Whether you're getting ready for a road trip or just popping to the store -- there's nothing worse than finding your car battery drained. Sure, you can always ask a neighbor for a jump to give your dead battery a boost and get you moving again, but they may not be at home. Having to rely on the chance that someone will be nearby isn't the best idea, which is why having your own battery charger is so important. Some models are capable of charging your battery enough that you'll be ready to get from point A to B within an hour. Alternatively, you could invest in a battery tender instead. Battery tenders or maintainers can extend your car battery's life and eliminate the need for a charger altogether when you use them regularly.
Battery maintainers are slow-working chargers that let you replenish the regular discharge that affects car batteries -- particularly when the vehicles aren't in use. Typically, they're connected to batteries during long periods of inactivity so that a car will be ready to go when used again -- but they can also be handy when regularly used on certain types of car batteries, regardless of driving frequency.
There are many different kinds of car battery maintainers -- you can get a smart battery charger, a solar battery charger, a motorcycle battery charger and more. Further, in each subgroup, some are better than others, with a choice of charging mode, battery voltage, the option for trickle charging and more.
Here are our picks for the best battery maintainers in a variety of categories, based on expert opinion as well as customer satisfaction. We'll update this list periodically. After the recommendations, read on for more information about how car battery maintainers work, how they differ from one another and how to use them efficiently and safely.
Deltran's Battery Tender brand is one of the most recognizable names in the fields of battery charging and maintenance, and it's for good reason -- the Battery Tender products are almost always recognized as some of the best on the market. Case in point: The Battery Tender Plus, a charger and maintainer that also ranked as best overall on CNET Cars' list of top chargers.
When the Battery Tender Plus is maintaining a battery, it delivers a continuous 1.25 amps of power until the battery is full, and then it goes into "float" mode. This means it doesn't deliver any more electricity until the battery drops from full due to standard discharge. When it does, the Battery Tender Plus boosts it back up to full, and then goes idle until further discharge occurs.
The Battery Tender Plus doesn't work with deep-cycle batteries, but it can charge and maintain lead-acid, flooded and sealed maintenance-free batteries, which makes it a versatile choice. While the charging feature is mostly recommended for vehicles with smaller engines (such as motorcycles, ATVs, and jet skis), it can maintain cars, SUVs and other larger vehicles.
If you're looking for a reliable car battery maintainer but you want to save a few dollars, there's no better choice for you than the Battery Tender Junior, another product from Deltran's popular line.
It costs less than the Battery Tender Plus, but you get the same car-battery charging (small vehicles) and maintaining (larger vehicles) capabilities. While the 0.75-amp output of the Junior is lower than the 1.25-amp output of the Plus (though more expensive models of the Junior have higher amperage), it's less of an issue if you're just using it to maintain a battery. Regardless of the difference in amperage, though, keeping the charger plugged in will offset the standard battery discharge.
All of this convenience and value makes the Battery Tender Junior the best-selling battery charger on Amazon. No doubt some of that success is due to satisfied customers' positive word of mouth, as the Junior has 4.7 stars out of 5 on the site, based on over 22,000 ratings.
The speed with which your vehicle battery is charged (even during long-term plugged-in maintenance) comes down to the power of your battery charger. Typically, this is measured in amperes. The higher the amperage, the more powerful (and, generally, the more expensive) your charger.
The Schumacher SC1355 is a reliable model from a trusted brand in automotive battery charging and maintenance. One of the things that makes this Schumacher battery maintainer notable, though, is that the amperage adjusts automatically in order to maintain your battery efficiently, up to a maximum of 1.5 amps. Like all car battery maintainers, it also shifts automatically into float charger mode when the job is done. The result is a maintenance process that specifically fits your battery each and every time you use it.
Another bonus of the Schumacher SC1355 is that it works as a deep-cycle battery charger as well as lead-acid battery maintainer. That means you can use it to charge the battery on a boat as well as on a car or smaller vehicle.
If you want to maintain multiple batteries at the same time, you'll need what's called a "multibank" maintainer. As the name suggests, these maintainers have multiple connections, each of which can be hooked up to a different battery in order to keep it full.
