Get a controller that diverts voltage above the maximum charging voltage of
the battery to a resistive load. In my case this is the water heater with
12V and 120V heater elements. 100% of the power of the solar panels will
go to charging the panels up to that point. You can't produce more power
than the panels are generating.

I personally use a Morning Star TriStar controller to control both my wind
generator and solar panels and it works great.

-- Geoff

Geoff Schultz wrote:
Get a controller that diverts voltage above the maximum charging voltage of
the battery to a resistive load. In my case this is the water heater with
12V and 120V heater elements. 100% of the power of the solar panels will
go to charging the panels up to that point. You can't produce more power
than the panels are generating.

I personally use a Morning Star TriStar controller to control both my wind
generator and solar panels and it works great.

-- Geoff
So, are you saying that if the panels are putting out 17 volts and the
battery is only taking 14, then 3 volts are applied to the heater? I
don't think that's the way it works.

Jeff wrote in
:

Geoff Schultz wrote:
Get a controller that diverts voltage above the maximum charging
voltage of the battery to a resistive load. In my case this is the
water heater with 12V and 120V heater elements. 100% of the power of
the solar panels will go to charging the panels up to that point.
You can't produce more power than the panels are generating.

I personally use a Morning Star TriStar controller to control both my
wind generator and solar panels and it works great.

-- Geoff
So, are you saying that if the panels are putting out 17 volts and the
battery is only taking 14, then 3 volts are applied to the heater? I
don't think that's the way it works.

That's exactly what I'm saying. It's called Diversion Mode and on the
controller you set the maximum voltage which is allowed to be applied to
the batteries. Anything above that is diverted to the load.

The only time that this occurs is when the batteries are fully charged.
The vast majority of the time the charging load of the batteries drops the
output of the solar cells to a voltage less than the maximum allowable
voltage and thus nothing is diverted.

For details please see the manual:
http://www.mrsolar.com/pdf/morningstar/TS_Manual.pdf


-- Geoff

Geoff Schultz wrote:
Jeff wrote in
:

Geoff Schultz wrote:
Get a controller that diverts voltage above the maximum charging
voltage of the battery to a resistive load. In my case this is the
water heater with 12V and 120V heater elements. 100% of the power of
the solar panels will go to charging the panels up to that point.
You can't produce more power than the panels are generating.

I personally use a Morning Star TriStar controller to control both my
wind generator and solar panels and it works great.

-- Geoff
So, are you saying that if the panels are putting out 17 volts and the
battery is only taking 14, then 3 volts are applied to the heater? I
don't think that's the way it works.

That's exactly what I'm saying. It's called Diversion Mode and on the
controller you set the maximum voltage which is allowed to be applied to
the batteries. Anything above that is diverted to the load.

The only time that this occurs is when the batteries are fully charged.
The vast majority of the time the charging load of the batteries drops the
output of the solar cells to a voltage less than the maximum allowable
voltage and thus nothing is diverted.

For details please see the manual:
http://www.mrsolar.com/pdf/morningstar/TS_Manual.pdf

Yes, this is how the tristar works. And for some people, it works
fine. However, for those of us whose power usage far exceeds the
charging ability, the diversion mode would rarely be turned on. In my
case, it would only happen if I had just run the engine, and at that
time the water tank is fully heated.

The diversion mode is suited to boats with excess generating
capability, such as trade wind passagemakers with wind or hydro
generation.

For systems where the solar panels will fall behind the load, the new
MPPT (Maximum Power Point Tracking) systems will generate more power
at the battery. Many panels will put out up to 17 Volts, and their
Wattage will be rated at this level. A normal regulator will reduce
this to an appropriate charging Voltage, perhaps 13.5 Volts if the
battery is discharged. However, the current is not increased so the
net Wattage will be reduced.

A MPPT controller is a DC-DC converter that will drop the Voltage down
without reducing the Wattage. An 85 Watt panel that can put out 5
Amps at 17V will put out 6.3 Amps at 13.5 and stay up at 85 Watts. A
normal controller would only allow 67 Watts.

Thus, the controller is not "creating more power than the panel
outputs," its adjusting the Voltage so that 30% of the power isn't
thrown away. As I've said, I've watched the current go from 8 to 10
Amps when the MPPT is turned on.

