Portable jump start units and booster packs

I have a DieHard 750 Portable Power jump starter & DC power source. It is a 12V 12Ah rechargeable unit with permanently attached 8-gauge cables with clamps on the ends. The cables are only 18" long, so you must connect the clamps directly to the posts on the battery you are boosting. You cannot connect the negative clamp to an unpainted metal surface away from the battery because the cable isn't long enough.

However, the unit has an ON/OFF switch. So... If the cables are connected prior to switching the unit ON, does that eliminate the risk of spark (and ignition of battery gases)?

I've also considered extending the length of the cables by using a separate set of jumper cables. Would that be a safe solution, provided I use 8-gauge (or better) cables?

Reply to
toronado455
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You can just put a multimeter between the cable clamps on volts and on amps to see if there is any current. The switch should be a safety or they would have made longer cables.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:
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Reply to
Mike Romain

You mean you think there could be current when the switch is OFF? Is that why you think I should test it with the multimeter?

Reply to
toronado455

That would be the only way it could spark when you connect it up. If the switch causes an open circuit, no issues. You can double check with the multimeter to set your mind at ease.

I would do that. I 'had' a battery explode in my face when disconnecting it after a charge. Once was way more than enough thanks, I still carry the scars.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:
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Reply to
Mike Romain

I bought my wife the Black & Decker VEC010BD (by Vector Automotive). It's got an on-off switch and an advertised 300 amps. I tried using it last night. I tried a bunch of different ways of connecting (none were final connection to ground post with switch on). I did get it to spark when making a final connection near a grounding wire clamp screw. When I finished the connection with the on-off switch it didn't spark.

It didn't start the car (Honda Civic LX) either, although I was able to use it the previous day when the lights weren't turned off. I think the previous dead battery incident coupled with brief driving (didn't really charge the battery) and another "forgot to turn the lights off" incident probably meant little charge left. I was able to use one of my Schumacher Mity-Mite jump starters (no power switch though) and it started it up the first time with the negative to the grounding wire screw.

So as a recommendation, I'd say don't get the VEC010BD, which I got for $35 at Wal-Mart. I thought it was a deal (also came with a 12V charging plug to charge the battery from the car and keep settings when replacing the battery. It's rather lightweight, which seems to mean it doesn't have enough to start a car unless you're just barely under the point where your battery won't crank the engine. There are larger B&D/Vector jump starters, as well as others including my heavier Schumacher Mity-Mite (I think they have a newer version with a different name - Instant Power?).

With the Schumacher unit, I've gotten desperate a few times (wouldn't start when connected away from the battery) and made a final connection at the battery's ground post, but I saw no spark. Probably stupid of me but I didn't know what else to do. I did turn my face away just in case. I think in a real worst case scenario and I'm at home, I could connect two (from different cars) in parallel with the ground away from the battery.

Reply to
y_p_w

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