If you only ever need to jump-start your car at home, then a plug-in charger/jump starter unit is a good choice. Otherwise, look at self-contained jump boxes.
Plug-In Jump Starters and Chargers
Most trickle chargers provide between 2 and 10 amps and have multiple settings. It’s typically better for battery life to provide some or all of the charge at a slow rate via lower amperage, but it isn’t always convenient to wait around for a 2-amp trickle charger to do its job. Some battery chargers have a Start setting that delivers a higher amperage. Depending on how dead the battery is, you may be able to turn on the charger, select the Start setting, and immediately crank the engine. The main benefit of buying a plug-in jump starter/battery charger is the charging part of the equation. Although the instant start you get from the Start setting of some chargers or a jump box is convenient, it isn’t great for your charging system. Since modern alternators aren’t designed to charge completely dead batteries, forcing one to do so can shorten its effective life span. If you have a charger on hand, and you can wait a while for it to do its job, waiting may save you a costly alternator repair bill down the line. The main drawback of plug-in units is that they have to be plugged in. Although some plug-in starter/charger units are small and portable, they don’t work if you can’t find somewhere to plug them in. If you decide to get a plug-in unit, look for one with features such as:
Multiple charging modes (6V or 12V, for example)Multiple amperage settings (2/10/75A, for example)Float charge option
Portable Jump Boxes and Power Packs
The other type of jump starter is typically referred to as a jump box because it is basically a battery in a box. A typical jump box consists of a sealed, maintenance-free battery that is permanently attached to a set of heavy-duty jumper cables. The whole thing is contained in a convenient (typically blow-molded plastic) package. Unlike plug-in units, jump boxes can’t charge a dead battery. However, they are portable and can provide the necessary amperage to start a car that has a completely dead battery. That makes a jump box the best choice for anyone who has to jump-start their car away from home. As long as you choose a unit with a big enough battery and you keep it charged up, you can carry it around in your trunk and never have to worry about being stranded with a dead battery. The downside of using a jump box is that driving around with a dead battery isn’t good for the alternator. If you make a habit of jumping a dead battery with a jump box and then driving around town, you may artificially shorten the life span of the alternator. The problem is that modern alternators require a 12V input from the battery to function properly, and a dead battery can’t provide that. In addition, it takes more work to charge a dead battery than to maintain a charge, and alternators are only designed with charge maintenance in mind. With that said, a good jump box can be a lifesaver, and you can reduce the potential damage to the alternator by driving around with a dead battery as little as possible. If you have a battery charger at home, use it as soon as possible. If not, enlist the help of a friend or neighbor or leave your car with a mechanic to have the battery charged. If you’re not sure why it went dead in the first place, a visit to a mechanic is also a good opportunity to have the charging and electrical systems checked for issues.
Portable Jump Box Features
If you decide to buy a portable jump starter, some of the features to look for include:
Internal battery with high reserve capacity Heavy-duty cables and clamps Air compressors Emergency lights Radios 12-volt accessory receptacles Inverters
Plug-in Jump Starters vs. Portable Jump Boxes
Since plug-in jump starters and portable units each have strengths and weaknesses, you may want to get one of each. If you can only afford one, a portable unit is probably the way to go because you can use it wherever you are. However, pairing a portable unit with a plug-in charger/jump starter means you’ll be able to charge the battery when you get home, which can save you money and headaches in the future.
Making Your Own Jump Box
Since a jump box is basically a sealed lead acid battery with built-in jumper cables, it’s technically possible to make your own. However, buying a jump box is usually cheaper than building one. Some repair facilities build jump boxes by strapping several batteries to a hand truck, wiring them in parallel with heavy gauge cables, and connecting a good pair of jumper cables. This setup provides a ton of reserve capacity, but it isn’t portable. If you want to make your own jump box, the best and safest way is to obtain a sealed, maintenance-free battery with high cranking amps (CA) and cold cranking amps (CCA) ratings, in addition to a battery box big enough to fit it inside. The battery box is an important part of the equation; although sealed lead acid batteries usually don’t leak if they tip over, they can and often do leak due to age, overcharging, and other factors. The last thing you need to make your own DIY jump box is a set of jumper cables. You don’t have to permanently attach them to the battery box, but you can if you want to.
