Jim,

Your initial assumtions should be correct.
But- - -
You have to be a more specific in your request for confirmation.

Mutimeters have many functions and scales, even if it is autoscaling it
still may have 14 functions.

If you are trying to measure output voltage with the panel in sunlight,
you may see nothing because the charge controller may need the attached
battery to supply the reference voltage for it to "switch on".

If you are measuring continuity or resistance, then you should get
nothing in the reverse direction (which in this case is red to red) but
you will at least see the blocking diode forward bias in the forward mode.

Is that a help??

Matt Colie

James wrote:
We acquired a flexible Uni-solar 32W panel. There are two wires leads a
red one and a black one. Which is (+) and which is (-)? I was thinking
that Red was (+) but I'm not receiving any readings through the charge
controller. When I reverse the leads I get a reading on my multi-meter.
Thanks, Jim

"Matt Colie" wrote in message
...
Jim,

Your initial assumtions should be correct.
But- - -
You have to be a more specific in your request for confirmation.

Mutimeters have many functions and scales, even if it is autoscaling it
still may have 14 functions.

If you are trying to measure output voltage with the panel in sunlight,
you may see nothing because the charge controller may need the attached
battery to supply the reference voltage for it to "switch on".

If you are measuring continuity or resistance, then you should get nothing
in the reverse direction (which in this case is red to red) but you will
at least see the blocking diode forward bias in the forward mode.

Is that a help??

Matt Colie

James wrote:
We acquired a flexible Uni-solar 32W panel. There are two wires leads a
red one and a black one. Which is (+) and which is (-)? I was thinking
that Red was (+) but I'm not receiving any readings through the charge
controller. When I reverse the leads I get a reading on my multi-meter.
Thanks, Jim


Disconnect the controller. In the sun ( don't shade the panel ) you should
be able to measure open circuit panel voltage of around 18 to 20 volts. If
you short out the panel using your amp meter you should get around 2 amps
or. If your controller is connected to a battery that needs charging and
your panel is in sunlight you should be able to measure somewhere around 1
amp of charging current. If your controller has ever been connected to the
battery with the polarity reversed it is probably bad.

Matt Colie wrote in
:


James wrote:
We acquired a flexible Uni-solar 32W panel. There are two wires leads
a red one and a black one. Which is (+) and which is (-)? I was
thinking that Red was (+) but I'm not receiving any readings through
the charge controller. When I reverse the leads I get a reading on my
multi-meter. Thanks, Jim



Is now a good time to remind everyone that a solar panel
MUST...MUST...have a blocking diode in series with it because it will
DISCHARGE the battery in darkness with reverse current if it doesn't?

This diode is PROBABLY located in the charge controller, hence the one-
way resistance reading. NEVER HOOK A LIGHTED PANEL TO YOUR OHMMETER or
when it's connected to a battery!

32W/12V = 2.8A on its best day. Why do we need a charge controller??
Use an ammeter and lemme know every time you see 2A out of it at noon.
If your bilge pump cycles, you'll lose AH every day if this panel is the
only power source. 2.8A is nothing....to those big honkers in the
bilge...(c;



Larry
--
Why is it, in any city, all traffic lights act as if they have rotary
timers in them, like they did in 1955, and are all set to create
maximum inconvenience and block traffic movement, entirely?

Hi Larry,

I agree that a solar regulator is probably not really required if the battery bank is much larger than the solar panel maximum output - especially for sealed batteries that recombine the hydrogen and oxygen.

Is it true, however, that you always need a reverse blocking diode on all solar panels that don't have one in-built? I have a 45w panel connected without a blocking diode and without a charge regulator to a 880amp hour deep cycle battery bank and in the dark I can't measure any appreciable reverse current flow (less than 0.020 amps).

--
Best Regards,

Bert van den Berg
CruzPro Ltd.
www.cruzpro.com
35 Keeling Road, #A4
Henderson 1008
New Zealand

Tel: 64-9-838-3331
Fax: 64-9-838-3332


"Larry" wrote in message ...
Matt Colie wrote in
:


James wrote:
We acquired a flexible Uni-solar 32W panel. There are two wires leads
a red one and a black one. Which is (+) and which is (-)? I was
thinking that Red was (+) but I'm not receiving any readings through
the charge controller. When I reverse the leads I get a reading on my
multi-meter. Thanks, Jim



Is now a good time to remind everyone that a solar panel
MUST...MUST...have a blocking diode in series with it because it will
DISCHARGE the battery in darkness with reverse current if it doesn't?

This diode is PROBABLY located in the charge controller, hence the one-
way resistance reading. NEVER HOOK A LIGHTED PANEL TO YOUR OHMMETER or
when it's connected to a battery!

32W/12V = 2.8A on its best day. Why do we need a charge controller??
Use an ammeter and lemme know every time you see 2A out of it at noon.
If your bilge pump cycles, you'll lose AH every day if this panel is the
only power source. 2.8A is nothing....to those big honkers in the
bilge...(c;



Larry
--
Why is it, in any city, all traffic lights act as if they have rotary
timers in them, like they did in 1955, and are all set to create
maximum inconvenience and block traffic movement, entirely?

