Trickle charging batteries with solar panels

Left to their own devices, lead-acid batteries slowly discharge themselves. This is bad news for several reasons. Firstly, and fairly obviously, it means there is less power left in your batteries when you return after a couple of weeks absence than when you left. A tad annoying on your first evening back to find the lights dimming.

Secondly, it really isn't good for lead-acid batteries to be left discharged. Lead sulphate slowly forms on the plates, and gradually the battery loses capacity. A battery that is left deeply discharged can be almost useless within a few months - one that is kept fully charged can last many years.

You don't need much power to replace the self discharge, so even a small solar panel is an ideal solution to keep the battery bank in tip-top condition.

A good rule of thumb is to use a solar panel whose rated power in watts is around 1/10th of the rated capacity of the battery bank, in Ah. So a 10W panel would be ideal for a typical 100Ah leisure battery for example. To be honest, most of the year you would get away with even less - but a 10W panel would ensure the battery was topped up even in the depths of winter.

The Spectra solar panels are often used for trickle charging. The smaller panels in the Kyocera range are also ideal for the job.