While there are two-bank battery maintainers and chargers that allow users to charge up two batteries at once, our pick for the best multibank maintainer is the Battery Tender 4-Bank, which has four ports that allow just as many vehicles' batteries to be kept full at the same time. This makes it a great model not just for a multicar family, but also for an automotive enthusiast who may have a collection of cars in their home garage.
Just one note: Some customers have reported that the battery clamp cables from each port are shorter than they'd like, so you may need to park your cars creatively. Still, that's an issue that's fixed relatively easily and shouldn't stand in the way of reliable battery maintenance.
Using a car battery maintainer is not without risk. Any time you're working with electricity, there's the chance you can receive a shock, so when using a maintainer or an automatic battery charger you'll want to make sure you follow the included instructions to the letter.
It's also helpful to have a maintainer that has as many built-in safety features as possible. When it comes to that, it's hard to outdo the NOCO GENIUS10. An updated, smaller and more powerful version of NOCO's G7200, the GENIUS10 has built-in protections against overheating, overcharging, short-circuit and open-circuit accidents. It's also spark-proof and has reverse polarity protection, which means that connecting the cables in the incorrect order to the battery terminals won't cause damage. These features all ensure that the GENIUS10 protects you, your battery, your car and itself.
In addition to being safe, the GENIUS10 also packs quite a bit of juice. The 10 amps of charging power allow it to maintain vehicle batteries of any size.
Recreational vehicles differ from most vehicles on the road in that they run on deep-cycle batteries. A deep-cycle battery is a special kind of lead-acid battery (most cars use standard lead-acid batteries) which is meant to be deeply depleted during regular use. This means that deep-cycle batteries need to be charged up regularly or maintained consistently.
It also means that many maintainers designed for standard lead-acid batteries won't work with deep-cycle batteries, so if you drive an RV, you'll need one that does, like the Ampeak Smart Battery Charger and Maintainer. Ampeak's deep cycle battery charger has three separate charging modes that can deliver up to 8 amps of power and an automatic float mode that allows for battery maintenance.
The Ampeak Smart Battery Charger and Maintainer is great for the RV battery in your life, but that doesn't mean it's not versatile, as well. It can also charge gel and AGM batteries, and can handle a host of vehicle sizes -- from lawnmowers to trucks.
The terms "trickle charger" and "battery maintainer" shouldn't be used interchangeably, but the Foval Automatic Trickle Battery Charger is both. Like a trickle charger, it delivers a "low and slow" charging mode designed to replenish a battery. Like a battery maintainer, it has a float mode that allows it to keep a battery fully powered without overcharging.
As motorcycle batteries are smaller than car batteries, they require less charging power, so the Foval unit's single amp is more than enough to provide maintenance. That said, it can work on larger vehicles as well, just so long as they use lead-acid, flooded or sealed-maintenance batteries.
Finally, it's hard to beat the price of the Foval Automatic Trickle Battery Charger -- it's the cheapest model on the list -- and a small price to pay to keep your motorcycle battery properly maintained when it's not in use. It's also a highly regarded motorcycle battery charger, with 4.7 stars out of 5 on Amazon, based on customer ratings.
Using a solar charger or maintainer isn't just good for the environment, it's also convenient. You still have to hook it up to your car's battery, but you don't need to hook the other end up to an electrical source. That means you can maintain your battery wherever you are, so long as there's some sunlight for a solar panel to collect.
When it comes to the solar battery maintainer category, you can't beat the Suner Power 12V Solar Car Battery Charger & Maintainer. It's available in a variety of wattage levels, but for the purposes of this piece we're focusing on the BC-6W model, which delivers 6 watts of power. It offers a continuous charging process, but also has a protection against overcharging, meaning you can leave it plugged in as long as you need to without worrying about damaging the battery.
Another great feature of the Suner Power 12V battery charger and maintainer is how easy it is to use. You can hook it up to the battery by plugging it into your car's lighter dock, if it has one. If it doesn't -- or if your car's lighter won't operate when it's off -- it comes with alligator cables, as well.
