Forum Home
PC World Chat
Thread ID: 75430	2006-12-28 23:07:00	What a holiday festival (car related).	Nomad (952)	PC World Chat

Post ID	Timestamp	Content	User
510572	2006-12-29 09:27:00	When you parallel up two batteries, it doesn't matter a toss whether you connect the neg lead to the battery terminal or to an earth. I always use the battery terminal by preference because that gives a lower impedance path and more current for starting. Also, if the battery is flat, it won't be gassing so it is quite safe to connect the leads direct to the dud battery. Always connect to the good battery first, then make the final connection to the flat battery. It should not be hazardous under any conditions, provided that the battery caps are screwed in. They should have a double chamber at the top that prevents flashback anyway. I have connected external supplies to all sorts of delicate electronics over the years and never had a problem, and IMHO the blowing of electronics during jump starting of another vehicle is just an old wives' tale, and even the sparking etc is not going to do any harm unless there is a reasonable sized inductance involved. If anything it might possibly temporarily corrupt any computer involved, requiring a reset, but that would be isolated as well, presuming that the idiots don't try all this with the ignition switch on! All in all there is unlikely to be any problem caused by jump-starting with another battery, except in those instances where the clot doing it has crossed over the polarity. Most electronics today should be protected against that, but I wouldn't count on it. Can't see batteries exploding upwards either, the blast of acid etc would go up, but the battery case would be driven down, though it might shatter and spray acid around. Bear in mind that it is secured by a metal clamp as well so it won't be flying anywhere in a hurry. Urban myth material. :waughh: Now to wait for somebody to tell me their aunt's husband's father's brother in law did it and destroyed a Rolls Royce right in front of its titled owner, straight up, got it right from the horse's mouth. Cheers Billy 8-{) :2cents:	Billy T (70)
510573	2006-12-29 09:30:00	Can't see batteries exploding upwards either, the blast of acid etc would go up, but the battery case would be driven down, though it might shatter and spray acid around . Bear in mind that it is secured by a metal clamp as well so it won't be flying anywhere in a hurry . Billy 8-{) :2cents: It wasnt clamped - being charged with no caps on the cells .	sam m (517)
510574	2006-12-29 09:31:00	Ok, yeah "jumped" the jump start worked. I plugged the earth at the dead car's paint on the side (inside the hood) like a body bracket - which had its blue paint. I will try to plug it elsewhere next time. :)	Nomad (952)
510575	2006-12-29 09:33:00	I once leaped out of a truck that wouldn't start, ran around to where the battery was located, gave it a good kick with my steelcap, and it exploded all over me. Bit of a hardcase. Stuck out in the bush all night, No sympathy from the boss man when he turned up in the moning and saw what I had done.... ......Just needed a tap on the terminal and she would have fired right up.... Muhahahaha. No horses around here, Mouthy or otherwise.	Metla (12)
510576	2006-12-29 09:35:00	Jumped? Do you mean you could successfully start the car? The best place to connect to is actually not the body but the engine block. I usually plug the -ve to a lifting hook on the engine or a large bolt like a head stud or even the alternator bracket (care needs to be taken to ensure jumper cables away from any moving parts like pulleys and fans etc) Yeah could be the paint. Yeah "jumped" - jump start worked. What is a lifting hook on the engine?	Nomad (952)
510577	2006-12-29 09:48:00	Yeah could be the paint. Yeah "jumped" - jump start worked. What is a lifting hook on the engine? Lifting hook was probably bad choice of word. It is just a heavy steel bracket bolted to front / top part of the engine. It normally has a large hole for a "D" shackle to go through it so the engine can be lifted in and out. I usually connect -ve to that because it is definitely earthed and usually sit proud of anything on the engine so easy to connect to.	sam m (517)
510578	2006-12-29 16:43:00	The Automobile Club of America (called AAA) wanted all their tow truck drivers to use a substantial chassis or engine bracket part as the final ground connection for a couple of good reasons, even though there might be some urban legends involved . Usually when a tow truck arrives on the scene of a "dead battery" the club member has tried for a while to get the engine started, totally running what may have been a low charged battery to a fully dead condition . At that point there has been a lot of hydrogen gas generated and the next electrical spark may cause an explosion . So . . . the attachment to a part at least on a different area than directly to the battery is a safety matter . IF the battery should flash off the hydrogen, then at least the driver's eyes would have been looking in a different area and not directly at the battery when or if it happens . Don't say that batteries don't blow up or down or even sideways . . . I have seen a few in all the years I was manager/mechanic for a tow company in Anaheim where we attended to the dead battery calls at Disneyland and Knott's Berry Farm . Investigating the damage was up to me and I had to determine the cause of the explosion . . . most times to the chagrin of the car owner when I told them that the driver had followed all AAA protocols and the fault was in the battery and not the jump starting . I have seen fenders ruined . . . radiators shredded . . . . hoods blown off some vehicles . Most times the tow truck driver was bathed in acid and would use the water cans on the truck to douse himself and call the shop to get help . Sometimes the driver of the vehicle was also innundated with the same acid and shrapnel and the tow driver would share his water to help them too . It wasn't nice . . . and it certainly ruined the final part of a trip to the "Enchanted Kingdom" for a few AAA members . If the owner of the car took his claim to court to recoup for repairs etc, then the judge would always ask if the driver did it right in the first place . . . and if there's a set of rules, urbane or not, then the judge would usually side with the