maintaing fully charged batteries

[Anthony P]

My wife and I own a 2022 Airstream 19-foot CB Bambi Trailer. We bought it new from the factory and it's equipped with 2, AGM 12-volt batteries and one 100-watt solar panel. When it was winterized in mid-November 2022 its batteries were fully charged. It's stored in a location that receives direct sunlight to the solar panel for the majority of the day. We live in the Puget Sound region of Western Washington and during this winter have experienced periodic days of sunshine along with the normal overcast and rainy weather that the region is known for. I have the battery switch in the "off position." I check the batteries at least every couple of weeks and the trailer's Monitor Panel consistently indicates fully charged batteries with a reading of between 13.3-14 volts. I haven't charged the batteries using shore power since we winterized, and the 100-watt solar panel appears to be maintaining the full battery charge. We're first-time trailer owners and are new to trailer battery maintenance along with the use solar power. Is it normal for the solar panel to keep the batteries fully charged, even during the winter in a maritime climate or am I missing something? Any input would be appreciated.

[AlbertF]

Originally Posted by Anthony P

Is it normal for the solar panel to keep the batteries fully charged, even during the winter in a maritime climate or am I missing something? Any input would be appreciated.

Yes.

You have no power draw, unless the propane detector is wired before the master switch like some older trailers.

Even 20% efficacy for 6 hours per day is 180 Wh per day, or one kilowatt hour every 6 days. You would have no trouble keeping conventional lead acid batteries charged.

[AlbertF]

Originally Posted by AlbertF

Yes.

You have no power draw, unless the propane detector is wired before the master switch like some older trailers.

Even 20% efficacy for 6 hours per day is 180 Wh per day, or one kilowatt hour every 6 days. You would have no trouble keeping conventional lead acid batteries charged.

Make that 120 Wh per day. My math was off.

Another thing to note - you can buy small solar panels for maintaining batteries that produce less than 10 watts.

[field & stream]

Similar to the above response, the simple answer is that this performance is not surprising.

I think of these questions in terms of amps stored and consumed rather than watts. Propane detectors use about .2 amps, or 5 amp hours per day. A 100w panel at 20% efficiency for 6 hours would provide about 10 amp hours at 12v.

However, other devices may be drawing power even when the Airstream provided switch is set to “off” since it is not a true battery disconnect switch. Power still may be being provided to the radio presets, the subwoofer, or the tv antenna if it’s left switched on. Many owners choose to have a true disconnect switch added.

If you really want to know and monitor what is going on with your electrical supply and demands, look into the shunt based battery monitors such as the Victron 712. They are great!

[Anthony P]

Thank you for your response and the suggestion about the battery monitor!

[ROBERT CROSS]

I did with AGM's and still do with LiPo, charge fully and completely isolate, (switch disconnect) and leave in the AS for winter storage.
11yrs with the Lifeline AGM's and 6 with the Lithium BB's. SFSG.

Bob
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[Boxite]

I believe propane detectors are hot-wired to the battery and cannot be turned off with the battery switch unless the system is modified.

[ROBERT CROSS]

Originally Posted by Boxite

I believe propane detectors are hot-wired to the battery and cannot be turned off with the battery switch unless the system is modified.

Ours...

Bob
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[tjdonahoe]

Yep solar keeps the batteries charged up, kinda like magic monies well spent

[ROBERT CROSS]

Originally Posted by tjdonahoe

Yep solar keeps the batteries charged up, kinda like magic monies well spent

But why keep charging if charging isn't needed during winter storage?

Bob
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[field & stream]

Originally Posted by ROBERT CROSS

But why keep charging if charging isn't needed during winter storage?

Bob
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Good point, but charging probably is needed unless there is a true disconnect switch. The parasitic loads and the battery self discharge rate are draining the stored energy. No real risk, a good converter or solar controller will keep the batteries from being overcharged.