Comparison of the best battery maintainers for 2022
Best battery maintainer overall
Best battery maintainer for the price
Best battery maintainer based on amp range
Best multibank battery maintainer
Best battery maintainer based on safety features
Best battery maintainer for RVs
Best battery maintainer for motorcycles
Best solar-powered battery maintainer
What is a car battery maintainer?
When considering purchasing a battery maintainer, it's important to remember that it's not the same thing as a battery charger -- although there are many models that do both. A charger is designed to give a charge to a battery, filling it up from a depleted state (and, depending on the charger, maybe even bringing it back from the dead). A "smart" charger automatically shuts off when the battery is full, while a manual charger continues to deliver the same charge as long as it's plugged in. The latter poses the risk of overcharging.
"Overcharging or undercharging a battery hinders the battery's ability to work properly," says Melanie Musson of 4autoinsurancequote.com. Melanie creates written and video content on the topics of automation technology, vehicle safety and insurance. "Overcharging chemically changes the battery and when that happens, the battery won't be able to recharge to the capacity that it should. Thankfully, car batteries are designed with safety features to prevent explosions, so the overcharged exploding battery is essentially an urban legend. Undercharging a battery leads to sulfation. When you try to recharge the battery, the sulfation blocks the charge from doing its job of recharging."
By contrast, car battery maintainers are all "smart" -- they have sensors that allow them to "know" when they're connected to the battery terminal of low batteries and full ones. Once a battery is completely charged they stop delivering a charge. Also, the charges that they deliver are typically of lower amperages than those of battery chargers. Since maintainers are used for maintenance during periods when cars aren't going to be used, time isn't of the essence when charging. This means that a maintainer can give a battery a "low and slow" charge, which is better for its health than a faster charge or a jump.
"We always try [to] charge our lead-acid [car] batteries nice and slow," says Charlie Williams of review site Workshopedia.com. Williams has over 15 years of automotive and DIY experience across a variety of industries. "They don't heat up as much, hold their power for longer and have a longer lifespan. Fast charging will cause issues and reduce battery lifespan over time. So always trickle charge when you have the time to do so."
Though battery maintainers work similarly to trickle chargers (chargers that come in smart or manual varieties and deliver consistent low-level charges to batteries) -- and sometimes the terms are even used interchangeably -- they are not the same thing and should not be used in place of one another. Trickle chargers are meant to be disconnected when they're done charging, while battery maintainers can be left plugged in. Remember, since all battery maintainers are "smart," they won't deliver any charge to a battery that's already full. Sometimes maintainers are called "float chargers," after the "float" mode in which they remain. In this mode, they activate to refill standard discharge and then turn off again. This may cause some confusion, but they're distinct from trickle chargers.
"A battery maintainer is designed to support floating and absorption charges," says Musson. "A battery maintainer will only send a charge to the battery when the battery can accept a charge. So, as the battery reaches full charge, the maintainer stops charging the battery. It doesn't send a continuous charge that could lead to overcharging."
If a maintainer is versatile, it can work with several different vehicles -- and even if it only works with lead-acid batteries, you should be able to maintain multiple batteries with it. If you have a single-bank battery maintainer, you'll only be able to hook up one battery at a time, but if you have a multibank device, you can hook up as many batteries as the maintainer allows.
Battery maintainers are used for just that -- maintenance. Every day that a vehicle goes without being used, the battery experiences a slight power loss. That's simply how lead-acid batteries, which power most vehicles, work. However, if you leave a battery maintainer connected to your car's battery, it will replenish the daily loss of power, bringing the battery back to 100% charge before shutting off. The next day, it will do the same thing, and so on, for as long as its alligator clips are hooked up.
Not every kind of battery maintainer works on every kind of battery type. Again, most vehicles use lead-acid batteries, but this isn't a hard and fast rule. There are some kinds of vehicles -- like RVs and boats, for instance -- that operate using deep-cycle batteries (as an aside: deep-cycle batteries are a category of lead-acid battery, but in a vehicular context, the latter term is often used to refer to cranking lead-acid batteries, which do not fall under the deep-cycle classification). Deep-cycle batteries operate by discharging more power at once, thereby making regular charging necessary, even during periods of use. While some maintainers will work with both lead-acid and deep-cycle batteries, make sure you know what kind you have before buying a maintainer so you can ensure that you get one that's compatible.
