Bridge car, confused...
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... it is generally recommended not to leave the engine of the donor car running before 'briding' the two cars. I don't see the reason for this and I don't do it like that in practice. I feel safer when the donor car's engine is running so that I don't have to shut down two cars. Is there a technical reason why the engine of the donor car should not run? Thank you very much in advance.
No one wants to hold the end of the cable while it is reeled up by the engine cooler fan of the donor car.
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... it is generally recommended not to leave the engine of the donor car running before 'briding' the two cars. I don't see the reason for this and I don't do it like that in practice. I feel safer when the donor car's engine is running so that I don't have to shut down two cars. Is there a technical reason why the engine of the donor car should not run? Thank you very much in advance.
There is no perfectly 'right' answer, and it depends on the state and type of the two car batteries, and the quality/capability of the alternator on the 'better' vehicle. Historically, the main issue was that the alternator diodes would 'blow' during the jump-start if the donor car was running. The surge current into the dead car's starter was too high, especially with good jump-lead connections. You also need the donor car and it's battery to have enough capacity when the two vehicles are initially connected (both vehicles off, mediocre donor trying to feed large dead battery could result in two nearly dead batteries, sigh). Then there a lot of 'safety' choices as to which leads to connect securely first, and what happens when a lead slips, hence it's normal to connect the two chassis last (little chance of failure and short circuit at this stage, compared to slipping of the power terminal). That said, on larger modern vehicles the alternator diodes now have good capacity (see articles/ videos [e.g. merlin's garage] on using them as welders!) so blowing the diodes on those beasts is less likely. Finally, just because there's a lovely big terminal next to the battery's negative, doesn't mean it is actually a secondary chassis connection. On my car it's the common point for the positive connections - Oops.
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I have 2 cars and 1 truck. I keep rechargeable lithium jump boxes in each. They keep enough charge to work for quite awhile (I have not had one fail for lack of keeping a charge, in fact I have the same one work twice without a recharge). They each have small jumper cables which are very safe to attach. Once attached, power it on and then start your car. Has worked for all 3 vehicles in the 3+ years I have had them. If they don't then you can look for a donor car. Not exactly cheap, but worth it to not need a donor car. We have hot summers but does not an effect on them). Don't know about cold weather. I do know you want to charge them in ambient conditions. They charge with USB cable adapter in AC outlet. They could probably be charged from inside the car with USB port to 12VDC adapter. NEXPOW Car Jump Starter, 1500A Peak
"A little time, a little trouble, your better day" Badfinger
100% agree with the jump pack. I have a RAV4 Hybrid with some jinky software that drained the 12V when off in the early days (OTA updates fixed it eventually). The jump pack keeps me from having to find a donor when it randomly decides to stop. I've even jumped a full size pickup from it.
Hogan
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... it is generally recommended not to leave the engine of the donor car running before 'briding' the two cars. I don't see the reason for this and I don't do it like that in practice. I feel safer when the donor car's engine is running so that I don't have to shut down two cars. Is there a technical reason why the engine of the donor car should not run? Thank you very much in advance.
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100% agree with the jump pack. I have a RAV4 Hybrid with some jinky software that drained the 12V when off in the early days (OTA updates fixed it eventually). The jump pack keeps me from having to find a donor when it randomly decides to stop. I've even jumped a full size pickup from it.
Hogan
last year I had 2 batteries (1 for car and 1 for truck) go bad the same day. what are the odds. They would not hold a charge. Jump packs came to rescue. I bought them both at the same time and still had some refund credits. (3 year warranty). Turns out they came from same batch of batteries from manufacturer. Some sort of factory defect no doubt.
"A little time, a little trouble, your better day" Badfinger
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I miss manual transmissions: 1) Get in the car, turn the key to On. 2) Push in the clutch, put the car in gear. 2) Have friends push your car. 3) Let clutch out to engage transmission, engine turns over and starts.
That only works if the car DOES HAVE a clutch... nowadays is not granted anymore
M.D.V. ;) If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about? Help me to understand what I'm saying, and I'll explain it better to you Rating helpful answers is nice, but saying thanks can be even nicer.
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I miss manual transmissions: 1) Get in the car, turn the key to On. 2) Push in the clutch, put the car in gear. 2) Have friends push your car. 3) Let clutch out to engage transmission, engine turns over and starts.
My first car was fitted with a crank. Never used it though, pushing easier.
>64 Some days the dragon wins. Suck it up.
