Visit our Popular Forums

**newhaul** · 01-06-2017, 06:27

Dotdun aparently you nor anyone else actually read the files you linked to for the renogy panels. The pdf states that there are 2 bypass diodes in the junction box . ( which are also blocking diodes) . These are the panels I install most of.

**newhaul** · 01-06-2017, 06:30

People here is the answer to all of the voltage at junction issues you seem to not get or state . Differing voltages will equalise to a common aparent voltage when hooked together at a node. Jm2cw.

Zach · 01-06-2017, 06:34

Question, as I bought a pair of the reonogy panels to play with as well...

I've been having a hard time finding manuals that list what the lowest input voltage is of MPPT controllers. Lots of information in white papers for low-low dc voltage boost controller information on the web, but they are set up for charging 9v batteries with < 10watt panels...

Does anyone have a recommendation for a charge controller that even lists the input voltage cut-off?

ramblinrod · 01-06-2017, 06:52

Quote:

Originally Posted by TeddyDiver

Sometimes you make perfect sense and sometimes not, like above. But can you recognize what's wrong?

The reference statement is 100% correct if there are no bypass diodes. If there at bypass diodes, each panel in series can deliver different current.

DotDun · 01-06-2017, 06:55

Quote:

Originally Posted by newhaul

Dotdun aparently you nor anyone else actually read the files you linked to for the renogy panels. The pdf states that there are 2 bypass diodes in the junction box . ( which are also blocking diodes) . These are the panels I install most of.

Please explain how a the 2 diodes are connected such that they serve as both bypass and blocking functions.

ramblinrod · 01-06-2017, 06:59

Quote:

Originally Posted by newhaul

People here is the answer to all of the voltage at junction issues you seem to not get or state . Differing voltages will equalise to a common aparent voltage when hooked together at a node. Jm2cw.

Dude, that is what I have been stating for 3 days now. Only Dot doesn't get it.

ramblinrod · 01-06-2017, 07:03

Quote:

Originally Posted by DotDun

Please explain how a the 2 diodes are connected such that they serve as both bypass and blocking functions.

They pass current in the forward direction and lock it in reverse. The panel impedance typically blocks reverse current naturally.

**newhaul** · 01-06-2017, 07:04

Quote:

Originally Posted by ramblinrod

Dude, that is what I have been stating for 3 days now. Only Dot doesn't get it.

Rod no you havent said that exactly. You have to remember sometimes its not what you say but how you say it. (I did read between the lines with all these posts any you did say that but not with these exact words. )

DotDun · 01-06-2017, 07:16

Quote:

Originally Posted by ramblinrod

They pass current in the forward direction and lock it in reverse. The panel impedance typically blocks reverse current naturally.

ARGH!!! This is getting difficult. In the context of solar panels, bypass diodes and blocking diodes serve 2 different functions and are connected in the circuit differently. A single diode CANNOT serve both purposes!

TeddyDiver · 01-06-2017, 07:17

Quote:

Originally Posted by newhaul

People here is the answer to all of the voltage at junction issues you seem to not get or state . Differing voltages will equalise to a common aparent voltage when hooked together at a node. Jm2cw.

Get over it, shaded solar panel turns into a power sucker when installed in parallel ie there's no effective voltage to equalize. In the presense of blocking diodes there's no common node becouse the shaded panel is effectively open circuit.
Bypass diodes and blocking diodes are the same components but the first one wired parallel and second one in series with the PV string ie one cannot replace another.

BR Teddy

ramblinrod · 01-06-2017, 07:51

Quote:

Originally Posted by TeddyDiver

Get over it, shaded solar panel turns into a power sucker when installed in parallel ie there's no effective voltage to equalize. In the presense of blocking diodes there's no common node becouse the shaded panel is effectively open circuit.
Bypass diodes and blocking diodes are the same components but the first one wired parallel and second one in series with the PV string ie one cannot replace another.

BR Teddy

OMG.
2 solar panels connected in parallel create 2 common nodes.
One at the positive connection, one at the negative connection.

The panel presents a high impedance to the circuit. If there is
sunlight on the panel it becomes a voltage source and
develops a voltage across it which passes current through it directly proportional to the amount of sunlight up to the panel limit (which is sorta a fixed value but not really).

The voltage between the common nodes is one and the same. Has to
be; it is a parallel circuit. If one panel is shaded, current passed (in the positive direction only) drops. The voltage between the common nodes may change slightly, but it is still a common node. One voltage. A common node can't be two different voltages at the same time, nor can current travel in opposite directions at the same time. They either contribute or negate. Because a panel that isn't contributing current presents a high impedance to one that is, the shaded panel can't negate (unless there is something wrong with it)

This is solar panels 101, first lesson. If after 3 days of discussion you still don't get it, I have to accept you may never.

ramblinrod · 01-06-2017, 11:09

Quote:

Originally Posted by newhaul

Rod no you havent said that exactly. You have to remember sometimes its not what you say but how you say it. (I did read between the lines with all these posts any you did say that but not with these exact words. )

I have said it in so many different ways I can't count that high and still the same incorrect response.

**Paul Elliott** · 01-06-2017, 11:59

Quote:

Originally Posted by Zach

Question, as I bought a pair of the reonogy panels to play with as well...

I've been having a hard time finding manuals that list what the lowest input voltage is of MPPT controllers. Lots of information in white papers for low-low dc voltage boost controller information on the web, but they are set up for charging 9v batteries with < 10watt panels...

Does anyone have a recommendation for a charge controller that even lists the input voltage cut-off?

This is a good question, and I don't have an answer for you.

So, the reason I replied is to warn you about a potential problem with the Renogy panels. When I was doing the testing described earlier, I noticed that one of my panels was not behaving properly with partial shading. It turned out that the mid-string connection to the bypass diodes was not properly soldered. The two bypass diodes connected from panel (+) to panel (-), but the midpoint connection was open.

This doesn't affect the unshaded panel output in any way, but the panel effectively has one string of 36 cells with a double-diode bypass. It could make a difference in a serial panel connection. It will be easy enough to fix that open connection, I just need my heavy-duty soldering iron.

ramblinrod · 01-06-2017, 13:16

Quote:

Originally Posted by Paul Elliott

This is a good question, and I don't have an answer for you.

So, the reason I replied is to warn you about a potential problem with the Renogy panels. When I was doing the testing described earlier, I noticed that one of my panels was not behaving properly with partial shading. It turned out that the mid-string connection to the bypass diodes was not properly soldered. The two bypass diodes connected from panel (+) to panel (-), but the midpoint connection was open.

This doesn't affect the unshaded panel output in any way, but the panel effectively has one string of 36 cells with a double-diode bypass. It could make a difference in a serial panel connection. It will be easy enough to fix that open connection, I just need my heavy-duty soldering iron.

Reno you has a recall on 100 W semi flex. Not your panel model but maybe same issue?