Double Jump

[JimD]

My wife's 2013 e88 (n52) seems to have a shorted or otherwise catastrophically failed battery. It was working fine and when she went to start it after lunch it was completely dead. My son got their first and jumped her but it still wouldn't start. I had better cables so I tried when I got there. Still not much happening, after several minutes charging from the other car running ~2000rpm it would very slowly turn over a tiny bit. I went nose to tail so we could jump battery to battery (we had been using the terminal under the hood). Finally my son thought of using his car on the terminals under the hood with mine still on the battery. It started. Ran OK too. But wouldn't restart after she shut if off.

So if your car is in the same kind of condition, and you have two people with cables, you might want to try this.

The battery in my 2009 e88 is still working fine. My daughter lost a battery similar to her mom's however. Just quit.

[The Wind Breezes]

The problem with jumper cables is not only are they usually thin gage, cheap copper plated aluminium which will cause massive voltage drop at the hundreds of amps required to start the engine, but the interface between the clamps and the posts is also shitty which again causes voltage drop. Like in your case, the voltage goes too low to crank the engine over without really drastic measures. The solution is to use heavy gage full copper cables and a bolt on or otherwise appropriate contact interface. You can also use a higher voltage, but that probably will cause more issues than solutions and if you're equipped to do that you probably have a battery you can just drop in as a replacement.

[champignon]

Jump starting a car is a potentially hazardous situation, and there are reasons to exercise caution in the process. If you have never participated in a car jumping session that resulted in the subject battery exploding, then perhaps you would see this exercise as benign, but sometimes it is not.

About 15 years ago a friend and I went down to a remote part of Southern Utah on a camping trip. His truck would not start one morning, and another motorist in the campground tried to jump my friend's truck with the jumper cables going directly in between the two vehicles, + to +, and - to - terminals. The result was that the dead battery in my friend's truck exploded, and spewed battery acid everywhere, which burned some holes through my friend's clothing, if you want an idea of how hazardous the stuff is . . . . . If it happened to hit you in the eyes, you could be blinded.

Since then, I've always taken the position that the proper and safe way to jump start a vehicle is to take the jumper cables and put the plus directly to the plus, but the minus goes from the "donor" vehicle to a grounded area in the recipient car, either a designated negative post, or just another area of bare metal under the hood. This way it is very unlikely for an errant spark to cause a battery explosion.

I would be EXTREMELY cautious about doing anything that involved having 3 vehicles hooked up, or any other non-standard jumping arrangement. There are worse things than not being able to start a jumped car with jumper cables or with a "battery box." You can always get a wrecker to come out, or get a mobile battery replacement. I'd take one of these fallback options way over the risk of getting sprayed with battery acid from an exploding battery, having once seen the results of that, first hand.

[minirips2]

Champignon-
I've also been too close to a jump-induced battery explosion. It will indeed forever change your attitude about jumping cars. I was lucky to only lose my best pair of jeans over it. I wouldn't do it again without proper eve protection. A good habit is to keep a full pair of goggles with your jumpers, because you never know...

[zx10guy]

Originally Posted by champignon

Jump starting a car is a potentially hazardous situation, and there are reasons to exercise caution in the process. If you have never participated in a car jumping session that resulted in the subject battery exploding, then perhaps you would see this exercise as benign, but sometimes it is not.

About 15 years ago a friend and I went down to a remote part of Southern Utah on a camping trip. His truck would not start one morning, and another motorist in the campground tried to jump my friend's truck with the jumper cables going directly in between the two vehicles, + to +, and - to - terminals. The result was that the dead battery in my friend's truck exploded, and spewed battery acid everywhere, which burned some holes through my friend's clothing, if you want an idea of how hazardous the stuff is . . . . . If it happened to hit you in the eyes, you could be blinded.

Since then, I've always taken the position that the proper and safe way to jump start a vehicle is to take the jumper cables and put the plus directly to the plus, but the minus goes from the "donor" vehicle to a grounded area in the recipient car, either a designated negative post, or just another area of bare metal under the hood. This way it is very unlikely for an errant spark to cause a battery explosion.

I would be EXTREMELY cautious about doing anything that involved having 3 vehicles hooked up, or any other non-standard jumping arrangement. There are worse things than not being able to start a jumped car with jumper cables or with a "battery box." You can always get a wrecker to come out, or get a mobile battery replacement. I'd take one of these fallback options way over the risk of getting sprayed with battery acid from an exploding battery, having once seen the results of that, first hand.

The explosion risk is about any hydrogen gas present in the area around the battery which has vented out from the battery (dependent on the type of battery). At my first job out of college, the company I was working for had a funded research project through the EPA and various power companies to test off gassing of electric vehicles. Keep in mind this was many many years ago. The testing environment was an actual house the company purchased in a residential neighborhood. I remember the one test vehicle which was a passenger van which weighed 4 tons due to all the batteries. We didn't even get to complete the charge cycle as about an hour or so into the test, the level of hydrogen reached the LEL (lower explosive limit). The test was terminated and we immediately vented the garage.

Another story about a car battery was told by my friend. Pretty hilarious. He was working at an auto parts store. A guy comes in complaining about something wrong going on with his battery. He drags my friend out of the store and goes to his car with the hood open. He says there's a problem with his battery and proceeds to slam a wrench across both the positive and negative terminals repeatedly in rapid succession. Friend says of course sparks were flying and before he could tell him to stop...BOOM!