Solar panel gloom

[molly 2]

Suspected for sometime that my 100 w flexible solar panels is down on output . I have just checked the open circuit voltage ,midday perfect sunshine reading
16.5 volts ,batterys full ,is that low enough to call goosed .how efficient will it be at that voltage .

 

[trevskoda]

Some put out 19v, but that should work ok, its the amps output that matters, check output from regulator to batteries, if 6 amps good, flexies are not the best as they heat up and don't do the biz, also short life span.

 

[Derekoak]

I have 4 year old semi flexible 160watt total. Max open circuit 18v. My maximum peak wattage in the last week was 132watt. As the sun will never be vertical to the panel in the uk I think that is good enough. My mppt gives peak volt and watts and daily watt hours so you can tell. Without that it is more complicated to tell.

 

[molly 2]

Some put out 19v, but that should work ok, its the amps output that matters, check output from regulator to batteries, if 6 amps good, flexies are not the best as they heat up and don't do the biz, also short life span.

Most I have seen a grim 2 amps panel about 5 years old . But never shown much more

 

[Nabsim]

If your batteries are fully charged Baz you shouldn’t be getting anything from your controller. You need to know what your panel spec is really, here is one of mine but it’s 150W panel. I am currently pulling between 16 and 19 volts and it’s light overcast here so I don’t think you have a problem but no expert by any means.
High Efficiency Monocrystalline PV Module
Product code
SGM-150W-18
Maximum power(Pmax). 150W
Voltage at Pmax(Vmp). 17.8
Current at Pmax(Imp). 8.43
Open-circuit voltage(Voc). 22.3

 

[molly 2]

If your batteries are fully charged Baz you shouldn’t be getting anything from your controller. You need to know what your panel spec is really, here is one of mine but it’s 150W panel. I am currently pulling between 16 and 19 volts and it’s light overcast here so I don’t think you have a problem but no expert by any means.
High Efficiency Monocrystalline PV Module
Product code
SGM-150W-18
Maximum power(Pmax). 150W
Voltage at Pmax(Vmp). 17.8
Current at Pmax(Imp). 8.43
Open-circuit voltage(Voc). 22.3

The voltage is not taken from controller but open circuit from the panel . Seem to remember open circuit spec 22 v .

 

[1 Cup]

I've disconnect my hole output system 10 june. only controller and diesel heater conected still.to bat
Solars input is useless now as not needed. Lol

 

[trevskoda]

Problem with many folks vans they have lots to run and charge, tv satellite laptop phones hele landing lights on the roof, submarine pen underneath and missile sys on the roof LOL.

 

[wildebus]

Suspected for sometime that my 100 w flexible solar panels is down on output . I have just checked the open circuit voltage ,midday perfect sunshine reading
16.5 volts ,batterys full ,is that low enough to call goosed .how efficient will it be at that voltage .

if that 16.5V really is Voc (so read at the panel with the controller disconnected), it is not good and likely points to an issue. If I give an example of how one controller works .... the Victron MPPT Solar Controller will not even wake up until the Panel voltage is >5V more than the Battery - so if you had a Victron controller with your panels, the Leisure Battery would have to be under 11.5V before the solar would do anything at all.

With the battery full, you really can't tell what the panel is capable of - you need a demand of at least 8A (could be battery charge or something else) with a 100W panel to see what the panel could output. A
s an example, from around 15:00 my 270W array are only putting 100W and dropping all the time - but that is because that is all the batteries are accepting and not a limit of the panels. This is evident at the jump in power at 15:10 and 16:45 - which is when the fridge gets powered up. And as soon as the compressor no longer takes power, the solar harvesting drops back again. And even then at these jumps I don't know if the solar is peaking or not.

 

[molly 2]

if that 16.5V really is Voc (so read at the panel with the controller disconnected), it is not good and likely points to an issue. If I give an example of how one controller works .... the Victron MPPT Solar Controller will not even wake up until the Panel voltage is >5V more than the Battery - so if you had a Victron controller with your panels, the Leisure Battery would have to be under 11.5V before the solar would do anything at all.

