I want to build a solar panel with a bunch of solar cells that I have and all together produce 18v and 1.25amps. My battery is 18v and 3.2 amps. So am I correct by assuming that it will take roughly 3 times longer than normal to charge my laptop battery under perfect solar conditions?

Best answer:

Answer by Mark G
You will need a higher voltage than the battery to recharge it.

As the applied voltage increases current will begine to flow into the battery in the reverse direction from when it discharges. The amount of current used during charge will depend upon how much additional voltage above the battery potential is applied, the internal resistance of the battery, and the abiiity of the charger to supply the current at the rated voltage.

The amp rating of the charger is a capability of the charger to supply upto the rated current while being able to supply the rated voltage.
If your battery demands more current than your charger can supply the charging voltage will be pulled down to a lower potential. Conversly if the battery doesn’t demand much current only the amount of current required by the battery will be drawn from the charger.

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