I recently purchased an Emergency Jump Starter, the kind that connects directly to the battery and frame (I know how to jump start a car safely). I check it with the "test" button monthly, but would really like to be sure it'll work for me when I need it.

Can I just take it to a mechanic, and ask them to hook it up to some kind of tester?

I am NOT a "car guy" kind of guy, and appreciate the help.

Yes they have a tester to check how many amps it can pump out, same one they use to tell you if your car battery is good.

Its just a battery and can be tested like any battery.

I do feel the need to point out that many of these devices can't actually start a car that has a completely dead battery. Think of it more as a battery helper.

Thanks!

That'll be one of the questions I'll be asking, then, is if it can crank the car by itself. I bought it when I was having intermittent starting problems, and it would be working with a low battery in those situations.

Strangely enough, the problem hasn't recurred since I bought it.

(And to whoever/whatever might be listening, that is appreciation, not complaint, I recognize the joy inherent, and am not asking for a demonstration of it's value!)

I would be tempted to disconnect the existing battery and to hook this device to the leads and see how it doe on its own. You need to be careful to avoid shorts and sparks, lead-acid batteries produce hydrogen gas that can burn or explode, but it is pretty simple. Most battery leads can be worked with a 5/18" nut driver.

While the terminals are off I would go ahead and clean the posts and terminals. A wire brush is standard but I've found a green scrubbie from the kitchen to be easy and effective. Once you use it on a lead terminal post I wouldn't use it in the kitchen. And wash your hands. Once clean a little petroleum jelly will help keep the terminals free of corrosion.

In the popular mechanics thread it was claimed that at least one of these jump starter has a 30 volt battery. If this is true you could kill some electronics pretty quick. With the car battery in place, it acts as a HUGE buffer that will suck juice out of the jump starter (whose voltage will drop well below 30v under that massive load). Without the car battery you've just hooked your car electronics to 30 volts, which may or may not be fatal.

The 30 volt claim puzzles me, though. Don't believe it without further checking. A 12 volt battery would make much more sense (to me, at least), in which case it would be safe.

This used to be a bad idea: alternators put out a lot of spikey noise that would kill $$$ engine electronics, but the battery would act as a huge "capacitor" of sorts and smooth out the power. I don't know if this is still the case, but I'd avoid cranking the engine without the car battery in-circuit.

I'm not sure the 30v is right anyway. Had Blast posted it a day I'd suspect a prank. As it is... there may be 30v somewhere inside this thing but not at the terminals.

What I want to get it is a set of jumper cables with a switch in the middle of the cable, so that I can make the connections and then activate the cable while out of harm's way. If the center switch happened to have a voltmeter, fuse, and enough smarts to not allow a backwards connection then so much the better...

Why don't you just buy a spare 12v auto battery, store it in your trunk with some jumper cables, and take it out and recharge it with an inexpensive 120vac trickle charger every month or so?

That's why your last connection is to the frame of the disabled vehicle, and you tap it first to make sure you've gotten it straight.





That's what this is, in a compact, versatile package with a built-in test indicator, permanently attached cables, trouble light, and 12v cigarette lighter and USB sockets.

It will not only start my car when my battery's low, it'll provide an additional 12v power source in an emergency.

I just want to know for sure before I need it that it will do the job.

What I've read so far has just confirmed my decision to skip on these jump starters. They don't work well enough to be reliable, IMO. And the problem they try to solve can be minimized through maintenance and routine. A pound of prevention and all that.


The biggest risk are IMO:
- Charging circuit not charging (mechanical or electric error). Check charging circuit as part of your scheduled maintenance.

- Battery failure: Too old battery. Check and replace. Also part of regular maintenance.

- Every day drive doesn't last long enough to completely recharge the battery. Consider topping up the battery once or a couple of times each winter season.

- Leave the lights on. You can minimize the risks through routine, but someday someone will foul this up. You could consider adding a cut-off switch (at 11-something volts) that supposedly turn off all power drain to save some minimum power so you can start the car. I've seen these in the shape of an extension cord for plugging into your 12v socket. The marketing typically sells them as preventing your piezoelectric cooler from draining your battery.

All in all, I consider myself good enough covered by jumper cables for the rather small risk of battery failure. If the jump starters actually had enough power to start my car with a totally dead battery I would perhaps reconsider.