- No, usually not right away: a battery that truly reads 0 volts usually points to a faulty battery, not an empty one, and a jump starter cannot fix that.
- For a heavily discharged battery that still has some low voltage, the ForceStart function on an AutoXtreme jump starter can help.
- ForceStart temporarily switches off the standard detection, so the jump starter also recognizes a battery below the normal threshold.
- If starting still fails after a few attempts, the battery probably needs replacing.
A flat battery is annoying, but most jump starters solve that easily. If your battery truly reads 0 volts, that is a different story. We explain the difference and when a jump starter still helps.
What does it mean when a battery reads 0 volts?
In short: a healthy battery that is simply flat usually still shows a few volts, even after standing still for a while. A battery that truly measures 0 volts more often points to a fault, for example an internal short circuit in one of the cells. You do not fix that by charging it, but by replacing it.
What is the difference between deeply discharged and faulty?
Deeply discharged means the battery has run flat, for example because a light was left on or the car stood still for weeks. It usually still shows a low voltage, often a few volts. A faulty battery has an internal problem: a shorted cell, dried-out plates, or simply old age. That battery often measures zero or close to zero volts and does not come back, not even with a jump starter or a battery charger.
What does ForceStart do with a deeply discharged battery?
Our jump starters normally detect the battery terminals first before delivering power. That is a safety measure against reverse polarity. With a heavily discharged battery, that detection can sometimes just fail, because the voltage is too low to detect. ForceStart temporarily switches off that standard detection, so the jump starter still delivers power and the battery gets a chance to recover. Use this function deliberately and check yourself that the clamps are on the correct terminals before you switch it on.
How do you know if your battery needs replacing?
If starting still fails after a few attempts with ForceStart, or the voltage immediately drops back as soon as you disconnect the jump starter, the battery is probably faulty. A garage or battery specialist can confirm that with a charger that has a test function. In that case, no jump starter helps, however strong: the battery needs replacing. If you doubt whether the problem really is the battery, also check the alternator and the wiring. A healthy battery that keeps running flat often points to something other than the battery itself.
Can you prevent your battery from deeply discharging yourself?
Largely yes. Do not leave lights or accessories on when the engine is off, and charge your jump starter regularly too, so it is ready to go when you need it. If your car stands still for a longer period, for example during a holiday or storage, even a healthy battery slowly runs down. We go into more detail in jump starter maintenance: charging and storing.
Which jump starter do you choose for a deeply discharged battery?
Choose based on the CCA for your engine, as always. A car with a regular petrol engine is well served by the Boost Mini 3750 (620 CCA). If you expect to deal with a deeply discharged battery more often, for example with a car that is driven rarely, a model with ForceStart and some extra reserve, such as the Boost Pro 8250 (960 CCA), is a good choice.
| Feature | Deeply discharged battery | Faulty battery |
|---|---|---|
| Voltage | low, often still a few volts | often zero or close to zero volts |
| Cause | a light left on, long standstill | internal short circuit, old age |
| Fixable with a jump starter | yes, often with ForceStart | no |
| Next step | charge, then just drive | have it tested and replaced |
- Starting power: 960 CCA, with ForceStart for a deeply discharged battery.
- Capacity: 16,000 mAh, good for several starts per charge.
- Extras: power bank, flashlight, and a 3.7-inch LED screen.
Frequently asked questions
Can a jump starter start a 0 volt battery?
Usually not right away. A battery at a true 0 volts often points to a fault, and a jump starter cannot fix that. If there is still some low voltage, ForceStart can help.
What is the difference between a deeply discharged and a faulty battery?
A deeply discharged battery usually still reads a few volts and recovers with charging. A faulty battery often measures zero volts due to an internal problem and does not come back.
What is ForceStart?
ForceStart temporarily switches off the standard detection of the battery terminals, so the jump starter also recognizes a battery below the normal voltage threshold and still delivers power.
How do I know if my battery needs replacing?
If starting fails after a few attempts with ForceStart, or the voltage drops back immediately after disconnecting, the battery is probably faulty. Have it tested at a garage or battery specialist.
Which AutoXtreme jump starter has ForceStart?
The function is built into our jump starters for starting deeply discharged batteries. Otherwise, choose based on the CCA your engine needs.
