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What to do when your starting battery is flat.


As the old TV commercial for blokes’ undies said: ‘One day you’re going to get caught, with your pants down’. The 4WD equivalent is jumping aboard for a day’s bush drive, to find that your starting battery is ‘dead.’



There’s nothing quite so depressing as dim dash lights and a dull ‘click’ from the starter motor solenoid, indicating a severe lack of engine cranking amps.  Should that happen, you have several options.

Option one is using your auxiliary battery as a booster, either by switching its isolation system, or via a pair of jumper leads.

Option two is attaching jumper leads to a donor battery in another 4WD in the convoy.

Option three is using a portable jump-starter kit.

Smart bush travellers have the ability to use any one of these three options.

In the OTA 75 Series we have an under-bonnet, lead-acid ‘marine’ auxiliary battery that combines high cranking power with some deep-discharge capability. It runs a 30-litre beverage fridge from the alternator when we’re driving and is charged by solar when we’re camped, but it has the same cold-cranking-amp capacity as our starting battery, so it’s a good backup volt box.

We carry a set of long, truck-rated jumper leads, with inbuilt circuit protection.

We also carry a 1200-amp, compact Projecta Intellistart lithium-ion, jump-starting battery unit. It retains change almost indefinitely – at least a year – so an annual charge ensures it’s always ready for an emergency. It also has an inbuilt torch and USB ports, so it’s handy camp-power backup for electronic devices.

This backup trio ensures we can always get started, even if the main battery is dead.

A backup battery and jumper leads are pretty much in everyone’s ‘must carry’ kit these days, but a portable jump starter is not an automatic inclusion. We’ll look at the available types.


Portable jump-starters

In the olden days the only jump starting source was another starting battery. A battery or two was commonly seen on small hand trucks in used car yards, where they could be wheeled quickly between non-starters.

The next step was a much more portable dry-cell battery pack that was more compact, but very expensive, so not many people went down that route.

The arrival of compact lithium batteries changed the jump-starter scene, permitting the design of small, charge-retentive packages that were easy to pack away in any vehicle. Pricing varied from around $50 up to $1000, depending on amp-capacity. These units also had the ability to charge smart devices.

Most recently, we’ve seen the arrival of non-battery, capacitor jump starters. These jump starters don’t have the long-term charge-retaining capacity of lithium units, but can deliver plenty of cranking amps. Pricing is similar to that of lithium jump starters.


What’s best

As with most high-tech devices, you get what you pay for.  Cheaper units have less current output and will not start a large-capacity petrol engine, let alone a high-compression diesel. Don’t expect a sub-$150 jump starter – either lithium or capacitor type – to start your 4WD engine.

The best jump starters are in the $250 -$1000 range,

A deciding factor may well be the fact that a capacitor type doesn’t hold electrical charge for more than a short time. To jump-start an engine it’s connected to the flat battery and it draws current until it’s charged – a one to three-minute operation, normally. 

Surprisingly, that works, because most ‘flat’ batteries have enough capacity left to change the capacitor bank. An alternative is charging it from another electrical power source, such as an auxiliary battery.

In contrast, a lithium jump-starter retains charge that’s used to provide an instant jump-start. Our Projecta test unit has held full charge for almost a year, without needing topping up.

Because the capacitor type has no internal battery it has almost limitless charge and recharge life. A lithium unit is good for between seven and 10 years, before needing battery replacement.

There are plenty of review videos on they internet, so it’s worth doing plenty of research before you buy.




























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