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| Thread ID: 80785 | 2007-07-05 05:25:00 | 12v Jump Starters. | Cicero (40) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 565989 | 2007-07-06 03:03:00 | I query the need for 900 amp jump start cables, that amperage seems just a bit over the top unless you are trying to crank over a diesel truck, I would suggest 200 amp would be more than adequate. Assuming you are going to jump off a modern car with printed circuit boards, it would be a good idea to invest in one with built in surge protection, no point in cooking expensive electronics. | KenESmith (6287) | ||
| 565990 | 2007-07-06 03:50:00 | Bigger cables are better than small ones. Every milliohm costs 1/10 of a volt when 100 amps goes through it. 900 amp cables don't magically cause 900A to be forced into the recipient vehicle. The gel battery in one of these units is only 17Ah or so. The maximum output current is "100 amps for 5 seconds" for the ones Jaycar sell. When used to jump start a car, you will be relying on it to put some charge into the main battery. Then during the start, the current is mostly coming from the (lower impedance) main battery. Surges aren't a problem: the maximum voltage is that of this portable battery. It's very different from connecting the electric system of another car. Such a unit is useful: if it's used as a power source frequently (for a computer, etc.) if it's always kept charged. if it's in the car when it's needed. (This often means that it's not fully charged always). if it's not used too often. (And if the car isn't too hard to start . Gel batteries don't last long if they are run down too much.) It's a good idea to not leave the lights on. |
Graham L (2) | ||
| 565991 | 2007-07-06 03:59:00 | Bigger cables are better than small ones. Every milliohm costs 1/10 of a volt when 100 amps goes through it. don't forget most of them loose a lot at the clamp join. cheap clamps and crappy crimped connectors loose a lot, often its better to make your own cables. |
tweak'e (69) | ||
| 565992 | 2007-07-06 06:22:00 | I think we can assume light are not left on deliberately. | Cicero (40) | ||
| 565993 | 2007-07-06 06:40:00 | Has anyone ever autopsied the cables sold as "400 amp" jumper cables? They have (at most) a 2mm cross section flex and LOTS of insulation to make them look heavy duty. I suspect the jump starter cables would be similar. When I last had to jump start a colleague's diesel ute, the "400 amp" jumper leads got very hot very quick and would not carry anything like the power needed to even try to operate the starter. Left my car running for 15 minutes while jumpered to his battery, dual (parallel) sets of leads were needed to get enough transferred to his battery before it would start. Cicero, join up with the AA (the Automobile Association, not the "other AA") and call them when it happens? Both our cars have reminder alarms if you leave the light on, plus LED interior lights that don't flatten the battery if left on. |
godfather (25) | ||
| 565994 | 2007-07-06 06:53:00 | I bought a similar packaged battery from the Warehouse some time ago, godfather . The cables I removed (because I didn't want the unit for starting cars) were fairly solid . The copper was (from memory) bigger than 19 mm^2 cable . "Jumper cables" are a different category, and I'm sure that many are total rubbish . But I assume that there will be packaged batteries with economical cables, too :D The "900 amps" is probably a little optimistic, too . A 1000 A analogue meter will probably overshoot to near full scale for a very brief time when the starter operates . But no car starter will require a steady 900A for even a second, so it doesn't matter . ;) Don't despair, godfather . As the price of oil rises, plastics will become so expensive that it will be cheaper to use more copper and less plastic . :thumbs: |
Graham L (2) | ||
| 565995 | 2007-07-06 07:17:00 | Have you checked the price of copper lately though? I built an 80 amp LV AC supply, fed by a variac. I needed a couple of metres of high current cable, so though - use the "400 amp" jumper lead cable. Hence the discovery. Bought some monster audio cable then, it works just great. A few turns on a 160 Watt toroidal 230v primary transformer, fed by the variac. |
godfather (25) | ||
| 565996 | 2007-07-06 15:00:00 | Good to see you two had a opportunity for a nice tech talk,meantime will stay with using other cars battery,and use my rather expensive charger to keep things in order. | Cicero (40) | ||
| 565997 | 2007-07-06 15:54:00 | I bought a similar packaged battery from the Warehouse some time ago, godfather . The cables I removed (because I didn't want the unit for starting cars) were fairly solid . The copper was (from memory) bigger than 19 mm^2 cable . "Jumper cables" are a different category, and I'm sure that many are total rubbish . But I assume that there will be packaged batteries with economical cables, too :D The "900 amps" is probably a little optimistic, too . A 1000 A analogue meter will probably overshoot to near full scale for a very brief time when the starter operates . But no car starter will require a steady 900A for even a second, so it doesn't matter . ;) Don't despair, godfather . As the price of oil rises, plastics will become so expensive that it will be cheaper to use more copper and less plastic . :thumbs: Don't be confused by the term "jumper cables" . There are big differences in the concept . "Jumpers" are, really jumper cables and as such should be able to crank a vehicle without it having a battery at all . Real tow trucks have them . . . they are 0 or 00 gauge multi-stranded copper and will start just about anything . "Booster cables" are just the cheap things people buy and throw into their trunk for that rainy day when they find their battery is dead . . hoping the cables don't melt or the ends fall off from poor design and lousy crimping in thin metallic alligator clips . The wire usually has 4 or 6 strands and very stiff and cumbersome . The sheath is usually vinyl and melts when the wires get hot because the wires are 10 or 8 gauge and I wouldn't use them to light a headlamp without fear . Junk is as junk does <Forest Gump> |
SurferJoe46 (51) | ||
| 565998 | 2007-07-08 20:35:00 | Yes years ago I bought a set of jumper cables (booster cables ?) cos they were cheap - the ones next to them on the shelf were much dearer. I have had to use them several times over the last 15 years and they NEVER work. So I have to get a friends jumper cable set and it always works. So thing jumper cables (not sure what wattage) are useless - they should not really be sold. (But I suppose it is "let the buyer beware") Regards Digby |
Digby (677) | ||
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