tow company and tell the owner of the car that it was just an act of God in that case and it would have to go to a higher authority for payment . I personally have had the battery caps "pop" off the top of the battery when during the charge something made the pressure get too high . . . but I don't believe it was much of an explosion . . . if one at all . The battery caps are small distilleries . . . designed to condense the water that is driven out of a battery during liberation or storage of electricity . . . that way the water stays in the cells with little loss . This style is especially prevailent on "Non-Serviceable" battery types where the caps are actually sealed and cannot be removed for service . These batteries are supposed to be more cutting-edge in design, but I feel they are also a little more dangerous to the service person as one cannot see if the cells are indeed full of electrolyte and can therefor accept a charge or even be serviceable at all . The last time I had a really pants-wetting explosion from a battery was about 1966 when I was repairing an electric golf cart and somehow the brace that holds the hood up to access the whole electrical panel and batteries, fell across the relay pack . All 8 of the 6-volt batteries either exploded or melted from the fire . I had to get naked to get the acid soaked clothes off of me . . . and the shop owner had a good laugh as he stood there washing me off with the water hose and I stood there in almost freezing water in my one button union suit .	SurferJoe46 (51)
510579	2006-12-30 10:49:00	Usually when a tow truck arrives on the scene of a "dead battery" the club member has tried for a while to get the engine started, totally running what may have been a low charged battery to a fully dead condition . At that point there has been a lot of hydrogen gas generated and the next electrical spark may cause an explosion . Batteries only generate hydrogen when charging, not when discharging, the chemical reaction is different, so a run down battery isn't going to have any hydrogen around . The hazard exists principally during charging when the cells are gassing freely and the caps are off to allow the hydrogen to escape; then you can get a mother of a bang . Finally, if jump starting off another vehicle you connect to the dead battery first, then complete the connections to the donor battery, that way there are no sparks near the flat battery anyway (not that it matters much) . It would be a bit different if using a charger/starter trolley though, then you only have two leads to connect, but a flat battery still isn't going to have a hydrogen explosion . It could however have an internal short, and that might make life exciting when you throw a high current source across it, in fact that may well be the cause of the problem . If anybody cares to come up with the chemical reaction whereby a discharging or dead flat lead acid battery generates hydrogen, then I might change my opinion, but not until . Here's a starter for you ( . mpoweruk . com/leadacid . htm" target="_blank">www . mpoweruk . com) Cheers Billy 8-{) Discharge During discharge, the lead dioxide (positive plate) and lead (negative plate) react with the electrolyte of sulfuric acid to create lead sulfate, water and energy . Charge During charging, the cycle is reversed: the lead sulfate and water are electro-chemically converted to lead, lead oxide and sulfuric acid by an external electrical charging source . Gassing is the production and release of bubbles of hydrogen and oxygen in the electrolyte during the charging process, particularly due to excessive charging, causing loss of electrolyte . In large battery installations this can cause an explosive atmosphere in the battery room .	Billy T (70)
510580	2006-12-30 18:27:00	Who said batteries exploded through a bonnet?? Gas occupies air - a battery has space between the plates and the top of the battery. If flammable gas is in this space and it ignites then an explosion occurs. If the battery is sitting on a concrete floor then it cant go down - it goes up.	sam m (517)
510581	2006-12-30 23:02:00	Billy, you're probably right about the charge - discharge generation of explosive gasses . . but when a tow truck driver arrives at the scene he has little or no idea of what went down with the problem . If the driver got someone to try to "jump" them thru puny and ineffective cables like they sell at cheap-o parts houses, then they might have generated hydrogen gas . . . it's just not worth the risk of trying to play the odds . If the battery had a high resistance to being recharged . . or even frozen by temperatures, then there's always a danger . IF the vehicle for some reason had a very low battery and got jumped and then after the assistance drove away . . and the owner got a wild hair and decided to try to see if the battery's OK now and will work next time . . . and then proceeds to shut the engine off and try to restart it again . . . that's also a possible scenereo for destruction . Just a few minutes of charging a battery by a modern alternator can create a discharge of hydrogen . . . more so if the battery is in a heat-soaked car that's been parked in a blacktop parking lot . . . add dry cells or a bad or shorted plate to post connection and there's a possibility of something going very wrong . Discharging rapidy thru attempts to start the engine or even throwing a wrench across the posts to see if there's life in the battery can however cause a battery to immolate . . . not of it's own, but perhaps a shorted plate or a bad connection from corrosion and poor maintenance caused the failure in the first place . One things for certain . . . never second-guess a customer with his car . . . always assume the worst and be glad when things don't go boom . And something I failed to mention is that modern tow trucks and service vehicles (as designated by AAA) require that the jumper cables have the usual alligator clamps on the receiving end of the jump, but the servicING vehicle will have either a modular jack that is usually affixed in the push bumper area or a full-time connection that is single-throw dual-pole switched to allow the driver to be a distance away from the vehicle being jumped . Remotely switching the power to the cables is just another safety device to help keep the human element out of the formula .	SurferJoe46 (51)
1 2 3