Selecting the correct portable starter for your needs doesn’t have to be a time consuming process. Buying one with zero consideration is asking for disappointment however, and there are few key aspects you need to consider to ensure the device will meet the demands of your specific application. Luckily Jump Starter Expert has you covered. Follow this simple guide and you’ll be on your way to finding a jump box in no time at all.
The Difference between Cranking and Peak Amps and How Many Do I Need?
The main consideration when looking for a jump starter is the electrical current your application will require. But before getting into this, an important clarification is the difference between cranking and peak amps, as certain jump starters will only quote one of these values.
Peak amps, as you may imagine, refers to the highest current the jump starter will push out in a short, initial burst when cranking your engine. This is to get the starter motor turning and begin the cranking motion of your engine. This high current kick quickly decays, however, if your motor doesn’t start straight away, towards a value it can deliver more sustainably. This more stable current is then referred to as the cranking current, and is the current the jump starter will deliver if extended cranking of the engine is needed to get things going. The jump starter actually replicates the battery of your vehicle in this respect, which also features different peak and cranking current ratings.
The cranking current is therefore a more accurate measure of the jump starter’s true capability. At times, the initial peak current jolt will be sufficient to get the engine started before the output of the device decays. A more extended crank may be required at other times however, in which case, if the cranking ability of the jump starter is insufficient, you may not ever actually be able to get your vehicle started, no matter how hard you try. Cranking should not continue for more than about 5seconds though and reference should be made to the detailed guide on jump starting your car to get more information on the best way to actually use your jump starter to avoid damage to both your battery and the jump starter itself.
So What Size Jump Starter Do I Need?
It is somewhat difficult to provide definitive values on the cranking currents required by different engines as even there is a wide variation between the multitude of engine designs currently on the market, even with similar cylinder capacities. The following, however, is a rough guide for petrol/gas engines:
- Four cylinder petrol/gas – 150-200A
- Six cylinder petrol/gas – 200-250A
- Eight cylinder petrol/gas – 250-300A
Diesel engines require significantly higher cranking currents than petrol/gas engines of the same size, more than two times that of petrol engines, and so guidelines for diesel engines are as follows:
- Four cylinder diesel – 300-400A
- Six cylinder diesel – 400-500A
- Eight cylinder diesel – 600-700A
So, before purchasing a jump starter, consider “what size jump starter do I need?” Consider carefully the engine size and number of cylinders your vehicle has, and whether your vehicle is petrol/gas or diesel fueled. Then determine the approximate cranking current you will require from the above data and proceed to next important consideration.
What is the Lowest Temperature My Portable Starter is Likely to Be Needed?
As mentioned in the car battery maintenance guide, temperature can have an enormous impact on the performance and lifetime of a battery. In cold climates, a lead-acid battery can lose more than 50% of its cranking current output, which will apply directly to lead-acid battery based jump starters as well (such as the Stanley car jump starter or the JNC heavy duty). Lithium-ion based jump starters (such as the Brightech compact jump starter air compressor and the Volitiger ultra portable unit) show a smaller decrease in performance than lead-acid, but to err on the side of caution, assume they will also lose up to 50% of their cranking current capacity in very cold climates.
Cold climates would be regions where the outside temperature during winter frequently drops well below 20-30°F (approximately -5 to 0°C). In these climates, double the cranking current requirement you found in the guidelines of the first step to ensure that you have enough available if you find yourself stuck on a cold day, which, as you can imagine, is the time you are most susceptible to finding your vehicle battery unable to turn your engine over.
As mentioned in the previous section, jump starter manufacturers often do not report both the cranking and peak current outputs of their devices. The best advice therefore, if only the peak current rating is available, is to definitely not buy a unit with a peak current rating lower than what you determined from the guidelines in the first section with the allowance for the effect of cold temperature in this section (if necessary). This is only asking for disappointment. Purchase a jump starter with the highest peak and cranking current rating your budget will allow, but don’t even bother if the peak current on the unit you’re interested in is lower than what your application might demand.
What Safety Features Do You Need?
Although the use of a portable jump starter is fairly straight forward, there a number of risks inherent in their operation. Below is a list of typical safety features available on jump starters along with their function. Before purchasing a jump starter, check to see that the unit has the safety systems in place that you deem essential, which will depend on your familiarity with jump starting cars, and your general predisposition towards mishaps (:)):
- Short circuit protection – Possibly one of the most vital safety features on a jump starter, as a short circuit can potentially lead not only to serious damage to the jump starter, but also a potential explosion of the battery bank inside the device. Short circuits occur when the jump leads are touched together leading to a very high current passing between the positive and negative terminals. Thankfully, most jump starters have short circuit protection as a minimum, but there are a few that don’t. So be sure to do your due diligence and check before purchasing if you feel you need this feature.
- Over-current protection – limits the current the jump starter will deliver to its peak rated current preventing damage to the device.
- Overload protection – protects the unit from receiving a current higher than the manufacturer’s specification when charging. This may happen during a surge from the mains power feeding the jump starter’s charger.
- Overvoltage protection – prevents too high a voltage from being applied to the unit when charging. Again, this can happen during a mains power surge.
- Overcharge protection – the charging circuits on more basic jump starters will not automatically stop charging the device when the batteries are full. With overcharge protection, the charging circuit will “float” charge the jump starter once full, and won’t keep increasing the voltage applied to the cells, which could then overcharge and destroy the battery pack.
The remaining criteria in this guide are also important considerations, however, the cranking current requirement under the lowest temperature you might need to use your jump starter, and the safety features needed are the primary ones.
Having an air compressor or a manual tire pump with you is possibly as important as having a jump starter and luckily there are a good amount of jump starter air compressor combo units available if you don’t already have a tire pump (e.g. the Brightech compact jump starter and the Stanley multi function).
Any Additional Functionality Required?
Most modern jump starters have many additional features, most common of which are listed below. Although not essential, I personally like my device to have them. Decide whether you would like yours to have them as well:
- Multiple device charging ports – USB for charging phones, MP3 players and tablets; Laptop charger outlets; Other DC voltage outlets for various common devices.
- LED Flashlight – useful for assisting you at night. Often additional lighting modes are also available including strobe lighting and SOS signaling to alert others to your aid.
As this guide shows, choosing a jump starter is a fairly straight forward process, requiring only three key considerations – the cranking and peak current requirement of your application, compensation for low temperature operation, and the safety features you feel are essential for the device to have. Two additional considerations concern whether you would like the device to include an air compressor for pumping your tires and any additional features you feel your device should have. So before buying your next jump starter (or your first), be sure to run through this quick guide, and you’ll any disappointment in your purchase.