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That only works if the car DOES HAVE a clutch... nowadays is not granted anymore
M.D.V. ;) If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about? Help me to understand what I'm saying, and I'll explain it better to you Rating helpful answers is nice, but saying thanks can be even nicer.
On manual transmission cars? Well, I can easily see that you could replace the mechanical speed stick with, say, a pushbutton panel giving input to some microprocessor managed clutch and gearbox movements. I just haven't seen it yet. I wouldn't want it, though! I've been driving so much on (very) slippery ice that I demand a mechanism that sets the wheels free rolling so I can regain control over the car when it has lost the grip. (If your automatically controlled shift has an option for that, then you do have a clutch, perfectly usable for the purpose discussed here. It just has a user interface different from a pedal.)
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My first car was fitted with a crank. Never used it though, pushing easier.
>64 Some days the dragon wins. Suck it up.
If the car is located on a flat, clean road: Maybe. If the reason why the battery is dead is that you have just dug your car out of a meter of snow, where it has been sitting since September and the battery didn't take the cold well, then pushing the car up on the road may be quite a task!
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No, quite the opposite. When you try to start a second car from the donor's battery it will draw maximum current. And you can drain the battery within just a few seconds if not careful. So always start the engine of the donor car first, so the alternator helps to keep the battery protected. You really do not want two cars with flat batteries at the same time.
Richard MacCutchan wrote:
And you can drain the battery within just a few seconds if not careful.
Eeeeh ... My battery has a capacity of 65 Ah. To drain it in one hour, you would have to draw 65A. To drain it in 3 seconds, 1/1200 hour, you would have to draw 78,000A. At 12V, that is 936 kW - almost a megawatt. Of course that wouldn't be possible. Long ago, I worked with a company making minicomputers. They bought 5A/150A power supplies from a subcontractor claiming that they were shortcut safe. So they tested if it was true: Held a large screwdriver across the poles. The power supply survived, but not the screwdriver: It melted, and they had to cut it away from the poles with an angle grinder. I can't imagine what 78,000A would do, and I wouldn't want to stand close when it is tested. (Actually, the thought of 78,000A scares me a lot more than the thought of 78,000 V!)
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Richard MacCutchan wrote:
And you can drain the battery within just a few seconds if not careful.
Eeeeh ... My battery has a capacity of 65 Ah. To drain it in one hour, you would have to draw 65A. To drain it in 3 seconds, 1/1200 hour, you would have to draw 78,000A. At 12V, that is 936 kW - almost a megawatt. Of course that wouldn't be possible. Long ago, I worked with a company making minicomputers. They bought 5A/150A power supplies from a subcontractor claiming that they were shortcut safe. So they tested if it was true: Held a large screwdriver across the poles. The power supply survived, but not the screwdriver: It melted, and they had to cut it away from the poles with an angle grinder. I can't imagine what 78,000A would do, and I wouldn't want to stand close when it is tested. (Actually, the thought of 78,000A scares me a lot more than the thought of 78,000 V!)
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... it is generally recommended not to leave the engine of the donor car running before 'briding' the two cars. I don't see the reason for this and I don't do it like that in practice. I feel safer when the donor car's engine is running so that I don't have to shut down two cars. Is there a technical reason why the engine of the donor car should not run? Thank you very much in advance.
Yes, if the donors engine has just been started the regulator of the alternator will run at max power to recharge the battery. If you at that moment connect another drained battery the there will be a power surge before the regulator adjusts that might fuse the diodes on the alternator.
Wrong is evil and must be defeated. - Jeff Ello
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On manual transmission cars? Well, I can easily see that you could replace the mechanical speed stick with, say, a pushbutton panel giving input to some microprocessor managed clutch and gearbox movements. I just haven't seen it yet. I wouldn't want it, though! I've been driving so much on (very) slippery ice that I demand a mechanism that sets the wheels free rolling so I can regain control over the car when it has lost the grip. (If your automatically controlled shift has an option for that, then you do have a clutch, perfectly usable for the purpose discussed here. It just has a user interface different from a pedal.)
Automatic has "N" (Neutral), but it still is not the same. In most (if not all) automatic shift, you have to press the brake in order to be able to change to "R" (reverse) or "D" (forwards). And in the moment you press the brake, then most of the effords of your pals pushing the car get wiped.
M.D.V. ;) If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about? Help me to understand what I'm saying, and I'll explain it better to you Rating helpful answers is nice, but saying thanks can be even nicer.
