Newbie question about solar panel voltage

[R8kid]

Hi everybody,

I installed a small solar panel system to experiment with,
I compared the voltage of my home with the voltage of the
inverter and the voltage of my home is more stable than
the voltage that the inverter produces.

The voltage of the inverter fluctuates allot. Is this normal
or should I buy something like a power conditioner to
fix this issue?

Thanks in advance.

[SunEagle]

Hi everybody,

I installed a small solar panel system to experiment with,
I compared the voltage of my home with the voltage of the
inverter and the voltage of my home is more stable than
the voltage that the inverter produces.

The voltage of the inverter fluctuates allot. Is this normal
or should I buy something like a power conditioner to
fix this issue?

Thanks in advance.

What you have described could be due to you wiring your solar panel directly to the inverter which will result in a voltage fluctuation. You need to use a battery to feed the inverter and a solar charge controller between the panel and battery. Also if that inverter is much bigger wattage rating then the battery it can easily drain it.

So let us know what size wattage inverter and solar panel (watts, Vmp, Imp) rating you have and we should be able to fill in the blanks about battery and charge controller size.

[R8kid]

What you have described could be due to you wiring your solar panel directly to the inverter which will result in a voltage fluctuation. You need to use a battery to feed the inverter and a solar charge controller between the panel and battery. Also if that inverter is much bigger wattage rating then the battery it can easily drain it.

So let us know what size wattage inverter and solar panel (watts, Vmp, Imp) rating you have and we should be able to fill in the blanks about battery and charge controller size.

Thanks for your reply. I got the 12V solar panel of 50 watts connected to a 12V/24V charge controller of 20A, the charge controller is connected to a small 12V battery of 17AH, and the inverter is connected to the battery, the inverter is a 300 watts pure sine wave inverter. I haven't connected anything yet to the inverter because of the fluctuations I detected.

I don't know the meaning of Vmp and Imp yet, I'll have to get back to you on that.

[SunEagle]

Thanks for your reply. I got the 12V solar panel of 50 watts connected to a 12V/24V charge controller of 20A, the charge controller is connected to a small 12V battery of 17AH, and the inverter is connected to the battery, the inverter is a 300 watts pure sine wave inverter. I haven't connected anything yet to the inverter because of the fluctuations I detected.

I don't know the meaning of Vmp and Imp yet, I'll have to get back to you on that.

Ok. The Vmp is the Maximum voltage output of the panel under load and the Imp is the Max current it can generate under the perfect sunlight. My guess for that 50 watt panel the Vmp ~ 17.5volts and the Imp ~ 2.8amps.

It sounds like you have all the components except that the 300 watt inverter is pretty big for that 17AH battery.

When you stated voltage "fluctuations" what do you mean? Is the voltage "swinging" high and fast or does it just dip down and then recover back to normal. Sometimes inverters are very inefficient and can draw a lot of power even though nothing is plugged in yet.

Besides some type of "load" on the battery or resistance in the circuit changing due to bad wire connections something is altering the inverter output.

Just checking but you also need to connect the CC to the battery first before you connect the panel to the CC and then connect the inverter to a fully charged battery.

[R8kid]

Just checking but you also need to connect the CC to the battery first before you connect the panel to the CC and then connect the inverter to a fully charged battery.[/QUOTE]

When you stated voltage "fluctuations" what do you mean?

In my home, the voltage does not fluctuate more than 7 volts, but on my solar system, sometimes it drops from 230V to 060V.

Just checking but you also need to connect the CC to the battery first before you connect the panel to the CC and then connect the inverter to a fully charged battery

My English isn't that well, here is how I connected my system:
Solar Panel -> Charge Controller -> Battery -> Inverter

Besides some type of "load" on the battery or resistance in the circuit changing due to bad wire connections something is altering the inverter output.

It may be bad wire connections, I just pressed a M5 cable connector to the wires, do I have to solder the cable to the M5 connector?
If that is the case can I use any type of soldering wire?

When I measure the battery only it is 13.20V direct current, is this normal?
So the inverter is receiving receiving 13.20V instead of 12V
If I connect my devices to a fluctuating inverter, will it damage my devices?

