Winter Time AGM Battery Removal?

Boomzoom

I live in Northern VT and the outside temp can get rather cold (down to -28F or lower) in the winter. This is my first time with RV batteries that are AGM style.  I've always removed my previous batteries in the past and stored them inside the house for the winter.  I was informed that this is not necessary with this style of battery.  Is this true?  It would be costly mistake if I needed to remove them due to such a cold winter climate.  What do you do??

Admin note:  Subject line edited to clarify type of battery—Verna, T@B Admin

webers3

I remove mine and every so often connect battery tender to keep it charged, I would remove it regardless of what type it is

Michigan_Mike

You should be fine if you fully charge your battery before putting your trailer away for the winter months.  The AGM batteries are more susceptible to heat and are supposed to perform better in temperatures down near -40°F.   As noted by Weber 3 above, a battery tender is a great way to keep the battery fully charged and float the charge as needed while not in use during the winter months.  

Cbusguy

I always have removed batterys from anything being stored over the winter and brought inside the house.    be it a motorcycle, Rv, boat or spare car.   

ecstatic

Can anyone comment on the proper order of events to unscrew the terminals from the batteries?

pthomas745

@ecstatic Negative first.

https://www.cartalk.com/radio/puzzler/lesson-learned-hard-way

pthomas745

A fully charged battery will hold a charge for months.  The "self discharge" is very low.   Just turn the battery switch, pull the fuse if you don't have a switch,  or remove the negative cable, and nothing else needs to be done.  I carry a spare battery (35ah) and it has been sitting in the garage since May.  I just ran out and hit it with the multimeter:  12.59V. 

A day or two every month would be fine.

If anyone knows, since I can't seem to find it on the web:  when does a battery get "damaged" by low temperatures?  This paragraph comes from the battery FAQ I read:

"Even though battery capacity at high temperatures is higher,  battery life is shortened. Battery capacity is reduced by 50% at -22 degrees F - but battery LIFE increases by about 60%. Battery life is reduced at higher temperatures - for every 15 degrees F over 77, battery life is cut in half. This holds true for ANY type of Lead-Acid battery, whether sealed, gelled, AGM, industrial or whatever. This is actually not as bad as it seems, as the battery will tend to average out the good and bad times. "

So, why do people remove batteries that will not be used in the winter?  I realize the capacity will decrease (which is why a car might not start).  But, it doesn't seem to damage the battery.  And, judging by the statement above, people who live in hot climates might be urged to remove batteries while storing the trailer during the summer months. But, you never hear of people being concerned by this.

Am I missing something?

Sharon_is_SAM

As long as the AGM battery is fully charged cold temperatures basically put the batteries to sleep, limiting self discharge so the danger of freezing is minimal.  If you needed to use the battery in this condition, you would find a reduced capacity until the temperatures climb to normal.  Here is a nice piece of info on AGMs.  They report AGMs tolerate temps to -40 F or lower.

https://www.solar-electric.com/learning-center/agm-battery-technology.html/

Everything I have read indicates that a fully charged AGM does not need a battery tender due to extremely limited self discharge and low sulfation rates.  Also, I am curious...does the 400 manual recommend storage with a battery tender?  They did not design the battery area to be easily accessed let alone  removing the battery and it appears they intentionally used a battery that could be basically tucked in and ignored.  

Cbusguy

I have had a battery freeze and crack with the expected result.

For as easy as it is to remove it and take where it is warm and more secure, it is worth the 5 minutes it takes.

Less hassle than winterizing the plumbing

Sharon_is_SAM

@CBusguy, an AGM, Gel or wet cell?

I don’t think it is feasible to remove the 400 single 235 amp battery.  Too heavy, some of them are framed in to hold them in place.  
Not to mention risking damage to the TaB, battery or your back.  There is no need to remove them.

tabiphile

There is minimal danger that a properly topped off fully charged battery will suffer from being left in the cold. Batteries from my lawn tractor, snowblower, chipper, camper etc. are stored without any special care in freezing temperatures. I have never encountered a problem. A cautious person would charge these and store them inside. I don't. An AGM should be fine as long as it is charged. A battery tender should not be needed. 

Cbusguy

@Sharon_is_SAM it was a wet deep cycle in a boat.    That winter lost the starting battery wouldn't hold a charge and the trolling motor battery cracked.   The odd thing is I don't remember it being super cold.   Both were charged before storing

It was before agms, gels and lithiums......dating myself

@tabiphile so are those machine s stored in your garage or in a barn or tool shed.   Makes a big difference

Sharon_is_SAM

@Cbusguy, yeah - wet cells are prone to that.  That's why the AGMs are so versatile.  The only thing they don't like is heat and they need certain charging programs.

