Message: #24493 Date: May 18, 2005 From: "Robert L. Nuckolls, III" Subject: Re: Full Charge on Battery?
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>I chanced apon this site.  The suggestion that an Odyssey Battery may not 
>be getting a full charge unless it receives a voltage of 14.7 volts is 
>made.  If true, this could be a problem for electrically dependent engines.
>Any clarification would be appreciated.

   (update 12/11/05: I note that the controversial posting on the
Battery Tender website cited above has been pulled but here's the data
I posted that refuted Battery Tender's claims)
	The 14.4 to 14.7 value is recommended for rapid recharge
    of the battery . . . and probably assumes that the battery
    was deeply discharged before the re-charge cycle begins.
    The charging recommendations publication for Odyssey can
    be found at . . .

     . . . where we read that the fast recharge voltage
    should not be sustained for more than 24 hours. They
    recommend reduction to a "standby" charge value of
    13.6 to 13.8 volts. A value that is consistent with
    the rest of the lead-acid battery industry. One could
    use the numbers on this chart for ANY lead-acid technology
    except that I would say that you don't leave the fast-charge
    level on for more than, say one tank of fuel duration
    or much less than 24 hours. Any battery in an airplane
    should be fully recharged in about one hour after
    starting the engine.  This is the reason for the "75%
    rule" on alternator sizing in certified ships. If one
    has used a max of 45A on a 60A machine to run the
    airplane, you have 15A left over to quickly recharge
    a deeply discharged battery. Boosting the voltage
    to 14.7 increases the battery's willingness to accept
    energy . . . but this level should not be maintained

    Check out page 8 of . . .

    and you see the same kinds of fast charge and float
    voltage ranges. Same goes for Panasonic where on
    page 3 of the same doucment we find 13.7 as a recommended
	float charge and 14.7  as a recommended fast charge voltage
    at 25C.

    Bottom line is that ANY lead acid battery by ANY manufacturer
    will ultimately achieve 100% charge at 13.8V at 25C. It'a all
    a matter of how long you want to wait. If you're in a hurry,
    then jack the voltage up a tad for a SHORT period of time to
    speed up the recharge process. If your system is not endowed
    with a automatic recharge/float voltage controller . . . well
    shucks. Guess we'll have to compromise and set the critter up
    for 14.2 and quit worrying about it. That's the lead-acid
    set-point of choice for light aircraft since Duane Wallace
    bolted the first batteries into the C-140/C-170 products nearly
    60 years ago.

    With respect to the writer's objections about "Pulse Current
    Amps" take a peek at . . .

    The graphical data for battery performance under various loads
    is quite specific and yields factual engineering data. The
    fact that Odyssey quantifies their batteries in a different manner
    than some industry standards doesn't automatically mean that
    their product is inferior or that the company is trying to
    obscure any facts as to their product's performance.

    Take a peek at . . .

    . . . where we find the following definitions:

Cold Cranking Amps (CCA): "Discharge load measured in amps that a
fully charged battery at 0  F can deliver for 30 seconds
while maintaining its voltage above 7.2V"

    Hmmm . . . Odyssey gives similar data but at 25C. Could it
    be that the majority of Odyssey's customers use their
    batteries as more mundane temperatures wherein the high
    discharge rate performance data is more useful when plotted
    at the higher temperatures? Don't know. But I doubt that
    Odyssey believes they are competing with Die Hards and
    boat batteries. And what's all this 7.2 volt stuff anyhow?
    B&C has quantified their batteries for a 15 second dump
    based on dragging the battery down to and holding it at
    8.5 volts. This is easily accomplished with the tester that
    both B&C and the 'Connection use in their shops. See . . .

    Does that mean that B&C's marketing numbers are
    bad or that they're trying to obscure any facts? No, I picked
    that value 15 years ago because I didn't know of any starters
    that would continue to crank an engine all the way down to
    7.2 volts . . . And guess what? We DON'T do that test at

Reserve Capacity (RC):  "Number of minutes a fully charged battery
at 80.F can be discharged at 25 amps until the voltage drops below
10.5 volts."

    Well fooey, my e-bus runs only 5 amps . . . should I be bent
    out of shape that Odyssey or any other manufacturer doesn't
    give me a 5A value instead of the 25A value? Only if I'm
    an ignorant consumer likely to make decisions based on a
    particular manufacturer's marketing hype. If I'm a designer
    who deals in engineering facts and data, then what ever data the
    manufacturer supplies is GOOD data as long as it's accurate.

    If I need ADDITIONAL data plotted in some other venue, then it's my
    responsibility go get that data myself or request it from
    the manufacturer. Most have much more data than they publish
    and will supply it as needed.

    Deltran's position on Odyssey products is not well researched.
    It does not mirror any considered understanding of lead-acid
    technology in general nor Odyssey's engineering and marketing
    philosophies in particular.

    The short answer is, "I'm not going to lose any sleep over it."

    Bob . . .