Jump starter charges calculator
A 16,800mAh jump starter stores about 62Wh, enough for roughly 5 jump attempts or 3 phone charges on one charge, assuming a 3.7V cell rating and about 10Wh per attempt including losses.
Top the pack up every three to six months even unused; lithium packs self-discharge slowly and deliver less when cold.
Wh = mAh x 3.7V / 1,000; attempts = Wh x 0.85 / 10Wh; phone charges = Wh x 0.8 / 15WhMost packs quote mAh at the 3.7V cell voltage. Some quote at a different voltage, so if the listing states Wh, use that figure instead. Cold packs deliver less.
Jump starters by capacity
Prices from Amazon at the time of writing; they change often.
TREKURE Portable Car Battery Jump Starter 4000A 16800mAh Jump Box, Car Battery Jumper...4,000A peak / 8L gas / 6.5L diesel / 16,800mAh$35.99Check price on Amazon
S ZEVZO ET03 Car Jump Starter 4000A Jump Starter Battery Pack for Up to 8.0L Gas and...4,000A peak / 8L gas / 7L diesel$53.99Check price on Amazon
GOOLOO GP3000 Jump Starter, 3000A Lithium Jump Box (9L Gas or 7L Diesel)3,000A peak / 9L gas / 7L diesel$59.99Check price on Amazon
AstroAI S8 Ultra 12V 4000A Lithium Jump Starter Up to All Gas/12L Diesel4,000A peak / 12L diesel$72.18Check price on Amazon
GOOLOO A5 Jump Starter with Air Compressor, 4000A Portable Jump Box4,000A peak / air compressor$99.96Check price on Amazon
WOLFBOX MV24A 4000A Jump Starter with 160PSI Air Compressor, 12V Car Battery Booster...4,000A peak / 10L gas / 10L diesel / 160 PSI / air compressor$184.99Check price on Amazon
How many jumps do common pack sizes give?
Estimated from rated capacity at 3.7V, about 10Wh per jump attempt including losses, and 15Wh per phone charge.
| Rated capacity | Energy | Jump attempts | Phone charges |
|---|---|---|---|
| 8,000 mAh | 30 Wh | 2 | 1 |
| 12,000 mAh | 44 Wh | 3 | 2 |
| 16,800 mAh | 62 Wh | 5 | 3 |
| 20,000 mAh | 74 Wh | 6 | 3 |
| 24,000 mAh | 89 Wh | 7 | 4 |
| 26,800 mAh | 99 Wh | 8 | 5 |
How should I store and recharge a jump pack?
Recharge after every use and every three to six months in storage. Lithium packs lose a little charge each month, and a pack left at empty can drop below the level its protection circuit will recover from.
Heat is the bigger risk. A closed car in summer sun can far exceed the storage range most makers print in the manual. Keep the pack in the trunk or cabin shade, or bring it indoors during heat waves.
Frequently asked questions
How many times can a jump starter jump a car on one charge?
A typical 16,000 to 20,000mAh pack gives roughly 4 to 6 attempts on a healthy engine, fewer on a large or cold engine or a completely flat battery. Makers often advertise higher counts measured on small engines in mild weather. Recharge after any use rather than relying on the remaining charge.
Is mAh the same as jump starting power?
No. mAh is stored energy, which sets how many attempts and phone charges you get. Starting power is how much current the pack can deliver in a burst, which depends on the cells and wiring. A high-mAh pack with weak cells can store plenty yet fail to turn a big engine.
How long does a jump starter take to recharge?
Divide the watt-hours by the charger input watts and allow about 15 percent for losses. A 62Wh pack takes about 4 hours on an 18W input and about 2.5 hours on USB-C 30W. Fast-charge inputs only help if you use a charger that supports them.
Can I leave a jump starter in my car all year?
Most people do, but heat and cold both matter. Check the storage temperature range in the manual; interior temperatures in a parked car in summer can exceed it. In winter the pack still works but delivers less current, so keeping it charged matters more.