Can a gadget the size of a smartphone really jump-start a car with a flat battery? George Block finds out.
The only thing worse than returning to your car and realising you’ve left the lights on is the dreaded “click-click-click” as the engine turns over but fails to fire.
Previously, your options would be limited to finding a kindly stranger with jumper cables, getting on the blower to AA, or lugging around a bulky portable lead-acid car charger.
However, the falling price and improving energy-density of lithium batteries has given rise to a new type of jump starter, small and light enough to be carried in your pocket or stashed in your glove box. They also have USB ports, so can be used to charge smartphones, and generally retail for between $150 and $250.
The pocket jump starter that has enjoyed the most exposure in New Zealand is the Minimax Charger ($170 including shipping), frequently flogged on daytime television by TV Shop/Brand Developers Limited. We’ve had a mixed run with our recent trials of infomercial products so were sceptical of claims this pint-sized charger could jump-start a flat battery “up to 20 times”.
The Minimax uses a lithium-ion-cobalt battery with a capacity of 8000mAh, enough juice to fully charge an iPhone 6 four times over. Where it differs from a standard power bank is its ability to crank out a starting current of 200-400 amps, which should be sufficient to help a drained battery get your engine running from cold.
But unlike bulky battery starters used by roadside-assist mechanics, the Minimax can only jump-start your engine and lacks the capacity to charge your car’s battery. This means you still have to take the long way home to allow sufficient time (usually about 30 minutes) for the car’s alternator to recharge your battery.
We borrowed a six-cylinder 3.0L petrol station wagon, courtesy of Consumer reader Julian Maskell, as this is the largest engine the Minimax claims to be able to start (it’s not suitable for diesel vehicles). Then, we dropped a lead-acid battery drained to 11.7V into the car, just below the nominal starting voltage of 12V (roughly equivalent to leaving your lights on for a couple of hours).
When we connected the Minimax’s jumper leads to the partially drained battery and turned the key, the engine immediately started. Even more impressive is we then used the Minimax to start the car an additional 21 times, confirming the manufacturer’s claim it can be used to start a vehicle “approx 20 times”.
Next, we replaced the half-dead battery with a completely flat unit showing only 5V across its terminals. For a car battery to get this flat, you’d need to leave your heater and radio running all day or your lights on for several days. Even when fully charged, the Minimax was unable to start our station wagon with this fully dead battery.
Further laboratory testing confirmed that while the Minimax is more than capable of delivering the 200-400 cranking amps needed to start a car with a partially drained battery, it’s unable to deliver the huge boost needed for a completely dead battery.
Valentin Muenzel is an Australian battery expert who runs battery technology start-up Relectrify. He says the lithium-ion-cobalt chemistry used by the Minimax is an established technology used in high-current, rapid-drain batteries, and is typically safe.
Valentin says while there is consumer concern over lithium batteries after the Samsung Galaxy Note 7 recall, that was a unique case there are millions of phones, laptops and electric cars happily using lithium-ion batteries without problems.
However, he did say lithium batteries could be more susceptible to failure if they’re mishandled or overheated, and suggested these tips for prolonging your battery’s life:
Although it’s the most heavily advertised, the Minimax is far from the only compact lithium jump starter/power bank available. Similarly-priced units are available from Mitre 10 ($249, 16000mAh).
While it can’t start your car if you’ve returned from holiday to discover a completely flat battery, the Minimax can handle most dead-battery dramas. It’s also reasonably good value compared to other lithium jump starters on the market, and has sufficient capacity to keep a couple of smartphones going on long trips while still retaining the ability to jump start your car. We think it’s a worthy addition to your glovebox, but hang on to your old jumper cables just in case.
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