How to Wire and Use a Solar "Trickle" Battery Charger

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Small solar panels are ideal for trickle charging car batteries, caravan batteries and boat batteries. Small panels for trickle charging can also be used to keep batteries topped up that supply low-power sources such as outdoor lighting, electric fences.

This article explains how to work out the type of panel that is best for you and how to wire it up.

What you need (Voltage)

You need a panel with a voltage slightly higher than the voltage of your battery and an input that will average around about the amount that your battery runs down when you leave it. For instance, an AKT Solar “12V panel” has an output of around 16V which is optimal for charging 12V battery systems such as in cars, caravans and canal boats.

What you need (Blocking Diode)

Then make sure there is a “blocking diode” that is fitted (normally in the panel’s junction box) as otherwise charge could leak out through the panel at night when the sun is not shining and the panel is not producing electricity. AKT trickle charging panels all come with blocking diodes attached as standard.

What you need (Power of Panel)

Normally a 5W panel is suitable for a typical car that is left for long periods and will keep it topped up even in winter if the car is outside or near a window.

For larger batteries such as in a caravan or canal boat where there may also be further low-level drains on the battery such as a security system or electronic equipment on standby, a 10W panel is usually more suitable, particularly to keep the battery topped up in winter.

Similarly, if you have a small output on the battery, such as an electric fence or light used at night, you can match your trickle charging to the use made of a battery. For an electric fence, a 10W panel attached to a battery is typically sufficient. For a light, it may be that a 20W panel is more appropriate. Although if there is not a regular output attached then you should generally use a charge controller with panels over 10W.

How to wire the panel to the battery

Then to attach the battery charger simply wire the panel direct to the battery, + of the panel to the + terminal of the battery and – from the panel to the – terminal of the battery. All you need to do then is leave the panel in sunlight and it will keep your battery charged.

Contact us for more information

Please feel to write to us if you have any questions. We’re always happy to help with any queries.

Contact: +44 (0) 7722 465 643



Source by Simon Milward