Solar charge controller

[yvonne]

We had a 80 watt solar panel installed on our trailer by the dealer. He also installed a controller. Reading the controller manual, I am worried the controller is not adequate for the panel. The manual says quote "maximum solar array voltage rating of 25 volts ". Please give advice. Thanks.

[Frederick L. Simson]

The manual says quote "maximum solar array voltage rating of 25 volts ".

I think you may be confusing Watts and Volts. Your controller is fine for your [b]12 volt D.C. system.

The manufacturer is just warning you not to assume it will run 110 volt A.C. appliances.

[Byron Kinnaman]

We had a 80 watt solar panel installed on our trailer by the dealer. He also installed a controller. Reading the controller manual, I am worried the controller is not adequate for the panel. The manual says quote "maximum solar array voltage rating of 25 volts ". Please give advice. Thanks.

Check the specifications of the actual solar panel. Most will output a maximum of 17 to 17.5 volts which is below the maximum input voltage rating of your controller per your quote.

FYI. Watts = Volts x Amps.

Byron

[Morgan]

I think you may be confusing Watts and Volts. Your controller is fine for your [b]12 volt D.C. system.

The manufacturer is just warning you not to assume it will run 110 volt A.C. appliances.

Fred,

I think what it's referring to is the maximum voltage from the solar panel(s).

Most 12V panels have an open circuit voltage of about 20 volts, so Yvonne should be perfectly safe.

[Byron Kinnaman]

I think you may be confusing Watts and Volts. Your controller is fine for your [b]12 volt D.C. system.

The manufacturer is just warning you not to assume it will run 110 volt A.C. appliances.

I don't think that quite right. There are solar panels for 24 volt systems, which would mean higher than 25 volt output in full sun. The warning is only use solar panels designed for 12 volt systems. Has nothing to do with 110 volt AC.

[Frederick L. Simson]

Most 12V panels have an open circuit voltage of about 20 volts, so Yvonne should be perfectly safe.

Thank you for clearing that up.

[Scott S.]

We had a 80 watt solar panel installed on our trailer by the dealer. He also installed a controller. Reading the controller manual, I am worried the controller is not adequate for the panel. The manual says quote "maximum solar array voltage rating of 25 volts ". Please give advice. Thanks.

I know just next to nothing about these systems.... but I'd like to ask what it cost you to install?

[Rick B]

We had a 80 watt solar panel installed on our trailer by the dealer. He also installed a controller. Reading the controller manual, I am worried the controller is not adequate for the panel. The manual says quote "maximum solar array voltage rating of 25 volts ". Please give advice. Thanks.

I have an 80 watt panel on my Bigfoot and the charge controller indicates maximum 25 watts. Under ideal conditions, my panel kicks out 5 amps or so, so I could have about 4-80 watt panels ( 5 amps x 4 panels = 20 amps) and close to reach the maximum output of the controller (assuming that I had the space on the roof)

[Byron Kinnaman]

I have an 80 watt panel on my Bigfoot and the charge controller indicates maximum 25 watts. Under ideal conditions, my panel kicks out 5 amps or so, so I could have about 4-80 watt panels ( 5 amps x 4 panels = 20 amps) and close to reach the maximum output of the controller (assuming that I had the space on the roof)

I think you're confusing watts and volts. I also think you're confusing inputs and outputs. Don't you mean your charge controller indicates maximum of 25 Volts input. Input typical 25 Volts Maximum. Output, varies from a few amps to lots of amps. My guess for an 80 Panel the controller output would be specified in the 8 to 12 Amp range.

FYI 5 Amps or so is about 80 Watts.

Now for bit of basic electricity and Ohm's Law.

Ohm's Law. E=IR (E=Volts, I=Amps, R=Resistance
P=IE (P=Watts, I=Amps, E=Volts)

Therefore Watts = Volts x Amps.

Remembering basic Algebra I=P/E, E=P/I

[Rick B]

I have an 80 watt panel on my Bigfoot and the charge controller indicates maximum 25 watts. Under ideal conditions, my panel kicks out 5 amps or so, so I could have about 4-80 watt panels ( 5 amps x 4 panels = 20 amps) and close to reach the maximum output of the controller (assuming that I had the space on the roof)

Thanks Byron - it is maximum 25 amps output, thus about 4 - 80 watt panels would generate about 20 amps There is no way the output is anywhere near 12 amps according to the meter (which alternates between volts and amps)

Rick

[Greg Yother]

FYI 5 Amps or so is about 80 Watts.

Now for bit of basic electricity and Ohm's Law.

Ohm's Law. E=IR (E=Volts, I=Amps, R=Resistance
P=IE (P=Watts, I=Amps, E=Volts)

Therefore Watts = Volts x Amps.

