Review on 🔋 Sunway Solar Car Battery Trickle Charger & Maintainer: 12V Solar Panel Power Battery Charger for Automotive, Motorcycle, Boat, Marine, RV - With Cigarette Lighter Plug & Battery Clamp by Ryan Koser

EDIT: I ended up returning them because the batteries were slowly draining over weeks. Maybe I should have bought the one with higher power! However, I give them 5 stars because they deliver the advertised amperage. PS instead I installed quick couplers; They do an excellent job of preventing battery drain. **************** I have a few cars that have not been driven much due to COVID related restrictions. We could go out and drive them around every week to recharge the batteries but my wife and I have a second home so we can't do that when we're there. As a result, both batteries were dead when we returned home. So I bought two of these 1.5w solar chargers. I've installed them both on the inside of car windshields. I didn't want them outside because (i) they could be stolen and (ii) they could be damaged by rain. Neither windshield is tinted, so I didn't think it would make much of a difference. They were in almost full sun for most of the day (and where I live we get a lot of sunny days). I decided to use a voltmeter to measure the output and (for both units) I got about 18V and 8mA. Watts = V x A, so the output power is (18 x 0.008) = 0.144 W, which is only about 10% of the specified power. I wasn't too happy so I emailed tech support. They responded very quickly and politely asked me to send photos of how I checked the voltage and current. So the next day (also sunny) I went outside and repeated the test (and got the same results). BUT then, in fairness, I decided to repeat the tests, but this time with a block on the windshield (ie outside the car) rather than inside. And it made a HUGE difference. Voltage = 20V; Current = 71mA. So the performance was now at 1.42 = MUCH closer to spec. Time will tell (i) if this keeps the batteries charged and (ii) if the units can withstand the rain, but for now they work as advertised, so 5 stars for that (and for the quick response from tech support).