|
Care and Feeding of batteries |
Vince
Endter Writes:
I have attached a picture of my new radio battery
setup. I purchased (8) AA
1800 mAh batteries from Zbattery.com and an eight AA battery holder from
Radio shack. I also purchased an adapter from radio shack that fits in my
radio aux power plug. The battery holder has 9V clip connections.
Radio
shack has 9V clip leads. I made a cable to go from the battery pack to
the
radio. Now I have almost twice the 1050 mAh that comes with the clip on
battery (which is actually aftermarket, standard is 650 mAh). It should
last 7 to 8 hours. When I get on the ground I can unplug my battery cable
and I still have all of the 1050 mAh in the clip on pack to use. If I am
going for a world record in Zapada, I can install Alkali batteries in the
pack and get 2800 mAh (and another couple of volts).
Vince
Gilbert Griffith Writes:
Dave
Broyles has written about nicads and most of what he says is pretty
straight
forward. Except for the fact that
nicads do not discharge in a
linear
fashion.
Being a
world renown Icom dealer, and fastidious repacker of battery packs
for two
local schools and many other pilots, I
have studied the antics of
numerous
nicads from radios, video recorders and cameras, not to mention
mobile
phones.
My
method is to fully charge a pack and then monitor the voltage while a
known
load is connected to the pack, when the voltage drops to 1 volt per
cell, I
terminate the test.
I have
a computer program which will log voltage against time by taking a
measurement
every few seconds and displaying it on a graph.
The
normal response goes something like this.
Assuming
about 1.4 to 1.5 volts as the initial voltage, with a 1C load,
within
a few minutes the voltage quickly drops to 1.3 to 1.2 volts and
maintains
this level, dropping at a much slower rate, for the (usual)
capacity
of the battery, at which point the voltage has dropped to 1.1
volts. Thereafter the voltage drops off quickly to
below 1 volt in a matter
of a
minute or two. Can you imagine the
curve on the graph?
It is easy
to see the early death of a cell or two by the notches in the graph.
What
this means is that the small voltage drop from say 1.3 to 1.1 volts may
take an
hour or so at a load of 1C so you can see that it is almost
impossible
to tell whether the battery is 1/3, 1/2 or 2/3 charged by merely
measuring
the voltage.
When
repacking I use AA size cells of 1000mAh capacity. I have tried NiMh
batteries
of (claimed)1100mAh capacity, but was never able to get more than
600mAh
out of them. It is possible that they
do not like the high discharge
rates
that nicads will tolerate, which can be up to 1.2 amps during transmit
on some
radios. Video cameras are really
vicious with their current demands.
A
battery therefore of 1000mAh (1Ah) having a discharge rate of 1C, should
last an
hour delivering a current of 1 Amp at the rated voltage for that pack.
I have
built a constant current sink which will apply a selected load,
independent
of the voltage applied, so that I can discharge the packs at a
known
steady rate, usually 500mA or 1000mA.
Anyone
who has a Garmin 38 will notice the voltage scale starts high with
full
batteries, and quickly drops to half scale, where it sits for hours
until
the batteries go flat suddenly.
Incidentally, this scale on the
Garmin
is calibrated for alkaline batteries and that is why nicads read low
even
when fully charged.
The
only way I have found to test a pack is to do a full discharge test or
two and
study the graphs.
The
only reliable way to be sure of a full battery is to charge overnight
the day
before flying, preferably at 1/10C which is the normal amount
supplied
by the wall charger that comes with your radio. It is quite safe
to
leave it on for a couple of days, and some of the newer high capacity
batteries
may require 15 to 20 hours at this rate to reach their full
charge. Even if they are already half charged, it is
still OK to put them
on the
wall charger overnight, as long as they don't get too warm they will
be
OK. If you are in doubt about the rate
at which you charger actually
charges
your battery packs, it is a relatively simple matter to make a patch
cord to
break the circuit and insert an ammeter to monitor the charging current.
