How Long Does a Jump Starter Hold a Charge?
4 lessons in this series, 11 min in total
- How Long Does a Jump Starter Hold a Charge? 3 min read
- Can You Leave a Jump Starter in Your Car? 3 min read
- Should You Keep a Jump Starter Plugged In? 2 min read
- Do Jump Starters Work in Cold Weather? 3 min read
This lesson draws on NOCO’s GB40 and GB70 guides, Clore’s JNC660 manual, Battery University’s BU-802b and BU-702, and Automoblog’s GB40 review. How we research explains the method.
How fast a charged pack drains: lithium vs lead-acid
Every battery loses charge as it sits: that’s self-discharge. Lithium packs also have a protection circuit, electronics that guard the cells and draw a little power. Battery University’s room-temperature figures:
- Lithium-ion: about 5% in the first 24 hours, then 1-2% a month, plus about 3% for the protection circuit.
- Lead-acid: about 5% a month, or closer to 3% at 68°F (20°C). At 86°F (30°C), it needs a recharge after 6 months.
Battery University calls the two similar (lithium vs lead-acid jump starters covers other differences). Its lithium-ion figures run higher for cells kept full, as a jump starter is:
| Lithium-ion self-discharge per month | 32°F (0°C) | 77°F (25°C) | 140°F (60°C) |
|---|---|---|---|
| Full charge | 6% | 20% | 35% |
| 40-60% charge | 2% | 4% | 15% |
These are general cell figures, not jump starter measurements; NOCO publishes no exact lithium chemistry or self-discharge rate. Battery University adds that self-discharge typically doubles with every 18°F (10°C) rise, which matters most in a hot car (next lesson).
When to recharge it
- Before first use. All three ship needing a full charge; Clore says 24 hours for the JNC660.
- After every jump. Clore says immediately. NOCO sets no rule, but a used pack has less in reserve.
- Every 3 months in storage. That’s Clore’s rule. NOCO gives no number, so check a NOCO pack’s four charge LEDs (25/50/75/100%) on the same schedule.
- Before winter and long trips. Automoblog’s reviewers, who got a GB40 from NOCO, found it held charge longer than expected but still charge it before road trips.
- When the gauge drops. On the JNC660, yellow means recharge; red means recharge now.
Lead-acid also risks sulfation, an oxidation layer on the negative plate that blocks current flow. Battery University says low charge causes sulfation and to recharge stored lead-acid when it falls to 70%. Clore says never to leave the JNC660 completely discharged, because the damage could be permanent.
A charger can keep some packs topped up: see whether to keep it plugged in.
How many years a jump starter lasts
None of these makers gives a lifespan in years; all three carry a 1-year limited US warranty. Battery University’s storage data points to heat as a major cause of permanent capacity loss, shown in the next lesson.
The JNC660’s battery can be replaced through Clore’s Technical Service line. NOCO’s guides say only NOCO should replace the GB40 and GB70’s lithium battery.
Worn-out checks:
- JNC660: Clore’s load test is a 100-amp load for 6 seconds after a full charge. The battery is good if it holds 9.5 volts or higher.
- GB40 and GB70: NOCO says to stop using it and contact NOCO if the battery gets excessively hot, smells or looks deformed.
Where you keep the pack changes these numbers, so read can you leave a jump starter in your car next.