With the battery full, you really can't tell what the panel is capable of - you need a demand of at least 8A (could be battery charge or something else) with a 100W panel to see what the panel could output. A
s an example, from around 15:00 my 270W array are only putting 100W and dropping all the time - but that is because that is all the batteries are accepting and not a limit of the panels. This is evident at the jump in power at 15:10 and 16:45 - which is when the fridge gets powered up. And as soon as the compressor no longer takes power, the solar harvesting drops back again. And even then at these jumps I don't know if the solar is peaking or not.
View attachment 109870

Thanks for info , I did take the reading from SP leads but it was connected to charge controller Sargent 328 with built solar controller serving both batterys i will check again with SP disconnected when full midday sun allows , if the flexi is down I intend to replace with 120 watt max as stated by sargent .ps I took your advice and bought lead carbon battery from alpha . BAZZ .

 

[TR5]

To get an idea of the max amp output of a panel you divide the wattage rating by the voltage.
Simple you may think, but what voltage do you use - the panel open circuit, or the max output after the controller?

Example:
100w panel / open circuit say 19v = 5.263amps
100w panel / max controller out 14.4v = 6.94 amps.

Obviously there are some losses, so this would only be a guide - but which voltage should you use to calculate, anyone know?

 

[Nabsim]

To get an idea of the max amp output of a panel you divide the wattage rating by the voltage.
Simple you may think, but what voltage do you use - the panel open circuit, or the max output after the controller?

Example:
100w panel / open circuit say 19v = 5.263amps
100w panel / max controller out 14.4v = 6.94 amps.

Obviously there are some losses, so this would only be a guide - but which voltage should you use to calculate, anyone know?

I don’t know but looking at mine I have seen the amps if you use Pmax so I would guess that’s the figure

 

[wildebus]

To get an idea of the max amp output of a panel you divide the wattage rating by the voltage.
Simple you may think, but what voltage do you use - the panel open circuit, or the max output after the controller?

Example:
100w panel / open circuit say 19v = 5.263amps
100w panel / max controller out 14.4v = 6.94 amps.

Obviously there are some losses, so this would only be a guide - but which voltage should you use to calculate, anyone know?

#1. It depends on the controller. If you have a PWM controller, any voltage from the panel that is above the battery voltage gets discarded (chopped) - so if we used your numbers ... 100W harvesting with 19V into the controller and a battery at 14.4V would mean an instant reduction of around 25%. If the battery was at a more likely 13V, you would be losing over 30%. So that is reason #1 to use an MPPT controller instead of PWM.
An MPPT will convert excess voltage into greater current - so again taking your example and ignoring losses, you might be putting in 5.26A INTO the controller, but you would be outputing 6.94A OUT to the battery.

The info needed is actually on the back of the panel usually - I just took this photo of a 100W panel kit .... It shows Maximum Power Voltage - Vmp; and Max Power Current - Imp. Multiply the two together and you have the Maximum Output of the Panel (100W)
If you had this panel using a PWM Controller and harvesting 100W, the maximum current to the battery will never exceed 5.62A; If you have via an MPPT controller, that greater voltage gets converted to more current and if the battery were at say 13.0V, the controller outout to battery would be 7.7A (again, ignoring all losses).

These graphs show the current alteration between different input voltages on MPPT controllers - one array is in series (PV voltage fluctating between 50-54V) and the other is in parallel (voltage between 17.3-18.3V) - and how the input current varies greatly between the two otherwise similar arrays but the output current (to the same battery bank) is within 5% of each other.

 

[wildebus]

Talking about Panel voltages, this might be interesting to see .... Have a look at what happens at about 15:30 yesterday....

Heavy Cloud and Rain Storm (talking sufficient to knock out Satellite TV reception) - Solar harvesting drops right back due to the dark and the PV Voltage goes right up near to the Voc level.