If you have lead-acid batteries, which is the most common type of car batterieshydrogen gas will be discharged in large quantity. The least that you would want is to be run over while trying to rescue your battery. Turns out the friend's car didn't need a jump at all, there was something wrong elsewhere in the car. Sign up or log in Sign up using Google. Be protected as you start the process of jumpstarting. Click here to add a comment.
What purpose does this serve and does anyone else do this?
Jumper cable mistake may be costly
Connecting the positive terminal of each battery to the negative terminal of the other battery will result in a huge surge of electrical current between the two batteries. The "professional" left the scene and us! FireMarth FireMarth 7 years ago 1 Tried to jump a friends battery, and my idiot friend hooked up the jumper cables backwards. Possibly, but not likely. However, should I be wary that something may have been damaged that I'm not noticing?