The 10 Best Trickle Chargers

If you just want a car, mower or motorcycle to start after months in the garage, the NOCO Genius1 covers it. Car and Driver picked it as the best overall maintainer in its tests. It plugs straight into a wall outlet, handles 6-volt and 12-volt batteries, and has a setting for lithium packs. A built-in sensor adjusts the charge for a hot or freezing garage. Its low output means a flat car battery takes a day or more to refill.

The Battery Tender Junior is built for the small batteries in motorcycles, ATVs and riding mowers. It brings a 12-volt battery up to full, then drops to a gentle float charge and can stay connected all winter. A ring-terminal lead can stay bolted to the battery, so hooking up later takes seconds. It carries a five-year warranty. It won't charge lithium batteries, and it's too weak to refill a big car battery in a reasonable time.

Anyone whose car or truck sits for weeks at a time will find the Battery Tender 3 Amp a good fit. One button picks the battery voltage, and it has a setting for lithium batteries. The cords are long enough to reach from a wall outlet to the engine bay, and the clamps won't spark if they touch. The status lights are dim in daylight, and it can't bring back a battery that has gone fully dead.

Pick the NOCO Genius10 when you want one box that both recharges a run-down battery and minds it through storage. It has enough power to refill a car battery in an afternoon, and it handles trucks, boats and RVs as well as lithium packs. A manual mode can coax a battery up from almost nothing, and it can sit connected for months. It's more power than a motorcycle battery needs, and it costs well above a basic maintainer.

Cold garages and long layups are what the CTEK MXS 5.0 is designed for. It charges in stages and then pulses the battery now and then to keep it full, and a winter mode adjusts the charge when it's freezing. A recondition setting tries to revive a tired lead-acid battery, and the case shrugs off splashes and dust. It works only on 12-volt lead-acid and AGM batteries, so it's no help for lithium or vintage 6-volt cars.

When a battery is run down and you need the car tomorrow morning, the Schumacher SC1280 can refill it overnight. It switches between a fast charge and a gentle hold, and a digital screen shows the voltage and how full the battery is. It can also test a battery and has a mode for one that has sat too long. The cooling fan is loud, it's bulky to leave on a shelf all winter, and it has no lithium setting.

Owners of SUVs, pickups and boats that sit for a season should look at the NOCO Genius5. It has enough output to top up a big battery overnight, works on 6-volt and 12-volt systems, and has a lithium mode. A sensor tunes the charge to the garage temperature, and a mounting bracket comes in the box. No outlet has published a test of this exact model. A fully dead battery needs a manual mode that you should watch.

Spending little still buys a smart charger: the Foval 1000mA keeps a 12-volt car, mower or motorcycle battery topped up. It comes with both clamps and ring terminals on a long cable, and it carries a safety mark from an independent testing lab. Its program ends in a float charge, so it can stay hooked up for weeks. There is no lithium setting, and the warranty runs only 18 months.

Owners of an old 6-volt tractor or classic car who also keep newer vehicles can use the Black+Decker BM3B on both. A slide switch picks the voltage, and it comes with clamps, ring terminals and a bracket for hanging it on a wall. Once the battery is full it holds a float charge, and it carries an independent lab's safety mark. It has no lithium mode, and its low output makes refilling a flat car battery slow.

Cars, boats and tractors parked far from an outlet can stay topped up with the POWOXI Solar Maintainer, a small panel for a dashboard or deck. It plugs into a lighter socket or clips to the battery, and a diode stops it from draining the battery at night. It only puts out a trickle, so it slows battery drain rather than recharging. Many cars cut power to the lighter socket with the key off, so use the clamps then.