Many DiYers confuse the function of a battery maintainer with a trickle charger. A trickle charger provides a constant low charge rate to a battery, but it’s not Smart enough to shut off when the battery is fully charged. So it continues charging a fully charged battery, causing permanent damage. A battery maintainer, on the other hand, checks battery charge and shuts off when the battery is fully charged. As the battery discharges, it kicks in again to keep it fully charged.
A maintainer will check the condition of your battery periodically and charge only when it needs topping off. It can be left on all the time without harming your battery.
When to use a battery maintainer
Use a battery maintainer when you don’t plan on using your vehicle for periods of two weeks or more. All lead-acid batteries self-discharge at the rate of 1-2% per day, depending on ambient temperatures. In addition to self-discharging, vehicle batteries also have a constant drain from the vehicle’s computers. The self-discharge and current drain can cause an unused battery to be almost 50% discharged in a few weeks and dead within a month. Non-use from Covid-19 lockdowns has proven that vehicles must either be driven or placed on a battery maintainer.
Lots of companies have entered the battery maintainer marketplace and some of them have absolutely no experience, so it pays to avoid the newcomers. Solar, Battery Tender and CTEK are well known companies that have been making battery chargers and battery maintainers for a long time. Their products are well made and are worth the money.
Must-have features for a battery maintainer
Not all car batteries are standard lighting ignition (SLI) flooded lead acid style. Many newer cars and trucks with start/stop technology use absorbant glass mat (AGM) batteries which require a special charging routine. Plus, if you plan to use your battery maintainer on your gasoline-powered outdoor power equipment equipped with a gel style lead-acid battery, you’ll need a charger equipped with a GEL recharging cycle.
For more car and light truck applications, all you need is a 2 or 4-amp battery maintainer.
Table of Contents
Battery Tender is probably one of the most widely known brands to us motorcyclists. The Deltran Battery Tender company has been around since 1965 and has been stocked by powersports dealers around the country for years. The Battery Tender Junior is one of the company’s most popular models and is a great relatively low-cost Smart battery tender in a small package. Plug it in and forget about it.
The Battery Tender Junior incorporates a “brain” which allows the tender to detect when the battery has reached a full charge, then reverting the tender into float/maintenance mode to keep the battery at the optimum voltage. This unit also continuously monitors the state of charge and switches back to charge mode if necessary, making the unit a set-it-and-forget-it type of application. Two LEDs on the front convey the charger’s status. The Junior comes with a four-step charging program (Initialization, Bulk Charge, Absorption Mode, and Float Mode), is spark proof, and reverse polarity protected all the while coming with a five-year warranty. If you like to be on the cutting edge of technology, Battery Tender also makes the Power Plus™ 75A Booster Battery Charger w/Wi-Fi to connect your phone via the Battery Tender app to receive notifications and check your battery status with your mobile device. The Battery Tender Junior comes with a five-year warranty and can be used with AGM, and Gel cell batteries.
Amazon Basics Battery Charger
Whether you like it or not, Jeff Bezos has infiltrated nearly every facet of our lives, including keeping your motorcycle battery topped up (unless you have a lithium one).
With the Amazon Basics Battery Charger you get a sleek and compact charger that plugs into any 120v outlet and delivers 12V at 800mA for lead acid, AGM, and gel type batteries for less than 20. It uses alligator clips to attach to the battery terminals and features reverse polarity protection, meaning it won’t turn on if you have the clips attached to the wrong terminal. Having O-ring attachements would have been nice, but for the price they are understandably not included.
Backed by a one-year limited warranty, it includes a fused ring terminal harness and can safely be used indoors, say, in a garage.
Noco Genius 10-Amp Fully-Automatic Smart Charger
The Noco Genius 10 really is a powerhouse when it comes to battery chargers, maintainers, trickle chargers, and desulfators. Designed for 6-volt and 12-volt lead-acid automotive, marine, and deep-cycle batteries, it also works on flooded, gel, AGM, and maintenance-free batteries. As an added bonus, it can also keep lithium-ion batteries in tip top shape.
The genius of it all comes in the many features Noco packs it with. An integrated thermal sensor detects the ambient temperature and alters the charge to eliminate over-charging in hot climates and under-charging in cold climates. It can charge batteries as low as 1-volt. Or, if your battery truly is a goner but you want to give it one last shot, you can use the all-new force mode that allows you to take control and manually begin charging dead batteries down to zero volts. Finally, the Noco Genius automatically detects battery sulfation and acid stratification to restore lost battery performance for stronger engine starts and extended battery life.
