This is my first year owning a camper and right now is the first time I have had the camper in storage for an extended period. I cannot store the camper where I live so it is in storage around an hour drive away (which makes maintenance and projects very difficult).
My current question is about battery maintenance while in storage. I have been reading websites about RV electrical and have learned a lot but I am still struggling with some of the final details. Please understand that I am starting from absolutely zero knowledge of this topic.
It is clear that over the winter I should remove the batteries from the camper and store them inside. For that I will need some kind of standalone boost charger to top off the batteries during the winter. But what about maintaining the batteries while in storage over the summer? Currently I have not taken the camper out of storage for approaching two months and the next planned camping trip is another month away. It is too much work to remove the batteries multiple times over the summer, so the topic is how to maintain the batteries while the batteries are in the camper in storage during the summer.
It seems that the easy rule of thumb answer is to plug the camper into shore power for an overnight once a month. But if that requires loading the camper on the truck and bringing it home once a month that is a lot of work. Especially if it is not actually necessary. I think that the one month rule of thumb is for wet cell batteries and my understanding is that AGM batteries can last longer in storage (i.e. AGM batteries have slower discharge).
To be more exact, I have two 12V Lifeline Group 27 AGM batteries. There is an official Lifeline Battery Technical Manual on the Lifeline website which says this about storage (and this is essentially the same as I have read on several other RV electrical sites): In storage batteries should be boost charged every 90 days or when the open circuit voltage drops to 12.5 volts, which corresponds to approximately 75% state of charge. Boost charge batteries using a constant voltage charger set to 14.4 to 15.0 volts.
Now, the challenge is to understand what this is saying. It sounds like I could last up to 90 days in storage if I can learn how to measure the open circuit voltage. That means bringing the camper home to charge the batteries only after 3 months rather than every month, which is a big difference, and a better chance I will take the camper out camping in that period rather than needing to bring it home only to charge the batteries.
But I am still struggling with the details.
Since these are AGM batteries I cannot test the specific gravity with a hydrometer. Rather, I need to test with a voltmeter. So my understanding is that I need a decent quality digital voltmeter to test the open circuit voltage. There are so many voltmeters on Amazon, where do I start? Could someone point me to a specific example of a decent quality standalone voltmeter?
What kind of standalone charger will I need for boost charging the batteries over the winter? Could someone point to a specific example of a decent quality charger? Might that charger also include a voltmeter, so possibly I can purchase the boost charger now and use that as the summer storage testing volt meter also?
Then once I get a voltmeter the next question is how to use it to test the open circuit voltage. Here is the official description again from the Lifeline Battery Technical Manual (and again this is essentially the same as I have read on several other RV electrical sites): An easy method to estimate the State of Charge of the battery is by measuring its Open Circuit Voltage. This measurement should be made after the battery has been at rest for a minimum of four hours with the battery shut off from it's charging source and load.
The camper has a battery disconnect. I have no solar panels (yet). If the camper is not connected to shore power and I have the battery disconnect turned on I assume that should satisfy the requirement for disconnecting from any load or charger. From the above it needs to be disconnected for at least 4 hours.
So then can I test the batteries without taking off the main cables to the battery terminals? I have two 12V batteries hooked up in parallel. So do I test by placing the test probes of the voltmeter onto the opposite terminals of the two batteries, one probe on each battery? In other words, place the test probes on the two battery terminals that the main positive and negative cables which connect the batteries to the camper are connected to. Is it that easy, or am I still missing some details?
Lance 850 truck camper
2016 Ram 3500 regular cab long bed 4x4 DRW 6.4L HEMI gas