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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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 Posted: Sat Feb 17, 2007 5:05 am Post subject: Battery Charging |
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2/17/2007
Hello Bob Nuckolls, You wrote:
"Time: 08:09:59 AM PST US
From: "Robert L. Nuckolls, III" <nuckollsr(at)cox.net>
Subject: Re: 24v vs 27 volt power supplies
....skip..... Similarly, a battery charger of any size has no way of
knowing how many batteries
are connected . . . the act of adding more individual batteries appears no
differently to the charger than if you'd simply connected a single, larger
battery......skip....."
Could you please make clear in which manner multiple batteries should be
connected to the charger -- either in series or parallel?
Also if the battery charger has some defined limited output of current, such
as 6 amps, would that not affect the rate at which multiple low state
batteries could be initially charged?
Thanks for your always helpful inputs.
OC
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nuckollsr(at)cox.net
Guest
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| Posted: Sat Feb 17, 2007 6:43 am Post subject: Battery Charging |
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At 08:03 AM 2/17/2007 -0500, you wrote:
| Quote: |
2/17/2007
Hello Bob Nuckolls, You wrote:
"Time: 08:09:59 AM PST US
From: "Robert L. Nuckolls, III" <nuckollsr(at)cox.net>
Subject: Re: 24v vs 27 volt power supplies
.....skip..... Similarly, a battery charger of any size has no way of
knowing how many batteries
are connected . . . the act of adding more individual batteries appears no
differently to the charger than if you'd simply connected a single, larger
battery......skip....."
Could you please make clear in which manner multiple batteries should be
connected to the charger -- either in series or parallel?
|
Batteries are charged by impressing a specific votlage
across their terminals. E.g. you charge a 12 volt lead
acid battery by holding its terminals at 13.8 to as much
as 15 volts . . . See:
http://www.aeroelectric.com/Pictures/Curves/schumacher_3.jpg
You wait for a period of time -OR- until recharge current
drops below some nominally low value. I've heard Concord
folks cite "100 milliamps" as the indication that the battery
is no longer converting discharged chemistry into charged
chemistry. After this time, it's useful to drop the charger's
output voltage to a "sustaining" level that cannot charge but
only offset internal leakages (self discharge) currents that
exist in EVERY battery technology.
To insure that all batteries in an array of two or more
see the same terminal voltage during the recharge-sustain
process, they must be in PARALLEL.
| Quote: | Also if the battery charger has some defined limited output of current,
such as 6 amps, would that not affect the rate at which multiple low state
batteries could be initially charged?
|
Absolutely. A 1.5A charger can deliver 1.5AH of charge
per hour. Hook dead 32, 18 and 10 AH batteries in
parallel and you've tasked the charger with delivering
enough energy to replenish all batteries in the array . .
or 60 AH. One should expect this process to take 40+
hours to complete. All batteries are being recharged on
the same time curve with each getting a share of the
1.5 AH/HR that's available from the charger.
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
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TH-SR
Joined: 13 Jan 2006
Posts: 22
Location: WI
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| Posted: Sat Feb 17, 2007 7:25 am Post subject: Battery Charging |
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Speaking of battery charging, a recent issue of Sport Aviation had an
article entitled "Pulse De-sulfator for Lead-acid Batteries." It described
the process of resurrecting weak or sulfated batteries, and included some
theory and a schematic of a circuit to address the process. I'm just
wondering what this community has to offer on the subject...
Here's a link to the authors site:
http://www.geocities.com/powertugs/eaa79parts.html
Todd Henning
Scratch CH701 Builder
--
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_________________
Todd
CH701 |
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klehman(at)albedo.net
Guest
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| Posted: Sun Feb 18, 2007 12:54 pm Post subject: Battery Charging |
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http://www.shaka.com/~kalepa/desulf.htm
CH701 wrote:
| Quote: |
Speaking of battery charging, a recent issue of Sport Aviation had an
article entitled "Pulse De-sulfator for Lead-acid Batteries." It described
the process of resurrecting weak or sulfated batteries, and included some
theory and a schematic of a circuit to address the process. I'm just
wondering what this community has to offer on the subject...
Here's a link to the authors site:
http://www.geocities.com/powertugs/eaa79parts.html
Todd Henning
Scratch CH701 Builder
|
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chasb(at)satx.rr.com
Guest
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| Posted: Sun Feb 18, 2007 3:27 pm Post subject: Battery Charging |
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Bob,
Assume you have two 17 AH batteries hooked in parallel, one is dead or very low, the other has a decent charge. If a "smart" charger will continue a high voltage until both batteries are charged before dropping to a sustaining level, can the charged battery in this case be damaged while bringing (or attempting to bring) the low or dead battery up to a fully charged state?
Charlie Brame
RV-6A N11CB
San Antonio
--------------------------------------------------------------------------------
[quote]Bob Knuckles wrote:
You wait for a period of time -OR- until recharge current
drops below some nominally low value. I've heard Concord
folks cite "100 milliamps" as the indication that the battery
is no longer converting discharged chemistry into charged
chemistry. After this time, it's useful to drop the charger's
output voltage to a "sustaining" level that cannot charge but
only offset internal leakages (self discharge) currents that
exist in EVERY battery technology.
To insure that all batteries in an array of two or more
see the same terminal voltage during the recharge-sustain
process, they must be in PARALLEL.
-------------------snip---------
Absolutely. A 1.5A charger can deliver 1.5AH of charge
per hour. Hook dead 32, 18 and 10 AH batteries in
parallel and you've tasked the charger with delivering
enough energy to replenish all batteries in the array . .
or 60 AH. One should expect this process to take 40+
hours to complete. All batteries are being recharged on
the same time curve with each getting a share of the
1.5 AH/HR that's available from the charger.
Bob . . .
