How long does a jump starter hold its charge?

What the manufacturers actually say

"Holds charge for a year" claims are common, but few makers put a maintenance interval in writing. These are the figures we could find in documents from the manufacturers themselves.

The GOOLOO figures come from its US product page. The NOCO figures come from a GB40 user guide edition with a micro USB input; later versions of the GB40 may differ, so check the guide that came in your box.

Standby time is not the same as a check interval

A standby claim describes how long a fully charged unit might still have enough left to start a car if you never touch it. A recharge interval is maintenance advice. When a maker publishes both, plan around the shorter one. GOOLOO's own advice to recharge every 3 months is a better guide to real life than the 24-month headline, because nobody wants to find out on a cold morning that their unit was at the bottom of its range.

What drains a stored jump starter faster

• Heat. GOOLOO tells owners not to store the GP4000 in a vehicle parked in hot weather for long periods. A boot in summer sun is the classic example.
• Leaving it switched on. The GB40 turns itself off automatically after seven hours. That protects it from being left on for days, but a unit used as a torch or power bank and then forgotten still keeps drawing until that point.
• Using it as a power bank. Charging a phone from the USB output takes from the same battery you need for a jump. Top it up afterwards.
• Charging in the cold. NOCO's charging range starts at 0°C. Plugging in a unit straight from a frozen car is outside that range, so let it warm up indoors first.

A simple routine that works

1. Charge it fully as soon as it arrives.
2. Put a reminder in your phone every three months to read the charge gauge and top it up.
3. Do an extra check in October or November, before the cold mornings that flatten weak car batteries.
4. Recharge after every jump or long power-bank session.
5. In a heatwave, take it out of the boot and keep it indoors.

Common mistakes

• Trusting the box. A headline standby figure is a best case, not a promise for a unit that has spent a summer in the boot.
• Using it straight from the box without a full charge. NOCO's guide says the GB40 ships partially charged.
• Charging it in a freezing car or garage, outside the stated charging temperature.
• Forgetting it after a jump. The next flat battery is rarely convenient.

Related reading

• NOCO GB40 vs GOOLOO GP4000
• NOCO Boost GB40 review and GOOLOO GP4000 review
• Jump starter or jump leads?
• What to keep in a car emergency kit and our emergency kit picks
• More about NOCO

Frequently asked questions

Can I leave a jump starter in the car all year?

You can, but heat is the problem. GOOLOO's GP4000 page warns against storing the unit in a vehicle parked in hot weather for long periods, and NOCO's GB40 user guide lists a storage range of -20°C to +50°C based on average temperature. In a UK summer, a boot in full sun is the worst place for it. Keep it in the cabin footwell or bring it indoors during heatwaves, and check the charge more often if it lives in the car.

How do I know how much charge is left?

Use the unit's own gauge. The GB40 has four charge LEDs for 25%, 50%, 75% and 100%, and its user guide explains what each colour means. For other models, the user guide explains the gauge. Read it every time you do your check, not only when you need a jump.

Can I recharge a jump starter from the car?

Yes for both of these models. NOCO's GB40 guide says it can be recharged from any USB port, including a car charger. GOOLOO's GP4000 page says it can be fully recharged in about 5 hours through a 12V car outlet. Treat it as a top-up on the road, not a substitute for a full charge at home.

Does cold weather drain a jump starter?

Both makers publish temperature limits, and the charging limit is the one people miss. NOCO's GB40 guide gives a charging range of 0°C to +40°C, so charging a unit that has spent the night in a frozen car is outside that range. Let it warm up indoors before plugging it in. For cold-weather starting, check the operating range in your own user guide.

Should I recharge after every jump?

Yes. A jump uses a large burst of energy, and the next one may come weeks later when you have forgotten about it. Recharge to full as soon as you are home, then go back to your normal check routine.