On Feb 9, 8:33 am, Jeff wrote:
Geoff Schultz wrote:
Jeff wrote in
:

Geoff Schultz wrote:
Get a controller that diverts voltage above the maximum charging
voltage of the battery to a resistive load. In my case this is the
water heater with 12V and 120V heater elements. 100% of the power of
the solar panels will go to charging the panels up to that point.
You can't produce more power than the panels are generating.

I personally use a Morning Star TriStar controller to control both my
wind generator and solar panels and it works great.

-- Geoff
So, are you saying that if the panels are putting out 17 volts and the
battery is only taking 14, then 3 volts are applied to the heater? I
don't think that's the way it works.

That's exactly what I'm saying. It's called Diversion Mode and on the
controller you set the maximum voltage which is allowed to be applied to
the batteries. Anything above that is diverted to the load.

The only time that this occurs is when the batteries are fully charged.
The vast majority of the time the charging load of the batteries drops the
output of the solar cells to a voltage less than the maximum allowable
voltage and thus nothing is diverted.

For details please see the manual:
http://www.mrsolar.com/pdf/morningstar/TS_Manual.pdf

Yes, this is how the tristar works. And for some people, it works
fine. However, for those of us whose power usage far exceeds the
charging ability, the diversion mode would rarely be turned on. In my
case, it would only happen if I had just run the engine, and at that
time the water tank is fully heated.

The diversion mode is suited to boats with excess generating
capability, such as trade wind passagemakers with wind or hydro
generation.

For systems where the solar panels will fall behind the load, the new
MPPT (Maximum Power Point Tracking) systems will generate more power
at the battery. Many panels will put out up to 17 Volts, and their
Wattage will be rated at this level. A normal regulator will reduce
this to an appropriate charging Voltage, perhaps 13.5 Volts if the
battery is discharged. However, the current is not increased so the
net Wattage will be reduced.

A MPPT controller is a DC-DC converter that will drop the Voltage down
without reducing the Wattage. An 85 Watt panel that can put out 5
Amps at 17V will put out 6.3 Amps at 13.5 and stay up at 85 Watts. A
normal controller would only allow 67 Watts.

Thus, the controller is not "creating more power than the panel
outputs," its adjusting the Voltage so that 30% of the power isn't
thrown away. As I've said, I've watched the current go from 8 to 10
Amps when the MPPT is turned on.- Hide quoted text -

- Show quoted text -

Yes, i agree. I want to add my support again for this explination and
any negative comments (except maybe those negative comments against
practical sailor's reliability) that followed my post early in this
thread are unjustified. Let's face it, the affordable controllers that
have historically been available are simple an did little more than
keep the voltage at 12.6 volts, and if the voltage of the batteries
exceed the voltage of the panels, the controller will prevent the
batteries from draining. In this arrangement, the panels were setup
with enough cells to insure that 12.6 volts would be reached in
overcast days (or they would be useless), which means on sunny days
you end up with 18 even 19v. New controllers can match the panels to
the batteries better ... and without any snake oil, you get more bang
out of your solar cells.

In regards to practical sailor, they have demonstrated their
independence and willingness to tell it like it is, perhaps that is a
better description than reliable. If they measure a 25% increased
output in AMPS with the new technology controllers, I can take that to
the bank. However I will concede there are problems with some
articles. When it comes to bottom paints, I realize as I read the
articles the limits to their testing. To be really scientific and
valid the tests would be repeated on a second set of samples by a
different organization or employees, but it's amazing what they do for
limited $. The article on winches was just way off the mark. Also
they recently had an article on 2006 editions of two books in regards
to 12V boat systems, that was extremely poor, one of the books in fact
does not have such an edition. I could not get a response back from
them when I pointed it out. Perhaps the loss of their star editor has
a big influence, I don't think he would have let that article on
Winches fly. But .. it is real refreshing to read their articles,
especially boat reviews. I am getting tired of reading boat reviews in
sail magazine that are absolutly meaningless, and really hate to read
words such as "we only had light winds today, but judging from this
boats design it will be a real performer" ... do meaningful
journalism, go out and sail the boat again on a windy day would
you ? In that light, Practical Sailor looks reliable to me, just not
scientifically so.

Geoff Schultz wrote in
:

You can't produce more power
than the panels are generating.


Ok, here's a little electricity for everyone....

