How car jump starters work?

Question

I would like to know how those commercially available jump starters provide hundreds of cranking amperes to start cars?

Simply, what is the electronics behind this?

Here is an example jump starter:

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Any explanation / hint would be very much appreciated.

Thanks, Mike

Phil Allison · Accepted Answer

**  Another Groper ......**  It weighs 20 pounds .    It comes with a charger.....    Hint ,  hint    ????........  Phil

Joel Kolstad · Answer

They have a battery inside of them! A brick-sized battery can easily provide

100 amps for a little while (typically it'd be something like a 12V, 2Ah battery, which will provide 100A for about 1 minute... and that's only if the car's battery is completely dead).

I've never taken one apart, but I believe it's just some simple charging circuit and probably a good-sized Schottky diode to prevent incorrect hookup.

Phil Allison · Answer

"Joel Kolstad"**  From the size and weight ( 21 pounds) of the unit,  SLA battery of about 18 AH is more likely.At circa  $31  it comes well within the cost too........ Phil

Stanislaw Flatto · Answer

- a well charged battery, for the few seconds till the motor starts (or NOT). Won't work if your original battery developed a short!StanislawSlack user from Ulladulla.

zwsdotcom · Answer

The battery is connected directly to the outside world on the alligator clips; you connect it up wrong, you fry...

The complexity of the charge circuit depends on the product model. Some of them have a simple LED state-of-charge indicator and these models tend to have slightly more complex charge circuits. These products are designed to be plugged into AC longterm, and as such they are float charge circuits - typically an adjustable regulator (TO-220 package, like an LM317) and a current-limiting resistor.

John - KD5YI · Answer

A diode can't prevent incorrect hookup.

Spehro Pefhany · Answer

Four can. Best regards, Spehro Pefhany-- "it's the network..."                          "The Journey is the reward"             Info for manufacturers:  software/hardware/analog  Info for designers:

Jim Thompson · Answer

Or some variation of....or                                        ...Jim Thompson-- |  James E.Thompson, P.E.                           |    mens     ||  Analog Innovations, Inc.                         |     et      ||  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    ||  Phoenix, Arizona            Voice:(480)460-2350  |             ||  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  ||                  |    1962     |             I love to cook with wine.      Sometimes I even put it in the food.

How car jump starters work?

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