Battery Chargers: Which one do you need?

Battery Chargers: Which one do you need?

Modern battery chargers adapt to diverse battery types and needs.

Looking for a battery charger? If so, you’ve probably found there are many more options than there used to be. Selecting the correct one comes down to understanding why they’ve changed and thinking specifically about how and where you’re going to use it. From wheeled to portable, manual to automatic, multiple battery stations to weather-safe chargers, there are many things to consider.

Most importantly, chargers have evolved to meet the needs of changing automotive battery technology and service, so let’s take an inside look at the task at hand, charging the battery.

The Stages of Charging

With a typical flooded lead-acid battery, we had it easy. Chargers had low, medium, high and boost. As technicians, we used a hydrometer or load tester to determine battery condition. We might have added water. We connected in the charger, set the charge level and time, and walked away. On a flooded lead-acid battery, that was fine, but it can be damaging to other types of batteries.

Battery charge

Battery charging occurs in stages which are controlled by the charger. The bulk stage, which comprises the majority of the charge cycle, is where the charger holds a constant current, and the voltage increases as the battery charges.

During the absorption stage, which is approximately the final 20% of the charge, the charger holds the voltage and decreases the current until the battery is fully charged. The float stage then reduces voltage and provides only low current, essentially becoming a battery maintainer at this stage.

Equalization is an additional mode, specifically beneficial for flooded lead-acid batteries. This is a calculated over-charge, where the voltage is increased above typical peak charging voltage and held for a limited amount of time. This removes any sulfation on the battery plates, effectively equalizing the strength of the electrolyte in each cell.

What’s the harm?

Old, flooded lead-acid batteries were forgiving, and when that’s all there was, chargers needed to operate in only one way. But now we’re seeing sealed lead-acid (SLA), absorbed glass mat (AGM), gel, enhanced flooded (EFB), deep cycle and lithium-ion batteries…and all of them on a regular basis.

What’s most important to understand is that the technology of each one of these batteries brings with it specific electrical differences that result in a different charging profile. The recommended voltage and current required during each stage of charging requires precise control to prevent battery damage, and battery chargers must be able to deliver these different profiles as a result.

If the required charging profile is not used, the battery may be overcharged or undercharged. Overcharging an SLA battery can cause excessive gassing, and the excessive pressure is released through a pressure relief valve. The lost hydrogen and oxygen gasses ultimately aren’t recombined, and the electrolyte level is diminished. AGM batteries are very sensitive and easily damaged by overcharging, and overcharging a gel battery can cause bubbles to form in the electrolyte gel.

Lithium batteries have only two stages of charging, constant current and constant voltage, and they too can be damaged if the correct charging profile is not used. Much like we’ve learned about the use and charging of the batteries for our cordless tools, vehicle batteries must be treated with the same respect.

Making it Easy

How do today’s chargers manage all of these options? With microprocessor control. It’s a necessity, but it doesn’t mean complicated. They’re just as easy to use, and, in many cases, easier. We don’t have to think about how we want to charge a battery. We just select the battery type to ensure the proper charging profile, and let the charger do the rest.

If you prefer traditional selector knobs/dials and an analog gauge, you can still get this design, but with the same microprocessor control that makes them safe for AGM and gel batteries. Be sure to do your research to verify their functions before you buy.

More Features

Polarity detection is one of my favorite features and will warn you if polarity is reversed when connecting the charger. We all know mistakes happen. Reversing polarity has never been good, but on today’s cars, you DO NOT want to reverse polarity. Bad things happen. I’d rather know than make the mistake.

Re-flashing or updating a vehicle control module is an increasingly common practice, for both performance “tunes” and routine service procedures. For some shops, it’s an everyday occurrence. It’s critical to maintain battery voltage during these procedures, and re-flash power mode is one of the more commonly requested features on new chargers.

Some chargers come with a memory saver port and a cable to plug into the OBD port. Some offer battery, starting and charging system diagnostic features. Partial charge modes provide a quick 75% charge for testing. Digital screens, multiple language options and automatic charging are even more features designed to add efficiency to our workflow.

As difficult as it can be to stay current with new technology, today’s battery chargers make it easy by offering the options to safely charge today’s batteries and service today’s vehicles in a variety of different platforms, so you can choose the one that works best for you. TS

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Don’t Forget the Basics

Every now and then, I get tunnel vision during diagnostics, and forget to think about the big picture.

2000 Jeep Cherokee

We’ve all made the mistake, at least I know I have. Every now and then, I get tunnel vision during diagnostics, and forget to think about the big picture. And this last episode even violated my cardinal rule: don’t leave a malfunction indicator light (MIL) unresolved.I always recommend fixing every problem that causes the MIL to illuminate. I hear the excuses all the time about why people would rather live with the light, but I always tell them, even if the immediate cause of the light doesn’t affect the dependability of the vehicle, if something else happens that does, you’ll have no idea of knowing. That’s the beauty of computer controls. You always know when something is going on.Just a couple weeks ago, a friend called me because they were having trouble with the transmission in their 2000 Jeep Cherokee. It was shifting erratically, and it occurred after driving on a very hot day. The fluid was dark in color, and when it last had been changed was unknown.This particular vehicle was located in Arizona, so phone-only troubleshooting was the only option. I decided to focus on the condition of the fluid and the hot climate. We’ve all faced neglected and burnt transmission fluid and had to make the decision of change or not to change. Some say change it, but some say that may cause the transmission to completely fail, so leave it alone.I decided to roll the dice, and, in this situation, I decided the fluid should be changed. Then, knowing the climate, I decided to dig in and focus on the other factors that could affect the fluid. After asking questions, I learned that the cooler in the radiator had been bypassed and the only cooler was a small aftermarket unit. I also discussed the fact that if the fan clutch was not operating properly, it could cause a problem with cooling as well.Taking my advice, the Jeep’s owner changed the fluid and filter, installed a new radiator, reconnected the transmission lines to it, installed a new aftermarket cooler in line and installed a newfan clutch.After performing all the work, the transmission continued with its erratic shifting. No better, no worse. The next day, unexpectedly, the engine stalled when coming to a stop. This had never happened before. The Jeep’s owner decided to check for trouble codes and found a code for the throttle position sensor (TPS).He didn’t think about looking for codes before because the MIL was already illuminated for another problem. He was “living with the light.” After replacing the TPS, not only did the engine run better than it had in a while, but the transmission shifted perfectly and has ever since.Of course, it all makes perfect sense. I wasn’t there to see the MIL, I didn’t think to ask if it was illuminated, and on or not, I didn’t even think to check for codes. My tunnel vision in this case only made me think about the transmission fluid, not the information the transmission needs to know in order to shift properly. Luckily, the outcome was good and the owner is happy knowing the transmission is serviced and the fluid is being properly cooled. TS

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