Battery question for winter

[scooterjm1]

I have two 12-volt deep cycle batteries connected in parallel. I have a disconnect switch wired in. I know pretty much nothing about batteries and the past few hours of googling have given me no more insight than I had going in. But I assume they are lead-acid batteries because both of them mention lead on the labels.

I live in an area where winters are mixed, with each month featuring periods of very cold (occasional lows below 0F) as well as periods where the lows barely dip below freezing and the highs can be in the low to mid 40s.

Last year we stored our trailer (outdoor storage lot) for 4 months and I brought the batteries home to keep in my basement on trickle chargers for the winter.

This year, however, we have learned that a campground that we enjoy near our home is open year-round. So we would like to take advantage of that every time the weather is "warm" enough and we expect to camp at least once a month throughout the winter.

My question is: Assuming these are lead-acid batteries, is having them connected to shore power for 2-4 days a month enough to keep them from getting damaged during the colder periods when they are not connected to anything, or do I really need to bring them home between each camping trip? My battery compartment is a tight fit so I'd really prefer to not have to do that unless it's absolutely necessary.

 

[SpencerPJ]

Given your situation, I think you will be fine leaving them in. If I were you, I certainly would look at batteries, and fill with distilled water as needed. If you are uncertain how, watch a couple videos. If you exceed a month, can you still find a way to ensure they are recharged? And last, I would be certain to have a full disconnect, or simply remove the ground wire, there seems to always be small / parasitic draws that kill em.

 

[scooterjm1]

I would be certain to have a full disconnect, or simply remove the ground wire, there seems to always be small / parasitic draws that kill em.

Adding a kill switch was the very first modification I made to the camper after we bought it, as those parasitic draws were aggravating! The second modification was slapping waterproof stickers in multiple places to remind me to actually use that kill switch.

 

[John From Detroit]

My question is: Assuming these are lead-acid batteries, is having them connected to shore power for 2-4 days a month enough to keep them from getting damaged during the colder periods when they are not connected to anything,

Short answer YES.
Longer answer... Some disconnects are total. Some are not.
if yours is not consider lifting the NEGATIVE lead (the one that runs off to who knows where (the chassis)) from the batteries to insure total disconnect.

But two months without charge, and no discharge, should not bother 'em at all provided they are full up when you disconnect.
NOTE.. When you re-connect.. DO NOT be surprised if there is a spark... Normal.

 

[rvlifer]

The info already provided is goid and you should be ok but it all delends on your rv. The first rv i owned never charged the battery bank above 50% no matter how long it was plugged in. It was a forest river.

Pulling the negative lead is a good safety.

If you want to be sure you need a good battery monitor.

 

[zapatasghost]

Given your situation, I think you will be fine leaving them in. If I were you, I certainly would look at batteries, and fill with distilled water as needed. If you are uncertain how, watch a couple videos. If you exceed a month, can you still find a way to ensure they are recharged? And last, I would be certain to have a full disconnect, or simply remove the ground wire, there seems to always be small / parasitic draws that kill em.

I'd be wary of leaving them out in the cold! I've always taken mine off for winter storage in my garage on a charger/maintainer. But sounds like you have much more experience!

 

[Derby6]

Unhooked mine for 8-9 months near SLC. No issues when I returned and reconnected.
At home I pull and put in warm garage but not an option in my snowbird unit scenario.

 

[Mark_K5LXP]

A fully charged lead acid battery will not freeze until about -80F. One that's 50% charged will freeze at -10F. So starting off with a fully charged battery is your best preventative.

Depending on the battery, it's age, and it's condition they will typically self-discharge 5 to 10% per month. But lead acid batteries being a chemical reaction, that self discharge rate will slow a bit when cold. So, that full charge you start out with at the beginning of winter is likely enough to carry you through to spring but a periodic top off with a tender or multistage charger/converter will only help. Your one use/top off per month ensures they'll be properly stored.

As a caution, a cold battery can freeze as you use it. If you start off with a fully charged battery and let's say it's sitting at -10F, if you discharge more than 50% the electrolyte will freeze and likely damage the battery. This is how many car batteries in northern climes meet their demise. The battery is sitting outside at some subzero temperature and the headlights accidentally get left on. Once that depth of discharge crosses the freeze point the electrolyte turns solid and as ice it can destroy the plates and separators. Maybe not a huge problem with RV's in use (below zero camping isn't typical) but just making the point of keeping state of charge during storage as close to 100% as possible both to mitigate freeze risk and to preserve the health of the battery in general.

The only caveat to charging cold batteries is the charger needs to compensate (increase voltage) for that temperature. One that's set for charging at nominal operating temperature (77F) will undercharge a battery that's cold. Some maintainers sense state of charge through various techniques which results in a complete charge irrespective of temperature but it would be good to know if it's capable.

Per above you can use a kill switch but in my view unless you need to use one often they add an unnecessary point of failure. There is nothing more sure than loosening a clamp and lifting a cable.

Mark B.
Albuquerque, NM

 

[RayIN]

Lead-acid batteries self-discharge @ 3%/month, so fully-charged LA batteries will easily withstand 6 months of disconnected storage and have 82%+charge remaining.
reference: renogy.com
Otherwise I agree with Mark.

 

[Kirk]

I would be certain to have a full disconnect, or simply remove the ground wire,

Doing this should be just fine. When we began using a storage lot all that I did was to lift the negative battery cable and reconnect it when we went to use it again. It sat as long as 8 months in one case and was fine. The only factor that might play a part is the age of the battery involved. An old battery that is near the end of life will not last as long.