Dead Battery Jumping by Ray Cellar


I've been in the battery 'biz' for 15 years or so, and jumping a dead battery is no big deal if you take your time and think before 'jumping' - so to speak...

  1. Identify the POSITIVE (red) end of one of the jumper cable clamps - attach it to the POSITIVE (+) terminal of the dead battery.

  2. Attach the other POSITIVE cable clamp on the other end of the jumper cable to the good battery's POSITIVE post or terminal.

  3. Attach the NEGATIVE (black) jumper cable clamp nearest the good battery to the good battery's NEGATIVE (-) post or terminal.

  4. Attach the remaining NEGATIVE jumper cable clamp to a good engine ground point on the dead battery's vehicle away from the dead battery - I always 'test' this last connection by barely touching the clamp to the engine to see if it 'sparks' to any great degree - which it might if the dead battery is really dead.

Some words of caution here...batteries generate hydrogen while charging AND cranking...if you have been cranking heavily (bad for the starter) on your regular battery and have run it down, you have been generating lots of hydrogen gas inside the battery and hydrogen being lighter than air, migrates out through the battery's vents and will explode if a small spark is in the area...loose battery terminals are the usual problem when a battery explodes, but a spark from the jumper cables can do the same thing...ALWAYS wear some kind of eye protection when jumping batteries - it's not the battery acid that will hurt you (I have splashed it in my eyes several times and it washes right out with fresh water without permanent damage) it's the 'shrapnel' from the exploding battery case that does the real damage, and without glasses you are a prime target for same!!!!

You don't have to remove the dead batteries cable connections to attach a battery charger, assuming it's a charger of the same voltage. I don't recommend using a large charger's booster setting on a regular car battery, it's best to let the dead battery charge at a lower, normal (10-20 amps) setting for 15 minutes or so and then try to start. As a rule of 'thumb' you should never exceed 20% of a batteries amp hour capacity when recharging...most smaller car batteries are in the 40-65 amp hour range, which would call for no more than a 10 amp battery charger (my recommendation as the best, all-round type charger for overnight use). If you use a small 2 amp charger on a dead battery - expect a long wait before it will be charged up again...if you have 50 amp hour battery that's stone dead, you have to 'pump' those 50 amp hours back into the lead plates, therefore your 2 amp charger would theoretically take 25 hours (50/2). The last 20% of a battery charge can take as long as the first 80% to complete, so I always us a factor of at least 150% when trying to anticipate when a dead battery will be fully charged, and in this case it could take about 38 hours with that 2 amp charger!...Using a 10 amp charger would complete the same task in about 7.5 hours (50/10x1.5).

One last word of caution while using battery chargers....ALWAYS hook the charger leads to the battery BEFORE you plug the charger into the AC house current - with the charger unplugged, there is little chance of a spark if you hood the leads to the proper polarity...

Then, ALWAYS unplug the charger from the AC wall socket BEFORE you remove the leads from the charged battery - again you want to avoid a spark while removing the leads - and please, wear those protective eye glasses when using that battery charger!

If all the above fails, park your loaf on a big hill so you can get up some speed before jamming it in gear to bump start...you guys with the auto trannys need a really BIG hill!!!



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