Furstrated- Unable to get rated solar Amperage

[Sunking]

The Technician visited me second time, What he did-
1)Replace wire Lugs (Wire connectors going into solar panel end)
2)Added second Controller
Panel 1 & 2 in PARALLEL = Controller 1
Panel 3 & 4 in PARALLEL= Controller 2

However I am still at half of specced wattage (1000W or 8A x 4 panels = 32A)
I'll be happy even at 700W! I enquired about MPPT controllers and he says MPPT is not successful in India? Why?

I can only guess the technician is referring to sales not being successful. Otherwise I am confident by the advice you have been given by locals in your area have no idea what they are doing. If they did they would have never sold you 30 volt panels for a 24 volt battery using PWM controller. That alone tells us they are ignorant.

As I stated before with any PWM controller Output Current = Input Current. You need to fully understand what that means. Your panels are rated 7.94 amps and with 4 in parallel a total current of 31.76 amps. So the maximum charge wattage on the battery is 31.76 amps x 24 volts = 762 watts. Problem is your panel voltage is too low to push that much current.

With a MPPT controller Output Current = Panel Wattage / Battery Voltage. 1000 watts / 24 volts = 42 amps.

So if you want your system to work, use the right equipment and hardware. As state din my first post there is nothing wrong with the equipment. All of your problems are Operator Error in design and implementation.

[mapmaker]

I'll be happy even at 700W! I enquired about MPPT controllers and he says MPPT is not successful in India? Why?

Your technician isn't too smart. You asked us for advice on this forum. You got good advice here, and you got a good explanation why you need an MPPT controller.

If you keep asking why your system doesn't work correctly, you will get the same answer, or maybe you will get no answer because you have already been told the answer.

--mapmaker

[bhvm]

The Technician visited me second time, What he did-
1)Replace wire Lugs (Wire connectors going into solar panel end)
2)Added second Controller
Panel 1 & 2 in PARALLEL = Controller 1
Panel 3 & 4 in PARALLEL= Controller 2

The outputs of both controllers are now combined (parallel) and joined to battery.
The results is I'm seeing about 240 watts on each controller, which means close to 500W total or 20A Charging.
However I am still at half of specced wattage (1000W or 8A x 4 panels = 32A)
I'll be happy even at 700W! I enquired about MPPT controllers and he says MPPT is not successful in India? Why?

[Sunking]

the distance is about 30ft. I wanted 4 sqmm but couldn't get any. I have also enquired about mppt controller and they're about 250 dollars. the seller suggested me to straight away go for Solar inverter wish mppt for 350 dollars. I'll pass on the spec here so you can judge. thanks.

4 mm^2 is safe, but still a bit small for 8 amps, but not bad which puts you at roughly 3% voltage and power on the wiring.

FWIW 1 mm^2 was border line safe and resulted in 38% power loss with 8 amps @ 30 volts.

[bhvm]

the distance is about 30ft. I wanted 4 sqmm but couldn't get any. I have also enquired about mppt controller and they're about 250 dollars. the seller suggested me to straight away go for Solar inverter wish mppt for 350 dollars. I'll pass on the spec here so you can judge. thanks.

[Sunking]

the tech team is here.
they advised we replace the wires of 1sqmm to 2.5sqmm. I brought 4 rolls of wires.

in the end I have 4 pairs of 2.5 mm wires (joint free ) coming from panels to controller. one pair for EACH. I took a temporary reading and I can already notice 50 percent improvement. each 8a rated panel is delivering 3 amps at 5pm. perhaps they'll ramp up to 7 amps in noon. feasible?

How long are these cable runs? (One-Way distance)

One of the most important factors in a design is limiting voltage loss to 2 or 3 % or less. With a 30 volt panel 2% is only .6 volts. With 8 amps of current and lest's say a One Way Distance of 25 feet (8 meters) would require a minimum of a 6 mm^2 copper cable. I do not know how long of a run you have but at 2.5 mm^2 with 8 amps is only good for 14 feet or roughly 4 meters One-Way.

[bhvm]

the tech team is here.
they advised we replace the wires of 1sqmm to 2.5sqmm. I brought 4 rolls of wires.

in the end I have 4 pairs of 2.5 mm wires (joint free ) coming from panels to controller. one pair for EACH. I took a temporary reading and I can already notice 50 percent improvement. each 8a rated panel is delivering 3 amps at 5pm. perhaps they'll ramp up to 7 amps in noon. feasible?

[inetdog]

They look like 1 Sqmm to the eye. Today I will see if I can make series connection at panel itself and Combine 2 cables to bring power downstairs. Will that help? If wires are hot means they're wasting half the power, aint it?

1 mm² in area would be the equivalent of US #17 AWG.
1 mm diameter would have and area equivalent to smaller than #18 AWG. Either of those would be too small for 10A on a long term basis.

Now the fact that the wires are getting noticeably warm/hot does not by itself meant that you are losing a lot of power, much less half the power, but in this voltage sensitive environment (single panel in particular) it is not a good thing.

[bhvm]

They look like 1 Sqmm to the eye. Today I will see if I can make series connection at panel itself and Combine 2 cables to bring power downstairs. Will that help? If wires are hot means they're wasting half the power, aint it?

[inetdog]

yes they're the same size. I'll replace them and report back. let's see if it improves amperage.

Not a sure improvement, but worth looking into. I would measure the voltage at the panel and at the CC end of the wires before I went to too much trouble replacing the wires. Unless I knew for sure that they were smaller than #14 AWG (if shorter than 25 feet) that is.

