A portable jump starter is a handy tool to carry in your car. Having high-capacity starting power in your trunk eliminates the need to rely on strangers or wait hours for roadside assistance when your battery dies. But here is the big question: is it safe to leave a portable jump starter inside your car 24/7?
Safe? Probably. Smart? Not so much.
If you have a portable jump starter, take a look at how professional service technicians use their equipment. Educate yourself about how extreme vehicle interior temperatures can affect battery chemistry. You will learn a lot about the best practices for jump starter storage year-round.
What the Professionals Do (and Why They Do It)
Professionals use their jump starters multiple times during a given shift. As a result, the units are brought back to the shop and plugged into charging stations at the end of the day. Professional-grade jump starters rarely sit dormant in a hot or cold truck for extended periods of time.
According to Clore Automotive, there is a lesson to be learned here. Professionals know that a jump starter is only as good as its last charge, so they inspect their units daily. They top off internal batteries using vehicle AC/DC charging adapters or by plugging units into wall outlets between calls.
As a consumer, you’re not going to use your jump pack every day. You might only use it once or twice per year. So routine charge and discharge don’t apply. Nonetheless, understand that most professionals would not leave a jump starter in a truck indefinitely. They know what temperature extremes can do to internal batteries.
The Risks of 24/7 Vehicle Storage
Leaving a portable jump starter in a glove box or trunk for months on end means not maintaining it. The practice also introduces very real risks tied to temperature extremes and natural battery self-discharge. Here are three key concerns according to Clore Automotive:
1. Heat Degradation
Temperatures inside a parked car can quickly exceed 130°F during the heat of summer. Trunk temperatures can get even higher. Here’s the problem: high heat accelerates the chemical processes inside both AGM and lithium jump-starter batteries. Continuous exposure to excessive heat speeds up internal self-discharge, degrades battery capacity, and poses risks of thermal swelling.
2. Reduced Cranking Power
Cold temperatures don’t do nearly as much harm, but they do impact how a jump starter works. As temperatures drop, an internal jump starter battery can lose a significant portion of its cranking capacity. So leaving a unit in a freezing car overnight will impair its ability to start the car the next morning.
3. Natural Self-Discharge
Portable jump starters are essentially rechargeable battery packs. Unfortunately, all rechargeable batteries naturally lose charge over time. So a jump starter stored in a trunk for six months could actually be useless when you need it.
Best Practices for Jump Starter Storage
It is not necessary to carry a portable jump-starter into the house every night. But if you are willing to employ some best practices, you’ll get longer life and better service out of your unit:
- Bring the unit into the house when temperatures are extreme.
- Establish a regular charging routine. Quarterly charging should be sufficient.
- Invest in a commercial-grade charger rather than a consumer-grade battery pack.
Leaving a portable jump starter in your car at all times offers a certain peace of mind. Just remember that portable jump starters are battery packs. They need routine charging. They also need to be protected against temperature extremes. Understanding the risks and following the rules is your best bet.
