Need help regarding Solar Panel DIODES

samadniazi · April 2017

Hi , I am new to Solar Energy.. I bought (1) 150w Solar Panel , the problem i am facing is that, i am getting volts 19v but after connecting load , i am unable to see AMP using Ampere Meter.. and Fan is also moving too slow.. so I have opened the Junction Box and see too many Diodes.. so i just checked every diodes it seems to be dead.. even Current is not passing from each .. I want to know why there is so many diodes in 1 solar panel.. Diodes (10a10) Pictures are attached for reference.. Should i have to buy all of these 15 diodes for my 1 solar panel... or i can use only 3 diodes???

https://ibb.co/fDxJFk

https://ibb.co/kc0uo5

https://ibb.co/ezBOgQ

https://ibb.co/jJ1TFk

waiting for your reply...

mcgivor · April 2017

The diodes are there for the purpose of bi passing strings of cells in partially shaded conditions and should remain as designed. Are you trying to power the fan directly? If so the fan is probably dragging the voltage down, a charge controller and battery should be used. How did you check the diodes? they are unlikely to have failed, IMO but anything is possible,

samadniazi · April 2017

mcgivor said:

The diodes are there for the purpose of bi passing strings of cells in partially shaded conditions and should remain as designed. Are you trying to power the fan directly? If so the fan is probably dragging the voltage down, a charge controller and battery should be used. How did you check the diodes? they are unlikely to have failed, IMO but anything is possible,

Yes i am directly connecting a small dc fan with it.. And i have checked diodes using multimeter . and I have also checked it with a 12v power supply by putting diode in between Load and supply Terminal from Both sides but the current is not passing from both sides..

samadniazi · April 2017

so i have to buy all these 15 diodes ???? i have seen a video on youtube he was using only 3 diodes on his 200w solar panel...

Photowhit · April 2017

You have 15 diodes, but they are only serving 3 connections. I find this odd too, I guess just a money saving deal, though perhaps Bill or someone else electronic savvy could shed some light. I suspect Bill knows something about how his BP solar panels were wired...lol.

His setup;

Normal panel wiring;

Image: https://us.v-cdn.net/6024911/uploads/attachments/13383/5189.jpg

I just picked up the image, I believe you can ignore the added diode, it clearly shows 3 in the box.

Photowhit · April 2017

Diodes job in life is to keep current flowing in one direction. They are there so a shaded area won't pull down unshaded areas.

How have you measured the panel? How large a fan are you connecting? Watts and volts amps, type (brushed or brushless)... Panels in good direct sun will produce about 75% of their panel rating.

mcgivor · April 2017

Looks like 5 small diodes in parallel instead or 3 larger ones, did you check the diodes using the ohms or diode check on your meter, should have continuity when + is connected to the side without the band and - on the band side, when reversed there should be no continuity (or M ohms) Diodes are cheap if you have to replace them.

samadniazi · April 2017

Photowhit said:

Diodes job in life is to keep current flowing in one direction. They are there so a shaded area won't pull down unshaded areas.

How have you measured the panel? How large a fan are you connecting? Watts and volts amps, type (brushed or brushless)... Panels in good direct sun will produce about 75% of their panel rating.

I am using a Car radiator Fan motor.. it consumes 4a @12v on a battery...

mcgivor · April 2017

You need to have a battery in the system, preferably with a charge controller, the battery will act as a buffer and prevent the voltage output of the panel from collapsing, a CC will regulate the charging and if there are load terminals, will prevent the battery from being drawn down too low, most cheap CC have load terminals.

samadniazi · April 2017

guyz after installing new diodes.. still its not producing enough power just 19volts .. amps not showing and fan is also moving very slow

https://ibb.co/h8XXRQ

https://ibb.co/m7tT0k

samadniazi · April 2017

Friends... My new diodes again gone bad.. All of 6 new diodes not working.. Panel is just producing volts but no 0 amps .. What is the reason of this?

Photowhit · April 2017

Well, you'll never measure current with that meter, the symbol next to the 'Amps' '~' is a sine wave, so it's designed to only measure AC current. This is common for inexpensive clamp meters to only measure DC voltage.

Image: http://www.clipartbest.com/cliparts/niB/Bdg/niBBdgkMT.jpg

The fan, particularly if used may have more resistance now than spec'd. you also don't have good connections with a wire just shoved into the MC4 connections, also a very thin wire, not sure about your distances.