[bhvm]

yes they're the same size. I'll replace them and report back. let's see if it improves amperage.

[inetdog]

The ones in Series panels are warmer than other wires. What does that say?

Mostly that says that if they are the same size as the others they must be carrying more current.
That is also consistent with the individual panel voltage being too low to delver the needed current to the batteries.

[bhvm]

here's a voltage chart of typical requirements.

http://www.trojanbattery.com/BatteryMaintenance/Charging.aspx

Daily bulk is nearly 30V, and Equalization is 31 volts. To perform EQ, you need to start with fully charged batteries.
You will need to provide about 3 volts more, because of inherent losses internal to any charge controller. So you really need panels that can supply their full amps at 35 or 36 volts.

I'd suggest you plan to wire your panels, 2 in series, to get 60 or 70V, AND obtain via mail order, a proper MPPT charge controller. At this point, from not having been charged properly, your batteries are likely pretty well trashed.

About the only thing you can do at this point is look at
http://www.vitronicscontrols.com/sol...t-charger.html from the same vendor you got the PWM charger from. Maybe they can exchange it.
Or look at another brand of MPPT controller that can handle 80Vdc from the PV array.

Thanks for deep insight. The Current controller seems happy at 60v.
I am going to ask them about MPPT ones. They're also sending in a technician tomorrow. He'll check stuff and let us know. I am also doubtful about wires. I feel that the wires are slightly warmer. The ones in Series panels are warmer than other wires. What does that say?

[Mike90250]

here's a voltage chart of typical requirements.

http://www.trojanbattery.com/BatteryMaintenance/Charging.aspx

Daily bulk is nearly 30V, and Equalization is 31 volts. To perform EQ, you need to start with fully charged batteries.
You will need to provide about 3 volts more, because of inherent losses internal to any charge controller. So you really need panels that can supply their full amps at 35 or 36 volts.

I'd suggest you plan to wire your panels, 2 in series, to get 60 or 70V, AND obtain via mail order, a proper MPPT charge controller. At this point, from not having been charged properly, your batteries are likely pretty well trashed.

About the only thing you can do at this point is look at
http://www.vitronicscontrols.com/sol...t-charger.html from the same vendor you got the PWM charger from. Maybe they can exchange it.
Or look at another brand of MPPT controller that can handle 80Vdc from the PV array.

[bhvm]

Dear all, Thank you for detailed replies. let me reply one by one.

No, it's not the controller, a 24V battery needs over 33V for proper charging and equalizing. And everything has loss. MPPT controllers have least loss, only 5%. PWM (like the kind you have) will have 30% under good conditions, because you end up with power mis-matches that the MPPT solves.




Stop doing that. you can fry your controller.

In series, you ADD voltage, the amps stay the same. 8 amps would be correct for panels in series. Panels are fine, controller is working.
In parallel, you ADD amps, so 2, 8A panels would expect 16 amps, if the voltage was correct for the batteries.

1) I thought charging a 24v System shall use MAX 27v. Because I have never seen a battery bank charged to more than 26.5v in practical. Is there a difference in solar charging and mains charging protocol? In college projects, we used to happily charge a 12v battery bank with 15v transformer. I eXtrapolated the same and thought 31v panels would be good enough and minimize losses. hence i brought such panels. I think I made a mistake here.

2) The Controller I Brought is a very expensive (By indian Standards) and Is supposed to support maximum 500W worth of panels. I am running it happily since morning. I Have put 2 panels in series and the controller shows a maximum of 150w solar being extracted (6A in my Ammeter). Thinking 50% bucking loss, I was atleast expecting 250W (30 volts by 8A something)

3) When going from series to parallel, or so on, I did not gain or loose any Amps I feel. The Controller shows about 150W in series mode, and 140W in parallel mode. This is the confusion.

Let me try to explain: Power (watts) = Volts X amps

A solar panel has its highest voltage (Voc) when there is nothing connected to it. that means the amps are zero and the power (volts X amps) is zero.

A solar panel has its highest current (Isc) when it is connected to a short circuit. In that case its voltage is zero and the power (volts X amps) is zero.

To get any power out of a panel, the current must be somewhere between 0 and Isc, and the voltage must be somewhere between 0 and Voc. For your panels, in parallel, that maximum power voltage (Vmp) is too low to charge a 24 volt battery. Don't forget that a panel's Vmp is also temperature dependent. That means when your panels are in the hot sun, their Vmp drops even lower.

When you put your panels in series the Vmp is about 62.8 volts. That's fine if you have an MPPT controller which can lower the voltage while increasing the current. An MPPT controller finds that point (volts X amps) where maximum power occurs.

Your controller pulls the voltage down while NOT increasing the current. Since it has to pull the voltage down from about 60 to 30 volts, without increasing the amps, you lose half your power.

--mapmaker

May I know how much drop in Volts I get due to heat? damm! Indian summers are hot! Its already 42.C Ambient in noon (That 110F+). On No Load voltage, I got 31v on My meter. Do you think its going down to something 24v on load? As a result no charge??
When panels are connected to controller, The panel voltage is whatever the Battery voltage is. This is also confusing. Or Is the controller bringing the panel to its knees and all it gets is Float battery voltage with poor Current output? I dont think a 60V panel could be brought to knees without significant Amps. Atleast 8 Amps as the spec says.