In article ,
Eric F. Richards wrote:
(Mark Zenier) wrote:


So anyone with a concern for truth and justice, (and a bit of a flippant
attitude) is hateful?

If his concern was about "truth and justice" AND he'd redirect his
postings to ANY politics group instead of flooding us with them here,
it would be a different story.

In my OPINION (note that I know when to use that word), his worldview
is colored by an unfortunate anti-US bias that a small but vocal
minority in Canada have. Were you here 'round 9/11/01? Remember
psycho-Jim, who was mad on 9/11 for two reasons? 1) not enough
Americans were killed and 2) he couldn't get any music on his radio
that day?

As for his point of view, I might share some of his views. But I
would never, ever consider him an objective observer.


Solar cells have a voltage vs. current curve that's roughly square.

|___ Open Circuit voltage
| ====____. maximum power point
V| \ \
| \ \ "Constant" Current
| \ \
| \ \
|---------------
I ^ available current depends on incident light

The no load voltage is determined by quantum physics and is roughly
constant. The current available is determined by the cell area and
the incident sunlight.

In practical terms, if you don't put the cells in a situation where
they're outputting enough current to damage their internal wiring,
you can hook them up and they'll provide a roughly constant current for
charging a battery. You wouldn't want to use too high a voltage array,
as you could damage the battery.

Bzzzzzt. You were doing fine up to there. Unless you are addressing
alkaline (Ni-Cd) batteries instead of Lead-acid batteries

Er, alkaline batteries are primary cells usually, except for those doggy
Rayovac rechargeables. And why would anybody use Nicads or NiMH cells
on a stationary system? Too small, too expensive. For Mike, at
a max of 4.5 amps, a single marine deep discharge lead acid would
probably be good enough.

And if the sunlight goes away, as it
does every day, leakage back through the cell can discharge the battery.

Bzzzzt. Minor problem, not a concern unless you have massively
parallel arrays.

So the simple "chargers" I've seen where switches to disconnect the
battery when its voltage got too high, or there wasn't enough sunlight.

Bzzzt. All chargers are solid-state, PWM based.

Not if you build your own. (Or dig back and look at a few magazine
construction projects).

If you want to be cost effective, you get a fancy charger that
transforms the load on the solar array to the maximum power point
to get the most bang for the buck.

Back on track again.

And if you're just hacking around, you probably won't want to spend
the $$$ for one if it only gets you from 50 watts to 80 watts.

Mark Zenier Washington State resident

(Mark Zenier) wrote:


Bzzzzzt. You were doing fine up to there. Unless you are addressing
alkaline (Ni-Cd) batteries instead of Lead-acid batteries

Er, alkaline batteries are primary cells usually, except for those doggy
Rayovac rechargeables.

Ni-Cds are alkaline, too, and I'm not talking about "D" cells, dummy.
Wet cell Ni-Cds with sodium hydroxide electrolyte and a layer of
mineral oil keeping the electrolyte from being exposed to air are used
in a fair number of systems. They're used in locomotives to start
them. Ni-Iron (Edison) cells are in those boxes at every crossing.

Ni-Cds are dangerous as hell, but handle temperature variation much
better than lead acid.

Bzzzt. All chargers are solid-state, PWM based.

Not if you build your own. (Or dig back and look at a few magazine
construction projects).


All *modern* ones. And a store-bought PWM charger can be had for $30.
And there are designs out there for build your own.

And if you're just hacking around, you probably won't want to spend
the $$$ for one if it only gets you from 50 watts to 80 watts.

If he's using lead-acid and the panel cannot charge faster than C/5,
he can do without a controller altogether. Probably don't want to do
that with a gell cell unless the rate is C/20 or so.

--
Eric F. Richards,
"Nature abhors a vacuum tube." -- J. R. Pierce, Bell Labs, c. 1940