[SunEagle]

In my home, the voltage does not fluctuate more than 7 volts, but on my solar system, sometimes it drops from 230V to 060V. How fast does it drop from 230v to 60V?


My English isn't that well, here is how I connected my system:
Solar Panel -> Charge Controller -> Battery -> Inverter That is the correct hardware connection profile. The Charge Controller requires a steady voltage to get it to properly work. So the first connection made is between the CC and battery. Then connect the solar panel to the CC. And then connect the inverter to the battery.


It may be bad wire connections, I just pressed a M5 cable connector to the wires, do I have to solder the cable to the M5 connector?
If that is the case can I use any type of soldering wire? Solder doesn't help and can actually make a bad electrical connection. Using a good "crimping" tool to attach the wire to the M5 connector (so it can't be pulled apart) will make a better connection

When I measure the battery only it is 13.20V direct current, is this normal? yes for battery that has just been fully charged
So the inverter is receiving receiving 13.20V instead of 12V The voltage on a full battery will settle down to about 12.7volts after a while. That 13.2 is just elevated due to just being charged
If I connect my devices to a fluctuating inverter, will it damage my devices? Some devices can be damage if the voltage fluctuates, like AC motors or compressors. Lights will just flicker on and off which may hurt them but is irritating to most people.

See my comments in BOLD above.

[Sunking]

The voltage of the inverter fluctuates allot. Is this normal
or should I buy something like a power conditioner to
fix this issue?.

Perfectly normal especially cheap battery inverters. It gets amplified even more when your wiring, battery, and panel wattage are undersized. Which is the case for you.

I got the 12V solar panel of 50 watts connected to a 12V/24V charge controller of 20A, the charge controller is connected to a small 12V battery of 17AH, and the inverter is connected to the battery, the inverter is a 300 watts pure sine wave inverter.

If we work backwards from your 300 watt inverter requires #6 AWG cable from the inverter to a 12 volt 200 AH battery connected to a 20 amp MPPT/PWM controller connected to a 200 wat panel if using MPPT or 300 watt panel if using PWM. So basically just about everything you have is way undersized to support your inverter.

[R8kid]

Thanks very much for the replies

How fast does it drop from 230v to 60V?

It fluctuates every half a second or so.

If we work backwards from your 300 watt inverter requires #6 AWG cable from the inverter to a 12 volt 200 AH battery connected to a 20 amp MPPT/PWM controller connected to a 200 wat panel if using MPPT or 300 watt panel if using PWM. So basically just about everything you have is way undersized to support your inverter.

Thank you very much, I think I will have to learn more about sizing a solar panel system. I bought the 300 watt pure sine wave with the thought that
I could use it in the future in another setting, I did not do any sizing calculations. I just needed a simple system to experiment with. And I was planning to buy a 1200 watt inverter

[SunEagle]

Thanks very much for the replies



It fluctuates every half a second or so.



Thank you very much, I think I will have to learn more about sizing a solar panel system. I bought the 300 watt pure sine wave with the thought that
I could use it in the future in another setting, I did not do any sizing calculations. I just needed a simple system to experiment with. And I was planning to buy a 1200 watt inverter

If the voltage is dropping from 230 to 60 within a second then I believe Sunking is on the right track that your battery is being pulled down somehow by the inverter and that 50 watt panel is not providing enough to keep a constant charged on the battery.

Can you borrow another smaller inverter at maybe 100watts or a bigger battery (fully charged) to test your 300w inverter on?

[R8kid]

Nope, it will be a long time of saving again before I can replace the battery or the solar panel

[foo1bar]

I haven't connected anything yet to the inverter because of the fluctuations I detected.

I'd try it with something - something that won't be harmed by the voltage fluctuations. (and/or is cheap/easy to replace)

My suggestion would be a small lightbulb. for example, a 3W or 5W night-light.
And re-measure with that small consistent load.

[SunEagle]

I'd try it with something - something that won't be harmed by the voltage fluctuations. (and/or is cheap/easy to replace)

My suggestion would be a small lightbulb. for example, a 3W or 5W night-light.
And re-measure with that small consistent load.

Good suggestion. Maybe some type of load will stabilize the output and a small wattage light probably will not be hurt.