Remembering basic Algebra I=P/E, E=P/I

I needs me some more basic schoolin' on this one. I'm startin' from scratch here so bear with me. OK, so if Amps = Watts/Volts, then where are you getting the [b]16 volts to arrive at 5 Amps when you have an 80 watt panel? Why wouldn't it be [b]12 volts?

[Rick B]

Thanks Byron - it is maximum 25 amps output, thus about 4 - 80 watt panels would generate about 20 amps There is no way the output is anywhere near 12 amps according to the meter (which alternates between volts and amps)

Rick

My controller is a Go Power GRP 25, with specs as follow - clearly indicating 25 amps, but also 26 V Max Voc Array Voltage (don't know what 'Voc' means)

Go Power! Electric Inc.
GPR-25 Solar Charge Regulator
25 Amp Digital Charge Controller

GPR-22 Solar Charge RegulatorProvides Superior Battery Protection

Solar charging systems need a quality regulator to protect batteries from overcharge.

The Go Power! 25 amp Regulator (GPR-25) offers full battery protection by regulating the current flowing from your solar panel system into the batteries, thus keeping your batteries balanced and working at peak performance.

The GPR-25 Amp Regulator replaces the analogue meters of the past. With the regulator’s digital Liquid Crystal Display (LCD), you can read both the battery voltage and solar charge current; it switches between the two readings at 10-15 second intervals.

Under the digital display is a coloured battery voltage gauge. Red indicates the battery is in danger of complete discharge, yellow warns that the battery is getting low, and green verifies the voltage is within premium working range.

This regulator has the expanded capability to handle up to 395 Watts (at a typical Vp of 17.3V) of solar charging power. The thin, compact design of this regulator makes it easy to install, and the black face plate allows it to blend with almost any decor. Custom colours and private labeling are available.
Specifications
Description Value
Nominal Voltage 12 V
Rated Current, Continuous 25 A
Array Voltage, Max. Voc 26 V
Current Consumption, Charging, Typ. 20 mA
Charge Termination, Selectable 14.1/14.4 ± 0.2 V
Charge Resumption 13.0 ± 0.3 V
Operating Temperature Range -40 to 85° C (-40 to 185° F)
LCD Operating Temperature -10 to 55° C (14 to 131° F)
Dimensions

Size 107mm x 190mm x 19mm (4.25” x 7.50” x 1.6”)
Weight 172 g (6.02 ounces)
Warranty 5 years

[Byron Kinnaman]

My controller is a Go Power GRP 25, with specs as follow - clearly indicating 25 amps, but also 26 V Max Voc Array Voltage (don't know what 'Voc' means)

Go Power! Electric Inc.
GPR-25 Solar Charge Regulator
25 Amp Digital Charge Controller

GPR-22 Solar Charge RegulatorProvides Superior Battery Protection

Solar charging systems need a quality regulator to protect batteries from overcharge.

The Go Power! 25 amp Regulator (GPR-25) offers full battery protection by regulating the current flowing from your solar panel system into the batteries, thus keeping your batteries balanced and working at peak performance.

The GPR-25 Amp Regulator replaces the analogue meters of the past. With the regulator’s digital Liquid Crystal Display (LCD), you can read both the battery voltage and solar charge current; it switches between the two readings at 10-15 second intervals.

Under the digital display is a coloured battery voltage gauge. Red indicates the battery is in danger of complete discharge, yellow warns that the battery is getting low, and green verifies the voltage is within premium working range.

This regulator has the expanded capability to handle up to 395 Watts (at a typical Vp of 17.3V) of solar charging power. The thin, compact design of this regulator makes it easy to install, and the black face plate allows it to blend with almost any decor. Custom colours and private labeling are available.
Specifications
Description Value
Nominal Voltage 12 V
Rated Current, Continuous 25 A
Array Voltage, Max. Voc 26 V
Current Consumption, Charging, Typ. 20 mA
Charge Termination, Selectable 14.1/14.4 ± 0.2 V
Charge Resumption 13.0 ± 0.3 V
Operating Temperature Range -40 to 85° C (-40 to 185° F)
LCD Operating Temperature -10 to 55° C (14 to 131° F)
Dimensions

Size 107mm x 190mm x 19mm (4.25” x 7.50” x 1.6”)
Weight 172 g (6.02 ounces)
Warranty 5 years

Specifications Explained.

Rated Current, Continuous is maximum current output from charge controller. Trying to exceed this by running lots of DC stuff will probably result in the controller shutting down.

Array Voltage, Max. Voc is the maximum voltage the controller will tolerate from the solar panel(s). Typical solar panels are between 17 and 18 volts.

Current Consumption, Charging Typ. is the current the charge controller is using while charging the battery.

Charge Termination, Selectable 14.1/14.4 ± 0.2 V is the battery voltage at which the charge controller disconnects from the battery. (it does this without your help).

