Can you recharge a car battery with a jump starter?

No matter what your make vehicle is, how expensive it was or how new it is, no matter how well it scores on reliability surveys, if it’s got a flat battery, it won’t start, and you have a problem. If you find your battery is flat when out on the road, then a jump starter is the perfect solution. It powers the starter motor to get the vehicle going again, which is when the alternator kicks in to power the vehicle, and also recharge the battery, getting you mobile and avoiding expensive tow fees and the worry and danger of being stranded at the side of the road.

Starting a vehicle with a completely dead battery

But what happens if the battery is completely dead? If it has no charge at all, can a jump starter give it some charge if you leave it connected? It sounds like a great idea, use the jump starter to get some charge, then run the engine to recharge the battery without needing a dedicated charger.

Unfortunately, this doesn’t work. A jump starter works by storing energy within its own battery array, and then releasing it in short bursts to provide enough power to start a vehicle. However, while jump starter can put out high amp levels to provide a lot of power for starting even the largest engines, they are restricted by their own battery capacity in how long they can actually provide that power. Even a very powerful jump starter such as the Lokithor 2000 Amp JA301 cannot provide that power for more than a few minutes. It is enough to start a vehicle, but nowhere near enough to recharge a vehicle battery.

Lokithor 2000 Amp JA301 car jump starter

Understanding Your Battery

Car batteries work in a similar way to your phone battery, in that as they are used the battery charge drains, and they need charging up again to maintain power. In normal circumstances, this happens constantly as you use the vehicle, with the alternator being turned by the engine, powering the electrical systems of the car and recharging the battery at the same time.

If that alternator system fails, or if the vehicle is left unused for a long time, there is extreme cold weather or the battery is old, it may lose charge and fail to start the vehicle. In this case, a jump starter connected to the battery pushes a large current through the system to give the vehicle enough power to turnover and start. But this does not charge the battery itself.

Think about charging a phone, even with todays rapid charging it can take a while for a phone to charge fully. The same applies to your vehicle battery, indeed, even using a dedicated powerful charger, it can be 30 minutes or more before any charge is registered at all. Charging a battery completely can take as much as 8 hours.

A jump starter cannot sustain power output for that long, it simply doesn’t have the power reserves to charge a battery.

The Difference Between a Jump Starter and Battery Charger

Where the jump starter draws power from its own internal battery, making it completely portable and ideal for starting vehicles on the go in an emergency, a battery charger connects to the mains socket in your garage/home. This makes it unsuitable for use on the go, but it is also why it can charge your vehicle battery, as it has a constant flow of electricity to use to charge with.

In use, the charger converts mains electricity into the 12-volt supply batteries need, and it recharges the battery over time. Most in use today have protection circuits that prevent overloading the battery and so on for safety, but all are easy to use. Attach the charger the leads onto the appropriate battery terminals, switch the battery charger on and it will do the rest for you.

Because it doesn’t have to store electricity like a jump starter, it can maintain a supply to recharge the battery for as long as needed. However, a battery charger can be used for more than recharging a battery that has gone completely flat. If you have a vehicle that you only use infrequently, a weekend car for special occasions for instance, then a trickle charger, which works like any other charger but uses a smaller current to provide constant top up as the vehicle stands, can avoid the problem of a flat battery entirely.

Jump Starter or Battery Charger?

The question is, which do you really need, a jump starter or a battery charger? For peace of mind when travelling, the ability to get the vehicle moving rather than be left stranded at the roadside, a jump starter is an essential part of your emergency kit you keep in your vehicle permanently. It should be there with you whenever you use the vehicle, but especially in winter. With a combined jump starter that includes other safety features such as tire inflator, emergency light and so on, you have a compact but comprehensive toolkit to get you out of most situations.

Whether you need a battery charger is a difficult question. Its not portable, designed to be used from a mains electricity supply over a longer period. If you have an older vehicle, or develop some problem that requires the battery to be charged, it is very useful to have around, but in most cases a completely discharged battery will be caused by a problem with the battery itself, and as such a new battery is needed anyway.

The one area where a battery charger is as essential as a jump starter is if you have a vehicle, or more than one, that is not used too often. In this scenario, a trickle charger can save you a lot of time and money in replacing dead batteries and dealing with flat batteries every time you want to use the vehicle.

Both battery chargers and jump starters do important jobs, but one cannot really replace the other. They do very different things, and its important to understand which to use and when for the best results.

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