You could check the short circuit current with a hand held meter to give you a better idea if there is a problem with the panel.

jonr · April 2017

I agree, 10 to 20 amps would be more typical of such a fan. And you need a "DC ammeter".

mcgivor · April 2017

Try the following, connect the fan to a 12v battery, confirm it works, with your clamp on ammeter measure the current, this will confirm both are working. Next connect a 12v incandescent light around 25-50w to the panel, to verify the panel has output whilst measuring current, assuming your ammeter works, a simple restive load is a lot simpler to diagnose with. If there is no output check voltage between the negative terminal in the junction box of the panel and each positive string output, the anode side of the diodes, to confirm each string of cells has output, whilst the load is connected. Next measure across the diodes, the common connections of the 5 diodes, there should be no or very little voltage across them, if you read a voltage close to the panels rated voltage, the diodes have failed open circuit, or incorrectly installed and you may have only one string of cells providing output, the test needs to be conducted with sun across the whole panel. These are the tests I would conduct and it's a lot harder to put into words than just doing.

littleharbor2 · April 2017

I have two 12 volt automotive radiator fans running directly off of a 65 watt panel and they work great. Fact is when I first connected a single fan, rated at 80 watts it was running so fast I knew I had to change something. I connected both fans in parallel and got them running at a reasonable speed which has been running every day for over two years now.

I seriously doubt the panel is the problem. Hopefully you get all those diodes replaced in the correct orientation. Being that you are having difficulty operating and knowing you haven't got the correct meter for the task at hand it sounds like you really shouldn't be removing diodes. If you are trying to run the fan by just pushing those tiny wires into the MC-4 connectors you should expect things to not be working properly.

How far is the panel from the fan (how many feet of wire?) ? What gauge wire are you using?

mcgivor · April 2017

Photowhit said:

Well, you'll never measure current with that meter, the symbol next to the 'Amps' '~' is a sine wave, so it's designed to only measure AC current. This is common for inexpensive clamp meters to only measure DC voltage.

The fan, particularly if used may have more resistance now than spec'd. you also don't have good connections with a wire just shoved into the MC4 connections, also a very thin wire, not sure about your distances.

You could check the short circuit current with a hand held meter to give you a better idea if there is a problem with the panel.

You're right, couldn't zoom in and assumed by the negative reading was a DC, there are 2 AC positions on that meter , used a magnifying glass to confirm, failing eyesight and all, good spotting.

BB. · April 2017

OK, a few comments here.

Your meter, as Photowhit says, can only measure AC current. It cannot measure DC current. You need to get a DC capable current clamp meter like this one from Sears:

http://www.sears.com/craftsman-digital-clamp-on-ammeter/p-03482369000P

Next, the 5 diodes are in parallel--Equivalent of 1x larger diode (this may be a good thing--I have always worried that the 1x diodes would overheat if ran at rated current on a hot roof in a plastic J-Box).

And Photowhit's diagram is incorrect. Those are not blocking diodes, they are bypass diodes:

Modern solar panels used in systems these days do not use blocking diodes (older/smaller panels for direct battery charging without a charge controller is when blocking diodes are typically used).

Blocking diodes will have upwards of 10-12 volts or so "reverse voltage" (exact voltage will depend on specific panel wiring/configuration and loading+sun on panel). When you have a 60 cell panel (30 Volt Vmp) and 3 bypass diodes, you will have 20 cells or ~10 volts at Vmp across each diode. If a part of the panel is shaded, then the voltage will switch from "reverse" ~10 VDC to "forward" ~0.2-1.0 volts across a bypass diode (assuming full sun and a DC load on panel).

Solar cells are literately "giant" diodes. And they do not like much more than ~12 volts reverse voltage--If you have 10 amps in series (high voltage GT or MPPT charge controller), and shade one cell--That cell goes "high resistance" and could see close to 400+ VDC backwards across the cell (and destroy the cell/solar panel). With the bypass diode, instead, the bypass diode goes into forward conduction and "shunts" the current around the "dark"/high resistance cell and lets the current flow through the rest of the cells/strings in the panel+array.

Because you are seeing your DC fan run, there is current flowing (regardless of what your AC only meter says). We need to next look at the Vmp and Imp rating of the panel, and the current/voltage rating of your fan.

