RW Salnick wrote:

RW Salnick inscribed in red ink for all to know:

KLC Lewis inscribed in red ink for all to know:

"Larry" wrote in message
...

"John" wrote in
:


The manufacturer claims an increase
in current power of 30%.



What nonsense. The controller turns the panels OFF at the appropriate
time. It doesn't manufacture power from thin air. I wouldn't buy his
product because he lied to me.



Larry
--
Democracy is when two wolves and a sheep vote on who's for dinner.
Liberty is when the sheep has his own gun.




IIRC, Practically A Sailor did a test and review on those units, and
verified the manufacturer's claims.



How do the Maximum Power Point controllers work?

bob
s/v Eolian
Seattle



OK, nobody's answering me - I'll try it myself...

IIUC, the "power Point' controllers are basically DC-DC converters,
converting the 19 volts or so that the panels produce to 12.6 (or
something), thus drawing from the panels at their output voltage instead
of the battery's voltage. Presuming minimal change in current delivery,
this would represent an increase in delivered power.

OK, where am I wrong here?

bob
s/v Eolian
Seattle
Assuming the panels can be modelled as an ideal voltage source with a
(variable) series resistor (they cant but its a useful approximation)
you are extracting the *maximum* power from the panel when its loaded to
half its open circuit voltage, BUT you are unavoidably wasting the
*same* amount of energy in heating up the panel. (n.b. this does *not*
work for getting maximum *energy* out of a battery). I suspect they
will actually be boosting 9.5V up to 12.6.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:
'Stingo' Albacore #1554 - 15' Early 60's, Uffa Fox designed,
All varnished hot moulded wooden racing dinghy.

On Thu, 08 Feb 2007 21:31:26 +0000, Ian Malcolm
wrote:

Assuming the panels can be modelled as an ideal voltage source with a
(variable) series resistor (they cant but its a useful approximation)

Assume what you like...

Ian Malcolm wrote in
:

Assuming the panels can be modelled as an ideal voltage source

Geez. If boat technology gets any better, we'll be able to run a light
bulb off the panel, shining on the panel, and the panel will have so much
power boost there'll be a surplus to charge the batteries!



Larry
--
Democracy is when two wolves and a sheep vote on who's for dinner.
Liberty is when the sheep has his own gun.

Larry wrote:

Ian Malcolm wrote in
:


Assuming the panels can be modelled as an ideal voltage source


Geez. If boat technology gets any better, we'll be able to run a light
bulb off the panel, shining on the panel, and the panel will have so much
power boost there'll be a surplus to charge the batteries!

Why not see if you can patent that idea?
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Anyway, if it was possible to get a net energy gain, you'd still be
dissipating half the energy in heating the panel so you'd burn it up for
sure if you tried to get out more than you put in.

This may in fact be a problem in real life in hot climates unless you
have very good air flow over the panels, as the MPPT controller will be
working them harder and they *will* be getting hotter. Will the
supplier stand behind their product if its connected to an advanced
controller? If they are on an elevated mount, it may well be worth
spraying the backs with the thinnest possible coat of matte black paint
to help dissipate the heat.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:
'Stingo' Albacore #1554 - 15' Early 60's, Uffa Fox designed,
All varnished hot moulded wooden racing dinghy.

"Larry" wrote in message
...
Ian Malcolm wrote in
:

Assuming the panels can be modelled as an ideal voltage source

Geez. If boat technology gets any better, we'll be able to run a light
bulb off the panel, shining on the panel, and the panel will have so much
power boost there'll be a surplus to charge the batteries!



Larry

Here is something I posted to the "Cruiser's Forum", about MPPT charge
controllers. They are real, and in many cases will increase the charging
current into your batteries. No black magic is needed, but I suppose that
some designs will be better than others. What follows is mostly
theoretical:
-------------
MPPT stands for "Maximum Power-Point Transfer", and it is equivalent to two
switching regulators in series. It operates the solar panel at the load
where the panel delivers it's maximum output power, then converts whatever
Voltage this may be to a Voltage appropriate for the battery (depending on
the battery's charge-state).

This is in contrast to the series-pass, Pulse-Width-Modulation (PWM), or
shunt regulators. In these, the panel output is essentially connected
directly to the battery during the charge-acceptance portion of the charge
cycle, and the panel output is reduced once the battery approaches
full-charge.

An example from my boat: I have three BP 110W panels, wired in parallel.
Each panel has an open-circuit (no-load) output Voltage of 21.7V (ratings at
full noonday sun conditions, with a cell temperature of 25deg C). Each panel
has a short-circuit current of 6.9A. The panel has a maximum output power of
110W, at 17.5V and 6.3A. At any other output Voltage the panel will deliver
less than max power. When I am charging a low battery at (say) 12V, using a
non-MPPT controller (or directly hooking the panel to the battery), the
panel is not operating at maximum power. Looking at the output curve for the
panel, at 12V the panel will be delivering about 6.8A, which is 81.6 W. (I
am reading these Volt/Amp numbers from a chart in the panel specifications.)