With nearly 4,000 reviews on Amazon – 83% of them positive – the Noco Genius 10 is clearly a popular choice for keeping your battery alive and as healthy as possible.
How We Tested
The car battery chargers in this article went through two rounds of reviews. We started by searching retailers like Amazon, RealTruck, and Advance Auto Parts for top products, looking at factors such as battery type, voltage, customer ratings, and prices.
Our product testing team then ordered the car battery chargers that best met these standards. A team member tested each product on a 2004 Subaru Forester, taking note of how quickly the car battery charger could charge a car battery, versatility, ease of use, and value. Each car battery charger was given a rating out of 5 stars based on these criteria.
Best Car Battery Chargers Testing Process
To test each car battery, we unpackaged it and attached it to a 12.0-V wet cell battery. We started the battery charger according to the instructions and measured the voltage using a multimeter.
During testing, our review team recorded careful notes about each feature of every battery. Evaluation across our review categories is based on our in-person experience and online customer reviews.
By considering a battery charger’s voltage and amp hours, you can determine the approximate charging speed. Batteries that charge a car faster received a higher rating in this category.
Most car batteries are 12.0-volt. A higher voltage will charge a battery more quickly, but too many volts can damage your battery. A few volts above a battery’s rating are acceptable and even desirable, but a car battery charger must produce at least 12.0 volts to charge a 12.0-volt battery. Maintaining a consistent voltage is also important for charging speed and battery protection.
Not all car battery chargers will work with every type of battery. While most cars use a wet cell battery, some may use an AGM, gel, or lithium-ion battery. Chargers compatible with the most types of batteries scored best in this category.
Additionally, some car battery chargers have features such as overcharge protection and trickle charging options. Such features also contribute to a battery’s versatility rating.
Ease Of Use
An easy-to-use automotive battery charger has long clamp cables and durable alligator clamps. Battery chargers are also easy to use if they have long outlet cords and straightforward interfaces and instructions.
Our value score is based on the relationship between a battery’s rating in all other categories compared to the price.
Why You Can Trust Us
Each year, we test over 350 auto products on vehicles and in our testing lab. Our team of product testers thoroughly researches top products, unboxes and puts our hands on each component, and tests the items on real vehicles before making recommendations to readers.
We publish hundreds of product and service reviews to bring car enthusiasts detailed guides on automotive tools, detailing kits, car seats, pet products, and much more. For more information on our testing methodology and how we evaluate every product, check out our methodology page here.
Best Overall: Schumacher SC1280
The Schumacher SC1280 is a quick battery charger putting out 13.0 volts at a 15.0 amp current. It can fully charge a 105.0-Ah battery in 16 hours (this is relatively fast). The SC1280 is lightweight, portable, and easy to set up and use. It can automatically detect the battery voltage and adjust between 6.0-volt and 12.0-volt modes. While most cars use a 12.0-volt battery, 6.0-volt batteries are common in motorcycles. This charger includes a two-year warranty, trickle charging, and desulfation mode. It also has an automatic shutoff feature to help prevent overcharging. However, several reports say this automatic charging feature can malfunction.
- Cost: About 50
- Battery type(s): Standard (wet cell), absorbed glass mat (AGM), and gel
- Amperage: 15.0 and 3.0 amp modes
- Voltage: 13.0 volts
- Weight: 3.0 pounds (lbs.)
- Warranty: 2 years
What’s In The Box?
There’s nothing included with the Schumacher SC1280 other than an instruction manual. The clamps are permanently attached to the device, which is designed such that the clamps are easily wrapped and stored.
The alligator clamps are a good size with long cables and therefore easy to use. The power cord is also fairly long, making it easy to set up to SC1280. The device’s computer automatically detects the proper voltage, so all you need to do is attach the SC1280 and press the start button to enter charging mode.
The voltage was tested at 13.0 amps while the battery charger was in use, which is in the ideal range for a 12.0-volt car battery. This voltage stayed consistent throughout. Perhaps our favorite feature is the LCD display, which can even provide an estimate of your vehicle’s battery charge.
What Customers Are Saying
Amazon Review Score : 4.6 out of 5 based on over 10,000 ratings
Many users are impressed with the charging speed of the SC1280 and appreciate that it can automatically detect battery voltage and adjust accordingly. Several reviewers note that this battery charger restored otherwise dead batteries after other chargers failed to do the same. Many say this is the best battery charger they’ve ever used with several others mentioning how helpful the LCD screen is.