Also, we need to guess at the amount of sun (and position of sun) for your panel. More or less, your panel outputs current proportional to the amount of sun you have. If you have clear sky with full sun and the panel facing the sun directly, your panel can output near rated Imp. If the panel is not facing the sun square on--And/or you have clouds, or morning/evening sun, the panel will output much less than 100% Imp (just a little haze and not pointing panel at sun, you can get 50% or less of Imp very easily).

If the current requirements of your load is > Imp (or available Imp current), the voltage of the panel will "sag") and reduce the power available to your DC fan.

-Bill

Photowhit · April 2017

BB. said:

And Photowhit's diagram is incorrect. Those are not blocking diodes, they are bypass diodes:

I did say to ignore the added diode... I just wanted to show the single diodes in the J-box.

BB. · April 2017

No problem Photowhit. Just want to make things clear.

-Bill

Photowhit · April 2017

BB. said:

No problem Photowhit. Just want to make things clear.

....and I was being lazy, I am perfectly capable of photo editing, what I did for a living for awhile.... it was just late.

BB. · April 2017

Yea, and I was being lazy too. I found the first clip art that showed (very roughly) what I was trying to convey.

-Bill

samadniazi · April 2017

Thanks to all for help... Guys suggest me a battery for this 150w solar panel...

My Requirements: 3 Hours of backup @Night @LOAD 4amp
i want to connect a battery which can easily fully charge with solar panel .. in my city .. 7 hours of Full Sunshine is present @Day . plus i also want to use same load of 4a at day time for continuous when sunlight is present ..

BB. · April 2017

Be aware, few places actually get "7 hours of full sun" per day worth of light. For example:

http://www.solarelectricityhandbook.com/solar-irradiance.html

Multan Pakistan
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 60° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
4.78	5.38	5.54	5.69	5.66	5.62
Jul	Aug	Sep	Oct	Nov	Dec
5.19	5.20	5.50	5.76	5.15	4.62

Now--We have several assumptions/decisions to make... Is this backup power for a evening/night or two--Or do you want to run daily off of this array? 5% rate of charge is enough for a backup system (weekend/seasonal). 10%-13% rate of charge is highly recommended for a full time off grid power system. Also, if this is backup for afternoon power outages during hot weather (longer sun days) or monsoon season (stormy weather)--Looking the chart above will give you some ideas of how much sun you really get.

And normally, we design for the load--Not "just" for the size of the available solar panel. For example a 4 amp @ 12 volt load when the sun is present--That is a 7 hour load?

12 volts * 4 amps * 7 hours = 336 Watt*Hours per day (DC system)
336 WH per day * 1/12 volts * 2 days of storage * 1/0.50 maximum discharge = 112 Amp*Hour battery bank

Now sizing the solar array--You want to power your load from solar and charge your system during the same time (day time). I would suggest a 13% minimum rate of charge (remember, if you discharge your battery bank because of no sun, your solar array has to both recharge the battery bank and run your load at the same time):

112 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 274 Watt solar array

Now--If you do not need to run the loads when the sun is behind clouds--You could get away with a 1/2 size battery bank and 1/2 size solar array...

And sizing the solar array based on amount of sun you get per day... A nominal worst case calculation might look like:

336 Watt DC load * 1/0.61 DC off grid system eff * 1/0.75 less than ideal weather derate * 1/4.62 hours of December sun = 159 Watt array minimum

That is pretty close to your 150 Watt array... So--You decided how much "back power" you need vs just trying to run a system when the sun is available.

-Bill

samadniazi · April 2017

BB. said:

Be aware, few places actually get "7 hours of full sun" per day worth of light. For example:

http://www.solarelectricityhandbook.com/solar-irradiance.html
Multan Pakistan
Average Solar Insolation figures
Measured in kWh/m2/day onto a solar panel set at a 60° angle from vertical:
(For best year-round performance)
Jan Feb Mar Apr May Jun
4.78
5.38
5.54
5.69
5.66
5.62

Jul Aug Sep Oct Nov Dec
5.19
5.20
5.50
5.76
5.15
4.62

Now--We have several assumptions/decisions to make... Is this backup power for a evening/night or two--Or do you want to run daily off of this array? 5% rate of charge is enough for a backup system (weekend/seasonal). 10%-13% rate of charge is highly recommended for a full time off grid power system. Also, if this is backup for afternoon power outages during hot weather (longer sun days) or monsoon season (stormy weather)--Looking the chart above will give you some ideas of how much sun you really get.

