Today's Message Index:
----------------------
1. 09:29 AM - Re: Battery Set Up (Jim Griffin)
2. 10:34 AM - Re: Battery Set Up (Brian Lloyd)
3. 10:35 AM - Re: Battery Set Up (Brian Lloyd)
4. 02:43 PM - KC/STL Transition Training (John Alber)
Message 1
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| Subject: | Re: Battery Set Up |
--> Yak-List message posted by: "Jim Griffin" <jgriffint28@cox.net>
I ruined one battery, which I thought was due to a faulty battery and
internal short, and had the same discharge problem with the replacement
battery which I watched closely and checked the charge on. It would
consistently be discharged after a flight. This no longer occured after I
started running the radios off both batteries with a voltage step down.
I think Brian was right on this. I didn't do any calculations to figure it
out, just deductive reasoning. This all started after I added a cooling fan
to my radio set up along with a GPS. It may be that it is a problem that is
more apparent with higher current draw on the batteries.
Jim Griffin
----- Original Message -----
From: "Ron Davis" <l39parts@hotmail.com>
Subject: Re: Yak-List: Battery Set Up
> --> Yak-List message posted by: "Ron Davis" <l39parts@hotmail.com>
>
> Did you destroy two new Gills at the same time, or destroy one, replace
it,
> and have another failure? I ask because I, and several people I know DO
use
> the center tap methiod. I am sure that I don't replace batteries every
two
> months and if the other guys are replacing them they haven't mentioned it.
>
>
> >From: "Jim Griffin" <jgriffint28@cox.net>
> >Reply-To: yak-list@matronics.com
> >To: <yak-list@matronics.com>
> >Subject: Re: Yak-List: Battery Set Up
> >Date: Wed, 22 Sep 2004 15:02:53 -0500
> >
> >--> Yak-List message posted by: "Jim Griffin" <jgriffint28@cox.net>
> >
> >What you described is exactly what happened to my Chipmunk batteries. I
> >insisted that my mechanic install a 24 -12 V convertor and the problem
was
> >solved. I had destroyed 2 new Gill batteries before I figured it out.
Live
> >and learn
> >Jim Griffin
> >
> >
> >----- Original Message -----
> >From: "Brian Lloyd" <brianl@lloyd.com>
> >To: <yak-list@matronics.com>
> >Subject: Re: Yak-List: Battery Set Up
> >
> >
> > > --> Yak-List message posted by: Brian Lloyd <brianl@lloyd.com>
> > >
> > > On Sep 22, 2004, at 10:34 AM, Ron Davis wrote:
> > >
> > > > --> Yak-List message posted by: "Ron Davis" <l39parts@hotmail.com>
> > > >
> > > > I can see how an 80 amp center-tap load would be a problem (on 24 AH
> > > > batteries). If I had that big of a 12 volt load, I'd try to split
it
> > > > into
> > > > two 40 amp loads like a 110/220 AC three wire system.(floating
ground
> > > > would
> > > > be necessary).
> > >
> > > Well, I installed an 80A battery equalizer in my boat because I have a
> > > worst-case 12V load of about 70A between the 150W HF transmitter, the
> > > lighting, and the hydraulic pump for the autopilot steering, not
things
> > > you are likely to find in an aircraft. Also, my battery bank consists
> > > of four 225AH gel-cells configured in series-parallel to provide 450AH
> > > at 24V.
> > >
> > > You can get battery equalizers with much smaller capacities that 80A.
> > > Surepower's model 52102 24V/12V battery equalizer is rated at 10A,
> > > probably just about perfect for a CJ6A. Here is the link to their
> > > converter/equalizer brochure:
http://www.surepower.com/pdf/ebr_dcdc.pdf
> > >
> > > >
> > > > On the other hand a VHF comm on a 3 amp breaker and a transponder on
a
> > > > 5 amp
> > > > breaker (average combined load 1.7 amp) is unlikely to appreciably
> > > > affect
> > > > the life of your two 12 lead acid batteries.
> > >
> > > I disagree. I watched exactly that configuration destroy both
> > > batteries in Dennis Nickson's CJ6A in less than 2 months. If you
doubt
> > > me contact him. He reads this list but is out of town for a week or
so
> > > otherwise he would probably respond directly to the list.
> > >
> > > Even a very small load on the 12V center tap will cause significant
> > > overcharging of the top battery. With vented batteries you can get
> > > away with it for a little while as long as you make a point of keeping
> > > the top battery topped up with water and swap the batteries reasonably
> > > often. If you try to do this with sealed batteries they will die a
> > > quick death. They are dependent on the liberated O2 and H2
recombining
> > > at the opposite plate and if you produce O2 and H2 too quickly, it
just
> > > escapes into the case, generating pressure without recombining.
> > > Eventually the overpressure valve opens and vents the O2 and H2 to
> > > atmosphere. The battery dries up and loses capacity after that.
> > >
> > >
> > > Brian Lloyd 6501 Red Hook Plaza
> > > brianl@lloyd.com Suite 201
> > > +1.340.998.9447 St. Thomas, VI 00802
> > >
> > >
> >
> >
>
> Get ready for school! Find articles, homework help and more in the Back to
>
>
Message 2
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| Subject: | Re: Battery Set Up |
--> Yak-List message posted by: Brian Lloyd <brianl@lloyd.com>
On Sep 23, 2004, at 3:07 PM, Ron Davis wrote:
> --> Yak-List message posted by: "Ron Davis" <l39parts@hotmail.com>
>
> I guess I dozed off during the science part.
Apparently.
> I saw anecdotal evidence (one
> guy's battery failed after two months and he had a center-tapped
> battery).