This is the schematic of a solar panel:


--[cell]---[cell resistance]--

Now, what this controller with the variable inverter load in it is doing
is simplified into this circuit:

|--[cell]---[cell resistance]---|
| |
| |
|-[controller input resistance]-|

In any series circuit like this where the SOURCE has a series resistance
(impedance in AC and RF circuits), Load POWER is "optimized" to a peak
level whenever load impedance (resistance) EQUALS source impedance
(source resistance). Moving away from this optimum power peak in either
direction of load impedance creates LESS POWER in the load, in this case
the controllable inverter's panel input. If the inverter's loading of
the panel can be made to electronically change its load resistance on the
panel to the same resistance as the panel's own built-in resistance,
which is quite substantial, Yes, the power generated will be greater than
if the panel were simply connected through a blocking diode to the
batteries. Very ingenious.

This is NOT magic. It's math. The source voltage is 19VDC, that's what
the cell puts out due to the number of cells in series, a function of
silicon junction voltage. Just for demonstration of this effect, let's
say the panel cell resistance (which varies, by the way with cell
temperature quite a bit) is 10 ohms. Two simple electric calculations
are needed:
Power = current squared times resistance.
Current = Voltage divided by resistance.

Let's check 3 points...varying the load resistance...to see what power
develops in the load. Let's check a load R of 10 ohms, same as source,
for a reference. Total resistance is 20 ohms. 19V/20 ohms = .95A
circuit current. Now square that (.9025) x the 10 ohm load resistance =
9.025 watts "output" for the inverter to send to the battery, minus its
losses, of course, in conversion.

OK, now let's change the load resistance to 8 ohms (lower). Total
resistance is 18 ohms. 19V/18 ohms = 1.055A circuit current. Now square
1.055A (1.113) times 8 ohms = 8.9 watts...POWER OUT DROPPED OFF from our
peak.

OK, now let's change the load resistance to 12 ohms (higher). Total
resistance is 22 ohms. 19V/22 ohms = .8636A circuit current. Now square
..8636 (.7458) times 12 ohms = 8.94 watts...POWER OUT DROPS OFF THIS WAY
TOO!

So, if the panels resistance right now equals the controller's input
resistance, right now, the maximum power output peak of the panel will be
realized. This can be accomplished with a little electronic trickery in
IC regulators, probably custom made for this purpose, so that at any
panel resistance, the IC can sense and adjust the controller's load
resistance on the panel to maximize panel output. With switching power
supplies now in the 99% efficient range, this is very feasable.

By the way, this is the exact same reason we strive to make a radio with
an output impedance of 52 ohms connected to coaxial cable with an
impedance of 52 ohms connected at the top of the mast to a 52 ohm
antenna....because it creates maximum power transfer from the transmitter
to the antenna. (The radio is actually designed to match certain types
of antenna's natural impedances, not the other way around.) It even
works the other way on receive....so we use a 52 ohm input receiver, too.

This completes today's electrical lecture. Please read pages 324 through
468 in your textbook and complete the workbook section 3-6 to hand in by
tomorrow's class. The workbook answers are 40% of your grade in this
course. (God, they all looked like they could kill me when I used to
tell 'em this just before the bell rang.)....(c;

Larry
--
I just can't stand it when I don't know why something does what it does!

I had to learn how our ship's steam turbine plant worked, to the dismay
of the ratings in the engine room, even though I was an Electronics Tech.
If you need power, give me a little time to fire the boilers and get the
pressure up and we'll go!

Larry wrote in
:

Geoff Schultz wrote in
:

You can't produce more power
than the panels are generating.


Ok, here's a little electricity for everyone....

Thank you Professor Larry for the edification. I always enjoy it when
this forum is used to exchange information instead of throwing barbs at
one another.

I am of the personal opinion that boats should have a combination of
solar and wind. I believe that a wind generator gives you a much bigger
bang for the buck, but there are days when the wind doesn't blow and
likewise when it isn't sunny.

You need to regulate both sources. I spend about 6-7 months a year
cruising (at anchor) and rarely have seen the regulator regulate as my
power demands almost always exceed my wind/solar generation capacity.
Any time that I do see the batteries getting topped off, I can always
make more water. If you spend lots of time at a dock connected to a
power cord and your batteries fully charged, then yes, you do need
regulation. (I actually pull the fuse for the solar panels and feather
the generator at dock.)