With a MPPT controller, the panel would be operated at 17.5V, and be putting
out 110W. Switching the 17.5V down to 12V (assuming 95% efficiency, a number
I pulled out of the air) would give me 8.7 A into my 12V battery. This is a
28% increase in charging current.

Of course, the battery won't stay at 12V for long. As the battery Voltage
rises, the current-boost will be less. At 13.5V, a directly-connected panel
would deliver 6.75A (91W). With an MPPT controller the charge current (at
95% efficiency) would be 7.74A -- still one amp better.

Once the battery reaches full charge and the controller goes into
trickle-mode, an MPPT controller will have no advantage.

These numbers will be different in practice, as the panels won't see
constant full sun, and the panel temperature will usually be hotter. Still,
the MPPT controller ought to give some charging improvement. MPPT
controllers don't use fixed settings, but are constantly dithering the panel
load, monitoring the panel Voltage, and looking for the point of maximum
power.

These days, many panels are wired for 24V (instead of 12V) output, and the
MPPT controller can efficiently convert the output of these panels for use
in charging a 12V battery.

I still have the old-style controller for my panels, but I will probably be
installing MPPT before too long. I may end up putting a seperate controller
on each panel (instead of one controller driven by the three panels in
parallel), because my panels are often partially shaded, and I think I will
get more output if each panel can be independently optimized. I need to do
some testing or modelling to be sure of this. I can't easily add more
panels, so I need to make maximum use of the ones I have.
-------------
Hope this helps.
-Paul

After reading what I wrote below, I decided that it needed a small
correction/comment. It's down at the bottom. -Paul

"Paul" wrote in message
...

"Larry" wrote in message
...
Ian Malcolm wrote in
:

Assuming the panels can be modelled as an ideal voltage source

Geez. If boat technology gets any better, we'll be able to run a light
bulb off the panel, shining on the panel, and the panel will have so much
power boost there'll be a surplus to charge the batteries!



Larry

Here is something I posted to the "Cruiser's Forum", about MPPT charge
controllers. They are real, and in many cases will increase the charging
current into your batteries. No black magic is needed, but I suppose that
some designs will be better than others. What follows is mostly
theoretical:
-------------
MPPT stands for "Maximum Power-Point Transfer", and it is equivalent to
two switching regulators in series. It operates the solar panel at the
load where the panel delivers it's maximum output power, then converts
whatever Voltage this may be to a Voltage appropriate for the battery
(depending on the battery's charge-state).

This is in contrast to the series-pass, Pulse-Width-Modulation (PWM), or
shunt regulators. In these, the panel output is essentially connected
directly to the battery during the charge-acceptance portion of the charge
cycle, and the panel output is reduced once the battery approaches
full-charge.

An example from my boat: I have three BP 110W panels, wired in parallel.
Each panel has an open-circuit (no-load) output Voltage of 21.7V (ratings
at full noonday sun conditions, with a cell temperature of 25deg C). Each
panel has a short-circuit current of 6.9A. The panel has a maximum output
power of 110W, at 17.5V and 6.3A. At any other output Voltage the panel
will deliver less than max power. When I am charging a low battery at
(say) 12V, using a non-MPPT controller (or directly hooking the panel to
the battery), the panel is not operating at maximum power. Looking at the
output curve for the panel, at 12V the panel will be delivering about
6.8A, which is 81.6 W. (I am reading these Volt/Amp numbers from a chart
in the panel specifications.)

With a MPPT controller, the panel would be operated at 17.5V, and be
putting out 110W. Switching the 17.5V down to 12V (assuming 95%
efficiency, a number I pulled out of the air) would give me 8.7 A into my
12V battery. This is a 28% increase in charging current.

Of course, the battery won't stay at 12V for long. As the battery Voltage
rises, the current-boost will be less. At 13.5V, a directly-connected
panel would deliver 6.75A (91W). With an MPPT controller the charge
current (at 95% efficiency) would be 7.74A -- still one amp better.

Once the battery reaches full charge and the controller goes into
trickle-mode, an MPPT controller will have no advantage.

These numbers will be different in practice, as the panels won't see
constant full sun, and the panel temperature will usually be hotter.
Still, the MPPT controller ought to give some charging improvement. MPPT
controllers don't use fixed settings, but are constantly dithering the
panel load, monitoring the panel Voltage, and looking for the point of
maximum power.

These days, many panels are wired for 24V (instead of 12V) output, and the
MPPT controller can efficiently convert the output of these panels for use
in charging a 12V battery.

I still have the old-style controller for my panels, but I will probably
be installing MPPT before too long. I may end up putting a seperate
controller on each panel (instead of one controller driven by the three
panels in parallel), because my panels are often partially shaded, and I
think I will get more output if each panel can be independently optimized.
I need to do some testing or modelling to be sure of this. I can't easily
add more panels, so I need to make maximum use of the ones I have.
-------------
Hope this helps.
-Paul


Comment: I wrote "equivalent to two switching regulators in series", but
this isn't really true, or even helpful. The MPPT controller is essentially
a single switcher, with a power-sensing control loop. The rest of what I
wrote should be OK. -Paul