Do Solar Panel 12v Battery Tenders Work?

[MS50]

Typical solar battery tenders will maintain a battery, but it won't charge it. They will allow you to start a motor. The alternator takes over to charge the battery. If you partially or completely deplete a deep cycle battery, a standard sized portable solar panel will do nothing to recharge it. It must be placed on a charger to be replenished. If the battery is not subjected to significant drain, a solar panel should be OK. I've searched extensively for a way to charge my fishing boat deep cycle battery without hauling it off the dock to the marina for charging. Solar chargers that will actually charge the battery were at least 3ft x 2ft x 2in thick. This will take up the entire area of one of the jon boat seats. I also use an aftermarket overcharge device on my solar maintainer. Does it work? I have no clue. If a reasonably sized solar charger is available that will charge a battery, I'd be interested.

 

[Turpentine]

As said above. Yes they do. I use them on sporting clays courses and have around 50 of them ranging from $250 to $15. They do very well at maintaining a battery. However, if you deep discharge a battery below 12 volts per se, I would put it on a regular charger and bring it back up to full charge. Solar panels generally will not bring a battery back from a deep discharge. They serve better in a maintenance role.
The key to longevity of any battery is to keep it from going down to full discharge. If you fully discharge one, even a new one, it is generally done. I have run reconditioning or desulfating cycles on some batteries that have been fully discharged and made them usable again but that is hit and miss. Also, I've found that it is good to run a desulfating or reconditioning cycle on any battery from time to time even if it is in good condition. This will keep sulfating down and won't let sulfating get to the point that it shorts it across the plates. This is likely more answer than you were looking for but I have extensive experience with the topic.

 

[59FLH]

I see tenders for as cheap as 15$, How would it work on my rv battery for winter storage?
ty Don.

The $15 model? IME not very well.
Id recommend a panel with a Schottky diode, without this the current will reverse flow back to the panel and discharge the battery in periods of darkness and low light. These diodes are typically NOT found on the low priced panels.

Also the low priced panels have very low output some so low they wont power the “regulators” if you try to put one between the panel and battery.

Solar tenders work, but IME a $15 unit for long term on an RV battery? No.

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