Matt Colie wrote:

Jim,

Your initial assumtions should be correct.
But- - -
You have to be a more specific in your request for confirmation.

Mutimeters have many functions and scales, even if it is autoscaling
it still may have 14 functions.

If you are trying to measure output voltage with the panel in
sunlight, you may see nothing because the charge controller may need
the attached battery to supply the reference voltage for it to
"switch on".

If you are measuring continuity or resistance, then you should get
nothing in the reverse direction (which in this case is red to red)
but you will at least see the blocking diode forward bias in the
forward mode.

Is that a help??

Matt Colie

James wrote:
We acquired a flexible Uni-solar 32W panel. There are two wires
leads a red one and a black one. Which is (+) and which is (-)? I
was thinking that Red was (+) but I'm not receiving any readings
through the charge controller. When I reverse the leads I get a
reading on my multi-meter. Thanks, Jim


Thanks. You pointed me in the right direction. Jim

--

Bert van den Berg wrote:

Is it true, however, that you always need a reverse blocking diode on all solar panels that don't have one in-built?

Maybe on some panel types, but I'm with you, 33milliamps leakage from a
40 watt pair of CIS panels into a 500ah bank. Installing blocking
diodes would be a loser because of forward voltage drop when the panels
are high noon producing with near fully charged batteries. People who
say always install blocking diodes paint with too broad a brush.

Blocking diodes are a good idea when constructing higher voltage
series-parallel strings, to prevent damage to shadowed panels.

"Mark" wrote in message
ups.com...

Bert van den Berg wrote:

Is it true, however, that you always need a reverse blocking diode on
all solar panels that don't have one in-built?

Maybe on some panel types, but I'm with you, 33milliamps leakage from a
40 watt pair of CIS panels into a 500ah bank.

Don't follow. (also haven't seen previous part of this) ISTR the purpose of
the blocking diode is to prevent the battery from charging the solar panel
at night.

Regards,
Barry












Installing blocking
diodes would be a loser because of forward voltage drop when the panels
are high noon producing with near fully charged batteries. People who
say always install blocking diodes paint with too broad a brush.

Blocking diodes are a good idea when constructing higher voltage
series-parallel strings, to prevent damage to shadowed panels.

"BF Lake" wrote in
news:JPbkh.99541$hn.5563@edtnps82:

Don't follow. (also haven't seen previous part of this) ISTR the
purpose of the blocking diode is to prevent the battery from charging
the solar panel at night.



Stops the battery from reverse current through the solar panel when solar
panel voltage is lower, not just at night. This causes damage to the
panel's silicon junctions and reduces its life by causing migration of the
doping across the junction.

Never use a solar panel to charge a battery unless there is, at minimum, a
blocking diode to prevent reverse current.

Larry

Kitchen theories about it reducing solar panel output are nonsense. Solar
panel open circuit voltages are above 18V in bright sunlight. Six tenths
of a volt the diode drops means nothing. The panels are DESIGNED with
blocking diodes in mind.....

On Tue, 26 Dec 2006 13:08:48 -0500, Larry wrote:
"BF Lake" wrote in
news:JPbkh.99541$hn.5563@edtnps82:

Don't follow. (also haven't seen previous part of this) ISTR the
purpose of the blocking diode is to prevent the battery from charging
the solar panel at night.

Stops the battery from reverse current through the solar panel when solar
panel voltage is lower, not just at night. This causes damage to the

Yup. There is also another type of diode necessary with higher-voltage
(24v, 48v, etc) series connected panels and a good idea with a single
panel connected to a battery. People often confuse a blocking diode
with a bypass diode. The bypass diode protects the panel when cells are
shaded, etc. and most higher-end panels include a bypass diode, but few
include a blocking diode.

Why? Because PV cells are by nature a diode, and usually have very low
leakage. You don't normally need a blocking diode. However as you
increase the number of cells in parallel, or increase the size of each
cell (in other words, increase cell area) the leakage increases. If
you have a reasonably modern electronic charge controller, it will
function as a super-efficient blocking diode (much less than 0.6v drop).
You don't need another one.

Kitchen theories about it reducing solar panel output are nonsense. Solar

Wrong.

Let's say you have a solar array producing 10 amps (call it effectively
120watts). If your diode drops 0.6v, you are losing 6watts in that
diode. 6watts of 120watts is a 5% loss. I think 5% is significant.

panel open circuit voltages are above 18V in bright sunlight. Six tenths

Not necessarily correct. Panels are not designed for the blocking
diode, they are designed to provide high enough voltage to fully charge
a battery (14.5v) even when the panel is much hotter than room
temperature because it is sitting in the sun on a hot, still day. The
voltage produced by each cell may drop from 0.55v typical at 20C to 0.4v
at 90C. That is barely enough to do a full charge. Some people cheap
out and buy a 33 cell panel instead of a 36 cell. Unless you live where
it never gets hot, the 33 cell panels are proven to not have enough
oomph when they get hot.

sdb
--
Wanted: Omnibook 800 & accessories, cheap, working or not
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