Charging Battery Direct From Solar Panel

To charge a battery with a solar panel connect a charge connector to the solar panel.

Charging battery direct from solar panel.

Generally a fully discharged 12 volt 100ah battery needs 1200 watts of energy to be 100 recharged. Divide the wattage of the solar panel by the voltage of the battery to get the number of amps your charge connector needs to handle. Voltage drop in a single panel system as you can see in the calculation the voltage drop is 4 09 which will reduce the overall power delivered to the charge controller. The bulk phase first stage the bulk phase is primarily the initial stage of charging a battery using solar energy.

If you keep the panel connected as shown in your diagram it will absorb some power when it is not getting sunlight. When sunlight shines directs on a panel the charging speed gets a boost and charging cycles slow down on a cloudy day. Add a blocking diode on the positive rail between the battery and the panel or as previously suggested and the best solution imho use a small solar charge controller. Then run wires from the battery to the charge connector making sure to match the positive and negative poles.

Charge 100ah battery standard size solar panel is 58 inches by 27 inches 2 solar panel for 150 watts 12 volt each for 5 sunshine light hour takes to recharge 100ah 12 volt battery. The bulk phase will initiate when the battery reaches a low charge stage and that is usually when the charge is below 80. The position of the sun in the sky can impact a panel s charging speed.