Marty Michener wrote:
> Dear Jeremy:
> These suggestions are based on my four trips into tropical recording
> conditions with the HHb.
> All the posts I have read thus far keep referring to battery sets as thou=
> they were composed of units that behave as similarly as they
> look. Actually, I have been analyzing batteries since grad school in 196=
> and typically have found one or two in any set of eight used in series th=
> actually limit the overall performance, because the current flows through=
> all eight equally, despite the condition of each cell.
> Here is a very simple test I strongly recommend doing:
> Take a Portadisc caddy of 8 batteries fully charged, out of the unit.
> Place a resistor across the snap connector on the end that will draw SOME=
> but not a lot of current, for example 470 ohm.
> It will slowly get noticeably warm because 12 x 12 =3D 144, then divide b=
> R=3D470 is about 0.3 watt.
> I actually bought from Radio Shack some of those 9v battery snap
> connectors, and soldered a 470 ohm half-watt resistor to the leads. The=
> snap works with the end of the HHb battery caddy, so the test is easy to =
> whenever you want.
> Under this load of about 25 milleamps, now user a voltmeter to CHECK EACH=
> BATTERY for its voltage.
> Ideally you should get all of them to lie somewhere between 1.2 and 1.5
> volts. If one is much lower, replace it. I would even swap them around =
> get each set to be as closely matched as possible. If you have four sets=
> now, having three that are really matched would be better than four
> unmatched. Of my original FUJI set that came with the machine, here are =
> 1.36 1.37 1.37 1.36 1.37 1.37 1.37 1.37
> This set is labelled as 1.2 volts for 1550 mah. So with this low drain i=
> place, the resistor would last about 60 hours.
> The results of this test are even more interesting when they are drained =
> the end of a session, because that is when one or more drop below their
> rated 1.2 volts and may potentially become BACK CHARGED by the
> others. This will ruin a battery, and once it happens all bets about
> matching the set are off.
Note that NIMH are spec'd different than, say, alkalines. The 1.2 volt
spec is the expected voltage at 80% discharged.
The cell has to drop to zero volts to have a reversal, but it is the
reason I highly recommend not running the battery pac clear flat. As
I've stated, about a 70 - 80% reading on the Portadisc is probably as
far as you should go. That will give you nearly all the time the pac is
capable of giving you and should prevent killing a cell.
The sidebar is that for those that have been running their pac's down
until the Portadisc quits, you really, really need to analyze each cell
if having problems. You have probably damaged some cells.
Incidentally, my sets all test within 0.01 volts, except I tested them
while running the Portadisc. I buy them and keep them together as sets,
always treating each set as a unit as far as charging and discharging.
When they go unbalanced, I demote them to light headlamps and other such
tasks and get a new set. I also get higher capacity batteries each time
I buy, whatever the latest is. I buy to replace batteries that have
dropped out the bottom of my batch of batteries, but the new ones always
get first go in the Portadisc. My current two sets are nearly a year
old. The previous 1800mAh sets did not have problems and are still going
strong. Even between my two caddies, I have bought new sets at the same
time, and try and keep the usage between the two caddies fairly even. So
either one will run the Portadisc about the same.
I did a little measurement of my own today. I checked the current draw
off the fully charged pac into the portadisc. With everything full on,
recording, phantom power, light, digital output, headphones, max draw I
could get was 409ma. The current draw varies a surprising amount as it's
running, so a average would be lower than that.
The 80% working capacity of my 2000mAh batteries would be 1600mAh. So
even if the Portadisc ran steady at it's max, that's 4 hours run time.
> FIELD USE
> Regarding battery life in the field. I use the HHb on record-pause a lot,=
> because I am typically after one or two infrequently-calling species of
> birds, so I walk as if I were recording (quitely, stealthily) much or mos=
> of my field time. This drives birders nuts, because they always want to=
> talk about all the birds they see or hear. Viva las Cryptophones.
> My caddy life varies between about 2 and four real recording hours, and I=
> have only a rough idea how much of that time I spend
> listening in the Record-pause mode (88%),
> how much time in STOP (10%) and
> how much time playing back what I just recorded (perhaps 2%)
> Unlike Walt, I have seldom made one full disc by that time, due to the ho=
> mode. I too use the display light ON most of the time.
Note, I don't make a disk at a time normally. I did, to get a estimate
of the battery life, do this. In normal field usage my Portadisc is
typically on for 5 minutes or less at each site for survey recordings,
more if it's a good site for listening recording. I rarely listen to
what I record in the field. I probably do better than 90% of my on time
recording, most of the rest in record/pause.
The mix of pause vs record will vary a lot depending on what you are
recording. With the frogs I don't often have to sit and wait for calls.
I would expect that hardly any bird recordist would get away with as
little pause as I use. Except those who simply shotgun hoping something
will call while recording.
> Despite the radio shack set variance, I get a bit more field recording ti=
> from that set, indicating that the 1800 vs 1550 may reflect a real capaci=
> advantage. I am always skeptical since the COPPER-TOP scam several years=
I have found that the time I get does vary in proportion to capacity
ratings. Though one should take the ratings as estimates. With most of
the better companies the batteries will test slightly higher capacity
when new, but the capacity does slowly diminish with age. Then at some
point it starts dropping more rapidly, which is when I replace.
