Author Options:

Portable jump starter dead after two time used this is the second one Answered

Hello all new to the form. Every time I looked to fix or build something out of something else this website kept popping up all the time so I joined. Okay here's my issue I bought a jump start pack from AutoZone never did any research or anything just went and bought the cheapest one okay well I got a couple of use out of it before someone in my family busted it and I didn't want to replace the battery inside it so decided to buy another one now the second one I have no idea what happened it wouldn't hold the charge I was pissed well still am. Well I got to thinking is there any way to replace the battery and just wire it up to a wall


The forums are retiring in 2021 and are now closed for new topics and comments.
Jack A Lopez
Jack A Lopez

1 year ago

It is never fun to have things that seem to keep breaking, and maybe it is worse when you get the feeling you are throwing good money after bad.

So your recent experiences with failing jump starter appliances, have led you to ask, if the power a battery supplies, for turning a starter motor, could instead be supplied by mains power, that comes out of a wall receptacle.

"is there any way to replace the battery [of the jump starter gizmo] and just wire it up to a wall [?]"

I believe there is a way, and I believe the usual way this is done, is with a gizmo called, "battery charger starter."

Or it might be called "battery charger with jump start." Or there might be a slash between the words "charger" and "starter", as "charger/starter," to sort of say, well, it can do either of those functions.

Essentially this gizmo is a charger for a 12 volt, lead acid, battery, but with the capability, at the turn of a knob or flip of switch, to actually supply enough current to make a starter motor turn.

Actually the various modes of the "charger/starter" are different only in the magnitude of the current supplied (measured in amperes). Some typical numbers for these modes:

1-2 amperes, is for slow charge, or "trickle" charge

10-40 amperes, is for fast charge

200 amperes, is for engine starting

Of course the engine starting mode, is the most powerful, most special, most scary, mode this gizmo can be set to. Usually the manual that comes with the "charger/starter" has some words explaining this special mode, including warnings about only using this mode for a few seconds at time; i.e. the time needed to start an engine.

The other notable characteristic of the charger starter, is its shape. Typically it looks like a black box, with two wheels under it, and a big vertical handle on the back, for tilting it, for pushing it around the garage.

Link to images of "wheeled car battery charger starter"

The reason why that shape is common, is because the traditional design for this gizmo required a big heavy transformer, and this shape provides a way to drag such a heavy thing around, at least as far an extension cord will reach.

Actually, I guess that is the other notable characteristic of this gizmo. It has a cord, with a plug, for mains power, on one side, and a pair of thick cables, leading to two big aligator clips, to be connected to car battery, on the other side.

Essentially it is a power converter. It converts mains power (e.g. 50 or 60 Hz AC, at 110 V AC or 220 V AC) to DC voltage in the range of around 12 to 20 V DC, at currents I mentioned previously (ranging from around 1 A (for "trickle" charge) to around 200 A (for engine starting).

Anyway, I think this is the, uh, tricky part, for building a power supply capable of starting a car. Large current is needed, typically in the range from 50 A to 200 A. Exactly how much current, and how much time, in seconds or fractions of a second, depends on the starter, and how much work it needs to do turn the engine enough to get it started.

Also, as you have probably already guessed, for battery powered car, jump starting, gizmos, no power converter is needed, because the battery already supplies approximately the right voltage (around 12 to 20 volts DC), and the big current (50 A to 200 A) too.

I guess there are other things that can go wrong too. Sometimes there is a switch, a big beefy switch (capable of switching 50 to 200 A) , or relay, or maybe like 10 small relays wired in parallel, plus some sensors and logic, with the goal of connecting the big current at just the right time, i.e. when the starter motor is wanting it. If the jump starter you are using has some of those things {switch, sensor, logic} then perhaps its battery can be good, but those other things are causing problems.