Solar for keeping batteries topped off.

Disconnecting for short periods of time is always a convenient method.

Batteries left without a charging source, start to sulfate immediately, however. So if you're getting 9 years out of a set of batteries, by keeping a charging source available, you may get 10 or 11 years out of them.

My situation is longer term storage than most folks. My wife continues to work and I feel it's in my best interests to stick around. I also have a hand in my small business. What it adds up to is Winter storage in MN.

I have a temp compensated controller that is programmable. These devices keep my batteries charged better than I can with all types of chargers available. If I was to connect chargers or maintainers on my batteries, it would be about equal service life but I would have to monitor them 24/7 and that is improbable.

I'd suggest to install a 100W panel and inexpensive PWM controller. If you can get one with temp compensation, it will be better. The awful thing about solar charging, especially coupled with inversion to 120 V, is that once you get started, you want more.:)

The cheapest solution is to fully charge your batteries and just disconnect the neg cable for two months. Mine stay disconnected all winter(4 mos) and are 9 years old.

Temperature compensation is not an expensive option with the Grape Controller. It does depend where you live. The farther south or farther north you are the more important temperature compensation becomes, particularly with sealed jars.

IMO temperature compensation is not really necessary.
I boon dock 99 percent of the time (30-40 days at a stretch) with (2) 6v GC-2 batteries, 200 watts solar and a non temp. comp. MPPT controller. I never run out of power and my batteries are 7 years old and still going strong.

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I agree if it's getting mounted on the roof. It'll be at least a 100 watt panel and at a 30 amp or greater controller with room to grow, PWM? Trying to keep costs down as we are still working, with kids and only get out 30-40 nights a year.

pianotuna wrote:
Get a Grape 45 amp solar controller with a battery temperature sensor. Install 60 watts of solar for every 100 amp-hours of battery bank. For my further thoughts--surf here:

https://freecampsites.net/adding-solar/

Bluetooth? thats nice.

Sam Spade wrote:

Twain wrote:
Sitting varies from 2 weeks to 2 months. After 1 week of sitting the batteries are down the 12.1 volts. There is no disconnect switch, which I found unusual.

Well you need to repeat that test with a battery cable OFF.

IF.....the batteries go down to 12.1 after only a week then they need to be replaced. That is assuming a full charge to start with.

That was off, if I remember correctly. The unit is 6 months old so the batteries better be good. Then again, it has been to the dealer a couple of times for warranty work and it just sits in the lot, disconnected, waiting for them to get around to working on it, then it sits in between shops for who know how long. Yet another need for solar...

Boon Docker wrote:
In fact you could use a 10 watt panel.

You might get by with 20 but probably not 10.

Those are PEAK capacities; there will be some loss as the ideal sun angle changes, as it gets cloudy and some loss in the controller itself. And then there is an automatic 50 percent duty cycle.

Bill.Satellite wrote:
If the temps are going to be pretty low then I would not recommend this option as cold and discharged batteries do not go well together!

Unless they are severely discharged and it is REALLY cold, that is exactly backwards.

Batteries self discharge less and age chemically slower when cold.