Charging a jump starter too often will damage its battery

The idea of "battery memory" may be familiar to technicians who remember older rechargeable batteries. The concern was that charging a battery above a certain charge state could reduce its usable capacity over time.

According to Clore Automotive, that concern does not apply to the AGM lead-acid and lithium batteries used in its Jump-N-Carry and Booster PAC jump starters.

In fact, the opposite might be true, and allowing a jump starter to remain heavily discharged can be more harmful. With AGM batteries, remaining in a discharged state can accelerate sulfation, a natural process that occurs in lead-acid batteries. With lithium batteries, continued self-discharge can eventually bring the battery to a state where its battery management system prevents further charging as a protective measure.

For fleet shops, the practical takeaway is to follow the manufacturer's charging and storage recommendations rather than waiting until a jump starter is completely discharged before recharging it.

Clore recommends charging its jump starters regularly and says there is no need to avoid charging them when their state of charge is still relatively high.

All lead-acid batteries can be charged the same way

A battery may be labeled lead-acid, but that doesn't mean every lead-acid battery should receive the same charging profile.

Flooded lead-acid batteries are generally more forgiving of charging conditions than AGM batteries. AGM and spiral-wound batteries require more controlled charging, including appropriate voltage and a multistage charging process.

Using an inappropriate charging profile can reduce battery life and contribute to starting problems.

The same consideration applies when working with lithium batteries, as different lithium chemistries have different charging requirements. Techs should identify the battery type and follow the manufacturer's charging specifications before connecting a charger.

Battery repair modes are just a marketing feature

Battery chargers increasingly include repair or desulfation modes intended to help recover lead-acid batteries that have experienced poor maintenance or prolonged discharge.

Sulfation is a natural process in lead-acid batteries, and allowing a battery to remain discharged can accelerate it. Regular charging and maintenance can help limit the effects of that process.

Clore's PRO-LOGIX chargers, for example, include an automatic Battery Repair Mode. According to the company, the charger first evaluates how the battery accepts energy during an initial energizing phase. If the charger detects characteristics associated with sulfation, it can enter its repair mode before returning to the normal charging process.

However, a repair mode should not be viewed as a way to bring every failed battery back to service. A battery that has reached the end of its useful life still needs to be replaced. Repair features are instead intended to address conditions that can affect a serviceable lead-acid battery. Following the charger's instructions and the battery manufacturer's recommendations is still necessary when attempting to recover a battery.

Regular battery maintenance also remains more important than relying on a repair function after a battery has already deteriorated.

A low-power charger is enough to support reflashing

When it comes to module reprogramming/reflashing, every OEM specifies power requirements for both voltage and current. There are no OE current requirement below 55A and most now set the floor at 70A with late-model vehicles. That means a 20A, 25A, or even 40A power supply is insufficient to meet OE requirements while supporting a module reprogramming event.

OEMs often specify a current requirement higher than what was typically needed, meaning a 20A power supply might have been enough to support reflashing on a 2015 domestic vehicle, but it was not within spec. As vehicle complexity increases, so does power demand. 

A failed reflash can mean anything from having to restart the programming event to a module that needs to be replaced. Techs should make sure the power supply meets the requirements of the makes and models being serviced.

A high-output charger will overcharge the battery

When a power supply is operating in power supply mode, it is maintaining the vehicle’s electrical system at a specific voltage, rather than simply pushing its maximum available current into the battery.

For example, Clore’s PRO-LOGIX flashing power supplies can maintain a selected voltage from 13.1 to 14.9V. If the vehicle’s electrical system requires 8A, the unit provides 8A. If demand increases to 84A, the unit provides 84A.

By managing system voltage, the power supply provides the current needed to maintain that voltage. It isn’t simply forcing all of its available current into the battery.

Keeping battery practices current

Battery and electrical-system service has changed along with the vehicles being maintained, but the common thread is that the equipment needs to match the application. Technicians should rely on the battery, charger, and vehicle manufacturer's specifications rather than assumptions carried over from older equipment.