Why Do Battery Chargers Go Bad_

If your car battery is in immediate need of some electrons so it can get you home, you have two options: flag down a passerby with jumper cables or hook up a portable charger. While the former method is the time-tested way of getting juice to a drained battery, a battery charger is the safer, easier, and less risky method.

Battery chargers also seem like the most reliable method. After all, you just plug it in and use it – what could go wrong? But battery chargers aren’t impervious to failure. They do occasionally fail, and they can do so for a number of reasons.

Let’s get a refresh on how a battery charger works before we consider why one might fail.

How a Battery Charger Works

We’ve gone over this before, but if you haven’t yet read that article here’s the skinny: car batteries require 12 volts of direct current (DC). Household outlets run on 120 volts of alternating current (AC). Portable car battery chargers plug into the wall and use a power converter (which is different than an inverter)1 to turn 120 volts of AC into 12 volts of DC.

Battery chargers feed reduced-voltage DC current to the car battery at a very low ampere rating, a figure which represents the rate of flow of electricity. With a low ampere rating, electricity is slowly spoon-fed to the battery over a long duration of time. This safely and reliably charges the battery. For a quicker charge, some battery chargers may allow users to adjust the ampere rating for faster charging.

Making all this happen is a relatively simple and straightforward arrangement of wires that run first from the wall to the converter and then on to the terminal posts on the battery via jumper cables. There are no moving parts within the casing of a battery charger.

How and Why Battery Chargers Go Bad

Why do Battery Chargers go Bad?

Image courtesy of Pixabay

With such a simple system, there isn’t much to fail. Wires shouldn’t chafe or arc or fray within the protective enclosed casing of the charger; the power converter should likewise hold up to repeated uses without issue. With proper use, a battery charger is apt to last a long time.

That said, there is a chance for failure. Weather and conditions, for one. If the battery charger is subjected to a garage or basement flood and gets wet enough for water to seep through the encasement, you’ll want to replace the charger to avoid any issues. Water and electricity don’t mix.

If you keep the battery charger in the back of your vehicle, the constant jostling of the device during driving may, over a long period of time, loosen the wires. This can potentially lead to spotty connections that result in inadequate or incomplete charging. You’ll want to troubleshoot a finicky battery charger, but worry not – it’s relatively easy to do so.2

Perhaps the most concerning the potential failure is overheating. It’s normal for some heat to be generated during the charging process – something we’ve written about before – so a battery charger that’s hot to the touch shouldn’t be fretted over. However, if the charger is too hot to even briefly touch, that’s a sign to immediately stop charging.

These instances can often be tied back to the quality and sophistication of the battery charger. Low-end battery chargers are simple in nature and operation; once hooked up to a battery, they feed a constant source of voltage to the battery until they are manually turned off and disconnected by the user. These chargers do not monitor the state of the charge of the battery, so they don’t cease charging once the battery is fully juiced up.

When this happens, both the battery and charger can grow very hot as the charger attempts to force more current into a charged battery. The struggle amounts to an unstoppable force impacting an immovable object – and the result is energy that must dissipate into dangerous levels of excess heat.3 Left unchecked, there is a chance for either the battery or charger – or both – to catch fire.

The best way to avoid this worst-case scenario? Invest in a battery charger that can monitor the battery for charging status. When the battery becomes fully charged, these smarter chargers will either kick off entirely or go into a trickle-charge mode that over time feeds the battery only enough juice to keep it fully charged.

Is The Problem The Battery Charger – Or The Battery?

Battery charger or Battery?

Image courtesy of Pixabay

It’s easy to blame the battery charger if your battery doesn’t seem to be accepting a charge, but there are also good odds the battery itself could be the culprit. As batteries age, they lose their ability to take and hold a charge. After enough time they won’t charge at all. If you’ve been constantly trying to charge an old battery, there will come a time when the energy stored within the battery will simply be spent entirely. That’s when it’s time to buy a new battery.

The type of battery you have may also impact how and if it charges. Currently, there are three primary types of automotive batteries in general use: AGM, gel, and lead-acid. The most common remains lead-acid, but certain vehicles use the former two designs as well.

We won’t get into the weeds with how they differ, though this article illustrates the differences nicely. But suffice to say that each battery type requires a different level of voltage and current to charge properly. Some battery chargers offer different settings so they can properly charge all three types of batteries. Cruder models may only be designed to charge lead-acid batteries. Be sure you aren’t trying to charge a gel or AGM battery with a lead-acid battery charger, or otherwise inadequate charging, no charging, or even damage to the battery may occur.

You can definitely delve deeper into the different battery types and their charging requirements, but the above should be more than enough to understand the basics.4

Parting Thoughts

Battery chargers are simple and robust devices that can last a long time when used properly. The key, however, is knowing when and how to use them. Be sure to use the correct style of charger for the type of battery in your car and never overcharge your battery. If you can, purchase a battery charger with overcharge protection and adjustable settings for different battery types, such as NOCO’s highly-rated charger.

With a few proper precautions and the right battery charger, you can expect your charger to last for many years and many charges, breathing new life into your car batteries and saving you when a dead battery would otherwise leave you stranded.

Article Sources

Ride Digest uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. Converter vs. Inverter. Diffen.com. Accessed 24 Sept 2021.
  2. Smith, Alabaster. Troubleshooting 12 Volt Auto Battery Chargers. Itstillruns.com. Accessed 24 Sept 2021.
  3. Where the Energy Goes: Electric Cars. US Dept of Energy. Accessed 23 Sept 2021.
  4. 12 VOLT CHARGER TUTORIAL. chargingchargers.com. Accessed 24 Sept 2021.