Charging battery when connected to shore power

[gw1800]

Originally Posted by Dana anderson

While your plugged in charging from shore power your converter is running constantly, this will increase the usage time and wear and tear and have the converter die a premature death. Look at the expense of replacement then put the battery on a trickle charger.
Look at the cost 1. Run off of shore power. 2. Possibly wear out converter. P.s. A quality trickle charger will cut itself on and off and not overcharge. I use mine on lawn mower also all winter long.

A trickle charger is not the best type to use. It charges weather the battery needs it or not. A good battery maintainer that monitors the battery voltage, then only charges when needed.

Two of the best are the Deltran Plus and the Ctek. NOCO genius is another.
I have been using the Deltran for over 15 years on my motorcycle and trailer batteries.

[waverider64]

Being a newbie a couple years ago, I asked the service manager where I bought my trailer about what to do about the battery for winter. He said just take it out and store it in the cellar without a trickle charge. Then put the trickle charger on it about a week before picking up the trailer on the spring. As stated above, the battery doesn't lose a tremendous amount of charge over the winter.

[Chuck_S]

The battery would have lost even less charge over the winter if you'd simply disconnected the battery -- pulled the Negative connection -- and left it outdoors on the camper. Battery self-discharge is significantly greater in warm conditions vs cold. Like indoors vs outdoors.

-- Chuck

[NJKris]

Removing the batteries is a PITA. Those golf cart batts, at least GC15's are 64 pounds each and the only way to get them out of the box is using a battery lifter strap. I don't know why dealers tell new owners silly stuff like remove them.

[DawsonMobley]

Originally Posted by 5picker

Simply charge it, completely disconnect it and leave it in place. The battery will only discharge a few percent per month and even after 6 months the battery will still be about 90% charged. It won't freeze unless you see temperatures at/below -75°F.
No chargers, converters or electricity needed and no reason to baby it and tuck it in bed each night in some warm environment.

agreed...this is what I do as well. Another benefit you didn't mention to doing it this way is it's not good or necessary for any rechargeable battery to be topped off all the time if it is not being used.
I like to see my battery sitting at between 12.1 and 12.9 volts when it's not being used and I will plug it back in to top off the battery a day or two before we leave for a trip, keep it topped off while in use and then disconnect it when I get it home until the next trip. (I do check the voltage every few months just to make sure its above 12 volts but have never seen it get below 12.6 volts just sitting.)
I'm in Florida and have an agm battery and it will stay above 12.1 volts for a year or more as long as the battery is disconnected. The original lead acid battery lost charge at a similarly slow rate.

[adaycj]

I'm now 7 years into an AGM battery. It has been left in place for 6 winters so far in MI, only disconnected. I would recommend cleaning it off. Dirty slimy stuff can conduct a bit and cause discharge at a higher rate. I would actually disconnect the negative (or both), the disconnect switches never seem to disconnect everything.

My last tender/maintainer died and over discharged my previous battery. Did I say it was my last tender/maintainer? Yep, not wasting money or electricity on that thing again.

[Chuck_S]

Self discharge of lead-acid battery vs temperature. This included "flooded" and "AGM" both of which are lead-acid types of different construction.

Of course the battery has to be disconnected from everything and, as has been noted several tines but often ignored, camper battery "disconnects" may not do this -- check your system or merely remove the negative battery cable (or both).

-- Chuck

[BehindBars]

Originally Posted by Chuck_S

Self discharge of lead-acid battery vs temperature. This included "flooded" and "AGM" both of which are lead-acid types of different construction.

Of course the battery has to be disconnected from everything and, as has been noted several tines but often ignored, camper battery "disconnects" may not do this -- check your system or merely remove the negative battery cable (or both).

-- Chuck

That is a good chart, and I chuckle when I think about the self fulfilling exercise of bringing the battery indoors so it can be put on a battery maintainer. Bringing the battery indoors out of the cold is why it needs to then be put on a maintainer. Leave it out on the cold and it doesn’t even need charging.

It amazes me that some dealers may advise customers to bring batteries indoors for winter. Are they also still telling them not to set batteries on concrete floors (another piece of outdated advice)?

[adaycj]

Originally Posted by Chuck_S

Self discharge of lead-acid battery vs temperature. This included "flooded" and "AGM" both of which are lead-acid types of different construction.

Of course the battery has to be disconnected from everything and, as has been noted several tines but often ignored, camper battery "disconnects" may not do this -- check your system or merely remove the negative battery cable (or both).

-- Chuck

I don't disagree with you. Batteries self discharge. My own tests indicate less than 5% per month in a typical Michigan winter.

The image is ultimately from Power-Sonic, a manufacturer of batteries. Most people find it at
https://batteryuniversity.com/article/bu-802b-what-does-elevated-self-discharge-do but they attribute it to Power-Sonic.

Power-Sonic states in the document:
TOP UP CHARGING LEAD ACID BATTERIES
All batteries lose capacity through self-discharge, it is recommended that a “top up charge” be applied to any battery that has
been stored for a long period of time, prior to putting the battery into service.
To successfully top up charge a battery stored for more than 12 months, the open circuit voltage must be higher than 2.0
volts per cell, in this case, always confirm open circuit voltage prior to attempting top up charging.

Source:https://www.power-sonic.com/resource-center/

I take from this they are not suggesting a maintenance charge or trickle. This is a difficult topic because the voltage has to be temperature compensated, which is in the document. The 2.0v per cell means that at about 70 degrees the battery is at 25% (not good). I find that a Nov to April storage leaves me at about 80% state of charge (usually a little over).

[Chuck_S]

NE Ohio winters put my "yachts" and campers in winter storage November to April. Boats too big for indoor storage at the fairgrounds were on jackstands within 50 yards from Lake Erie. Full charge batteries completely disconnected and left on board. Lowest battery voltage "ever" in April was 12.3vDC or roughly 70% charged. Campers in unheated barns at the fairgrounds never got that low.

When I stored my little Honda S2000 during those Ohio winters I used a battery maintainer to preserve all the ECU and radio settings -- only need to misplace the radio code once to learn that lesson! Those with self-propelled campers will have different storage requires from those of us with trailers.

Camper (and boat) battery electrical system maintenance is a hobby in itself . I've had amphour meters of everything even as small as a 12' popup or a 16' "cabin cruiser."

-- Chuck