Charge Resumption 13.0 ± 0.3 V is the battery voltage and below where the charge controller connects to the battery and starts charging.

I needs me some more basic schoolin' on this one. 54.gif I'm startin' from scratch here so bear with me. OK, so if Amps = Watts/Volts, then where are you getting the 16 volts to arrive at 5 Amps when you have an 80 watt panel? Why wouldn't it be 12 volts?

I think you're attempting to equate input volts vs output current. They don't equate. The only thing you can equate is watts. That why solar panels are rated in watts.

Example; 80 Watt Solar panel output 17.2 Volts. Assuming you can get the full 80 watts out that would be 4.65 Amps.
Input into the battery, or 12 volt system, 13.8 Volts, 80 Watts, that would equal 5.79 Amps.
Note: Watts = Watts. Volts and Amps change.

That is an ideal situation. I doubt you'd ever get 80 watts out of an 80 watt solar array.

[Greg Yother]

I think you're attempting to equate input volts vs output current. They don't equate. The only thing you can equate is watts. That why solar panels are rated in watts.

Example; 80 Watt Solar panel output 17.2 Volts. Assuming you can get the full 80 watts out that would be 4.65 Amps.
Input into the battery, or 12 volt system, 13.8 Volts, 80 Watts, that would equal 5.79 Amps.
Note: Watts = Watts. Volts and Amps change.

That is an ideal situation. I doubt you'd ever get 80 watts out of an 80 watt solar array.

Great! OK, I'm almost there. Where are you getting the 17.2 volts? In my owners manual for the Harbor Freight 45w array (three 15w panels) it says:


15 watts per panel, 14.5 volts output (working)
Peak Voltage: 23.57 OCV (Open Circuit Volts)
Nominal Voltage:14.5 volts battery output


How would one come to the conclusion of 17 volts, other than just taking it for granted that most panels are around 17 volts? (say theoretically I want to make sure mine isn't the one weird solar array that ain't 17 volts).

[Byron Kinnaman]

Great! OK, I'm almost there. Where are you getting the 17.2 volts? In my owners manual for the Harbor Freight 45w array (three 15w panels) it says:


15 watts per panel, 14.5 volts output (working)
Peak Voltage: 23.57 OCV (Open Circuit Volts)
Nominal Voltage:14.5 volts battery output


How would one come to the conclusion of 17 volts, other than just taking it for granted that most panels are around 17 volts? (say theoretically I want to make sure mine isn't the one weird solar array that ain't 17 volts).

It appears that they have put a resister in series with the panel output to limit the current to around 1 Amp. With this low of a chargin current a charge controller isn't needed.
A series resister would explain the difference between open circuit volts (nothing connected) and Nominal Voltage: battery output (battery connected and charging).

[Greg Yother]

It appears that they have put a resister in series with the panel output to limit the current to around 1 Amp. With this low of a chargin current a charge controller isn't needed.
A series resister would explain the difference between open circuit volts (nothing connected) and Nominal Voltage: battery output (battery connected and charging).

I assume you arrive at 1 amp by taking 15w / 14.5v. So that means 3 panels would be about 3.1 amps, and 6 panels would be about 6.2 amps (90w / 14.5v), so I would need to use my 7 amp charge controller if I wired 6 panels in parallel? Am I getting the hang of it?

[Byron Kinnaman]

I assume you arrive at 1 amp by taking 15w / 14.5v. So that means 3 panels would be about 3.1 amps, and 6 panels would be about 6.2 amps (90w / 14.5v), so I would need to use my 7 amp charge controller if I wired 6 panels in parallel? Am I getting the hang of it?

The answer is yes and no.

You're got the right idea in theory. In an ideal world what you say would be true.

There's one more bit of information that missing that comes from the practical world Things like charge controllers require an input voltage that's generally a couple volts higher than the output voltage. This is so that the control circuits can work properly. In your case the input voltage might be too close to the output voltage for the controller work. The only way to tell is look at all the specifications.

[yvonne]

I know just next to nothing about these systems.... but I'd like to ask what it cost you to install?

Scott, I am sorry it has taken me so long to reply. I have been away from my computer. The trailer was prewired for solar at the factory and my dealer charged $1169 for an 80 watt Sharp solar panel with a controller and that included installation.

[peterh]

Scott, I am sorry it has taken me so long to reply. I have been away from my computer. The trailer was prewired for solar at the factory and my dealer charged $1169 for an 80 watt Sharp solar panel with a controller and that included installation.

If you're a good bargain hunter and handy with tools you can install a 50 watt system for $500 or less. My used 50w solar panel (eBay), charge controller, composite lumber (to build a new frame) and wiring ran about that much.

[Scott S.]

thanks! it looks slick, I just have to justify the expense to myself... shouldn't be hard.