The most concerning negative reviews are from customers who say the automatic shutoff feature failed to work. This can result in overcharging, which can permanently damage your car battery. While this doesn’t appear to be a common issue, it’s a concerning malfunction. Make sure the automatic shutoff works properly before leaving any charger on your battery unattended.
Most Rugged Design: NOCO Genius PRO50
Pros Includes 24-, 12-, and 6-volt charging modes High-quality components and clamps Very fast charging speeds
We recommend several NOCO battery chargers because all are built with reliable quality and backed by top-notch customer service. The Genius PRO50 is NOCO’s most powerful and versatile battery charger. In addition to offering many voltage and charging modes, this car battery charger features braided cable sleeves and the strongest alligator clamps of any battery charger that we’ve tested. Compatible with both gas- and diesel-powered vehicles, the Genius PRO50 is suitable for just about any battery you’d need to charge, even lithium-ion batteries. This charger is expensive and relatively heavy, so it’s not the best choice for those who only need a casual-use battery charger. For those with a fleet of batteries to maintain, the Genius PRO50 is a good item to keep in your garage.
- Cost: About 740
- Battery type(s) : Standard, AGM, SLA, VRLA, and lithium-ion
- Amperage : 25.0 and 50.0 amp modes
- Voltage : 24.0-, 12.0-, and 6.0-volt modes
- Weight : 17.7 lbs.
- Warranty : 3 years
What’s In The Box?
The Genius PRO50 includes a solid EVA carrying case as well as several different power cords (for North America, European Union, United Kingdom, and Australia outlet types).
The first thing that stood out to us about the Genius PRO50 was the quality of the alligator cables. While many of our other recommendations (including other NOCO products) have well-made alligator clips, the Genius PRO50 has thick, braided cord sleeves that provide extra protection and longevity.
This car battery charger is a little heavier than a portable battery charger, but still smaller than stationary units like the Schumacher SC1309. We do note the lack of a display screen to provide battery data. While this isn’t a necessity for a battery charger, it’s a modern feature that would be nice to include on a unit this expensive.
What Customers Are Saying
Amazon Review Score : 4.4 out of 5 based on over 250 ratings
Most reviewers rave about the charging speed of the Genius PRO50 battery charger. Those looking to top up batteries for large engines like this charger. They claim it’s capable of bringing dead batteries back to life in fairly short order.
A few reviewers are upset that there is no display screen. There are indicators for the voltage, battery type, and charging mode, but no screen to show battery status. Another complaint some have is that some units arrive damaged because of poor packaging. However, NOCO does include a three-year warranty and customer reviews speak highly of the company’s customer service.
Fastest Charging: Schumacher SC1309
Unlike the other battery chargers on this list, the Schumacher SC1309 is capable not only of charging a vehicle but also provides a good jump start. The built-in tester can detect battery charge levels and even has some diagnostics features. While a bit heavier than our other recommended best car battery chargers, the Schumacher SC1309 is versatile and charges quickly. It’s easy to operate and includes desulfation and float modes. The SC1309 can fully charge a 105.0-Ah battery in about 16 hours.
- Cost: About 175
- Battery type(s): Standard (wet), AGM, and deep cycle
- Amperage: 40.0 and 400.0 amp modes
- Voltage: 15.0 volts
- Weight: 30.0 lbs.
- Warranty: 1 year
What’s In The Box?
The necessary alligator clamps are the only item that comes with the Schumacher SC1309.
This battery charger is simple to use and has large, strong alligator clamps. We found it one of the easier chargers to operate. Its size and long clamp cables allow you to rest the charger on the ground (other smaller chargers with short jumper cables can’t reach the battery from the ground).
The voltage output is consistent at 15.0 amps, which is a little high for a 12.0-volt battery but not high enough to endanger battery health. This voltage also means a fast charge rate and minimal charging time.
What Customers Are Saying
Amazon Review Score : 4.5 out of 5 based on over 1,700 ratings
Satisfied customers express surprise with the SC1309’s charging speed. Many say they used this battery charger to rejuvenate long-dead batteries with little difficulty. Several reviewers mention being able to use the engine start feature to revive SUVs and other large vehicle batteries.
One recurring negative comment comes from customers who report that the SC1309 stopped working properly after a couple of months. While this doesn’t seem typical, it’s not uncommon either. This charger comes with a one-year warranty, and one reviewer says they received a replacement from the company.
