Should you Leave a Solar Trickle Charger Connected to a Battery? | How to Prevent Battery Damage?

Have you been faced with a flat car battery when your car was parked for a week or longer?

Are you considering using a solar trickle charger going forward?

While solar trickle chargers or maintainers are not meant to fully charge a dead car battery, they are a convenient way to keep your car battery topped up during the summer particularly if you are going to park it for 2 weeks or longer and if you have access to sunlight.

As with any charging system connected to the battery, there is the risk of damaging the battery if not used and sized properly.

So in this guide, I share findings from research on whether you should leave solar trickle chargers connected all the time, the risks associated with doing so, and how to prevent likely damage when using a solar trickle charger.

Why You Should Use a Solar Trickle Charger?

A solar trickle charger is one way to keep the 12V batteries topped up (above 12.4V) below which if kept for a time batteries suffer from sulfation – a common cause of battery failure.

Unlike the chargers that need to plug into the grid, to keep the battery charged with a solar trickle charger, all you do is:

  1. Place the solar panel such that it receives sunlight
  2. Connect the charger to the battery. There are usually two ways to do this:
  • You can plug the battery clamps onto the battery terminals (make sure that the clamp with the red positive wire is connected to the positive battery terminal and the clamp with the black wire to the negative terminal) or
  • plug the cigarette plug into the cigarette socket connector to charge the battery.

Can I Leave a Solar Trickle Charger on all the Time?

It depends on the capacity of the charger and the battery size (Ah).

It is generally okay to leave small solar trickle chargers connected to large capacity batteries without danger of damage to the battery from overcharging.

This is because compared to the battery size they are only pumping just enough current to keep the battery topped up and guard against both self-discharge and battery drain from the car’s electronics such as the car alarm.

For example, you can connect a 1.5W, 12V solar trickle charger connected to a 50Ah car battery all the time without the danger of ruining it – it is only pumping about 125 mA at the most.

On the other hand, if it is a smaller capacity battery like a 7Ah, you should not leave it charging all the time to avoid overcharging it.

You may also be interested in this article: How long it takes to charge a 12V battery at 6 amps?

Can You Overcharge with a Solar Trickle Charger? Is It Safe to Leave it Connected?

Yes, it is possible to overcharge a battery using a solar trickle charger if it is directly connected to a battery and supplies a high current to a considerably small battery capacity over a long period of time or does not have the inbuilt electronic module to prevent overcharging.

For example, an 8W solar trickle charger can overcharge a 7Ah or 10Ah battery if left connected to the battery all the time.

To avoid damage from overcharging, check the recommended battery sizes to connect to the solar trickle charger in the owner manual or if it has inbuilt protection against overcharging.

How to Prevent Damage to Battery Using a Solar Trickle Charger

Here are 3 tips that can help you safely use a trickle charger without damaging your battery.

#1. Only leave unattended recommended battery capacities connected to your solar trickle charger to prevent damage from overcharging.

Check the solar trickle charger owner manual. For smaller battery capacities, connect it to a charge controller with overcharge protection to prevent overcharging it.

#2. If the battery is dead, the solar trickle charger is not able to fully charge it fully. Instead, you should use a good quality 3 or 4 step battery charger.

You may also be interested in: How to safely use a car battery charger overnight

How Long Should You Leave a Solar Trickle Charger On?

You can leave the solar trickle charger connected to the battery provided:

  • it has a safety module to prevent overcharging of the battery (check the owner manual)
  • or you only connect it to batteries with the recommended capacity (Ah) and the car engine is not running.

Always disconnect the solar trickle charger before starting the car, or if the car engine is running.

Final Word

A solar trickle charger can be left connected to a battery if it has inbuilt protection against overcharging or if you connect it to the recommended battery capacity (Ah).

Always consult the owner manual to check the guidance from the manufacturer whether it is safe to leave it connected to the battery.

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