> The HHb percentage battery life is to me undecipherable in real use - the=
> numbers themselves are meaningless except on any one given day, you watch=
> the numbers whatever range they are, over, say, a period of fifteen minut=
> to one half hour. When you get three consecutive significant drops (why =
> they sometimes RISE???) you turn the unit off for two minutes and that
> writes the TOC onto the disc, then you turn it on and watch the battery
> numbers very carefully to get ready to swap them for a new charged set.
The numbers are a measure of voltage of the pac. They are pretty
accurate if you are using a set of alkalines, which drop fairly steadily
in voltage. Unfortunately NIMH don't drop much for the first 80% of the
discharge. I start thinking replacing the pac when it's got down to 97%.
And as I said will not go below 70% unless in the middle of a really
valuable recording. Typically I replace the pac early so I won't get
caught like that.
From my measurement of the Portadisc's current draw, it's not hard to
see how the voltage is going to vary. With the full recording load I
occasionally saw lows close to 200ma. There was far more variability in
the load than I expected.
> For emergencies in the rain forest, I carry a set of 8 Photo Lithium
> AA L91 (expensive, light weight, not rechargable) in case both caddys ar=
> discharged and I am still in good or unusual bird sound environment. In=
> Panama I had to rely on these, because the Cana field station only had 11=
> v AC electricity for three hours every evening, and no charger I have doe=
> NiMH that quick.
As I've noted, such chargers now exist. Though when you made your trip
it would have been touch and go to get them charged with what was
> QUESTIONS FOR THE GROUP, for HHb
> With NiCd batterys there were numerous FAST chargers available, and I had=
> several battery sets that showed me (this was the 1960's) that the fast
> charger actually kept the heavy duty batteries in better condition than t=
> slow chargers. Of course using NiCd s was a totally different world.
Yes, I'm dumping the very last of my Nicads this year. Just tired of
having batteries that hold so little. The remaining ones are well below
their original capacity.
The more recent info on Nicads says that a medium rate charger is best
for them. Over the history of Nicads the recommendations have changed
many times. And, the new pulse chargers can also do Nicads, making a
whole new set of parameters to consider.
> Question: What is the fasted way to charge all 8 NiMH AA batteries
> completely, given that you often do not have "all night" to wait till you=
> need the recorder again?
The fastest I have is the Maha MH-C401FS. This uses the new pulse
charging method which prevents bubble formation, which is the problem
that limits speed of charging and destroys batteries. Each one of these
will charge 4 batteries at a time, each battery is on a separate
controller so get's optimum charge. So you will need two of them per
pac. It has two settings, fast and slow. Fast will charge my 2000mAh
AA's in 1-2 hours. Slow will take 3-4 hours.
The Maha MH-C204F chargers I have will do about the slow rate. They also
have a conditioning cycle for fully discharging the batteries before
charging. It's in there for nicads, not really needed for NIMH, but I
put mine through it every couple months.
I'm very sure there are other chargers than these that can do fast
charge. They are just what I have. Both work off 12vdc, so can be run
off a car battery as well as off ac. So, I can fast charge in the field
as I'm rarely that long away from the Ranger. I have enough of them that
I keep a separate set with the field stuff so I don't have to be
organizing those each trip. I only have two of the new pulse chargers,
which cost more.
> Question: why don't we have a rechargeable Lithium ion setup for
> recording? For all my field computers, small MDs, palm pilots and video=
> machines bought in the last five years I typically get a "use it 4 hours,=
> recharge it in one hour" situation. Why not HHb if it is really to be fo=
> professional use? It is the only machine I own where the ration is
> reversed - use it four hours, recharge twelve hours. I know very few
> professions that can work on that ratio of downtime.
The people who had the most influence on the HHb's design other than HHb
was ENG. Those folks must get their recording, so wanted a recorder that
they could, in a emergency, get batteries anywhere. Alkaline AA's are
probably the most worldwide battery. So that's what it's based on, use
NIMH if you can charge them, otherwise use alkaline, or as you did lithium.
It would probably be possible to build a pac with Lion cells that would
fit in a Portadisc. But you would also have to build or buy a special
charger for it. I'm not sure if it would be safe to try using the
Portadisc's internal charger. The Maha MH-C777Plus charger comes to
mind, it's a universal charger for battery pacs and can do Lion. In
reality you would probably be better off rigging some standard Lion pac
to plug into the power input of the Portadisc. I expect you could find
some belt pacs that you'd have to do little more than change the plug.
As I just pointed out above, you can recharge the batteries fast. In
fact the 3-4 hour charge was available before the Portadisc came out.
That you can't in the machine is just fine by me. Fast charging produces
lots of heat, and a risk of leakage. I don't want that risk inside my
portadisc. Even though they did allow for that by putting the batteries
outside of the main case shell.
You should always check the manufacturer's specs before fast charging
NIMH. In theory they can be charged at a 1X rate in a properly
controlled standard charger, but not all manufacturers recommend such a
fast rate. A 1X rate, btw, means charging at a rate that is the same as
the capacity, thus taking one hour. Unless it's a pulse charger the
battery will get very hot. Pulse chargers are a new game and will
probably become much more common, and hopefully, cheaper.