Home Forums Hunting & Shooting Hunter's Campfire Battery maintenance

My, new to me, camp trailer has two 12 volt batteries wired negative to negative and positive to positive. I want to store the trailer over the winter and maintain the batteries in good shape for spring use. A couple questions. First, is there any need to disconnect the batteries from the trailer? I have turned the PERKO switch to off. Second, if I can leave the batteries wired as is what kind of battery maintainer do I need to hook up and to what terminals do I hook it?

I'm fairly certain that's a parallel connection which will keep it 12 volts but double the amperage. You should be able to use a regular trickle charger for 12 volt batteries. If it has a master disconnect, that's sufficient to isolate the batteries.

Disconnect em.
Put em in the Garage on couple layers of cardboard.
Hit em with a trickle charger every so often.
Any auto parts store sells trickle chargers or even harbor freight.


Bout it..

Why do they have to be dismounted and disconnected? Won’t one trickle charger keep them both up to charge if they remain connected?

Weather? If battery freezes no bueno? In a garage less likely?

With the master switch turned off there is no need to disconnect.
With your somewhat mild climate there is no need to remove them. Charged batteries will not freeze in our usual winter weather.
Batteries discharge at a slower rate when cool so actually a charge every month or two would be ok.
But the best would be an AUTOMATIC maintainer, and you could hook it up to just one battery, but I would do the + on one and the - on the other.
Check the water level also if they are the flooded type and you should be GTG.

On our little class c motor home….. I have the 12 volt master switch in the off position…..and keep a battery tender connected to the batteries 24/7/365

On our 5th wheel, it has a high dollar “float type” charge controller…..the 5th wheel is plugged into power at all time…..entire system energized! memtb

Battery Tender and be done with it.

Yes, but best practice is to "divorce" batteries and maintain separately.
You can do as asked, but 1 battery can pull down another, or give inaccurate readings.

No need to remove them. A fully charged battery, and especially one on a charger will not freeze.
ETA: fully charged freezes @ -92* F

This.

Two lead acid batteries in parallel can be bad ju-ju. LiFePO4 batteries usually have an internal BMS that makes the practice much safer.

Over a long period, a simple float charger can destroy a lead acid battery by electrolyzing away too much water. Be sure to get one that knows when to quit.

Lithium batteries are a whole different matter. If they're in good shape, they'll hold nearly a full charge for most of the winter. Just check them every so often. If they do need recharging, they can't be charged below freezing. They have to be warmed up first. In cold climates, they're better stored inside just so they can be topped up if necessary. All of the better ones have a BMS (battery maintenance system) built in that prevents them from charging when it's too cold. If it doesn't have a BMS and you try to charge it in the cold, it will be seriously damaged.

This is the way I do it but I'm in Alaska.

Curious as to what the cardboard is for?

So one cell in a 12 volt battery can pull down another?

Sounds like a water cooker...

I just keep the trailer plugged into 110. It will maintain the batteries.

My boat is a different story. It has one AGM deep cycle and a typical wet cell automotive battery. I put a charger on each every couple months.

I like to disconnect and store with trickle charger. Make sure you organize your wiring, zip tie it, and take pictures. Pretty easy to forget a wire or second guess yourself on what battery a wire goes to if you have multiple wires to each battery.

They make ones that know when to quit? Like the "automatic" one above?

Seriously, if you're dealing with wet, lead acid batteries, charge them until each cell is 1275-1300 on a hydrometer (be sure the plates are covered by liquid before charging) and it will store for three months or more below freezing since as storage temperatures below 50 degrees allows for almost nil charge loss on a fully charged battery.

Don't trust the charger, don't trust a voltmeter, test the chemical; its how a battery works. The greatest, most expensive chargers in the world will still operate by byproduct: open current voltage.

Even an automatic or maintainer will use liquid. The charger, whether automatic, super expensive or super cheap, once the plates are unsubmerged, will charge the battery more often and use more liquid. Some will not charge beyond the initial charge, which almost never brings the specific gravity to the point to where it won't freeze below zero.

It won't keep them from overcharging.