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Can a jump starter start a completely dead battery?
Updated
Often, but not always in the normal mode. Smart jump starters check the battery voltage before they send power, and a battery that is almost fully drained can read too low to detect. Most packs have a manual override or BOOST button for this case. It works by turning some safety features off, so use it with care.
Why the pack says nothing
NOCO's support guide says its Boost packs are designed to jump 12 volt lead acid batteries down to 2 volts. Below that, the Boost LED stays off because the pack cannot detect a battery. The NOCO GBX75 Amazon listing gives 3 volts as its override point, so check your own manual for the exact figure.
How the override works on each brand
| Brand | What you press | What the maker says |
|---|---|---|
| NOCO Boost | Manual Override button, held for 3 seconds | The white Boost LED flashes when override is on. Spark-proof and reverse polarity protection are both off |
| GOOLOO | BOOST button on the smart clamp cable | A blinking green light means battery voltage is too low. Press BOOST, the light goes solid, then start within 30 seconds |
GOOLOO's FAQ adds that no lights and no beep after you connect can mean the battery may be damaged.
Do it in this order
- Look at the battery first. AAA says a cracked or bulging case, or a rotten egg smell, means replace it. Do not jump it.
- Connect red to positive and black to negative or ground. Check both twice. In override mode nothing will warn you if they are backwards.
- Press the override or BOOST button the way your manual says.
- Try to start the engine.
- NOCO says to power the pack off before you remove the clamps, since the protections are off.
When it will not work
AAA notes that a battery with a shorted cell, or one that is simply too old, cannot store energy anymore. A jump sends power but cannot fix that. A single click with bright dash lights may point to the starter instead. If a few tries fail, stop and call for help.
Picks with an override you can read about
- NOCO Boost GBX75: the listing explains the override clearly. Caveat: no wall charger in the box.
- GOOLOO GP4000 and GOOLOO A3: both list a BOOST button. Caveat: owner reports on durability are mixed for both.
A jump starter is not a battery charger. After the engine starts, drive to recharge, then have the battery checked. See jump starter vs jumper cables.
Safety: never jump a frozen battery. Wear eye protection. Override mode removes the protection against sparks and reversed clamps, so follow the manual exactly.