Charging the batteries

Be warned, this post is a bit heavy on technical issues and one image.

Life in a trailer, especially boondocking, requires monitoring your battery capacity and usage. The first thing I did to help this when we had our ’92 25′ was get some Sears AGM batteries. This gave me a larger capacity and less worry about them. Changing both trailers to LED lighting helped a lot more. We purchased a couple of generators to help with charging when we needed it and ostensibly run the air conditioners with two of them running. I also purchased a set of portable solar panels. I had all the pieces lined up for extended battery usage, except one. Solar on the trailer.

This was accomplished early this year, shortly before we started our fulltiming/CalExit. In our travels since May (2017) the solar panels have performed fantastically! But events during our travels have made me rethink my charging methodology.

Before solar, there were two methods of charging. When we were hooked into shore power, the converter/charger will charge the batteries and provide 12v DC power. When towing, the tow vehicle will provide a small amount of charge through the 7pin umbilical cord. I remember my father hooking up our station wagon to the trailer and letting it idle for extended periods to give the trailer a charge while boondocking. I have not tried this method.

The converter/charger that came with the trailer was a single-stage charger, meaning it was either charging or not. On or off. This can wreak havoc with your batteries, especially if you leave it plugged in while ‘stored’, as we did. I replaced the converter/charger with a multi-stage version. This flavor will do a heavy, high amperage charge until the batteries reach a certain voltage. The next stage is a consistent, lower amperage charge until a different voltage setpoint is reached. The final stage is a trickle charge just to keep a preset voltage level.

The one issue/problem when adding a solar system, and its inherent charge controller, is to ensure that the two charging ‘brains’ don’t conflict with each other. Luckily the solar charge controller is adjustable in what voltage it shuts off at. This way I was able to research the voltage level for the shore power converter/charger and adjust the solar charge controller to just below that voltage. That way, if we were on shore power the 110V converter/charger would do its’ high amperage charge and get it to a voltage higher than the solar chargers threshold and the solar charging would be negated.

What change have I made in charging the batteries? Let’s lay a bit more groundwork first.

I no longer have 2 generators, I never did use 2 to run the air conditioner which made the 2nd one expendable. After our 4+ months on the road I never used our portable solar panels, therefore they are for sale (contact me for more info). We are now down to shore power charging, solar charging and generator charge (which is essentially shore power charging since the generator creates 110V AC).

The months on the road brought up some odd issues that have steered me to my new path. We had problems with our refrigerator when we started that were hard to diagnose and explain. It was not working when we left and started working mysteriously after we were in Arizona for a few days. It got weird again in Texas. When talking to the repair shop they mentioned that irregular 12V power has been seen to cause problems with refrigerator circuit boards. I changed the shore power cables and it started working just fine, making me think it was the cables, but maybe it wasn’t?

We did great on power for about another month until we were in Williamsburg VA. The spot for the trailer there was very shady and I noticed that the battery was down to about 82% capacity and the shore power was charging it slowly, if at all. I immediately thought it was the shore power converter/charger and ordered a replacement. Once it was swapped out, charging was back to normal.

That got me to thinking that maybe our refrigerator problems earlier were symptomatic of a failing converter/charger. I am now fairly convinced that is true as the refrigerator has not exhibited any type of issues, even when the internal fins were coated with ice due to humidity.

When we were in New York and taking advantage of some courtesy parking, we had some issues with the 15amp shore power that was provided. The electrical management system that I installed, before we left, would disconnect our power and reconnect continuously. It made the power connection unusable so we relied upon the solar to take care of the batteries. This allowed me to notice another aspect of the shore power converter/charger. When it is in its’ first stage of charging it uses a LOT of amps! I saw about 18 amps at one time! That was overloading our 15amp connection.

My next thinking was if I could turn off the shore power converter/charger, I could then control when I used it and turn it off when we are on 15amp. One option is to turn off the breaker but that would also make the inverter inoperative. I didn’t want that. I made my own solution. I got some parts at Lowes and created a device that the converter/charger plugs into and then it plugs into the wall. It contains a switch that I can easily turn on and off.

This relates to an ability for me to disable the shore power converter/charger when on a minimal power connection and allow the solar panels to exclusively charge the batteries.

The empirical proof is in. For the last three weeks, we have been on 15amp power, with the shore power converter/charger turned off, and we have full battery power going into each evening. I feel it is a great success.

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