[Further OT] More on Batteries

[KRFinch at dstsystems.com]

"The car battery thing is another "capacity" issue.  Most passenger cars
provide
very little resistance for a modern battery.  Try sticking one of those 6
month batteries in a high compression V8 with a lot of cubic inches.  ;-)"

For what it's worth, I am running 10.5:1 in my 1970 Skylark with a 455.
I've let it sit for 6 months before and it started up without a problem.
No ether, no jumpstart.

Just lucky, I guess.

- Kevin

                                                                                                    
                                 
                      Bradley Miller                                                                
                                 
                      <bradmiller at dslonramp        To:       <kclug at kclug.org>                      
                                 
                      .com>                        cc:                                              
                                 
                      Sent by:                     Subject:  Re: [OT] More on Batteries             
                                 
                      owner-kclug at marauder.                                                         
                                 
                      illiana.net                                                                   
                                 
                                                                                                    
                                 
                                                                                                    
                                 
                      05/13/2003 02:29 PM                                                           
                                 
                                                                                                    
                                 
                                                                                                    
                                 

> > That would make a battery dead in 10 days. I find that hard
> > to believe.
>
>That would be 10% of the 'remaining charge'. i.e.
>
>12V - (12V * 10%) = 10.8V
>10.8V - (10.8V * 10%) = 9.72V
>
>Which means the battery would be effectively dead after 24 days when it
has
>less than 1V of charge.  Is that believable for some battery types? Maybe.

Actually the voltage on NiCads is like 1.25 (not the full 1.5 of a dry
cell).   (There are some "hotter" Nicads that give out a full 1.5, but
we'll leave those out for now.)    Going by the voltage rate shown, they
would be down do .91 volts in only 4 days . . . and .9 volts is where
typical discharge cutoff voltage is.  (I raced RC cars for years.)   Now
instead what the "loss rate per day" is referring to overall
capacity.  Take a 1800 mah AA NiMH battery and apply a 10% loss per day on
the overall capacity.   The cell may show 1.1-1.2 volts after x days, but
it won't have any capacity (amp hours) left in it.

>However, what about alkaline batteries?  I'm looking at some Rayovac's
that
>have Dec 2009 written on them.  What about lead-acid batteries?  I've had
>lead-acid batteries in cars that sat for over 6 months and were still able
>to crank over the engine.

Apples and oranges here.  Alkaline batteries are a different beast and
don't have the same loss rate as a rechargeable type battery.   The car
battery thing is another "capacity" issue.  Most passenger cars provide
very little resistance for a modern battery.  Try sticking one of those 6
month batteries in a high compression V8 with a lot of cubic inches.  ;-)

-- Bradley Miller