Thanks for this, Jeff. Sorry I'm so slow to respond.
It tells me a bit more than I wanted to know!
I've sat through a few feeble videos from YouTube on the topic, so I'll
summarise: if anyone has a mechanical clock which they want to pass on
to future generations, it's probably a good idea to put a dot of some
kind of clock oil on the bearings every few years.
Look at how those "tree cams" work. They are solar maintained, and a
On Tue, 7 Jan 2014 21:34:07 +0000 (UTC), mroberds@att.net wrote:
Followups set to sci.electronics.design.
In sci.electronics.design Mr. B1ack <nowhere@nada.net> wrote:
Alternatives are, of course, Ni-Cad (charge memory effect
Much less of a problem in the real world than the vendors of all other
chemistries would have you believe. There will now be 500 follow-up
posts arguing this point to death.
Tell that to the three dead expensive cordless drills
I have in the toolshed ... all NiCad powered. They
died WAY before I'd gotten good mileage out of
them and the battery packs are so expensive it's
better to just buy a whole new drill/battery set.
I'll NEVER use NiCads again !
NiMH (<500 recharge cycles, sometimes much less)
The NiMH AAs I've used seem to give me more than that. YMMV.
You've counted ? Betcha it's really under 100 cycles.
I have a bunch of semi-dead ones that got that way
in less than 100 cycles ... lost half their capacity or
more, and I had decent chargers too.
NiMH batteries are also a pain to charge since you can't
really use voltage as an indicator of reaching a full charge
but instead have to measure the temperature ... they start
to get hot once fully charged.
and lead-acid 6v or 12v.
You can also get PbA in 2 V increments - Gates/Hakwer/Genesis/Enersys
"Cyclon" cells. Sometimes being able to get a 4 V or 10 V battery
makes the rest of the power supply design easier.
True, I've seen odd-voltage cells/batteries ... but with "odd"
comes *expensive*. As usual, the rules of mass-manufacturing
and mass-consumption are at work here ; "popular" batteries
cost a lot less. Usually those are 12v gels and wets.
Also, for really low-drain stuff like this, don't discount a plain old
alkaline battery. Energizer says their alkaline D cell will give you
about 20 Ah, when discharged at 25 mA from new to 0.8 V. That's a
little over a month of continuous runtime at 25 mA. About $1 each when
you buy several at once. Okay, maybe your device is at the top of a
radio tower, or down in a well, or stuck on a bobcat, or in some other
situation that makes it impractical to change the batteries.
http://data.energizer.com/PDFs/e95.pdf
That's my dilemma ... the devices are gonna be WAY off-grid,
some with cellular data links due to accessibility issues. I'm
looking for "affordable" solar/battery setups that'll keep working
for a minimum of two, preferably five, years. "Affordable" does
not have to mean "dirt cheap", but it can't be near what the
commercial datalogger people charge for their setups. For
$50-$75 I can combine an adequate Pb, or maybe Li-Ion,
battery and a one or two watt panel plus electronics to
charge 'em and efficiently siphon off tightly regulated voltage.
I'd *rather* have an "affordable" off-the-shelf solution - mostly
because of the way bosses think - but I just can't find one
anywhere. This seems odd, given the increase in the use
of remote sensing.
HOWEVER ... whip out yer Google and try to find something like the
"Li-Po Rider", but made to work with lead-acid batteries that doesn't
cost a couple of proverbial body parts. Look for something in a nice
factory box that you can show off to the boss as "See ! Off the
shelf !" and, well, I don't think it can be had for even several body
parts.
Powerstream sells a couple that might do what you want. They have this
board http://www.powerstream.com/solar-charge-alternate.htm that they
say they will program how you want; they have off-the-shelf versions
for PbA http://www.powerstream.com/pb-acid-charge-board.htm and NiMH/
NiCD http://www.powerstream.com/NiMH-NiCad-solar-charge-controller.htm
for $80 qty 1. They also have a smaller one, but it's designed for
48 V telecom stuff http://www.powerstream.com/48-pv-control.htm , for
$38 qty 1. I don't know if these chargers suck or not; I just know that
they exist.
I looked ... and they ain't bad. Still a "board" of course, no nice
artistic plastic box with a logo and plugs.
Their output-voltage range offering is quite broad (but only some
testing would show how stable it is). Some of the lithium/solar
chargers I looked at claimed "5-volt" output but actually varied
quite widely when the charging voltage changed. I guess they
meant a "nominal 5-volts" or "average 5-volts"
Seeed's LiPo Rider Pro is less than half the price ... though it
only charges at about 800ma max instead of the claimed 1800ma
for the above device. For MY purposes, even 500ma is more
than enough. Those using PI's or other boards that suck more
juice might lean towards Powerstreams product. We using
small Ard/ARM/Propeller/PIC-based boards can get by
for less.
The homebrew combo I mentioned - the TI battery manager
plus the little DC/DC converter - works beautifully, is cheap
and really easy to wire up. It kind of boils down to whether
I trust lithiums or Pb to last longer in the field given my
power production/consumption profile. Guess I'll have to
make a couple of each and actually put 'em out there in
the untempered environment.