> This proves the center-tap caused his battery failure much like my
> neighbor's flat tire this morning was caused by him eating pizza last
> night:
> Both happened, so one must have caused the other.
Now there is a specious argument if ever I saw one. In the former case
overcharging and undercharging do have an effect on battery life.
Pizza and tires clearly have nothing to do with one another. Might I
suggest another analogy?
This problem, that of center-tapping a 24V battery to get 12V, isn't
something new or something that I made up. It is a commonly understood
problem ... well, not so commonly understood as I am finding out here.
> Your 80 amp boat load (why didn't you buy a 24 hydraulic pump from
> Surplus
> Center in Lincoln, NE???) is no less convincing.
I was only pointing out that I had a real reason to use an 80A device.
SurePower makes both battery equalizers and 24V-to-12V converters that
range in capacity from 10A to 150A. It all depends on your
application.
The boat came with a 12V autopilot with pump. The pump is variable
speed bidirectional device so it can drive the steering in either
direction and is very specific to the autopilot. The cost to replace
the navigation computer (it has the power supply for the pump) and the
pump with their 24V counterparts was a whole lot more expensive than
using the equalizer and continuing to run the autopilot from 12V. So I
got the equalizer and simplified my electrical system for 12V loads.
> It's like saying that
> since 800 cups of coffee gives lab ratr cancer, one cup a day is
> certain to
> a human therefore causes liver cancer too.
Well, we weren't talking about rats, coffee, or liver cancer so I
haven't a clue how you came to any such conclusion. Color me dense.
> What does an equilizer do? It must either limit generator current
> (and I
> fail to see how this helps) or it must equalize the load by putting a
> dummy
> resistive load on the top battery. This will waste half of you energy-
> unless you happen to need the heat there in the Carribean.
It "must" nothing. The equalizer is essentially a switching regulator
and charge pump that has three terminals: ground, 12V, and 24V. The
regulator maintains the 12V terminal at exactly 1/2 the voltage of the
24V terminal. It is wired thusly:
,------+--------> 24V
| |
| B2
| |
E------+--------> 12V
| |
| B1
| |
`------+--------> ground
Here is what happens with no equalizer. As you draw current from the
12V tap you would only drain B1. If you charge while you are drawing
current from the 12V tap then the charge current for B2 is the sum of
the charge current going into B1 and the current in your 12V loads. B2
receives more charge current than does B1 and B2 charges more quickly.
Since B2 is more charged than B1, the voltage across B2 is much greater
than the voltage across B1.
The current through your 12V loads is always present so the charge
current for B2 will never drop to zero even when B2 is fully charged.
You are very quickly going to go into an overcharge state in B2. And
since the 12V loads are pulling down the 12V tap, the voltage across B1
drops and it never receives a full charge. So B2 is perpetually
overcharged to the point of destruction and B1 is perpetually
undercharged to the point of destruction. It just takes a little
longer to kill B1.
With the equalizer in the circuit, the equalizer takes power from B2
(it is a charge pump) and delivers it to the 12V tap. It is not a
resistive device. It actively takes power from the 12V/24V terminals
(from B2), and then delivers it between the ground/12V terminals. The
voltage maintained between ground and the 12V terminal is always
exactly 1/2 of the voltage between ground and the 24V terminal. This
ensures that both batteries are charged with exactly the same voltage
and maintained at the same potential. If the batteries have different
capacities the equalizer will still keep them at the same potential and
balance the load so that they discharge at the same rate.
I prefer this approach to having a separate 24V-to-12V converter
because, if the converter fails, you lose your 12V buss. If the
equalizer fails you still have the 12V coming from B1 so you can
complete your flight and continue to use your 12V loads.
> And for the record: batteries do have impedance-related issues, but
> the salt
> air has rusted my can opener so I won't open that can of worms.
In this case we are dealing with DC (steady-state) loads so only the
internal resistances of the batteries are at issue. If we had
high-frequency ripple then we could talk about impedance issues but
since that is not the case ...
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
+1.340.998.9447 St. Thomas, VI 00802
Message 3
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| Subject: | Re: Battery Set Up |
--> Yak-List message posted by: Brian Lloyd <brianl@lloyd.com>
On Sep 24, 2004, at 12:26 PM, Jim Griffin wrote:
> --> Yak-List message posted by: "Jim Griffin" <jgriffint28@cox.net>
>
> I ruined one battery, which I thought was due to a faulty battery and
> internal short, and had the same discharge problem with the replacement
> battery which I watched closely and checked the charge on. It would
> consistently be discharged after a flight. This no longer occured
> after I
> started running the radios off both batteries with a voltage step down.
> I think Brian was right on this. I didn't do any calculations to
> figure it
> out, just deductive reasoning. This all started after I added a
> cooling fan
> to my radio set up along with a GPS. It may be that it is a problem
> that is
> more apparent with higher current draw on the batteries.
This is indeed the case. The higher the current drain on your 12V tap,
the more damage you will do to the batteries. Sure you can center tap
if your load is really light but most people end up adding things
without thinking of the ramifications. It is best to do it right from
the beginning and never have to deal with the problem.
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
+1.340.998.9447 St. Thomas, VI 00802
Message 4
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| Subject: | KC/STL Transition Training |
--> Yak-List message posted by: John Alber <john@johnalber.com>
An acquaintance is looking for someone to do Yak 52 transition training for 2 or
3 people. The Yak will be in mid Missouri, about half way between Kansas City
and St. Louis.
Thanks.
John
John Alber
john@johnalber.com
Home 618-675-3553
Work 314-259-2144
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