Here are two things I do because I’m paranoid. First, I use goggles, not glasses (fear of acid in the eyes). Second, before doing anything, I open the hood, and use a bit of cardboard or whatever to swoosh up the air around the battery.
Here’s how I jump-start a car:
[ol]
[li]Connect to the **Positive Terminal **of the dead car[/li][li]Connect to the **Positive Terminal **of the live car[/li][li]Connect to the **Negative Terminal **of the live car[/li][li]Connect to a **metal piece **of the dead car[/li][li]Start the engine of the live car[/li][li]Try and start the dead car, find it not working, then give up a attach the cable to the negative of the dead car[/li][li]Start the dead car.[/li][/ol]
I’m not sure, but I think there may be an issue around step six. I’ve always had terrible luck finding a suitable piece of metal to attach to. There are sheet metal parts, but they’re painted. Frame bits are too thick to clamp to. There are sometimes a bolt head that I try, but I usually give up in frustration and just connect to the battery. Any suggestions?
Also, does revving the engine of the live car do anything? If the dead car won’t start on first try (and you know everything is fine, just the battery is dead), how long to leave them hooked up and the live car running?
I have the same problem with finding metal for the negative connection as well. But even after connecting to the negative post, I have to wait a while to start the dead car. Presumably what’s going on is that the dead battery needs to charge enough to help start the car. Otherwise, I’m trying to pull enough current through the cables to start the car and charge the dead battery.
The car I’ve had to jump is kept outside, and there’s always been at least a small breeze. I’m not sure how much Hydrogen would be able to build up in that situation.
A sidebar question off the OP’s, but… if a battery is connected yet not used, such as in an RV or tractor mower stored over the winter, why should it go dead? Yet, if there is no circuit, (i.e., disconnected) the battery has longer life? Either way, isn’t there only a potential with no current? Or, does the very fact that a circuit exists create a very small current at all times, if only in milliamps? Perhaps, the very resistance of the wiring of the circuit itself creates the current? If not, what then is the difference?
For mowers or tractors, the drain when the device is off is probably zero (or pretty close to it), so leaving the battery connected isn’t going to make it last much longer than disconnecting it. Cars are a different story - there is quite a bit of drain when the car is “off” (alarms systems, the radio, various electronics). In fact, VW had to provide solar chargers to New Beetle owners, because their batteries were going dead when the car was left sitting for only a short time.
Are there consumer versions out there just powerful enough to keep one alive? Fest Vangoes into hibernation in the fall, and her winter quarters are about 150’ down the driveway–too far from the garage to keep a trickle-charger or to lug the battery back and forth every time we want to move it a few feet to ease pressure on her tires.
Hydrogen is so light that it just floats away. And it’s so light that hydrogen gas has hardly any hydrogen in it, so it has hardly any energy in it. So hydrogen is a relatively safe gas – much safer than LPG or Town Gas or Natural Gas or Propane or almost anything used for fuel.
BUT
you will of course have hydrogen trapped at the top of the cells, and this will take some time to leak away: if sparked, this will blow the battery apart. AND
You can also boil the battery acid, causing it to convert to steam, and blow the battery apart.
So the conclusion is still the same: you don’t want any sparks around batteries, and you don’t want to short them out, because each Lead/Acid battery is a little bomb waiting to go off if not treated correctly.
I work with batteries and with mains electricity, and I know which one I’ve had more danger from: definitely the batteries.
Towing point under the front of the car. It is a solid part of the frame. Lifting point on the engine would be better, but obviously you’ve already looked around there. It’s a lot easier on old cars, which is just as well, since old cars used to need jump starting a lot more often.
Heavy current draw from the dead car may reduce system voltage on the live car just a bit, especially if you’ve got other accessories running (headlights, HVAC blower, etc.). If you’ve got the blower on max speed, and you (or someone sitting in the live car) hear its speed dip just a bit when you connect the jumper cables, then the voltage has gone down. Revving the engine just a bit, maybe to 1500-2000 RPM, is generally enough to get it back up to 14.5 volts; you’ll hear the blower come back up to the speed it was at before the cables were connected. Once you’ve got the alternator spinning fast enough to put out 14.5 volts, revving faster won’t get anything more out of it.
My buddy- a professional mechanic- shorted a wrench across battery terminals by being careless when he disconnected the positive. He swung the wrench too far and connected the terminals.
You should see the interesting scar his wedding ring gave him. You can see some of the ring’s detail imprinted in the scar (little flutes around the edge of the ring).
One of the lessons I was fortunate to learn vicariously.
What was the lesson you learned? Careful with the wrench? Don’t wear a ring while doing mechanical/electrical work?
My policy is the latter, as wrench accidents will inevitably happen from time to time. In a situation that might just cut your finger, wearing a ring might cause a degloving injury (i.e. all of the skin gets peeled off of your finger) or a complete amputation (or in your buddy’s case, an exacerbated burn). I have a snap-bolt on my keyring; any time I’m going to work on something, that’s where my wedding ring goes.