Over the last few weeks we’ve played around with an that does as it says on the tin; looked at the the , a tool strong and versatile enough to be your daily driver ratchet; and explored an , a device that cleans parts and tools without all of the hard labor. This week’s Cool Tool is a solar-powered battery trickle charger, a device that can keep your outdoor-parked cars topped up.

The rise of working from home and delivery services means that many Americans are driving way less than they used to. And while their cars sit, their batteries slowly drain. Then when they finally need to go someplace, they find their cars immobile due to dead batteries.

I’ve had this problem more times than I can count with the cars I have parked outside. I leave my apartment excited for a fun drive, hop in a car I haven’t driven in a while, then find out its battery has long expired. I have battery maintainers, but they are useless when these cars aren’t anywhere near an outlet.

The solution may be to harness the sun with a solar-powered trickle charger.

I recently purchased this Allpowers model from Amazon. It’s rated at 18 Volts and 10 Watts, sending out a maximum of 550mA to the battery. This is very much a maintainer, not something you want to use to charge a dead car battery.

Instead, you’re supposed to hook it up to a battery that already has a good charge. And provided there’s enough sun and you don’t have a parasitic drain, it should keep the battery topped up.

I’m currently using it to keep the battery of my Volkswagen Passat TDI wagon full.

The panel gives you a couple of options for connecting to the car. You can hook it up to the car’s 12V port or directly to the battery. I chose the latter option.

The best way to see how well these chargers work is to hook them up to a multimeter.

Under the hood and pointed nowhere near the sun, the Allpowers model puts out more volts than advertised and between 130 and 150mA. Pointed towards the sun, it actually puts out just as advertised.

Is it enough to keep a battery from dying? I intentionally let this car sit for a few weeks not driving it. Temperatures have dipped into the single digits, too. Yet, the car started up last night like it was driven just that day.

Another thing I like about this panel is that it doesn’t have to be mounted outside. The suction cups swing out and allow you to stick the panel to the inside of a window. This way I can worry a bit less about wind taking it away, snow, or vandals.

The real test will be seeing if it will survive a Midwestern winter. If it stops doing its job, you’ll hear about it.

I paid about $ for the Allpowers solar panel. These run anywhere between $ and $ or higher depending on how much juice you want out of it.

Do you know of a weird or unique tool that wrenchers can benefit from? Do you want to see us put a type of tool to the test and see how it performs? Shoot me an email or drop it down in the comments!