Today's Message Index:
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1. 09:01 AM - Re: 12v vs 14v System? (Eric M. Jones)
2. 06:57 PM - Re: Re: 12v vs 14v System? (Robert L. Nuckolls, III)
3. 07:14 PM - Re: Raise internal reg. Alternator voltage (Robert L. Nuckolls, III)
4. 08:39 PM - Re: Re: 12v vs 14v System? (sorry 'bout that) (Robert L. Nuckolls, III)
Message 1
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Subject: | Re: 12v vs 14v System? |
The problem with standardizing battery voltages is how the batteries are made.
This is not the same as "harmonizing" AC voltages (which elsewhere in the ISO
world are now all called 230 VAC, 50 Hz., with large tolerances. The US is 120VAC
60 Hz. by ANSI standards.)
Their are innumerable DC cells between 0.03V and 4.10 that are can be combined
to make batteries. These electrochemical combinations can be aimed at "something
close to 12V-14V", but there is not much you can do if they actually wind up
to be 11.76, 13.44, or whatever. One cannot set a general standard.
And yes, there are primary (non-rechargeable) and secondary cells (rechargeable),
various environmental problems and conditions, weight and operation conditions...and
Thomas Edison's 1.4 volts iron cells still work fine for many applications
today.
So yes, I am all in favor of standardization, but in batteries--don't expect standardization
just yet. This leads writers to use nominal terms.
en.wikipedia.org/wiki/Standard_electrode_potential_%28data_page%29
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=438367#438367
Message 2
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Subject: | Re: 12v vs 14v System? |
>
>It's probably too much to ask for standard terms to be applied to
>electrical systems after all these decades. [Wink]
Ain't gonna happen . . . batteries are chemical beasts with no
single cell offering anything closed to 12v. So combinations of
cells have to be joined until the target 'system' requirements
are met. In the case of lead-acid batteries, multiple cells in series
were '6-volt', '12-volt' and '24-volt' long before anyone stuck
them in a vehicle paired with a generator.
Boats and railroad cars featured '36-volt batteries' charged
at 42 volts. To this day, you can still buy a 32 volt lamp
for 'marine' application.
Emacs!
C Kettering's 1916 Delco-Light plant for rural applications were offered to
charge 16 lead-acid cells in series . . .
Emacs!
This would have nominally been a 32-volt battery charged by a generator
and (later a wind-mill) for a system voltage of 38 volts.
Delco Batteries
Just put a new battery in Dr. Dee's little red Saturn. Just for grins,
I sucked out most of the electrons in its off-the-shelf condition and
got this plot . . .
Emacs!
With a 5A load, you can see that it started out a closer to 13
volts and tossed
in the towel before it about 11 volts . . . i.e. an average output
of 12 volts.
Now, to stuff all those electrons back in at room temperature, I would need
to charge it at 13.8 volts for a few days . . . to get it stoked back up in
hours or less, a charge voltage of 14.2 to 14.8 is called for. Since
day-one, vehicles of all stripe have been said to operate at the battery's
maintenance voltage (i.e. 14v) while in fact, batteries delivered energy at
their label value of 12v (which is a more of an average over the discharge
curve of the battery).
Don't know if you could call it a 'standard' of any kind . . . but the
legacy vernacular for describing the alternator-battery combination speaks
of a "12 volt battery" in a "14 volt system."
Now comes the lithium family of cells. If you charge a stack of 4 cells
to the maximum rated charge voltage of 4.2 volts per cell, then you'd
have to do it in a 16.8 volt system.
Emacs!
Referring to the family of curves above, the 16.8 volt operation
gives you a "15 volt battery". But put the same array of cells
into your "14v system" tuned to lead-acid chemistry and you get a
"13.5 volt battery" while giving up about 1/2 its max rated
chemical capacity.
Hence, it's entirely proper and logical to speak of batteries
in terms of the manner in which they deliver energy and to speak
of systems in terms a nominal operating voltage within which
all accessories (including the battery) are obliged to perform
to design goals.
Bob . . .
Message 3
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Subject: | Re: Raise internal reg. Alternator voltage |
>I did think of the idea that Bob provided about putting a
>1N540x diode in line with the alternator feed. The worry I
>had about doing that was that perhaps this extension of
>the internal circuitry would have some unintended
>consequence.
No . . . been there . . . done that. BUT it ONLY works
if the diode is in the regulator's voltage sense lead.
It is unlikely that any commercial-off-the-shelf alternator
with an internal regulator will sense through the control
lead . . . all schematics I've had the privilege of viewing
sensed the alternator's B-terminal.
>For today, I was just putting the question out as a sounding
>board to see if anyone else ever noticed the same thing and
>what ideas everyone had.
I'm not 100% sure that my mental image of your
descriptions match the physical reality. How about
sketching, scanning and then sharing an architecture
drawing? The SCHEMATIC is the universal language
readable by any and all.
Bob . . .
Message 4
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Subject: | Re: 12v vs 14v System? (sorry 'bout that) |
At 20:55 2015-02-15, you wrote:
>>It's probably too much to ask for standard terms to be applied to
>>electrical systems after all these decades. [Wink]
>
> Ain't gonna happen . . . batteries are chemical beasts with no
> single cell offering anything closed to 12v. So combinations of
Don't know what happened to my supporting
figures. I'll re-craft the posting tomorrow
and straighten it out.
Bob . . .
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