How to use your battery maintainer safely
Like with any other automotive accessory, you'll want to make sure you use your battery maintainer safely. Whenever you work with a car's battery, there's a risk of electrocution, so you'll want to follow the instructions that come with your device. In a universal sense, it's essential that you keep your car off during the car battery charging process. You'll also want to keep the maintainer off until it's hooked up properly, but again, make sure to consult the specific instructions and reach out to the manufacturer if you have any questions.
When it comes to the health of your automobile, battery maintainers pose little risk. As mentioned, there's no risk of the overcharging that can ultimately damage a battery, so you can keep a maintainer plugged in as long as you want, regardless of the kind of vehicle you drive. Since these devices are electric, there's no worry of harmful discharge that could damage your vehicle or create any sort of human risk, though faulty wiring can always pose a fire threat.
5 things you need to know before buying and using a battery maintainer
What kind of battery does your vehicle use? If you have a standard car, odds are that it's a lead-acid battery, but you'll want to be 100% sure before making a purchase so you can be sure your maintainer is compatible and prevent a dead battery.
Do you simply need a battery maintainer or do you want a device that operates as a standard charger, as well? If you already have a reliable automatic battery charger this may not be a concern, but if you don't, there are many devices designed to fill both roles.
How many vehicles' batteries do you want to maintain at once? If there's only one, a single-bank battery maintainer is probably your best choice, but if you have more than one, opt for a multibank maintainer.
What kind of car battery maintainer do you want, in terms of power source? Most are electric, but a solar-powered maintainer is better for the environment -- plus, it can ultimately save you some money on your power bills.
How do you operate your car battery maintainer in a safe and effective way? You'll want to be sure you know and understand all of the manufacturer's instructions prior to use in order to minimize the risks of injury and property damage.
Written by Scott Fried for CNET Cars
Battery maintainer FAQs
What does a battery maintainer do?
A battery maintainer is like a battery charger, but it discharges power more slowly. Instead of quickly boosting a battery's power level, it charges your battery over the course of several hours. A slower charge is actually better for your battery, although this means that a battery maintainer might not be handy during an emergency. They're often connected to vehicle batteries during long periods of inactivity in order to prevent the unpleasant surprise of a dead battery.
Is a battery maintainer a good idea?
A battery maintainer is a good idea if your vehicle will be inactive for a long period of time. Every day a car isn't used, its battery power depletes slightly. If you keep your car in a garage for an entire season, you may come back to find that it won't turn on. However, if you keep the battery attached to a maintainer, it will boost the charge back up to 100% every day (or at least, every day that the maintainer has or is connected to power).
Can I leave a battery maintainer on all the time?
Yes, you can leave a battery maintainer on all the time. Like automatic battery chargers, battery maintainers are "smart," meaning that they can read the power level of your battery and apply a charge accordingly. If a battery dips down to 99% charge, for instance, the maintainer will boost it back up to 100% without overcharging it. The next time the battery dips, the charger will bring it back to 100% again. This will continue as long as the maintainer has power.
When should you use a battery maintainer?
You should use a battery maintainer if you won't be using your vehicle for an extended period of time. When not in use, vehicles' batteries slowly lose their charge, so after several weeks or months of inactivity, the battery may go completely dead. Keeping a battery maintainer hooked up to a battery during these periods will keep it fully charged for whenever you need it.
Who makes the best car battery maintainer?
There is no best battery maintainer -- only a battery maintainer that makes the most sense for your specific situation. We've selected the Battery Tender Plus charger and maintainer as our top model, and it's certainly a great pick, but if you want something for a different price, or with a different amp range or selection of safety features, you may opt for something else. You'll also need a different charger if your vehicle doesn't have a lead-acid battery, and you may opt for something less powerful if you drive a smaller vehicle (like a motorcycle).