From time to time, TTAC will highlight automotive products we think may be of interest to our community. Plus, posts like this help to keep the lights on around here. Learn more about how this works.

What did the bartender say to the set of jumper cables that walked into the bar? Why, he said “You’d better not start anything in here tonight,” of course!

But here’s the thing – there’s an excellent chance that natty set of thick 2-gauge jumper cables actually won’t start anything if you’re working with a battery that’s constantly flat. Constantly running a battery flatter than the Prairies is a one-way ticket to the town of No Start. That’s why trickle chargers were invented.

Designed to feed a small but measured amount of juice into a car battery, trickle chargers – also called battery maintainers – use electricity to replenish batteries at or near the same amount of self-discharge. Try to find one that shuts off at appropriate times, called a ‘float’ mode, so the battery doesn’t get overcharged like festival goers trying to buy a bottle of water.

Their most common use is to be connected when a car goes into winter storage, allowing the battery to remain at the ready for the first flick of the key next summer. Some also advocate the use of a trickle charger to boost a flat battery, since the gradual re-introduction of juice is easier on a battery than a sudden jolt. It takes a helluva long time, though.



We’ve gone through the options on Amazon and present our findings here. No more dad jokes, we promise.

(Editor’s note: As noted above, this post is meant to both help you be an informed shopper for automotive products but also to pay for our ‘90s sedan shopping habits operating expenses. Some of you don’t find these posts fun, but they help pay for Junkyard Finds, Rare Rides, Piston Slaps, and whatever else. Thanks for reading.)

This is a great unit, with its most annoying feature being its marketing. The sellers claim it to be a ‘battery tender’ (hey, it’s right in their name!) rather than a trickle charger … even though that’s exactly what it is. Technically, yes, it’s the only battery tender available but that’s because it’s their, y’know, brand name. Propaganda aside, this brand is one of the best known names in the segment, accruing thousands of real-world views, the vast number of which are positive.

It has the ability to switch between float to maintenance modes, meaning your battery won’t get overstuffed like a Christmas turkey. A quick connect harness is included in case your car’s battery is located in a hard to reach area. Reverse polarity protection saves on potentially expensive connection errors.

This diminutive little scamp is small enough to be flung in a toolbox and not consume too much space. As such, it is truly meant for maintaining the charge on a battery that sits unused over time. An intelligent microprocessor (is there any other kind?), provides different states of charge such as a bulk action which feeds at its highest rated current until the battery is 80% full.

Compare this to an absorption mode, one in which the unit gradually dials back the juice until the battery is all charged up. Once it fills the battery, it switches over to the maintenance function. It has selections for 12 volt or 6 volt with an even dozen being the default.

Like a good employee who’s on the ball, there are some trickle chargers that are capable of more than one task. This unit from Dewalt is a battery charger on wheels that can also act as a jumper pack to quickly zap a battery back to life if you need the car started right now. There’s also a USB port on board in case your smartphone is low on juice, too.

That’s all in addition to a household-style 120V AC outlet into which one can plug a power drill or waffle maker (what – you don’t have both of those at the ready in your garage?). Fully automatic high frequency charging delivers 3 stages, automatically switching from fast charge, to top-off, to shut-off mode. This is because charging up a battery is like filling a glass of water – the person doing the pouring needs to slow down as the glass fills to the top lest they make a terrible mess.

Weighing a svelte 1.3 pounds, this trickle charger from Black and Decker is used to keep batteries in stored vehicles and battery applications at optimal capacity during the off season – so don’t try boosting that dead project car with it, mmkay? It’s good for small voltage batteries in the likes of lawn tractors but also said to be fit for full-sized cars as well.

Owners can connect the battery charger and maintainer with the included battery clips or battery ring terminals. Charging automatically stops when battery is fully charged or topped off and switches to float mode monitoring to maintain charge. Built-in circuit protection guards against overcharging, reverse polarity, or short circuit. There’s also a built-in mounting bracket and one-year warranty.

Here we find a charger for 12V batteries that feeds electricity at a rated 4.3 amps. Its sellers take care to point out this unit can be used to perform test programs in order to establish the condition and performance of a battery and vehicle’s charging system. In honesty, most trickle chargers can do this but are not designed to easily do so.

