About Solar Chargers...

[eccerr0r]

Re: About Solar Chargers...

Definitely depends on the size of the battery versus wattage of the panel, but I'd say that a "dumb" 10W into a 50Ah battery you will need to water the battery and it could eventually cause damage if you never use the battery. At 10W it's about C/60, which is not horrible but still will cause eventual dry out. If it were a sealed AGM battery with proper recombination, then you won't have to worry about electrolyte loss.

Ideally you don't go way too much over about 3x the parasitic draw of the battery (for most cars it's 1W or so tops) if you can't regulate the voltage. But a simple shunt or series regulator will be sufficient to deal with water loss, but do keep in mind it's temperature dependent.

oh btw, a $0 way to maintain your battery if you don't care about ECU settings and less than say 3 months of non-use: just disconnect the battery. If it discharges without it being connected, you need a new battery anyway...

[EasyGoing1]

Re: About Solar Chargers...

Some of the higher-end solar chargers claim to have "intelligent" charge circuitry so they should at least in theory work just like a plug-in "smart" charger and stop charging once the target voltage is reached. The cheaper ones don't claim this and are likely just a constant "float" charge with no intelligence, though since most of these chargers are 10W or less this isn't likely to be an issue on the average 50-60 Ah car battery, smaller batteries (like motorcycle or power equipment) may have issues with this though.

The Cigarette lighter chargers will only work if the lighter jack is always "hot" (even with the ignition off), and even then I'm not sure how well they'd work with modern can-bus equipped vehicles. If the lighter jacks in the vehicle aren't "hot" with the ignition off (or if back feeding the lighter doesn't play "nice" with the can-bus) the charger would need to be wired directly to the battery.

That's a good point I had totally forgotten that my plugs turn off with the ignition... so some kind of direct connection will have to be made. I went out to use my car for the first time in at least a month and the battery was dead... so I should do something to prevent that from happening. It was the cheaper chargers that I was more interested in that apply seemingly such a small amount of current, it doesn't seem like it could hurt the batter but I wonder if it will help either or if its just a waste of money.

[dmill89]

Re: About Solar Chargers...

Some of the higher-end solar chargers claim to have "intelligent" charge circuitry so they should at least in theory work just like a plug-in "smart" charger and stop charging once the target voltage is reached. The cheaper ones don't claim this and are likely just a constant "float" charge with no intelligence, though since most of these chargers are 10W or less this isn't likely to be an issue on the average 50-60 Ah car battery, smaller batteries (like motorcycle or power equipment) may have issues with this though.

The Cigarette lighter chargers will only work if the lighter jack is always "hot" (even with the ignition off), and even then I'm not sure how well they'd work with modern can-bus equipped vehicles. If the lighter jacks in the vehicle aren't "hot" with the ignition off (or if back feeding the lighter doesn't play "nice" with the can-bus) the charger would need to be wired directly to the battery.

On my Mustang which doesn't get driven much in the winter I have an SAE quick disconnect (similar to this one: https://www.amazon.com/Battery-Tende...ps%2C55&sr=8-3) wired into the battery (I just use a plug-in battery maintainer since it is parked in a garage with plenty of electric outlets) which will work with most battery maintainers (both plug-in and solar) and allows quick connection without messing with alligator clips and risking shorts.

[EasyGoing1]

Those solar cell car battery maintainer devices ... look like they would be a good idea to use when you have a car parked without being driven for several weeks at a time ... is there any chance that those devices could cause any damage to a car battery? Or are they weak enough that it is nothing to be concerned about? And the other question is, do they actually help keep a battery charged? Looks like they plug into the cigarette lighter plug but not sure how that can charge the battery?