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chasb(at)satx.rr.com
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 Posted: Sat Jun 24, 2006 4:38 pm Post subject: PC-680 Revisited |
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My Odyssey PC-680 has been in my non-flying RV for about three years
- most of the time uncharged. It keeps a charge for months, and after
topping off, it started a new, cold engine repeatedly with no
problems. I'm impressed
The nomenclature that came with the PC-680 battery says it as a Dry
Cell. I remember an AeroElectric discussion a few years back about
lead acid, sealed lead acid, gel cell, and recombinant gas batteries.
According to the archives that I found, the PC-680 is described as a
Recombinant Gas and/or Sealed Lead Acid battery. I wonder if it
really is a dry cell or if that is just a manufacturer's line?
I recently bought one of the BB17-12 el-cheapo batteries to power an
electric gate. It is the same size and shape as the PC-680 but it is
labeled as a valve-regulated, sealed lead acid, rechargeable
battery. It seems to work flawlessly, though I don't think I would
trust it in my airplane.
Charlie Brame
RV-6A N11CB
San Antonio
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bob(at)bob-white.com
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| Posted: Sat Jun 24, 2006 5:08 pm Post subject: PC-680 Revisited |
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On Sat, 24 Jun 2006 19:32:11 -0500
Charles Brame <chasb(at)satx.rr.com> wrote:
| Quote: |
My Odyssey PC-680 has been in my non-flying RV for about three years
- most of the time uncharged. It keeps a charge for months, and after
topping off, it started a new, cold engine repeatedly with no
problems. I'm impressed
The nomenclature that came with the PC-680 battery says it as a Dry
Cell. I remember an AeroElectric discussion a few years back about
lead acid, sealed lead acid, gel cell, and recombinant gas batteries.
According to the archives that I found, the PC-680 is described as a
Recombinant Gas and/or Sealed Lead Acid battery. I wonder if it
really is a dry cell or if that is just a manufacturer's line?
I recently bought one of the BB17-12 el-cheapo batteries to power an
electric gate. It is the same size and shape as the PC-680 but it is
labeled as a valve-regulated, sealed lead acid, rechargeable
battery. It seems to work flawlessly, though I don't think I would
trust it in my airplane.
Charlie Brame
RV-6A N11CB
San Antonio
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Hi Charlie,
My understanding is that it's called a "dry" cell because if you break
the case, acid won't come out. The can be shipped as non-hazardous
because of that. These are starved electrolyte or recombinant gas
batteries using lead acid chemistry.
I have two in my plane and one in my motorcycle.
Bob W.
--
http://www.bob-white.com
N93BD - Rotary Powered BD-4 (first engine start 1/7/06)
Custom Cables for your rotary installation -
http://www.roblinphoto.com/shop/
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Ed Anderson
Joined: 10 Jan 2006
Posts: 475
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| Posted: Sat Jun 24, 2006 5:19 pm Post subject: PC-680 Revisited |
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Charles, the Odyssey is actually a "Wet cell". The electrolyte is embedded
in a material that is in effect like a cloth soaked in battery acid, so in
that sense, the acid will not spill out if you turn it on it's side. So it
is sometimes referred to as a "Dry Cell" since it does not leak liquid.
Ed
---
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_________________
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com |
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brian
Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA
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| Posted: Sat Jun 24, 2006 6:01 pm Post subject: PC-680 Revisited |
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On Jun 24, 2006, at 8:32 PM, Charles Brame wrote:
| Quote: |
<chasb(at)satx.rr.com>
My Odyssey PC-680 has been in my non-flying RV for about three
years - most of the time uncharged. It keeps a charge for months,
and after topping off, it started a new, cold engine repeatedly
with no problems. I'm impressed
The nomenclature that came with the PC-680 battery says it as a Dry
Cell. I remember an AeroElectric discussion a few years back about
lead acid, sealed lead acid, gel cell, and recombinant gas
batteries. According to the archives that I found, the PC-680 is
described as a Recombinant Gas and/or Sealed Lead Acid battery. I
wonder if it really is a dry cell or if that is just a
manufacturer's line?
