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Recharging your car's pandemic-drained battery: Wow, charging tech has sure changed

Smartphone battery innovation has benefited two simple tasks: jump starting and trickle charging car batteries. We take a look at some gadgets that'll get your cars up and running again.


Remember these old chargers? Paul Rako at EDN resurrected this classic dinosaur.

Image: EDN

I am a car guy. By that, I mean I watched all the Top Gear on offer, used up all the Grand Tour videos I could find, think of Jay Leno's garage as my happy place, and bought a muscle car as soon as I turned mid-life crisis.


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I am not a car guy when it comes to car maintenance. I can field strip a PC tower blindfolded, but it took me 15 minutes to figure out how to open the hood (what UK folks call the bonnet) -- the place that houses the engine and battery in most cars.

The reason I had to grease monkey up was that lockdown was ending and we needed to go out on a mission-critical errand. But, after ten weeks of sitting in the carport without being driven, both cars were stone cold dead.

We thought about calling AAA, but in our area, they don't replace batteries. They'll only get you started and then it's up to you to take the car to a repair shop. Both my wife and I have certain health issues that place us at higher risk. We've been isolating since mid-March, so engaging with the nice folks at the town's tire-and-battery store wasn't an option we were thrilled about.

I had to train up on how to repair and maintain car batteries. I kind of wish adults could earn merit badges because I pretty much earned one for this project. And, with my guidance, you can, too.

It's all about the amperage

Imagine you're sprayed with 120-degree (F) water, coming from a 1/4-inch spigot. You might be uncomfortable, and a small spot on your body might get burned, but that's about it. Now, imagine you're sprayed with the same 120-degree water, but it's coming out of a fire hose. Even if it wasn't scalding hot, it would be painful. But scalding hot could be deadly.

In electrical power, think of the voltage as temperature. Think of the water flow as current (or amperage). A car battery is typically 12 volts, not much more than our home electronics gadgets. A typical 9-volt gadget battery produces about 400mAh to 600mAh. Effectively, it can produce roughly five hundred milliamps for about an hour before it runs out of juice. A car battery has a capacity of about 48 amp-hours.

In other words, a car battery produces 96 times more current than a transistor radio battery. If you get a shock from a 9-volt gadget battery, you might feel a tingle. If you get a shock from a car battery, you could die.

Bottom line: When you start tinkering with car batteries, do it with care and respect.

How dead is dead?

OK, so neither of my cars would start. How dead were the batteries? As it turns out, most batteries that seem dead aren't dead, they're just mostly depleted. My batteries would still produce about 4 volts, but you really need something above 11 volts to crank an engine.

Generally speaking, if a battery can produce some voltage, it's often repairable. There are a lot of caveats to that, and since I'm not a mechanic, I'll point you to EDN, Cars Direct, Meineke, Car and Driver, and Pep Boys for various deep dives.

For our purposes, think about the following two questions. Do you need to go somewhere now? Do you need to go somewhere tomorrow? Depending on your answer, you'll use different devices to solve the problem.

Jumper cables are so last millennium


If you've been driving for more than a few years, you're familiar (at least in theory) with the idea of jumper cables. They're a bundle of thick cables with clips on each end that look like they're out of a 1930's sci-fi serial. 

The idea is you hook one end up to a dead battery on one vehicle and the other end up to a live battery on the other. The functioning vehicle gives up some of its juice to help the non-functioning vehicle start its engine. Once both vehicles are running, you disconnect the cables and rely on the alternator of the once-dead vehicle to send some electrical life to the formerly dead battery. If you drive it around for a while, your battery will get recharged.

There are some disadvantages to this approach. First, you need a second vehicle with a working battery. Both of our cars were dead. Or, you need a cooperative friend, neighbor, or good samaritan. We were social distancing so we didn't have much contact with our neighbors. You often need to convince your potential ally to hook their perfectly good car to your not so perfectly working car. Plus, if you don't hook up the cables exactly right, you could damage both cars -- not to mention giving yourself a potentially deadly shock.

But we live in the future. It's possible to use an iPhone charger on steroids to jump start your car. You think I'm kidding. I'm not.

The device I bought, the TrekPow G22 Portable Jump Box does, in fact, have a USB port where you can charge your phone. It also has a protected port where the provided set of battery clamps plug in.

This is a lithium battery box. At a little over a pound, it looks like just about every other external iPhone battery charger you've seen, except it's just a little bigger. The battery in the jump starter charges overnight when connected to a USB power dongle. According to the company, if you make sure to drain and charge the battery once every six months, it'll always be ready to use.

I was able to get both cars to start, although it took a few tries on the Ford. All told, I made about six attempts and started two vehicles, and used up only about half of the device's built-in charge. When I went out later that day, I just tossed the kit (it comes in a nice case that holds the cables and jump starter) in my car, so if I got stuck while out and about, I could zap it up once again.

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These are not your Daddy's trickle chargers


Because we're sheltering-at-home (and are likely to for quite some time), we decided to pick up two trickle chargers. These devices won't rescue a truly dead battery but can keep working batteries in good condition over the long haul.

Now, I don't know about you, but I remember the car chargers of my youth. They looked a lot like the image from EDN shown at the top of this article. My dad had this rusted box skinned in sheet steel that he would sometimes hook up to one of our cars. He had to crank the mechanical timer knob and another to specify the current going into the car. It was a pain, and it wasn't terribly reliable.

The chargers I bought are not like that. They're smart. Specifically, I picked up two Foxsur Automatic Smart Battery Charger/Maintainers, and that brings up an important point. This class of device is more properly referred to as a battery maintainer. The idea is it keeps the battery maintained, topped up, and ready to use.

They're smart. All you do is hook them to your battery, set it, and forget it. They charge until the battery is topped off, and then they stop -- all automatically. They adjust dynamically for the type of battery you have and for the condition of the battery you're charging.

Essentially, the only work you need to do is hook them to the battery and plug them in. They do the rest.

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Pandemic best practices

I could leave these battery maintainers connected to the cars at all times, but that doesn't seem necessary. In practice, I'll probably hook them up every couple of weeks, just to make sure the cars aren't left to sit for too long.

I bought two so that we could maintain both batteries at once, and while that cost a little bit more, in terms of making sure we're both able to use our vehicles, it's probably a smart decision.

My plan is to create repeating six-month calendar entries for charging the jump starter, and repeating two week entries for using the battery maintainers on the cars. That way, I can be sure the vehicles are ready for use whenever they're needed.

What about you? How are your cars doing? What measures have you taken to be ready in our wacky new reality? 

You can follow my day-to-day project updates on social media. Be sure to follow me on Twitter at @DavidGewirtz, on Facebook at Facebook.com/DavidGewirtz, on Instagram at Instagram.com/DavidGewirtz, and on YouTube at YouTube.com/DavidGewirtzTV.