It is difficult
to understand why anyone would neglect to charge all their
batteries
the night before a flight. All of the
Icom range can also be
plugged
into your car electrics and left to charge overnight in the same
manner.
The
newer models can be connected via their optional power cords, to large
(sealed)
lead acid batteries of 12 volts 1.2 or 2.4 amp hours, and will then
run for
days. When the large battery is flat,
just remove the plug and the
radio's
own battery will still be fully charged.
I have
seen expensive radio controlled models, planes and helicopters,
completely
destroyed because of flat batteries, to me this is inexcusable
and
possibly criminal negligence.
THE
ONLY WAY TO BE SURE OF A FULL BATTERY IS TO CHARGE IT OVERNIGHT BEFORE
THE
DAY'S FLYING.
If your
battery is 3 years old have it tested or replace it, especially if
you
find that it lasts less than the normal time.
Finally,
if you are carrying batteries about, maybe as a spare, make sure
the
terminals can't be shorted by other articles such as keys etc.
Hope
this helps your flying fun. (There's
not much going on here in Bright
at the
moment)
*************************************************************************
Gilbert Griffith, Bright, Victoria, Australia. cogito ergo avia
Homepage
http://www.home.aone.net.au/gilbert
"To try when your
arms are too weary,
to reach the
unreachable star."
------------------------------
Wuffo Willey
Writes:
I tried
everything and the battery for my Kenwood died. It
won't
hold a charge. My friend Kean Myron has
the same radio
and his
battery died about 6 months ago, they are about the
same
age and had the same use. He just
ordered a battery for
the
Kenwood and it cost about $90 and he has been waiting on it
for 4
weeks. I just found a site where the
same battery is
$43.95
They
carry all major brands inc. Alinco, Azden, E.F.Johnson,
Icom,
Kenwood, Radio Shack, Standard, Yaesu/Vertex,.
jim
http://www.sarrio.com/sarrio/nicad1.html#ordering
The
Raymong Sarrio Co.
6147
Via Serena St.
Alta
Loma,
Ca. 91701
1-800-413-1129
1-909-987-7761
(FAX)
You can
order with credit card.
--
WUFFO
WILLEY
Woof!
------------------------------
Tim Ward
Writes:
ernie
wrote:
>Another
side-note: I hadn't known
>of
the melt-down possibility with a gel cell 'till it was mentioned on the
>list
I don't
think you need to worry, ernie. I've never heard of a gel-cell
meltdown.
Nickle-cadmium batteries can and have melted down, but gel-cells
are
lead-acid chemistry.
On the
other hand, I _have_ melted 18-gauge wire with a 2.2 Ah gel-cell. Now
both
terminals are fused right at the battery. An easy way to do this is to
take
two of the quick-disconnect connections that slide on the battery
terminals
and solder them back-to-back. Slide one on to the battery
terminal,
and slide one side of one of those flat plastic-bodied auto fuses
into
the other. Then the terminal that you
used to have connected directly
to the
battery can slide onto the other leg of the fuse. Cheap, easy to fix
if a
fuse blows, and works like a champ.
Tim Ward
------------------------------
Gilbert
Griffith Writes:
Date:
Fri, 10 Sep 1999 10:22:49 +1000
From: Gilbert
Griffith <gilbert@bright.au.com>
To:
FSchwab@speedchoice.com
Cc:
hang-gliding@lists.utah.edu
Subject:
Re: Lithium Batteries
Message-Id:
<3.0.1.32.19990910102249.006aa644@mail.netc.net.au>
Content-Type:
text/plain; charset="us-ascii"
I've
just done a test on my GPS12XL with the following results.
10
volts 50mA
7.5
volts 65mA
5 volts
98mA
4.6
volts 110mA
4.5
volts GPS shuts down.
So it
looks like you are not going to get any advantage from batteries
below
1.1 volts per cell.
Chainsaw.
