need help with recharging a 12 V battery with a solar panel

[dcallet]

Hi everyone, I'm new to to the forum so forgive me if i'm not in the correct section of the forum.

I need to have a 12 battery recharge with a solar panel on a daily basis also I iwll have small device using hte battery. I know i need to have a soalr ocntroller ot make sure I don't over charge the battery and i need to know what type of solar panel i need to get, cannot be very big since hte device is to acquire date. I hiope I make senss in my question.

Denis

[Sunking]

Until you define how many watt hours and location no one can help you.

[dcallet]

located in Southern california and see attached the spec of the battery, the output of the device attached to the battery is 10MA

[Sunking]

OK I assume 10 milliamps for 24 hours a day is 12 volts x .01 amps x 24 hours = roughly 3 watt hours. So your battery is more than large enough to do the job and can run the device for roughly 40 days. If it were me I would just over cook the panel wattage and controller. The battery can take up to 3 amp charging current. Get you a 50 watt 12 volt battery panel and 5 amp PWM charge controller which is more than enough several times over. You can go as low as a 10 watt panel.

Personally if it were me and it is a remote device is just go out there once a month and charge it from my vehicle for an hour and forget solar.

[greenenergyscot]

Voltage Output

As long as the VOLTAGE output of the panel is more than 12 volts, 18 volts is normal, it will charge a 12 volt battery. How quickly it charges depends on the wattage.

[PNjunction]

As long as the VOLTAGE output of the panel is more than 12 volts, 18 volts is normal, it will charge a 12 volt battery. How quickly it charges depends on the wattage.

Actually no. You need a charge controller to limit the voltage, otherwise you'll end up cooking the battery. If the battery is small enough, it will try to reach the panel voltage at the end of absorb and end up cooking / plating the battery.

If the panel is low-voltage, like homebrew without an adequate amount of series cells in the panel, the battery will charge all right - but not fully. Sulfation or stratification is the reward long term. Old-school low-voltage panels of about 15v ocv were the rage at being "self regulated". Unfortunately, in heated conditions, the voltages dropped further. Add to that the typical homebrew long wiring runs that are poorly connected or running too thin a wire gauge , and you have a low voltage recipe for bad charging.

In other words, voltage is important and a CC is necessary, along with the right amount (18v ocv or a bit more) in the panel. Goofs or throw-away projects are a different story.

[inetdog]

But with only a 3 watt load, the CC or panel really could be just a battery maintainer, not really a charger.
Under those conditions, with the panel current limited to a low enough value, either by using a very small panel or using a series resistor, the battery will probably be just fine.
Figure out what the C/100 charge rate for the battery is, and go for that, as long as it is enough to cover the 3W load.