I recently bought one of the BB17-12 el-cheapo batteries to power
an electric gate. It is the same size and shape as the PC-680 but
it is labeled as a valve-regulated, sealed lead acid, rechargeable
battery. It seems to work flawlessly, though I don't think I would
trust it in my airplane.
|
There are a lot of words used to describe these batteries. Here is
some nomenclature that might help this make sense:
Lead-acid -- describes the chemistry. Electrical energy is stored as
a chemical change in lead plates using a sulphuric acid electrolyte.
All of the batteries we use in our airplanes are lead-acid unless
they are NiCd.
sealed lead-acid -- you can't add water to it.
AGM -- absorbed glass mat. The liquid acid electrolyte is held
between the plates by capillary action in a thin fiberglass mat so
you don't need a lot of electrolyte. Since there is no free
electrolyte to slosh around you can use it in any position. (Imagine
water held in a paper towel if you want to get an idea of what I mean.)
starved electrolyte -- AGM.
"Dry" lead-acid or "dry cell" -- starved electrolyte or AGM.
Gel-cell -- the sulphuric acid electrolyte is mixed with a binder
that turns it into something like Jello. This keeps it between the
plates and it can't slosh around. You can use these in any position.
Recombinant gas or RG -- this means that the excess hydrogen and
oxygen that would be allowed to bubble away at the end of the charge
cycle are made to recombine back into water at the plate. This keeps
you from having to add water as it doesn't escape into the atmosphere
like a typical "wet" battery but stays in the battery. Both AGM and
Gel-cell batteries are RG batteries.
Valve regulated, valve regulated lead-acid, or VRLA -- If you
overcharge an RG battery it will produce H2 and O2 faster than they
can recombine. The result is excess gas trapped in the cell. If the
overcharge is removed and the battery left to its own devices the H2
and O2 will eventually recombine. If the overcharge is allowed to
continue the pressure in the cell continues to rise. Each cell has a
pop-off valve that will relieve the pressure before the case bursts.
The only problem is, if this happens the water that is needed inside
the battery escapes into the atmosphere and now you have shortened
the life and capacity of the battery. As far as I have been able to
learn, all AGM and gel-cell batteries are VRLA batteries.
There are two big differences between AGM and gel-cell batteries:
1. They need different charging and float voltages. Gel-cells like
about 13.8V for charge and about 13.4V for float (charger applied all
the time to keep the battery maintained at full charge). Flooded cell
batteries and AGMs like about 14.2V for charge but only about 13.2V
for float. (These numbers are for a temperature of 20C. The voltages
need to be decreased as the temperature rises or increased if the
temps are cold.)
2. AGMs are *great* for delivering a LOT of current from a relatively
small cell. This makes them great for starting engines. Gel-cells are
not as good for delivering a lot of current but will give you more
charge/discharge cycles in deep cycle usage. In all probability you
want an AGM battery for your airplane but only if you are taking care
to prevent overcharge.
So you want to know whether the battery is AGM or gel-cell. Just
having someone tell you VRLA or "sealed" doesn't tell you much.
With regard to overcharge: neither AGMs nor gel-cells will tolerate
overcharge very well. It kills them pretty quickly. One interesting
thing is that you can split the difference between charge and float
voltages on a gel-cell and still get good service but need only one
voltage. You can't do that very well with an AGM battery.
OTOH flooded cells handle overcharge pretty well. It just makes them
bubble and give off H2 and O2 gas. As long as you don't overheat the
battery with a gross overcharge you fix the overcharge by adding more
water.
So the "el-cheapo" battery you have and the PC-680 are both "valve
regulated, sealed lead-acid, rechargeable" batteries. In all
probability both are AGMs as well. I am sure your "el-cheap" battery
would work just fine in your airplane too.
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
— Antoine de Saint-Exupéry
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery |
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trigo(at)mail.telepac.pt
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| Posted: Sun Jun 25, 2006 9:28 am Post subject: PC-680 Revisited |
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As usual from Brian, a very good description of batteries, easy to
understand and learn.
Now I know everything I need about that important part of my airplane,
thanks to this group and specially Brian Lloyd
Carlos
---
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