What's best for batteries and winter storage?

Sam Spade wrote:

tenbear wrote:
I use a trickle charger to keep the coach battery charged.

If that is really a trickle charger and not a smart battery minder, that is a BAD choice if you leave it connected all the time.

The coach battery is a maintenance free battery and is the OEM battery, and is now more than 10 years old. It can't be too bad a choice. It is a NAPA trickle charger.

If minimizing water loss is a primary fetish, recombinant battery caps will reduce it by >80%

Always go with the manufacturer's recommended temperature/voltage chart. They know their product. A re-brander or re-seller is NOT the manufacturer. Find out who manufactured the Out-Of-State or Dead-Hard battery, and go with their recommendations.

Newer car-jar RV batteries trend toward very low antimony hybrid plate construction and voltage requirements are utterly unlike those from the 2.75% antimony Lead Dioxide plate era.

Sam Spade wrote:

DutchmenSport wrote:
I think it's really 6 of one and half-a-dozen of another. Either way will return the same results.

I keep mine plugged into shore power 24x7 (at home -- Indiana, even in the winter).

In many cases the difference can be important.

If BOTH your tender and the built-in converter are well designed true float tenders, then is shouldn't make much if any difference.

Many RVs come with single stage converters with is equivalent to using a non-automatic battery charger which can float too high and "boil" off the water in the batteries.

P.S. This subject has already been discussed about a thousand times on here already. A simple search or two would be helpful.

My TT must have a good charger then, because it's been plugged in since the day I purchased it, and the batteries have never boiled over. Actually, in 3 years, I've never had to add a drop of water either.

My previous trailer, I had it for 8 years. About year 4 I had to get a new battery. The entire 4 years, I never had to add a drop of water. The second 4 years, I never added a drop. Sold the trailer, battery was still good.

You're probably right about the converter's though. Some work better than others. I also keep my battery cut-off turned on, so there is always parasitic draw. Maybe this also helps keeping them from over boiling, with a constant charge and discharge at the same time? Anyway... this camper ... 3 years strong and not a drop of water yet!

tenbear wrote:
I use a trickle charger to keep the coach battery charged.

If that is really a trickle charger and not a smart battery minder, that is a BAD choice if you leave it connected all the time.

pianotuna wrote:

smkettner wrote:
"best" IMO is temperature compensated solar.

X2

X3
Solar does a better job than I can with a few different chargers available and measuring with meter or hydrometer. You need a solar controller with temp compensation and it needs to have setting functionality to tailor to your batteries.

FWIW, I am charging two banks, a 2-6V bank and a three AGM bank with the single controller.

BTW, it also helps to have a module tilting mechanism if you live in snow country. My single big module will have snow on it for a day after a largish snowfall. The second day, it will have nearly all the snow off.

If I had your setup, I'd run the tender with only the batteries being powered. I'd also keep an eagle eye on how they are fairing. an equalisation procedure during storage would probably bring more longevity. A hydrometer will unfold any lack of battery health.

Winter Storage

Prior to placing batteries into winter storage make certain the electrolyte level is approximately 1.2" (13mm) above the top of the separators. The electrolyte level in very cold batteries will be lower than normal, so let batteries warm to a normal temperature before judging electrolyte levels.

Once the electrolyte level is correct ensure that the batteries are fully charged. Ensure that the battery tops are clean and dry.

See Information Bulletin 501 & 507.

Now the choice is whether to leave the batteries aboard your boat or remove and store in a cool dry area. If the batteries are stored aboard the boat, disconnect the terminal cables. This will prevent premature discharge of the batteries due to a ground in the electrical circuits or failure to turn a piece of electrical equipment off.

If the batteries become discharged, the electrolyte can freeze when stored below +20° F (70° C). Below shows temperatures at which electrolyte, in various states of charge, starts to freeze.
Specific Gravity

(cor. to 80° F/26° C) Freezing Temp
1.280 -92° F (-69° C)
1.265 -72.3° F (-57.4° C)
1.250 -62° F (-52.2° C)
1.200 -16° F (-26.7° C)
1.150 +5° F (-15° C)
1.100 +19° F (-7.2° C)

A 3/4 charged battery is in no danger of freezing. Therefore, batteries should be kept at least 3/4 charged, especially during winter weather. The frequency of checking batteries depends greatly on temperature. The effect of temperature on self discharge for the average fully charged, new, conventional battery in good condition is approximately as follows:

At 100° F (37.8°C) .0025 Sp.Gr. per day
At 80° F (26.7°C) .001 Sp.Gr. per day
At 50° F (10°C) .0003 SG per day

A fully charged battery stored at 80° F (26.7°C) will take 30 days before it self discharges 25 percent. At 50°F (10°C) the time period increases to 100 days. This will give you an idea of how often a battery should be checked.

Some makes of batteries will have a higher and some a lower rate of self discharge. This depends on the method of manufacture and purity of materials used.

I leave my RV plugged in, but I turn the circuit breaker for the converter off and use a Battery Minder to keep the house battery charged. I use a trickle charger to keep the coach battery charged.

I charge both AGM batteries fully and disconnect them from the trailer. I leave them in place all winter and recharge again in the spring. Batteries are 8 years old now and still working well. I do the same with the batteries in my truck. Charge em and disconnect them and leave them till spring. 8 years old on the truck batteries too.

DutchmenSport wrote:
I think it's really 6 of one and half-a-dozen of another. Either way will return the same results.

I keep mine plugged into shore power 24x7 (at home -- Indiana, even in the winter).

In many cases the difference can be important.

If BOTH your tender and the built-in converter are well designed true float tenders, then is shouldn't make much if any difference.

Many RVs come with single stage converters with is equivalent to using a non-automatic battery charger which can float too high and "boil" off the water in the batteries.

P.S. This subject has already been discussed about a thousand times on here already. A simple search or two would be helpful.

In an RV, #1 is a PD wizard 24/7
#1 in Boat, 24v mower, gas rider, and sxs suv all have tenders.
I quit using amy Schumacher w/ 15+ volts
If I had to depend on solar, I would need new batteries every year.
Between RVs being under cover (smart) and seldom winter sun, solar wouldn't even make the chart !