A series of eight LED lamps line up in a row like the pistons in an old straight-six BMW, illuminating to indicate the state of a battery’s condition. This is preferable to a simple on/off light as it tells the operator if they’re getting anywhere with their charging efforts. The charger is said to have a special reconditioning function that will revive and restore deeply discharged and stratified batteries, a task most others cannot perform.

One of my childhood buddies wanted to put ‘genius’ as his future profession in our high school yearbook. Trouble was, he had to ask us how to spell it. True story. This trickle charger from NOCO has no such problems, managing to correctly spell its own name the first time out. This thing is a powerful, professional grade battery maintenance tool designed to recharge all types of batteries including those found in 24V systems.

Its 5-amp constant current setting brings the goods when all you want is a trickle charger. A so-called repair mode dances a electric jig to revive old batteries that have, up to that point, given up the ghost. This is the largest unit in the Genius line, providing the heavy to work as a booster pack in a pinch as well.

If all you need is a quick hit to keep the battery in your not-oft used rig charged up, this might be the unit for you. Said to activate when it senses a battery reading below 12V and automatically shutting off when it reaches 12.4V, it seems to be a great solution to maintain the battery on a vehicle that suffers a parasitic draw or is simply stored for the winter.

Dead simple to operate, all one has to do is plug one end into the wall and clip the alligators to the positive and negative terminals on the battery in question. A dearth of readouts mean you’ll only know if the thing is working or not but if your only goal is to keep a battery juiced up so it’s ready to go once the snow is gone, this little outfit could deserve a place in your box of tools.

This curiously capitalized tool is marketed as a battery maintainer, doling out power to all types of 12V lead-acid batteries, including flooded or modern sealed maintenance-free ones found in just about every vehicle on the road today. Manual operation and endless fiddling is not required; just plug it in and leave it as the unit automatically takes care of charging and maintaining duties.

Beyond that, it will monitor the battery voltage and maintain a proper level with a float charging current that should prevent overcharging. With SAE quick release connection options including ring terminals on a 7.5amp fused circuit or old-school alligator clips, this unit should be compatible with the vast majority of machines except for their weirdo French car your homeroom teacher drove 30 years ago.

I use it with my 1967 Mustang and whenever the car is in the garage it’s plugged in. I’ve been using that set up for 5 plus years with zero issues. The actual Battery Tender is even older because I originally bought it for a gas scooter I had that would also sit for long periods.

Battery Tender Plus 1.25 Amp Battery Charger is the one I use. Used it on the Holdenized 8, and use it on the Isuzu Impulse. Priced right, just works.

Yep, I have one of these, although I haven’t needed it since I sold my LS460 with its mysterious battery drain issue. It worked perfectly with no apparent issues.

The Harbor Freight unit mentioned is not fully automatic. There’s some confusing language on the packaging, but it is not capable of turning off by itself. There’s a better unit for around $20 that works as well as anything on the list.

How is that DeWalt charging unit a trickle charger? That’s a commercial battery charger/jump unit. That’s like listing a 100 gallon air compressor in a list of emergency tire inflators.

If you open up a larger image of the CTEK-56, you will notice that on the top and bottom of the LED bargraph display, there are some squiggly curves….those are actually the voltage (top) and current (bottom) waveforms you would see if viewed with an oscilloscope, for each charging stage.

A worse than useless article because it doesn’t mention the specific out put of every charger and Moto and other small batteries must not be charge over 1/2 ampere (400 milliamps) as they’ll get warm/hot and damage their plates .

I have a Battery Tender Plus mounted under the hood permanently hooked-up to the battery with just a plug extending out of the grille. On cold winter nights I just plug it in to be sure I have a maximum charge in the morning. It’s never failed me

“Editor’s note: As noted above, this post is meant to both help you be an informed shopper for automotive products but also to pay for our ‘90s sedan shopping habits operating expenses…”

I’ve the Black & Decker and it’s some of the best $20 I ever spent. Keeps my lawn tractor battery happy over several years of winters. Before it, I’d have to buy a new battery every year. I’m now eight years on a single battery.

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I also twice used it to [slowly] charge a car. I’ve even used it to shock old DeWalt batteries back to life.

One that is sold in Costco is great. It is fully automatic and impossible to cause any damage – protected all around.

CTEK makes teh official Bentley battery charger, supplied with all new Bentleys. That’s good enough for me.

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