Battery winter storage

There's an tremendous amount of other data out there on the internet if one wishes to learn about it. It only took about a minute to find the information above from how-to sites, battery manufacturers, and charger manufacturers.

Thanks Gjac, I'm a 35-year science professional, It's how I pay my bills and feed my family. Keeping a battery charged means less loss of plates and solution, meaning a longer lifespan for the battery. I admit, my batteries (agm and lead-acid) did last longer once I started keeping the stored ones on float chagers beginning in 2000.
From Battery University:

...The recommended storage temperature for most batteries is 15°C (59°F); the extreme allowable temperature is –40°C to 50°C (–40°C to 122°F) for most chemistries. While lead acid must always be kept at full-charge during storage, nickel- and lithium-based chemistries should be stored at around a 40 percent state-of-charge (SoC). This minimizes age-related capacity loss while keeping the battery operational and allowing for some self-discharge...

From Schumacher:

...Since lead-acid batteries will not freeze if kept fully charged, store your battery on a float charger, in a cool/cold place to maximize its life. A battery that has frozen is usually void of its warranty...Sulphation is a constant threat to batteries that are not fully re-charged. A layer of lead sulphate can form in these cells and inhibit the electro-chemical reaction that allows you to charge/discharge batteries. Many batteries can be saved from the recycling heap if they are kept fully charged. A battery float charger will keep your battery fully charged, without over charging...For instance, flooded cell batteries as used for automotive applications, typically use lead alloyed with Antimony* to increase their mechanical strength. However, the Antimony also increases the self-discharge rate to 8-40% per month. This is why flooded lead-acid batteries should be used often, or if this is not possible, be left on a float-charger...

Tonijim wrote:
Wow! When I posted my query, I had no idea that the subject would yield so much reasoned discussion. Thanks to all posters, but I confess to continued confusion. I think I will go with the disconnect/trickle chargers. Thanks for all the info!

Jim

There is no reason to be confused. Either method will work fine. Some times people use a certain method that has worked for them over the years and feel comfortable with it. But science is science and what Pianotuna posted is science. When I used a battery maintainer and I lost power and drained my battery. Where I live power lines come down due to ice storms during winter months. So I choose to fully charge my batteries including an equalizing charge then remove the negative cables and let them sit over the winter. The colder it gets the slower the self discharge. My two 6 v Sam Club GC batteries are 9 years old and I dry camp 95% of the time and don't keep them on a constant charge even in the summer.

pianotuna wrote:
I've not seen one that does temperature compensated voltage.

I believe BatteryMinder makes several that are temperature compensated from 0F to 130F. Getting two of 'em for Christmas (but don't know about it).

The rate of self discharge goes down by approximately 50% for ever 10 degrees C temperature drop.

6% discharge at 25 C (charge voltage 13.5)
3% at 15 C (charge voltage 13.62)
1.5% at 5 c (charge voltage 13.74)
0.75% at -5 c (about 23 F) (charge voltage 13.86)
0.375 st -15 c (charge voltage 13.99)

A trickle charger at -5 may well be actually discharging the battery. I've not seen one that does temperature compensated voltage.

So, for storage, colder is better until you reach -60 c. It is probably better to disconnect the battery.

tplife wrote:
Disconnected, that battery maintains its voltage by eating its plates from the inside out. You're welcome to believe otherwise, but I would encourage you to learn more about how batteries work and maintain voltage between charges. A float charger maintains proper voltage and allows batteries to last a lot longer, particularly when not being recharged by an alternator with regular use.

Here in my area of Colorado where temps reach -20, I drive my coach monthly and leave the batteries alone. They don't freeze as long as they are fully charged. Never had a problem.

JNorton wrote:
Flooded lead acid batteries self discharge between 4 to 6 percent per month with discharge rates diminishing with lower temperatures. Typically a fully charged battery will suffer no ill effects being disconnected for winter. If you do choose to use a float charger use a holding relay to disconnect it from the battery in case the power fails. Make sure it is a float charger rated for your battery type. https://en.wikipedia.org/wiki/Float_voltage

Disconnected, that battery maintains its voltage by eating its plates from the inside out. You're welcome to believe otherwise, but I would encourage you to learn more about how batteries work and maintain voltage between charges. A float charger maintains proper voltage and allows batteries to last a lot longer, particularly when not being recharged by an alternator with regular use.

Yes, I did discover that the DLS-55 does not charge the chassis battery, my plan is to have the MH plugged in while in storage and have the wiring for charging the chassis battery come in through the firewall and plug the charger into an AC outlet inside the MH. I usually use a clamp that is held in by the wall plate screw.

Gene_M wrote:
Have not read all of the previous posts, just wanted to contribute a little here.

I have BatteryTenders on my tractor, motorcycle and the car I keep in the garage, they are always connected and charging when the vehicles are not in use. I have 7 years on the car and 8 on the MC and 11 on the tractor batteries.

Since the regular mode of the IOTA DLS-55 is to trickle charge there is the element of losing water due to charge boil, best not to leave it on a stock house charger. I am installing an IQ4 (smart charger add on from IOTA) on the DLS-55 converter/charger for the house battery and I intend to leave that plugged into shore power same as the others. Since I am new to RVing I'm not sure if the DLS-55 charges the chassis battery when the vehicle is not running, so unsure of that for the moment.

Other info, I just purchased a BatteryMINDer 1510 because it has a desulfate step that BatteryTenders do not.

Unless your RV has a Trik-L-Start or similar device your chassis battery is not being charged when charging the house batteries.

One needs to be careful when selecting battery maintainers. Some of them will actually put a load on the battery if the AC power is removed so one must be careful about it coming unplugged or other AC power loss. I discovered that some versions of the BatteryMINDer were like this when I was researching them.

Have not read all of the previous posts, just wanted to contribute a little here.

I have BatteryTenders on my tractor, motorcycle and the car I keep in the garage, they are always connected and charging when the vehicles are not in use. I have 7 years on the car and 8 on the MC and 11 on the tractor batteries.

Since the regular mode of the IOTA DLS-55 is to trickle charge there is the element of losing water due to charge boil, best not to leave it on a stock house charger. I am installing an IQ4 (smart charger add on from IOTA) on the DLS-55 converter/charger for the house battery and I intend to leave that plugged into shore power same as the others. Since I am new to RVing I'm not sure if the DLS-55 charges the chassis battery when the vehicle is not running, so unsure of that for the moment.

Other info, I just purchased a BatteryMINDer 1510 because it has a desulfate step that BatteryTenders do not.