The 1955 Chrysler Service Manual indicates the Model C-70 (Crown Imperial) was still a 12-Volt, positive ground system. As I recall, one of the arguments for positive or negative ground was the erosion rate of spark plugs' center electrode. Chrysler and Ford finally yielded to the General. In those days, carbon and lead fouling damaged spark plugs way before erosion set in. Novice grease monkeys like me had to be on our toes when we connected battery chargers or installed new batteries. On fast charge a lot of hydrogen and acid mist was generated as we poured the cobs to those miserable old batteries. Pops were frequent and battery explosions were not unknown. The presence of the acid fumes guaranteed rapid buildup of corrosion around the battery terminals. Sears' Diehards were a great improvement and they had a big share of the battery business when their improved quality and warranty hit the market. OEM batteries were typically good for only one year. In Des Moines, we even had an outfit that rebuilt old batteries by installing new guts into old cases. Our OEM 2005 Durango battery is nearly six years old and doing fine. I see it has an insulator around it, presumably to protect it against underhood heat. And, the two 6-Volt Trojan deep-cycle batteries in our RV are over 16 years old. They are kept charged by a rooftop solar cell. Interested parties may want to view: http://en.wikipedia.org/wiki/Alessandro_Volta to read up on the man whose last name is the basis for the word Volt and about early batteries. C-300'ly, Rich Barber Brentwood, CA 1955 Chrysler C68-300 From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of John Sent: Monday, June 07, 2010 2:22 PM To: mgoodknight@xxxxxxxx; Chrysler300@xxxxxxxxxxxxxxx; c300c@xxxxxxx Subject: Re: [Chrysler300] Quick-Disconnect Battery Cable 1956 was the first year that Chrysler used 12 volt negative ground systems. The one exception I can think of is on the Crown Imperial Limos and eight passenger sedans through at least 1954 used a 12 volt system but it was still positive ground. John Lazenby ----- Original Message ----- From: c300c@xxxxxxx To: mgoodknight@xxxxxxxx ; Chrysler300@xxxxxxxxxxxxxxx Sent: Monday, June 07, 2010 2:15 PM Subject: Re: [Chrysler300] Quick-Disconnect Battery Cable Marshall, I am not sure about 1956 300-Bs, but from 1957 forward, Chryslers all use negative grounding. 300'ly, Gary Hagy In a message dated 6/7/2010 2:36:09 P.M. Mountain Daylight Time, mgoodknight@xxxxxxxx writes: I misstated the reconnect sequence. I meant to say reconnect the "hot" cable first, the reverse sequence of the disconnect. I say "hot" instead of "pos" or "neg" because our c300s are positive ground systems, making the "hot" wires negative polarity. --------------marshall ---------- Original Message ---------- From: Ray Jones <hurst300@xxxxxxxxxx> To: Chrysler 300 Broadcast <Chrysler300@xxxxxxxxxxxxxxx> Subject: Re: [Chrysler300] Quick-Disconnect Battery Cable Date: Mon, 7 Jun 2010 14:45:31 -0500 Marshall is absolutely right. If the ground is attached first, it's way too easy for the carless wrench tightening the positive cable to touch ground. But, the real reason is that a battery is a storage devise for stored energy. Electricity, the stored energy, is a strange critter, it always wants to work. So if you hook up the ground first, and one or more items in the car are on, then there will be a spark as the connector gets near the + terminal. The stored energy will "Leap" across the gap to go to work and supply the items that are on, with power. If the + terminal is hooked up, and you are attaching the -, ground, last, then the work is done and there will be no or very little spark. This really comes in play if you have run down the battery and there is hydrogen gas laying on top of the battery. A product of heavy discharge. This is also why you ALWAYS attach the + jumper cable first to the Battery and the - cable to a ground somewhere away from the battery. i had a battery blow up in my face and I knew better, but was in a hurry and careless. The watchband he tells about became the "work" since it connected the power to ground and the watchband, not being real work, created a short. A tiny light bulb is work as is a big starter motor, and the electric critter is happy dealing with them. Take the work out and just put the Positive to ground, and they call that electric welding. Or in the case above wrist burning. Ray On Jun 7, 2010, at 1:58 PM, mgoodknight@xxxxxxxx wrote: The reason you should disconnect the ground cable first, reconnect the "hot" cable last is so that you don't risk shorting your circuit with your wrench as you work with the "hot" cable. A short circuit with good conductors (low resistance) such as a half inch box wrench will get very hot very fast with 200+amps running through it-----makes you want to turn it loose real quick!!!!!!! Take heed of that hazard and always disconnect the ground cable when doing any kind of work on your car that might bring you in contact with a "hot" terminal, especially if you wear a watch, ring, necklace, bracelet, metal belt buckle, or maybe other hazards. A friend of mine ignored that rule and once got a severe burn on his left wrist from contacting the power-in lead terminal of the distributor with his watchband while the engine was running. HE LEARNED!!!! 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