[b]
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nuckollsr(at)cox.net
Guest
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| Posted: Sun Feb 18, 2007 4:53 pm Post subject: Battery Charging |
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At 05:26 PM 2/18/2007 -0600, you wrote:
| Quote: | Bob,
Assume you have two 17 AH batteries hooked in parallel, one is dead or
very low, the other has a decent charge. If a "smart" charger will
continue a high voltage
|
No, a CONSTANT CURRENT flows until BOTH batteries present
a LOAD sufficiently low that (1) voltage rises to a level
consistent with a high state of charger or (2) the
charger goes into voltage limit where it now watches
for recharge current to drop below some nominal but
small value . . . 100 mA or less is typical. It doesn't
matter that one (discharged) battery takes the lion's
share of the current available. The chemistry in the
charged battery simply relaxes until the discharged
battery catches up to the partially/fully charged
battery.
| Quote: | until both batteries are charged before dropping to a sustaining level,
can the charged battery in this case be damaged while bringing
(or attempting to bring) the low or dead battery up to a fully charged state?
|
No, there are a number of myths circulated for
decades and even posited here on the List that
hooking a fully or highly charged battery to a
discharged one would cause (a) damage to one or
both batteries, (b) the dead battery would "suck
down" the energy stored in the charged battery,
(c) the charged battery to become over-charged
if they were connected in parallel to a charging
source, etc. etc. etc.
Yes, if you hook a fully charged battery to a dead-dead
battery, there is a momentary and relatively large
current flow from the hot battery to the dead one.
But if the connection is maintained and the energy
transfer measured, one soon finds that a tiny
(less than 1%) of the charged battery's energy
is lost into the dead battery. After all,
the charged battery delivers energy at something
just over 12.5 volts and 12.5 volts cannot
significantly charge a dead battery.
Hooking two good batteries (one discharged and
one charged) to the same charging source be
it a Battery Tender, other smart charger or
your aircraft's alternator presents no hazards
nor special concerns for outcome of things
once the charger's green "battery charged"
light comes on.
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
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nuckollsr(at)cox.net
Guest
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| Posted: Sun Feb 18, 2007 8:50 pm Post subject: Battery Charging |
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At 03:56 PM 2/18/2007 -0500, you wrote:
| Quote: |
http://www.shaka.com/~kalepa/desulf.htm
CH701 wrote:
>
>
>Speaking of battery charging, a recent issue of Sport Aviation had an
>article entitled "Pulse De-sulfator for Lead-acid Batteries." It described
>the process of resurrecting weak or sulfated batteries, and included some
>theory and a schematic of a circuit to address the process. I'm just
>wondering what this community has to offer on the subject...
>
>Here's a link to the authors site:
>http://www.geocities.com/powertugs/eaa79parts.html
|
This article offers one of the more robust desulfation
philosophies and probably the most popular version.
I wish I had more hard data on this class of battery
service aid. At the moment, I'm aware of no battery
manufacturer that endorse this technology.
Yeah, there are some who would suggest, "folks who
build batteries are not interested in user applied
technologies that prolong the life of their products.
It cuts into battery sales." To which I confidently
reply, "horse pucky".
I've been to the R&D labs of several manufacturers
and witnessed their efforts to fine tune chemistry,
manufacturing processes and field service recommendations
all of which go to improving on the manufacturer's competitive
position in the marketplace. They also publish recommendations
for how their batteries should be treated in the field
to improve on customer satisfaction. When I asked these
folks about desulfators, not a one said that they're
detrimental to battery service life but to a man, they
were unable to endorse them as having a quantifiable
return on investment after having tested several
products. Of course I don't know WHICH devices were
tested . . . perhaps they missed putting their hands
on Smiley Jack's One True Battery Desulfator.
I can see no reason why one should NOT use any of
these devices but I'm unaware of a single repeatable
experiment that says they're a really good thing to
do. If anyone runs across a report that proffers
any hard data, I'd be pleased to know about it.
My shop DAS computer went out the door yesterday
'cause it's also used to program the processors
for and exercise the finished product for a programmable
pressure controller I've been building for a client.
I've off-loaded the manufacturing so that I can
spend more time getting a new line of AEC products
on line. I'll be acquiring another computer in the
next few days so that I can resume the battery
charger experiments we've been conducting over
the past few days.
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
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echristley(at)nc.rr.com
Guest
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| Posted: Thu Feb 22, 2007 8:40 am Post subject: Battery Charging |
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CH701 wrote:
| Quote: |
Speaking of battery charging, a recent issue of Sport Aviation had an
article entitled "Pulse De-sulfator for Lead-acid Batteries." It described
the process of resurrecting weak or sulfated batteries, and included some
theory and a schematic of a circuit to address the process. I'm just
wondering what this community has to offer on the subject...
Here's a link to the authors site:
http://www.geocities.com/powertugs/eaa79parts.html
I wanted to make a Frankenstein combination of this circuit and one that
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Jim Weir laid out in a recent Kitplanes article for using a solar cell
to charge the battery. Basically, I would insert the desulfator in the
circuit where the green "charged" LED indicator would be in Jim's
circuit. The idea was that once the battery was fully charged, the
desulfating would be enough to keep it topped off and completely healthy.
After some investigation, I gave up. The deal breaker was that the
desulfator uses upwards of a 60V pulse. There would be no way short of
a disconnected master of isolating the pulse from the rest of the
airplane (and electronics that may not care for 60V pulses). I decided
that I didn't want 60V pulses around my 12V system at all. It's what I
call "setting a trap for myself", which I have a habit of doing
accidently, so I try to avoid doing it on purpose.
--
,|"|"|, Ernest Christley |
----===<{{(oQo)}}>===---- Dyke Delta Builder |
o| d |o http://ernest.isa-geek.org |
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