Is it advisable to upgrade from 12V to 24V solar system?

[kje]

We have a small 12V solar panels on the cabin that I am considering to expand. It consists of one 10W and one 30W panel in parallel, one 12 / 24V PWM regulator, and two 70ah lead acid batteries. Considering buying more/larger solar panels and a MPPT regulator that is more efficient. Is it beneficial to make it into a 24V system ? What is the benefits?

Consumption is low since it is a summer cottage that is not in use during the winter. The solarsystem has only been used for some 12V led light that hangs around in the cabin, and charging pc / mobile phones.

I've read that you can use smaller cable sizes at higher voltages with less power loss at 24V than at 12V. Can also have longer cables without equal power loss. Have read that one achieves faster charging on overcast with solar panels in series, because you achieves satisfactory charging voltage earlier. Are there other advantages to 24V ?

If the solarsystem becomes 24V I suppose I must run the existing 12V lighting via a 24-12 DC-DC converter. I assume the converter uses some power especially if it must be left on all the time?

I wonder therefore whether we should continue with 12V, or it pays to do it to 24V ?

[Sunking]

Not unless you are going to have a panel wattage of 500 watts or more.

What I can tell you based on your batteries, yu panel wattage is way to low to support them. With a PWM controller minimum panel wattage is 200 watts, or 140 watts with MPPT. Maximum panel wattage for your batteries is 315 watts with a PWM controller, or 210 watts with MPPT.

So if you are going to upgrade get rid of your panels and get at least 2-100 watt panels if you intend to stick with your PWM controller.

[kje]

Yes, I`m considering buying larger solar panels and a MPPT regulator.

Do you mean I should just use 12V if I have a panel wattage under 500W?

[Sunking]

Do you mean I should just use 12V if I have a panel wattage under 500W?

Yes Sir for no more load than you have.

Important thing is to match panel wattage > battery > Inverter to work with each other. As of now your panel wattage is way to low to support your batteries as I explained earlier. You have 40 watts of panels on a PWM controller feeding a 12 volt 140 AH battery. At best can only generate 2.2 amps of charge current. A battery needs at least C/12 charge current where C = Battery AH and 12 = 12 hour charge rate. So for a 140 AH battery you need at minimum 140 Amp Hours / 12 Hours = 11.6 Amp. To generate 11.6 amps on a PWM charge controller requires a panel wattage of 18 volts x 11.6 Amps = 208 watts. Call it 200 watts. So get you 2-100 watt battery panels wired in parallel and call it good.

You can make it 24 volts if you wish by wiring up your 2 batteries in series, and use 2-100 watt battery panels in series. But there is a catch. You would have to get another inverter, 200 watt 24 volt inverter to run everything you have now on your 12 volt inverter.

Inverter Wattage should not be larger than panel wattage. Your system is just so small there is not much benefit at this time to use a MPPT controller or move up to 24 volts. MPPT pays off when panel wattage exceeds 200 watts, and 12 volt system are good up to about 500 watts but 1000 watts is possible with a 80 amp controller but not recommended. Once you hit 500 watts 24 volts and MPPT is the best least expensive way to go.

[kje]

Thank you Sunking. Very helpful.

So for a 140 AH battery you need at minimum 140 Amp Hours / 12 Hours = 11.6 Amp.

Why do you divide on 12 here?

You would have to get another inverter, 200 watt 24 volt inverter to run everything you have now on your 12 volt inverter.

Ok, so I need to buy a 24V inverter like this one?

Inverter Wattage should not be larger than panel wattage.

Why?

[Svg09851]

Sunking,

Would the same amps (11.6) from two 200 watt panels be enough to charge four 6 volt golf cart batteries (each rated a 215ah @ 20hr) wired in both series and parallel. For a total of 12 volts n 430ah.

Regards

[Sunking]

Sunking,

Would the same amps (11.6) from two 200 watt panels be enough to charge four 6 volt golf cart batteries (each rated a 215ah @ 20hr) wired in both series and parallel. For a total of 12 volts n 430ah.

Regards

Hard to answer because I do not know your daily usage. But here is what I can tell you. Assuming you have a 40 Amp or greater MPPT Controller is a good match with 400 watts of panels into a 12 volt 430 AH battery.

[Svg09851]

Thanks for the quick reply n info!

[Sunking]

Thanks for the quick reply n info!

If you have the means and doing an up grade, make the move to 24 volts. It will double your room to grow.