Several users also mention receiving faulty products with scratches and other damages. The company appears to have a good record of refunding these mistakes, but it’s a pain not to get a functioning car charger from the start.
How To Use A Battery Tender
Anyone who has ever left their beloved car or bike unused for long periods will understand the pain. One day the weather is great and you’re excited to get it out on the road again. You remove the cover, you insert the key, turn on the ignition and – nothing, not even a light. The culprit? Usually a dead battery.
Enter Battery Tender. Battery Tender is a product of US Company Deltran which has been making them since 1965. Battery Tenders are essentially chargers with some tech worked in them making them better alternatives than ordinary chargers.
While chargers merely charge a battery, a Battery Tender uses microprocessor technology that goes beyond merely charging your vehicle, and is designed to keep the battery powered throughout long periods of hibernation, essentially prolonging its life.
Battery Tender Basics
First of all Battery Tenders are ‘float chargers’ or ‘maintenance chargers’, or devices that not only provide a continuous supply of voltage to battery terminals but are also processor controlled, allowing them to perform such tasks as refraining from charging a defective battery, employ spark free technology for safety, and use easy to understand green and red indication lights to help you determine what’s going on at a glance.
As per their websites’ definition for the Battery Tender Junior: ‘The BTJR battery charger has microprocessor controlled power electronic circuitry which enables it to perform and safely control a number of sophisticated charging functions’.
This is as opposed to a ‘trickle charger’, which is a less sophisticated although less expensive device. While its purpose is the same, it does not have the microprocessor technology to prevent it from, say, accidentally damaging batteries if you leave it charging a battery too long. Battery Tender uses the phrase ‘Trickle Charger With A Brain’, to describe their products, and that explains a lot.
Also important to know is that while Battery Tender is best known for their chargers, the company also offers a variety of related products. These include batteries themselves, and of course chargers that are designed for specific implementations such as those for Industrial, Farm and Garden and Marine use.
They also market various accessories for these products ranging from cables, wires and harnesses to even USB chargers and solar panels. These all carry the name ‘Battery Tender’ however, so it can get confusing.
It’s best to visit their website at http://www.batterytender.com or their page and use their product finder feature to find the one suitable for your vehicle.
How to Use a Battery Tender
As there are many Battery Tender models to choose from and an even larger number of applications, we will assume for this explanation that we are using the model Battery Tender Plus 12V @ 1.25A (Product number 021-0128), a popular model available on Amazon for 49.99 on a typical car a 12v battery. We will also be assuming that we are installing this on a vehicle with a typical 6 cell 12 volt automotive battery.
– Take all necessary precautions such as access to soap and water in case battery acid contacts skin, wearing eye and clothing protection, having someone nearby to call for help as necessary, and make sure you are working in a ventilated area.
– Locate the charger as far away from battery as cables allow.
– With the charger in ‘off’ position and its AC plug not connected to the wall outlet, position the charger’s AC and DC cords away from any of the vehicle’s moving parts ie. door, hood, fan blades, pulleys, etc.
– Locate the battery posts Positive (POS, P, ) and Negative (NEG, N.). Determine which post of the battery is grounded or connected to the chassis.
– Connect the battery chargers clip appropriately depending on your vehicle’s battery connections:
- For negative grounded vehicle, connect the Positive (Red) clip from the charger to the Positive (POS, P, ) ungrounded battery post. Then connect the Negative (Black) clip to any area of the vehicle chassis or engine block away from the battery. Preferably, connect to a heavy gage metal part of the frame or engine block. Avoid fuel lines, sheet metal body parts or the carburetor.
- For positive grounded vehicle, connect Negative (Black) battery charger clip to the Negative (NEG, N.) ungrounded post of the battery, then connect the Positive (Red) clip to the vehicle chassis or engine block away from the battery.
– If everything is in order you may now turn on your charger while it is plugged in an electric outlet, and your battery will charge. Take note of the following however:
- If a battery has a voltage less than 3 volts the Battery Tender charger will automatically not start. The battery should produce at least 3 volts for the charger to work.
- If a typical 12 volt lead acid battery that is not being charged nor supplying current load is producing less than a 9 volt output it is likely defective and needs to be replaced.
– Finally, here are the status indication lights and what they mean:
- RED LIGHT FLASHING – This indicates that the battery charger has AC power available and that the microprocessor is functioning ok. If the red light continues to flash, then either the battery voltage is too low (less than 3 volts) or the output alligator clips or ring terminals were not connected properly.
