SUNER POWER20W 12V Solar Battery Trickle Charger & Maintainer PRO, Built-in Intelligent MPPT Controller, Waterproof 12 Volt 20 Watt Solar Panel Charging Kits for Car Marine RV Trailer Boat Automotive

Fantastic. I left it plugged into my cigarette In my 2002 RV camper Van for a five month winter in freezing cold Reno NV. This was unattended in a storage lot for the entire 5 months. The Van started right up no problem!! This is an excellent item. It works as advertised!!

I got this for one of our Prius’s because it often goes over a month between outings and more than once I’ve had the auxiliary 12 volt battery totally drained due to the slow drain from the smart key system that is always on. I got a ring terminal pigtail for the battery (in the rear on my model ) and can easily plug this unit into it. It works like a charm to maintain the battery’s charge which improves the battery life as well as no longer finding a dead car when you need it. It is important to know whether or not your model keeps the 12v cigarette lighter outlet live when the car is off in which case you can use the stinger with the plug for that. I guess that is common on American vehicles, but not on foreign ones which need a connection to the battery. There are good videos on the process.The unit protects against reversing the polarity and has indicator lights that let you know if you made an error, as well as letting you know when it is providing charging power. It is durably constructed. I am quite pleased with it.

Great outdoor battery tender 12volt. Used on boat battery.

These seem quite reliable and are a no brainer to use -- had a lower wattage of same brand that went nearly 20 months of constant outdoor use... I figure that is good enough for what it was (one too many tropical storm appeared to KO), but this new one went right to work, so here's hoping...

Awesome product used it works perfect

Bought this over a year ago to maintain my AGM boat battery for the trolling motor. One summer now one winter. Boat is stored outside in Oklahoma. Got below 0 degrees with snow & ice. I duck hunt so it’s my time of the year. The solar panel is very tough, waterproof and works. Will be buying another for the motor battery soon.

Bought few years ago for my boat. Worked fine...Kept the charger connected all winter. Looked at it yesterday and the LED lgt when 1st connected flashes green but then stops...no other colors work. I think it's still charging. Will know 2morrowUPDATE: 3 May 2023.... it is still charging.... lgt just not working. However, main reason for this update is to tell everyone about their superior customer support (Jason): Jason emailed me after I posted this review and sent me a replacement panel free of charge, free shipping and allowed me keep the old one. Then just today I emailed him that the red flashing lgt on new one would flash when using cig lgt socket. he said that the car cig wiring is reversed and sent me an adpater....FREE of charge also. Should be here Fri. What outstanding customer service. Thank You Jason!!!

UPDATE: So while these chargers are everything I said they were, if you use it inside of a car, the plastic warps and the whole thing falls apart. So maybe good in a place that never gets warm or you're just going to use them outside (where they can be , but now feel cheated out stolen). I was once happy. but now feel cheated. DON'T BUY if you intend to keep INSIDE a car that gets a lot of sun! Yes I see the irony in that.Just got it, so don't know about the reliability, but my research says this is a dependable unit. It was easy peasy to set up. One car I could use the cigarette lighter plug, but the other I had to hook up straight to the battery. You have to be mindful of how you set up the clamps in that case. The light signals are a bit funky (flashing green means the collector is make electricity, solid green mean the battery is done, solid red means n and flashing red mean it's charging properly) so flashing red mean all good!This is a brilliant idea for people who have vehicles they don't drive often.