25W 12V Solar Powered Battery Charger & Maintainer, Built-in Smart MPPT Charge Controller, Waterproof 25 Watt 12 Volt Solar Panel Trickle Charging Kits for Car Auto Boat RV Marine Trailer

good maintenance charger when AC outlet not convenient
I’ll start this review out by saying that a truly valid evaluation of the performance of any charger for lead acid batteries would need to be done by scientists in lab conditions or testing staff at an organization such as Consumer Reports. Many factors come into play that determine how a charger can perform, such as battery type (deep cycle or automotive?), condition and age of battery when testing is started, size of battery in terms of rated and actual ampere storage and delivery capabilities, ambient temperature range in a given geographic location, average daily solar input (for solar chargers).
My first test was on the flooded lead acid battery in my 2019 Toyota Tundra pickup truck. The battery is Group 27F, rated at 710 cold cranking amps. Using an electronic multimeter I made 31 voltage checks over the period 5/3/2020 through 5/10/2020, starting measurements in the morning when there was good sunlight and stopping in late afternoon. A common recommendation for the fully charged “float” voltage of 12 V lead acid batteries is 13.5-13.8V. The SunEnergise 20 watt charger was never able to get the voltage above 13.08, and the LED indicator light never switched from flashing red to steady green, as it is supposed to when a battery is fully charged. On 5/11/2020 in the morning the unconnected voltage was 12.39; after 15 minutes of running the engine the voltage with the engine running was 13.60. As soon as the engine was stopped the voltage dropped down to 12.63. HOWEVER, there is an important consideration here, and it is the reason I don’t blame the charger for under-performing: during the first year of ownership the truck has only 700+ miles on the odometer, and most of the time sits unused. All batteries will slowly lose charge over time if not kept on a maintenance charger, and the consequence of this, if the voltage is allowed to go low enough for long enough a lead acid battery will be degraded and lose its ability to accept a full charge. The deep cycle batteries for my off-grid solar system are designed to tolerate repeated discharges for years that would quickly destroy an automotive type battery.
So, as far as I can determine, the Tundra battery has been moderately degraded, and it is not reasonable to expect ANY 20 watt solar charger to bring it up to the ideal float voltage. A more valid and fair test I did was on a Mighty Max ML35-12 sealed AGM battery rated at 35 amp hours, which is for the starter on my motor-generator arc welder. Again, this battery spends months sitting idle, but the difference is that it has always been connected to a 1.5 amp, AC powered “maintainer” (Schumacher SEM-1562A-CA) which keeps it at a steady float voltage of 12.95. On 5/11/2020 when I switched over to the solar charger the voltage went up to 13.03 and the LED light went to steady green. Two hours later, with moderate overcast of clouds the voltage dropped back to 12.88. Today at 12:45 PM, with moderate overcast the voltage was 13.66.
Some of the higher wattage AC powered chargers claim to have special charging algorithms that can at least partially restore lead acid batteries that have degraded and have a condition known as sulfation on the plates, but it’s better to avoid needing that by always keeping batteries on a maintainer. The two new dual purpose Napa batteries on my travel trailer, totaling 110 CCA were put on a 50 watt solar charger right from the start, and it maintains them at 13+ volts.
One complaint I have about the SunEnergise charger is that the battery clamps are made of a thin grade of steel, and the black and red plastic sheaths are also thin and flimsy. All the other components are substantial and well made. The instruction manual shows the float voltage as 13 volts; apparently the 13.5 – 13.8 V figures I mentioned earlier may not be a universally applicable ideal range. (The PowerStream Corp. website gives a good tutorial on many aspects of batteries.) I had a question about the rate of blinking of the red “charging” LED light, and sent an email query to SunEnergise about this and some other concerns to the tech support division. The tech adviser replied promptly and gave detailed and complete answers to all my questions.
I’ll continue to use this charger to keep my Tundra battery at a good level of charge since where I usually park it does not have a convenient AC outlet.

Easy to hook up
Versatile little panel. Use it to charge my batteries.

Solar charger is great
Where I store my travel trailer does not have electricity. It doesn’t take but a few times of moving the slide out in & out for the battery to be weak. This charger keeps it well charged & has been very dependable. When I first hooked it up it was showing that it was charging. I don’t know how low my battery was but when I went back to check on it. The battery was fully charge. Texas just went thru a week long bad winter storm. Sub zero temps with more snow than we have seen in years. We went from -4* F up to 80* F in week. The charger does not show any signs of damage or loss of capability to do its job. I would recommend this unit.

Solar panel for my RV
It didn’t work at all I threw it away. Very disappointed .