Rick's Free Auto Repair Advice

How to buy an automotive battery charger

Tips for buying an automotive battery charger

Don’t buy an old used car battery charger

Old battery chargers were designed to charge a battery at high voltage to shorten charging times. That was fine back in the days when cars didn’t have computers. But use one of those old chargers on your modern computer-equipped car or truck and you risk frying the expensive electronic components.

Buy a smart automotive battery charger

A smart charger will perform a diagnostic on the battery to determine the level of charge and the internal resistance. Based on those results, the charger can determine the proper charge rate and phase.

What is a battery charging phase?

There are at least 3 phases to recharging a battery. If it’s severely discharged, chances are high that its developed some level of sulfation. However, more sophisticated chargers can have as many as 7 phases (more on that below). For basic chargers, the first phase is Reconditioning.

Reconditioning phase

The reconditioning phase is designed to break down the sulfate crystals that formed during the discharge and return them to the electrolyte solution. If you skip the reconditioning phase and just try to recharge the battery by jamming in high amperage, the high resistance from the sulfate crystals will generate high heat that can warp the plates and damage the battery. Once the reconditioning phase is complete, the charger enters the bulk mode phase

Next, the charger changes to Bulk mode, charging at high amps but low volts to replace as much energy as possible

Bulk mode phase

In the bulk mode phase, the charger outputs high amps at low voltage. Recharging a dead battery in bulk mode takes between five to eight hours. The bulk mode accounts for about 80% of the battery charge. The rest is accomplished through the absorption mode.

Finally, the charger will change to the absorption mode to ensure that the charge penetrates deep into the sponge lead plates.

Battery absorption phase

During the absorption mode, the charger lowers the current (amps), while raising the voltage. A complete absorption mode for a dead battery can take as long as seven to 10 hours to fully saturate the lead plates. If you cut short the absorption mode, the plates will sulfate, shortening the life of the battery.

What a 7-phase charge looks like

This multi-phase charging protocol is used by the Solar ProLogix series of automotive battery chargers. Notice the differences in voltage and amperage between the different phases

7 phase battery charger graph


I like the Solar ProLogix chargers

Clore Manufacturing has been making battery chargers and jumper packs forever. They’re the brand professional use. The Solar ProLogix models are very smart chargers that can recondition a battery and fully charge it without any intervention from you. They charge standard lighting ignition batteries (SLI), absorbed glass mar (AGM), and Gel cell batteries (the kind you find on lawn mowers).

Solar ProLogix PL2310 battery charger

This model charger charges at the rate of 10, 6, or 2-amps. It charges 6-volt and 12-volt batteries.

Solar ProLogix PL2320 battery charger

This model charger charges at the rate of 20, 10, or 2-amps. It charges 6-volt and 12-volt batteries.

Solar ProLogix PL2410 battery charger

This model charger charges at the rate of 10, 6, or 2-amps. It charges 6-volt and 12-volt batteries. Just like the PL2310 model but also includes a battery maintainer function for keeping your battery fully charged over long storage periods.

Solar ProLogix PL2545 battery charger

Like the PL2320 model in terms of charging ability, this model also has a battery maintainer mode and a start assist mode. The star assist mode isn’t a jump starter; it’s a way to quickly charge a dead battery to get it enough energy to start the engine.

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Posted on by Rick Muscoplat

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