AA Advice: Do those mini battery jump packs really work?
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Many of us have seen chargers that will jump-start a car, charge a mobile and still fit in a bag or glovebox. If you’ve ever left your lights on or run a battery flat listening to your favourite tunes, this seems like the perfect accessory.
Usually, these jump packs use compact polymer/cobalt battery cells, which take up far less room than a conventional pack.
Typical models might comprise a 400amp unit, for about $200, and a 600amp pack for $220.
A 400amp model would be perfect for four-cylinder petrol models, while a larger 600amp would be suitable for harder-to-start diesel; the higher compression ratio and increased starter motor draw mean that diesel vehicles require a stronger battery to turn the engine over.
What you need to know
Products like these work well when the instructions are followed and the device is fully charged.
However, you could face a few potential issues if instructions are not followed. For example, if the battery is flat, you connect the polarity incorrectly and then use the override function, you can damage sensitive electronic components. The override feature bypasses the built-in safety features on the device.
For occasional use, jump packs from a reputable brand with clear instructions perform well. The only maintenance they require is charging.
They offer other benefits, such as being able to charge mobile devices on the go from the integrated USB charging ports. They incorporate a long-lasting LED flashlight, which is a welcome addition to any emergency kit.
Often vehicles don’t just need to be jump started; a diagnostic check should be carried out to determine what has caused the issue in the first place, and how to prevent another flat battery in the future.
Once you have jump started you’ll be fine, right?
Recharging the car battery using the alternator might seem like the easy solution, but it’s not idea. The alternator is only designed to supply enough power to maintain battery charge level and power the car. It’s a much bigger ask to totally recharge a dead battery, which requires a very high continuous current.
Even taking the vehicle out for a long drive won’t fully charge the battery. The only way to do this is with a proper battery charger.
If your battery is continuously weak and you are just avoiding a full charge or a battery replacement, it could reduce the alternator’s working life and cost you more in fuel and performance, if the alternator is always under unnecessary load.
A weak battery can also prematurely wear the starter motor. As the voltage supplied from a weak battery drops, it requires a higher current to compensate. The starter motor wasn’t designed for the higher current, and you can easily damage it.
If you are unsure of a battery’s condition or the car is turning over more slowly than usual, you can get a load test.