newer battery technology has improved battery performance and has minimized over-charging risks. It should be a consideration for all "serious" RVers to upgrade to high-tech batteries, sophisticated three-step chargers and high output automotive alternators. Electrical woes will certainly be minimized and under proper usage, completely eliminated.

Personally, I favor the multi-step battery chargers produced by Xantrex. In your case, I would use one as an add-on to your stock converter, allowing it to still be the "converter," and utilize the TrueCharge as a battery charger only.

As mentioned above, only rarely and under close monitoring does a battery bank ever approach the 65 to 70% charged level. A true, “fully charged” system is even rarer. Optimizing the 12-volt battery systems has become one of the most important challenges RVers face. We fear overcharging the batteries yet are confused when the battery bank is rarely charged properly or fast enough to suit our needs. 

Unfortunately, many existing charging converters were designed in a manner that achieves, at best, a compromised balance between the overcharge/undercharge extremes. The result is that many auxiliary battery banks never attain full capacity during the charging cycles, nor are they ever 100% fully protected from being overcharged. Each result minimizes the useful life of the battery bank and in some cases drastically shortens battery life. Adding a sophisticated battery charger will most assuredly help.


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