Solar panels don't care if there's no load attached to them, but wind
generators need a load to keep them from free-wheeling. As a result you
need a controller which can be used in diversion mode with a resistive
load. Due to space and $ constraints, I don't want to have multiple
controllers. I would rather put the cost of another controller towards
more generation capacity.


-- Geoff

On Fri, 09 Feb 2007 07:58:23 -0600, Geoff Schultz
wrote:

Larry wrote in
:

Geoff Schultz wrote in
:

You can't produce more power
than the panels are generating.


Ok, here's a little electricity for everyone....

Thank you Professor Larry for the edification. I always enjoy it when
this forum is used to exchange information instead of throwing barbs at
one another.

Unfortunately the information is wrong.

Geoff Schultz wrote:
You can't produce more power
than the panels are generating.

Larry wrote:
Ok, here's a little electricity for everyone....

Geoff Schultz wrote:
Thank you Professor Larry for the edification. I always enjoy it when
this forum is used to exchange information instead of throwing barbs at
one another.

Goofball_star_dot_etal wrote:
Unfortunately the information is wrong.

Well without any references or explanation and as an anonymous poster,
your word isnt worth anything near as much as if it was printed out on
used toilet paper . .

If I didnt have concerns about RFI, I am capable of designing and
building my own MPPT solar panel controller. It isn't rocket science,
any competent EE tech or HAM operator (e.g. Larry) could knock one up in
a weekend or two, its just that it would take too much time so unless I
cant find something to do that brings in more beer tokens, its easier to
just buy one. Also it gives you someone *else* to yell at if it b***ers
up your reception on VHF channel 16.


For anyone else considering designing a MPPT controller (or just curious),
http://www.intusoft.com/nlhtm/nl78.htm
is good reading and even has Spice models for various types of solar
panel.

To summerise, they conclude that peak power is delivered at 83% of the
open circuit voltage (rather different from my estimate of 50% as I
initially was using an model that was an extremely bad approximation to
a solar cell. I should have googled :-( ), which varies with temperature
and illumination, and that a 10% gain in efficiency is achievable.

This means, if the controller is under 10% of the panel cost, buy it,
its a no-brainer, otherwise get a bigger panel (gross
over-simplification ignoring cost of a liniar regulator, assuming you
CAN fit a bigger panel (or more), you need more power and assuming
price/performance for the panel is a streight line.)

--
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 Fri, 09 Feb 2007 17:45:41 +0000, Ian Malcolm
wrote:

Geoff Schultz wrote:
You can't produce more power
than the panels are generating.

Larry wrote:
Ok, here's a little electricity for everyone....

Geoff Schultz wrote:
Thank you Professor Larry for the edification. I always enjoy it when
this forum is used to exchange information instead of throwing barbs at
one another.

Goofball_star_dot_etal wrote:
Unfortunately the information is wrong.

Well without any references or explanation and as an anonymous poster,
your word isnt worth anything near as much as if it was printed out on
used toilet paper . .


You mean you would like me to post references to the equivalent
circuit AGAIN?

http://groups.google.co.uk/group/rec...13bf8612?hl=en

If people did some homework instead of making wrong assumptions before
posting them as fact, there would be less BS.


Here is a new link for you:
http://patft.uspto.gov/netacgi/nph-P...391&RS=6111391
or http://tinyurl.com/yobfz3


If I didnt have concerns about RFI, I am capable of designing and
building my own MPPT solar panel controller. It isn't rocket science,
any competent EE tech or HAM operator (e.g. Larry) could knock one up in
a weekend or two, its just that it would take too much time so unless I
cant find something to do that brings in more beer tokens, its easier to
just buy one. Also it gives you someone *else* to yell at if it b***ers
up your reception on VHF channel 16.


For anyone else considering designing a MPPT controller (or just curious),
http://www.intusoft.com/nlhtm/nl78.htm
is good reading and even has Spice models for various types of solar
panel.

To summerise, they conclude that peak power is delivered at 83% of the
open circuit voltage (rather different from my estimate of 50% as I
initially was using an model that was an extremely bad approximation to
a solar cell. I should have googled :-( ), which varies with temperature
and illumination, and that a 10% gain in efficiency is achievable.

This means, if the controller is under 10% of the panel cost, buy it,
its a no-brainer, otherwise get a bigger panel (gross
over-simplification ignoring cost of a liniar regulator, assuming you
CAN fit a bigger panel (or more), you need more power and assuming
price/performance for the panel is a streight line.)