------------------------------
Date:
Fri, 10 Sep 1999 09:16:47 +1000
From:
Gilbert Griffith <gilbert@bright.au.com>
To:
<FSchwab@speedchoice.com>
Cc:
hang-gliding@lists.utah.edu
Subject:
RE: GPS
Message-Id:
<3.0.1.32.19990910091647.006a4898@mail.netc.net.au>
Content-Type:
text/plain; charset="us-ascii"
At
18:35 8/09/1999 -0700, you wrote:
>Good
info page on batteries, Gilbert. The
only thing I'd take exception
>with
is your statement "And
>the
regular Nicad chargers don't put in enough current, you need to push in
>150mH
for 12-14 hours to get a full charge."
Did you
realise I am talking about the 1500mAH NMH cells here?
Maybe
in the US you have nicad chargers that have higher charging currents
than
the ones we have here in the shops. All
of the ones I see are for
older
nicad batteries of 500-700mAH and only charge at 50-70mA, this is not
enough
to charge the 1500mAH NMH cells overnight (if at all).
>
>Besides
over-discharge, over-charge is the biggest killer of NiCd/NiMh
>batteries. The mechanisms are different (heat and
corrosive gas formation
>for
over-charge), but charging a battery with a fixed current for a fixed
>time
without knowing its initial state of charge is a "BAD THING". You were
>absolutely
right in recommending a Pulse charger for maximizing battery
>life
- it can do an excellent job of monitoring the state of charge of the
>attached
battery and stopping the high-rate charge before battery damage is
>done.
>
>/frank
I agree
about overcharge being a problem, and, as you said, I think the
biggest
killer of battery packs is running them down to zero volts, thereby
reversing
the polarity on the weakest cells. I
get a lot of dead packs
because
of this. I tell customers that the most
important thing to do to
get
long life from a pack is to recharge it when the cell voltage is down
to one
volt, this usually means that they should switch off their radio as
soon as
it drops out of transmit, and not keep trying to get any more from
the
pack. The other thing I always tell
them is to stop charging if the
batteries
get warm.
I've
been putting temperature switches in all my repacks so that they will
stop
charging when hot. Icom have them in
all their packs. This also
provides
some protection against a melt-down if there is a short.
According
to most manufacturers, charging at 1/10C will not harm a cell
even if
you leave it too long. It will get
warm, but not hot.
The
fast chargers with sensing circuitry are the best, but they are also
the
most expensive and not really what a travelling pilot wants to carry
around. I make up simple car chargers with only an
82 ohm resistor to
limit
the current to about 150mA for my 1500mAH cells, it charges four at a
time
and can be left in the car overnight.
I've made a couple of chargers
for the
paragliding school that will charge 16 or more packs at once, with
different
plugs for each type of battery or radio, and different value
dropping
resistors for each plug. It is strictly
an overnight charger, but
cost
next to nothing using off-the-junk-room-shelf components.
On the
matter you mentioned about scanning maps for Oziexplorer. It will
use
just about any map, with BMP format being the best (IMO) but you have
to
calibrate each map you use, which can take a while. I took a couple of
weeks to
get all mine running. Each map is 12 to
14 MB in size! I just
counted
them and there's 81 files all over 12MB each.
US
Street Atlas would be great!!! But not much use here in OZ.
Chainsaw
------------------------------
Marc Whisman
Writes:
Date:
Thu, 09 Sep 1999 20:20:50 -0700
From:
Marc Whisman <marcw@sprintmail.com>
To:
Hang Gliding List <hang-gliding@lists.utah.edu>
Subject:
Re: GPS
Message-ID:
<37D87912.4D28@sprintmail.com>
Content-Type:
text/plain; charset=us-ascii
Content-Transfer-Encoding:
7bit
Gilbert
Griffith wrote
> The other thing I always tell them is to
stop charging if the
>
batteries get warm.
That's
interesting because I have an Icom A-22 aviation radio, and ever
since this
unit was new the batteries have always felt quite warm when
charging. I recently purchased a 1000 mah NIMH pack
for this radio and
it
doesn't get warm at all. It does take
longer to charge using the
Icom
charger, but they told me this would happen.
-Marc
------------------------------