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Automatic has "N" (Neutral), but it still is not the same. In most (if not all) automatic shift, you have to press the brake in order to be able to change to "R" (reverse) or "D" (forwards). And in the moment you press the brake, then most of the effords of your pals pushing the car get wiped.
M.D.V. ;) If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about? Help me to understand what I'm saying, and I'll explain it better to you Rating helpful answers is nice, but saying thanks can be even nicer.
Sure, cars with automatic transmission don't have a clutch. They never had! Ed Kautz, who I responded to, started his post saying "I miss manual transmissions:". It is certainly true that far more cars have automatic transmission nowadays - that is exactly what he is bemoaning. I did own an automatic transmission car for a few years, a rather strange one, a DAF66 with "variomatic" continuous variable transmission. Nice in summer, terrible in winter with slippery roads (even with studded tires). I decided never more to buy a car without a clutch (or another mechanism for setting the wheels free-running when skidding).
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Richard MacCutchan wrote:
And you can drain the battery within just a few seconds if not careful.
Eeeeh ... My battery has a capacity of 65 Ah. To drain it in one hour, you would have to draw 65A. To drain it in 3 seconds, 1/1200 hour, you would have to draw 78,000A. At 12V, that is 936 kW - almost a megawatt. Of course that wouldn't be possible. Long ago, I worked with a company making minicomputers. They bought 5A/150A power supplies from a subcontractor claiming that they were shortcut safe. So they tested if it was true: Held a large screwdriver across the poles. The power supply survived, but not the screwdriver: It melted, and they had to cut it away from the poles with an angle grinder. I can't imagine what 78,000A would do, and I wouldn't want to stand close when it is tested. (Actually, the thought of 78,000A scares me a lot more than the thought of 78,000 V!)
Just a thought...perhaps just problem with historical problems and exactly what problems might occur? Certainly at one point in time with a gas engine in a car when attempting to jump it from another gas engine car if you did it incorrectly you could at a minimum damage at least the electrical system of one car. That did include destroying a battery which of course would seem like it had 'drained' in seconds. So perhaps that is what was seen? I would suppose that it is possible that, at least with older EV batteries, that it might have been possible to destroy them also.
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On manual transmission cars? Well, I can easily see that you could replace the mechanical speed stick with, say, a pushbutton panel giving input to some microprocessor managed clutch and gearbox movements. I just haven't seen it yet. I wouldn't want it, though! I've been driving so much on (very) slippery ice that I demand a mechanism that sets the wheels free rolling so I can regain control over the car when it has lost the grip. (If your automatically controlled shift has an option for that, then you do have a clutch, perfectly usable for the purpose discussed here. It just has a user interface different from a pedal.)
trønderen wrote:
I wouldn't want it, though!
I know some construction workers and for years they would agree with that but more recently... "Things to Consider When Purchasing New Dump Trucks[^] "The automatic transmission eliminates the wear and tear of the clutch of the manual and automated transmission, and it is the easiest to drive, making it less fatiguing for the driver or operator. It also allows the driver to keep their eyes on the road and hands on the steering wheel, increasing safety. Additionally, the automatic transmission actually increases the engine torque in first gear to make the truck perform better when operating off-road and in soft soil conditions. Finally, these transmissions are more often the driver’s personal preference, making recruiting and retaining good drivers easier." If I looked it up right it costs $10,000+ to replace the transmission on one of those. And as a work truck that is something that end up getting replaced. Perhaps several times. So extending the life time might be a good idea. Also as a thought a standard dump truck has between 10-18 gears. Probably with that many getting it right all the time is unlikely.
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trønderen wrote:
I wouldn't want it, though!
I know some construction workers and for years they would agree with that but more recently... "Things to Consider When Purchasing New Dump Trucks[^] "The automatic transmission eliminates the wear and tear of the clutch of the manual and automated transmission, and it is the easiest to drive, making it less fatiguing for the driver or operator. It also allows the driver to keep their eyes on the road and hands on the steering wheel, increasing safety. Additionally, the automatic transmission actually increases the engine torque in first gear to make the truck perform better when operating off-road and in soft soil conditions. Finally, these transmissions are more often the driver’s personal preference, making recruiting and retaining good drivers easier." If I looked it up right it costs $10,000+ to replace the transmission on one of those. And as a work truck that is something that end up getting replaced. Perhaps several times. So extending the life time might be a good idea. Also as a thought a standard dump truck has between 10-18 gears. Probably with that many getting it right all the time is unlikely.