Rick's Free Auto Repair Advice

How to use a jumper pack.

The right way to use a jumper pack

If you improperly use a jumper pack, you can permanently damage it. Here are some tips on how to properly use a jumper pack.

Keep your jumper pack charged

Your jumper pack may contain a lead acid battery (usually an absorbed glass mat [AGM]) or lithium style battery. Both types self discharge when left unused for long periods of time. Generally speaking, lithium batteries tend to drop to 75%-80% charge within the first 30-days after charging. They then stay at that level for a while before dropping to around 30% after 60-180 days. Then can remain at 30% for about a year. Many lithium jumper pack manufacturers claim their jumper packs can hold a charge for a year, but as you can see, that’s misleading. Don’t be surprised if your lithium jumper pack is at 30%-50% charge after sitting for 90-180-days.

In addition to time since charge, both lead-acid and lithium batteries produce less power when they’re stored in extremely cold conditions like the trunk of your car.

In other words, no matter which type of jumper pack you own, you must keep it charged and keep it warm in order to get the most jumping power from it when you need it.

How quickly does your jumper pack lose its charge?

AGM batteries lose their charge in a linear fashion (see Figure 1), while lithium batteries tends to self discharge in stages (see Figure 2). Leaving either battery type in a discharged state for long periods can cause permanent damage.

jumper pack discharge rate
lithium jumper pack discharge rate

How often to charge your jumper pack depends on use and storage conditions

When used to jump a vehicle

Charge your jumper pack after every use.

WARNING: Leaving your jumper pack in a discharged state after use will cause permanent damage to the battery.

When stored indoors

Charge your jumper pack at least once every 3 months.

When stored in a cold vehicle

Charge your jumper pack at least once a month.

NOTE: Charging your jumper pack battery more often than every 3 months will not harm it.

Storage: Storing your jumper pack in moderate temperatures 50°F to 70°F will extend its charge and provide the most power when you need it.

How to use a jumper pack

Generating enough power to crank an engine causes the jumper pack to heat up very quickly, so cranking time should be limited to 6-second periods, with a 3-minute cooling off period between tries. Many lithium jumper packs automatically shut down after a 6-second cranking period to prevent the battery from overheating. Read the instructions on your pack to determine the recommended cooling off period.

Warning: Using the jumper pack to crank an engine for long periods can overheat the jumper pack and damage it.

Disconnect after jumping

Once the dead vehicle is up and running, don’t make the mistake of leaving the jumper pack connected. Many DIYers think they can recharge the jumper faster by leaving it connected to the running engine. However, the voltage of a running engine is much higher than the recommended recharging voltage.

Recharging your jumper pack from a running engine can cause it to overheat, resulting in battery failure. In fact, some lithium style jumper packs will shut down completely if left connected on a running engine

Avoid reverse polarity

Take the time to double check the polarity of the battery terminals before connecting your jumper pack. Reversing polarity can immediately blow fuses and possibly damage your jumper pack. DON’T GUESS! Use a rag and wipe off the top of the battery so you can see the polarity marking near the POSITIVE (+) terminal. Or, connect to the factory jump starting post under the hood if the battery is stored elsewhere. Always connect the negative jumper pack cable to a good ground point on the engine.

Clean your jumper pack cables after use

Corrosion buildup on battery terminal posts is not uncommon for discharged batteries. After using your jumper pack clamps, make sure you clean off any corrosion that has transferred to your clamps.

©, 2021 Rick Muscoplat

Posted on by Rick Muscoplat


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