And normally, we design for the load--Not "just" for the size of the available solar panel. For example a 4 amp @ 12 volt load when the sun is present--That is a 7 hour load?
12 volts * 4 amps * 7 hours = 336 Watt*Hours per day (DC system)
336 WH per day * 1/12 volts * 2 days of storage * 1/0.50 maximum discharge = 112 Amp*Hour battery bank
Now sizing the solar array--You want to power your load from solar and charge your system during the same time (day time). I would suggest a 13% minimum rate of charge (remember, if you discharge your battery bank because of no sun, your solar array has to both recharge the battery bank and run your load at the same time):
112 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 274 Watt solar array
Now--If you do not need to run the loads when the sun is behind clouds--You could get away with a 1/2 size battery bank and 1/2 size solar array...

And sizing the solar array based on amount of sun you get per day... A nominal worst case calculation might look like:
336 Watt DC load * 1/0.61 DC off grid system eff * 1/0.75 less than ideal weather derate * 1/4.62 hours of December sun = 159 Watt array minimum
That is pretty close to your 150 Watt array... So--You decided how much "back power" you need vs just trying to run a system when the sun is available.

-Bill

How you know i Live in Multan,Pakistan???

THanks bill for detail answer... but i still dnt understand,,,, which battery should i buy..??? 12amp or bigger????

Estragon · April 2017

I suspect that as a moderator of the forum Bill can see your ip address, which is often indicative of location.

As for battery sizing, you really need to understand and work with the numbers and trade-offs in Bill's post. A bigger battery gives you more availability for loads and reduces the need to deeply discharge, but brings a need to have larger sources to properly recharge. These are choices only you can make.

BB. · April 2017

Yes, I can see your IP address, and then plug it into something like this:

http://geoiplookup.net/
http://geobytes.com/iplocator/

But these are guesses and are not always correct.

Guessing at your location saves a round trip discussion of where you are at and I can at least have some sort of answer that will be helpful. 80% of the time or so...

Battery bank--As Estragon says--It depends on your needs and usage pattern. For a full time off grid system (charge during day, use at night) 4 amp * 7 hours * 2 days storage * 1/0.50 maximum discharge gives 112 AH

If you only want one day storage, then 56 Amp*Hour minimum.

If you will only use the loads when the sun is shining (9am to 3pm)--You might get away with a 40 AH battery or a bit less... Really depends on your needs.

-Bill

BB. · April 2017

The minimum battery I would suggest is an 8 hour discharge rate:

4amps * 8 hour discharge = 32 AH minimum

Assuming your solar panel is supplying current during the day when you are using the device.

-Bill

samadniazi · April 2017

Guys i have bought a cheap chinese 20a PWm Solar Charge Controller... Now i have to set it up.. i have connected a 12v 12amp Sealed Lead Acid battery... what should be best Charging Volt for this battery, I have Set my Charge controller to 14.4v ..
2nd After some minutes the charging symbol starts blinking, i have read its manual .. its something Float Charging..?? what is float charging mode???

https://ibb.co/cHfro5
https://ibb.co/gYJ0gQ

BB. · April 2017

For solar chargers, there are generally 4 modes:

Bulk: This is the charger taking all available charging current (power) from the solar panels and dumping them into the battery bank (100% of available solar energy)
Absorb: This is when the battery has reached the charging voltage set point (like 14.4 volts for your battery). The charge controller will limit charging current to 14.4 volts and eventually stop (either 2-4 hour typical timeout, or when the sun sets).
Float: This is the charging voltage that the controller will hold after it decides the battery is full (after absorb cycle is complete). If you draw power from the battery bank, the charge controller will supply additional current to hold 13.6 volts (or whatever setpoint is). This is to prevent the battery from being over charged--Too much voltage/current will overheat the battery and "boil" (electrolysis--Generating hydrogen and oxygen gasses from water)--Once a Lead Acid battery is charged, the controller drops back to a lower voltage to keep the battery charged with a mnimum amount of ch
No Current/Dark: When the sun has set, the charge controller generally "turns off" the solar panel circuit to prevent current flowing backwards from the battery bank to the solar array (reverse current protection to array).

-Bill

Need help regarding Solar Panel DIODES

Comments

Multan Pakistan
Average Solar Insolation figures

Multan Pakistan
Average Solar Insolation figures

Categories

Need help regarding Solar Panel DIODES

Comments

Multan PakistanAverage Solar Insolation figures

Multan PakistanAverage Solar Insolation figures

Categories

Multan Pakistan
Average Solar Insolation figures

Multan Pakistan
Average Solar Insolation figures