- RED LIGHT ON STEADY – When the red light is steady, a battery is connected properly and the charger is charging the battery. The red light will remain on until the battery is completely charged.
- GREEN LIGHT FLASHING – If the green light is flashing, and the red light is on the battery is greater than 80% charged and may is ready to be used. Preferably, leave the battery on charge until the green light is steady.
- GREEN LIGHT ON STEADY –When the green light is steady the charge is complete. You may keep it connected to maintain the battery for an indefinite period of time.
Please note it is essential to completely read and understand all included manuals and instructions related to the product. There are often particular details that are specific to certain conditions, vehicles and Battery Tender models you will have to familiarize with before you can fully utilize the products’ features.
Once you are able to use the product as it is designed however there is no reason you cannot make the most of your battery for many years, as indicated by the Комментарии и мнения владельцев of many satisfied users of this product.
Promoted Product: NOCO GENIUS1
The NOCO GENIUS1 is a high-performance, fully automatic battery charger designed to charge and maintain a wide variety of battery types, including lead-acid and lithium-ion batteries.
One of the standout features of the GENIUS1 is its ability to automatically switch between charging modes, depending on the condition of the battery. For example, it can charge a severely depleted battery using its Recovery mode and then switch to a Maintenance mode to keep the battery at its optimal charge level. This makes it a versatile option for automotive, marine and powersport applications. Another advantage of the GENIUS1 is its safety features. It is designed to protect against overcharging, short-circuiting, and reverse polarity, and spark-proof technology. Additionally, it has built-in smarts to be to detect a bad or damaged battery.
On top of that, the GENIUS1 is versatile. It’s capable of charging and maintaining a wide range of battery chemistries, including AGM, Gel, SLA, VLRA and LiFePO4 batteries. This means that it can be used for a variety of applications, such as charging car, truck and motorcycle batteries, marine batteries, and even golf cart batteries, without needing to purchase additional chargers.
Overall, the NOCO GENIUS1 ability to automatically switch between charging modes and its safety features make it a safe and convenient option for anyone who needs to charge and maintain batteries year-round.
Budget Pick: BLACKDECKER BM3B Fully Automatic 6V/12V Battery Charger/Maintainer
If affordability is your first priority, BLACKDECKER’s car battery charger will satisfy your budget. It’s really light on the wallet, and at 5 x 3 x 8.9 inches and one pound, it’s literally light, as well.
Fortunately, it comes with a few unique features and safety nets. It’s got one-touch automatic charging and both O-ring post and alligator clamp terminals for both battery post styles. It works on all 6- and 12-volt AGM, gel, and wet batteries, so it’s great for all kinds of other machines that have smaller batteries. It does only charge at a rate of 1.5 amps, but it has a reverse polarity check to make sure you don’t damage your battery in any way.
Buyers note that the device is reliable, but with its limited charge rate, it’s not going to do anything very quickly. It’s a great trickle charger for occasional use, but we’d upgrade if we were counting on it to maintain an expensive battery.
Affordable, 6 and 12 volt, reliable, compact size
Limited charge rate, not a good choice for a maintainer
Most Versatile: Schumacher SC1304 Fully Automatic Battery Charger Maintainer
Replacing the popular Schumacher SpeedCharge SSC-1000A, the new SC1304 Fully Automatic Battery Charger Maintainer keeps everything that made the old model great, and adds additional capacity and features at a comparable price. Peak charging is up to 15 amps, which is more than enough for any automotive battery; and it’s capable of charging 6 and 12 volt standard, AGM, and deep-cycle batteries.
It does lose the low-amperage two watt charging of the SSC-1000A, but has a three amp maintaining cycle that is suitable for most modern batteries. It’s still a compact battery charger, measuring 10.3 x 8 x 3.7 inches, and weighing three pounds. Its best feature is automatic, walk-away charging for both 6 and 12 volt batteries, which it detects and charges appropriately. Then, when the battery is fully charged, it switches to maintenance mode to keep them topped off and healthy for months.
You do need to know and select the battery type; and there’s a button for powersport or automotive/marine batteries. Cables store onboard behind the retractable carry handle. It only comes with alligator clamps and not ring type; and it doesn’t work as a jump starter, which other models in this price range can, although they may not have the same extensive feature set. A two-year warranty is shorter then we like for a car battery charger in this price range.
15 amp charging, 3 amp maintaining, 6 and 12 volt compatibility