Cbusguy

@Sharon_is_SAM I am an ounce of prevention kinda guy.     If I can top off the charge and store them in my basement then there is zero doubt they will be ready to go in the spring.   

Haven't had any issues since I have started to do it and for the small amount of work involved I will continue to do so.

Sharon_is_SAM

If I had a wet cell (that I could carry 😏), I would do the same.  

tabiphile

@Cbusguy...outside unheated storage shed for all but the camper...that's just outside storage.
Unless a battery has a weak cell or is extremely low on charge it should survive sub-freezing temperatures without a problem. You may need to recharge them after storage but if they are used on something that does not require much amperage (lawn tractor) you can probably just fire them up. I don't even disconnect the ground wires.
I'm far more worried about wintering over bad gas. 

ColoradoJon

Sharon_is_SAM said:

@Cbusguy, yeah - wet cells are prone to that.  That's why the AGMs are so versatile.  The only thing they don't like is heat and they need certain charging programs.

Wet Cell batteries are not necessarily prone to freezing.  AGM's can freeze and crack, too.  AGM's are essentially flooded lead acid batteries with a glass mat material that contains the electrolyte.  This is the only difference between AGM and flooded lead acid batteries.

What keeps a battery from freezing is its charge.  AGM batteries do not necessarily hold their charge better than flooded lead acid batteries (it depends entirely on how the battery is made, environmental conditions, etc.).

If you do not move your batteries indoor for the winter I would definitely keep your battery on a maintainer charger.  If it is a flooded lead acid battery you will want to check the fluid level monthly to make sure it is full.

I remove my two 6V batteries from the tub, but keep them in my unheated shed on a battery maintainer.  Mine are flooded lead acid batteries, so keeping them in the shed gives me accessibility to check the fluid levels, inspect their condition, and keep them dry/clean.

lkc001

If I could lift the battery out of the tub I would also store it in the garage.  I can't and it's not worth injuring myself.  I have a charger so I will hook up my charger, leave it in the tub & plug it into the garage @ once a month for a day.  I also cover my trailer so no snow/moisture can get to the battery.

ColoradoJon

@lkc001 - Do you have an AGM battery?  In my opinion the best reason to get an AGM battery is because they do not evaporate water, so there is very little maintenance.  I only pull my batteries because they are flooded batteries and require the addition of distilled water every once in a while.

For winter storage get a Battery Tender Junior.  It's small, safe, and will keep your batteries charged throughout the winter.  Just hook it up and leave it.  If you prefer temperature compensation, get the Battery Tender Plus model.

Battery Tender Junior

Battery Tender Plus

Boomzoom

Thanks everyone for the input.  A lot to think about when it has gotten to -34F during the winter here (not including wind factor).  Might just err on the side of caution and bring them in. 

Denny16

Sharon_is_SAM said:

@CBusguy, an AGM, Gel or wet cell?

I don’t think it is feasible to remove the 400 single 235 amp battery.  Too heavy, some of them are framed in to hold them in place.  
Not to mention risking damage to the TaB, battery or your back.  There is no need to remove them.

I agree with Sharon, the 2018 TaB 400 AGM weighs 200+ lbs.  you need to remove the frame that holds it in place, on later models, the battery was enclosed in ABS battery cover, that would need to be removed first:

You can see the battery cover to the right, not an easy or quick task to get to the battery.

Later models of the TaB 400 gave two 6-VDC AGM batteries mounted under a screwed down cove behind the cement bunk storage locker, even harder to get to.  Each battery weighs 100+ lbs, and requires disassembling if the center bunk storage area to gain access.  Next, they need to be lifted out from an awkward, limited space area, where you can not stand up.  You will need a battery pull strap to get them out.

With very limited danger of damaging a fully charged AGM battery, doubt it will get below the minimum threshold of -40F in most parts of North America.  
cheers

DenisP

While I live in Central Mass. we still can have cold winters. I fully charge the batteries before storage and check the charge (BMV 712) when I check in on our covered 400. Periodically I will attach a 100W solar suitcase to top off the batteries from 12.8 v to 13.1v.   I have used AGM batteries for several years in my boat, truck and cars so I feel confident in caring for the 400 this way especially since the batteries are so difficult to remove on a 2018 400. As a side note, I have a vintage VW bug which I store which previously had a wet cell freeze, split and eat through the floor. After that I purchased an AGM battery (fixed the floor first) and treat the same as the Tab without issue. YRMV.