Jump Starting with car Battery?

BC1100S said:

About a hundred years ago I was in -15F weather with a British sports car that had 20W-50 oil in it. It started.

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You may feel free to divulge the make of that car, and I promise it will go no farther. But I am guessing a 1972 MG Midget with chrome bumpers and SU carburetors. Arguably one of the finest and most dependable cars ever to grace our shores. I used to drive mine in cold weather, too, but never that cold! It takes a brave man.....

jconway607 said:

You may feel free to divulge the make of that car, and I promise it will go no farther. But I am guessing a 1972 MG Midget with chrome bumpers and SU carburetors. Arguably one of the finest and most dependable cars ever to grace our shores. I used to drive mine in cold weather, too, but never that cold! It takes a brave man.....

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With a comforter on your lap for heat?
OM

jconway607 said:

You may feel free to divulge the make of that car, and I promise it will go no farther. But I am guessing a 1972 MG Midget with chrome bumpers and SU carburetors. Arguably one of the finest and most dependable cars ever to grace our shores. I used to drive mine in cold weather, too, but never that cold! It takes a brave man.....

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Darn close guess, Mr. Conway! 1971 MGB. Chrome bumpers, SU carbs, high compression engine, no smog pump, twin 6 volt batteries wired in series under the rear deck, aluminum hood. Did 85,000 miles in it and only had to replace an electric fuel pump. The designers, in their wisdom, positioned it in front of the rear wheel exposed to all manner of road crap.

Sitting on the seat after a cold winter night in Toronto was like perching on a concrete block in a freezer. I loved that car.

Apologies for major thread derail.

The original post mentions Odyssey PC 680 battery is at 12.8 volts which seems really low to me. Normally they are charged at 14.4 to 14.7 volts and floated at 13.5 volts. The CTEK MULTI US 7002 charger is perfect for that particular battery's needs - especially if one has a persistent drain impairment. Of course finding the causal issue is best (sometimes easier said than done).

bogthebasher said:

The original post mentions Odyssey PC 680 battery is at 12.8 volts which seems really low to me. Normally they are charged at 14.4 to 14.7 volts and floated at 13.5 volts. The CTEK MULTI US 7002 charger is perfect for that particular battery's needs - especially if one has a persistent drain impairment. Of course finding the causal issue is best (sometimes easier said than done).

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From the Odyssey website:
"Full charged ODYSSEY battery voltage is 12.85 volts. ODYSSEY Batteries with less than 12.40 volts cannot reliably start big inch engines."
https://www.odysseybattery.com/Support/TechnicalInfo

RadioFlyer said:

From the Odyssey website:
"Full charged ODYSSEY battery voltage is 12.85 volts. ODYSSEY Batteries with less than 12.40 volts cannot reliably start big inch engines."
https://www.odysseybattery.com/Support/TechnicalInfo

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Two rally racing cars in my garage, both Toyota Celica GT Fours with 3S-GTE 2.2-liter turbocharged four-cylinder engines currently using this battery successfully. So not a large engine displacement but an insanely hot and demanding use case. Those batteries generally last one or two seasons of summer weekend track and rally racing and the drive to get back and forth. Wintertime cold weather cranking is very unreliable - often needing a boost if really cold (colder than -20C).

bogthebasher said:

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Two rally racing cars in my garage, both Toyota Celica GT Fours with 3S-GTE 2.2-liter turbocharged four-cylinder engines currently using this battery successfully. So not a large engine displacement but an insanely hot and demanding use case. Those batteries generally last one or two seasons of summer weekend track and rally racing and the drive to get back and forth. Wintertime cold weather cranking is very unreliable - often needing a boost if really cold (colder than -20C).

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The battery (any battery) does not assume the voltage that the charger applies in float mode once disconnected from the charger. The battery reverts to the voltage that its chemistry generates. The OP's observed voltage sounds perfectly normal.

RadioFlyer said:

The battery (any battery) does not assume the voltage that the charger applies in float mode once disconnected from the charger. The battery reverts to the voltage that its chemistry generates. The OP's observed voltage sounds perfectly normal.

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Agreed the voltage referenced is the minimum level not to be rejected per one of my Odyssey manuals if we are talking open circuit voltage:

"Unplug the charger and disconnect the battery from the charger. Let the battery rest of at least 10-12 hours and measure the OCV. If it is equal to or more than 12.80V proceed to the next step; otherwise reject the battery."