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Battery maintenance while camper is in storage

bobbolotune
Explorer
Explorer
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
19 REPLIES 19

TxGearhead
Explorer II
Explorer II
If you have a generator I would take it to the storage area and hook the generator up for an hour or so. If it's stored in a small enclosed area be aware of carbon monoxide. If you don't have a generator, it would be a good investment to expand your camping possibilities.
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Jack_Spratt
Explorer
Explorer
Kayteg1 wrote:
Disconnect the clamps and walk away.
Deep charge batteries can be left for a year with no problem. (mine golf cart batteries lasted 12 years with the practice)
Engine batteries are advised to be charged every 6 months.


x 2

Works fine with equipment that stays out all winter, boats and campers.
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2017 Big Horn FL3750

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Strabo
Explorer
Explorer
pianotuna wrote:
Add a modest solar charging system and leave the batteries in place.


Yup, i fully charge ours then use a solar mantainer to keep fully charged, i also disocnnect them from the rig. Works fine.
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352
Explorer
Explorer
Try the Battery Minder. It desulphates and charges. Done correctly, batteries have been known to last 10 years or longer
The manatees of Halls river Homosassa Springs Fl

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Kayteg1
Explorer II
Explorer II
Eric&Lisa wrote:
RinconVTR wrote:
I always remove the battery, bring it in the garage and place a battery tender on it.


Careful with this one. Make sure it is some sort of 'smart' charger. I had one of the Harbor Freight "Battery Tenders" cook & kill a battery. Don't go for the cheap charger.

-Eric


That could be because for this job you should use BATTERY MAINTAINER.
I've been using HF maintainers on my toys for over 20 years.
I think I have about 5 right now in my garage as often could not refuse $4.99 sale.
Sure over the years couple of them malfunction and one time not checking the battery for 4 or 5 months I lost it, but failure happen even on Prevost.
Bottom line, no matter how good charger/maintainer, always keep checking from time to time.

silversand
Explorer
Explorer
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).


Correct. When we store our camper for the winter in indoor heated storage (October till May), I completely disconnect our fully-charged AGMs........and don't do a thing till May. Just leave in the camper. Our AGMs hardly drops in charge at all over this long storage period. If you have the old lead/acid batteries, all bets are off...they'll be pretty well discharged after this length of storage without careful maintenance.

I've been doing this since 2007 (when I got rid of those pesky lead/acids), and replaced with AGM-- at 10 years old, they are still nearly as good as new.

I once had to do all that battery maintenance during storage with lead/acids, but none of that for me any more.

This is my experience; your mileage may vary with different AGM manufacturer/model.
Silver
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time2roll
Nomad
Nomad
Battery Tender is a brand name. Use the name accordingly to avoid confusion.

Eric_Lisa
Explorer II
Explorer II
RinconVTR wrote:
I always remove the battery, bring it in the garage and place a battery tender on it.


Careful with this one. Make sure it is some sort of 'smart' charger. I had one of the Harbor Freight "Battery Tenders" cook & kill a battery. Don't go for the cheap charger.

-Eric
Eric & Lisa - Oregon
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pianotuna
Nomad III
Nomad III
Hi bobbolotune ,

Make sure the battery bank is wired in a balanced manner.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

bobbolotune
Explorer
Explorer
AnEv942 wrote:
Simply testing volts, any inexpensive multi-meter, analog or digital, will work.
If the batteries are installed in camper, they are already tied together, no need to jump terminals between. Testing one battery will show average of both batteries. If there is no load/charge source being removed-then no need to wait. To test individual health obviously they'd need to be disconnected from each other, and waiting a bit to watch as they stabilize.
IF your disconnect positively disconnects from any parasitic load that will work instead of pulling cables for summer storage.


Many thanks AnEv942. I now understand. This exactly answers my questions.

I thought I had one more question about where to place the test probes of the voltmeter for testing two batteries installed in the camper. But from what you said about the batteries already tied together I looked back at a diagram of RV batteries wired in parallel. The positive terminals are wired together and the negative terminals are wired together. So, it makes sense that I can test from any positive terminal or wire to any negative wire or terminal. It should make no difference because the terminals are wired together, as you said.

So I have been searching Amazon for multimeters. This multimeter seems to have good reviews. I am going to order it unless someone offers a better suggestion:

INNOVA 3320 on Amazon

As to the other suggestions in other replies. I am really trying to avoid needing to take the batteries out during the summer. The batteries are big and heavy and it is difficult to get them out of then back into the compartment. As to solar, it is on my wish list but for longer term. Right now I am trying to figure out what to do right now and for the rest of this summer.

While of course there are alternative approaches I think my plan as described in my original post is the best for me right now for my current specific circumstance. It follows the recommendation in the manufacturer technical manual for my Lifeline AGM batteries, to boost charge after 90 days or when the batteries drop to 75% charge (open circuit 12.5 voltage). Now that I believe that I understand how to test open circuit voltage for that 75% charge level, it seems that question is fully resolved. Thanks to all who responded!
Lance 850 truck camper
2016 Ram 3500 regular cab long bed 4x4 DRW 6.4L HEMI gas

RinconVTR
Explorer
Explorer
I always remove the battery, bring it in the garage and place a battery tender on it.

time2roll
Nomad
Nomad
pianotuna wrote:
Add a modest solar charging system and leave the batteries in place.
+1
Still need a battery switch to disconnect the TC.

towpro
Explorer
Explorer
something we left out. your current 27 series battery might have 70 amp hours?

you already have around 1amp of electrical load in your camper without even turning on a light. its the CO and Propane detectors.

1 amp will draw your 27 series battery dead in 70 hours. But you don't want to drain a battery past 50% so every 45 hours your going to need to charge that battery.

Now during winter storage (with 0 load), I hit mine with a 15A schumacher 3 stage charger every month.

on my Wolf Creak I have AGM batteries which have less self discharge,and they should be good for 6 months without a charge (and 0 load), but I have a battery switch installed that turns off battery power to everything, but still leaves solar cells connected. Even through my classic accessories poly pro 3 cover the solar gets enough sunlight to keep the AGM's charged all winter.
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Matthew_B
Explorer
Explorer
pianotuna wrote:
Add a modest solar charging system and leave the batteries in place.


That would be my vote if you have sunlight on the camper. Make sure it has a quality charge controller so you don't fry the batteries by too high of a voltage all the time.

If it is stored under cover, I would go the disconnect route. Add a disconnect in the system somewhere, and completely power down the camper. 2 months won't drain a battery all that much. If you have a good charge setup on the truck, it will get the battery in shape while driving home. Plus time plugged in while provisioning the camper at home should suffice before you head out.