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
------------------------------