24v setup

[Nunclud]

I presently use a 24V inverter, conneted to 2 units of 12V deep cycle dry cell batteries in series, presently charged through the grid mains.

Now, I want to add a solar charging system to it while maintaining the grid supply(no constant supply)
I have two options, using 150watts/12V panel or 200Watts/24v panel.

My question is,
1. how many panel will i require if i choose any of these panels and how will i connect them(series or parallel)
2. How many AMP controller will i need too.
3. How long will it take to fully charge the batteries based on the advised panel selection.
4. How much load can i connect on the system while it is on charged by the solar system and still get good charge time.



Thanks in advance.

[Sunking]

Most of your questions cannot be answered as you have not provided enough information starting with battery capacity. When connected to the mains, power is only limited to how much current the charger can supply. So if 20 amps x 24 volts x 24 hours = 11,520 Watt Hours.

A 20 amp charge is about right for a 200 AH battery. If the mains fail, the batteries can only supply 20 amps for 10 hours, or 20 amps x 24 volts x 10 hours = 4800 watt hours.

We need to know what AH capacity your 24 volt battery is. But I can tell you this; Your panels need to generate C/10 to 10% of the AH rating. So if they are 200 AH need to generate 20 amps. If you use a MPPT controller the panel wattage required to do that is Watts = Charge Current x Battery Voltage. So if the battery is 24 volts at 200 AH you need 20 amps x 24 volts = 480 watts.

A system designed that way takes roughly 4-5 days to recharge if the battery completely discharged which is a huge No-No. You only discharge your batteries 20% in a given day. Solar is extremely limited power. Going back to out example of a 20 amp main charger with 24 volt 200 AH battery can provide you with 11,520 watt hours per day. A 500 watt solar panel is the right size for that battery, but can only generate 2000 watt hours per day. Huge difference between 11,520 wh and 2000 wh. To equal the mains would take a 3000 watt solar panel and a 24 volt 1000 AH battery to be equal.

You cannot use a 12 volt panel to charge a 24 volt battery unless you have 2 or more panels. With MPPT controllers you wire as many panels in series as the controller will allow. Example most high power controllers allow at least 150 Voc input. So if you had 240 watt panels with a Voc of 40 volts each, you could wire three panels in series. But at 720 watts requires a 720 watts / 24 volts = 30 amp controller.

[Nunclud]

Most of your questions cannot be answered as you have not provided enough information starting with battery capacity. When connected to the mains, power is only limited to how much current the charger can supply. So if 20 amps x 24 volts x 24 hours = 11,520 Watt Hours.

A 20 amp charge is about right for a 200 AH battery. If the mains fail, the batteries can only supply 20 amps for 10 hours, or 20 amps x 24 volts x 10 hours = 4800 watt hours.

We need to know what AH capacity your 24 volt battery is. But I can tell you this; Your panels need to generate C/10 to 10% of the AH rating. So if they are 200 AH need to generate 20 amps. If you use a MPPT controller the panel wattage required to do that is Watts = Charge Current x Battery Voltage. So if the battery is 24 volts at 200 AH you need 20 amps x 24 volts = 480 watts.

A system designed that way takes roughly 4-5 days to recharge if the battery completely discharged which is a huge No-No. You only discharge your batteries 20% in a given day. Solar is extremely limited power. Going back to out example of a 20 amp main charger with 24 volt 200 AH battery can provide you with 11,520 watt hours per day. A 500 watt solar panel is the right size for that battery, but can only generate 2000 watt hours per day. Huge difference between 11,520 wh and 2000 wh. To equal the mains would take a 3000 watt solar panel and a 24 volt 1000 AH battery to be equal.

You cannot use a 12 volt panel to charge a 24 volt battery unless you have 2 or more panels. With MPPT controllers you wire as many panels in series as the controller will allow. Example most high power controllers allow at least 150 Voc input. So if you had 240 watt panels with a Voc of 40 volts each, you could wire three panels in series. But at 720 watts requires a 720 watts / 24 volts = 30 amp controller.

Thanks for the info,i forgot to mention that each of the two batteries is rated 12, 200AH @ C-10. This is what is written on them.
I also plan to use an MMPT controller and with more than 1 panel. A friend advised me to used 10 units of the 12v/150w panel with a 30AMP controller but i need to know if i need that much in number.

If i am to go with this friends advise, how will i wire the panels, series or parallel or both.

[evpower]

Using MPPT controler is good idea and you do not need to care about input voltage of the solar panel. The MPPT controler care about input voltage to find best power up to 150V.
MPPT controler with 20Amps will be enought for only two solar panels in serie. Please check link to MPPT controler below.

MOD NOTE. Advertisement link removed. Do it again and you will be banned.

[Sunking]

Using MPPT controler is good idea and you do not need to care about input voltage of the solar panel.

Sorry that is incorrect information. The advantage of MPPT is to allow you to use high voltage panels.

[Sunking]

Thanks for the info,i forgot to mention that each of the two batteries is rated 12, 200AH @ C-10. This is what is written on them.
I also plan to use an MMPT controller and with more than 1 panel. A friend advised me to used 10 units of the 12v/150w panel with a 30AMP controller but i need to know if i need that much in number.

If i am to go with this friends advise, how will i wire the panels, series or parallel or both.

Forget your friends advice. I assume you are going to configure the batteries at 24 volts? You should.

Your batteries have a minimum and maximum amount of charge current they can accept. It has to be high enough to generate some heat and most importantly some gassing. That is required to keep the electrolyte stirred up and dissolve soft lead sulfate crystal that accumulate on the plates and grids form normal operations. On the flip side the current cannot be so high to generate excessive heat, gassing, and corrosion of the grids and plates. Put another way a window. Generically the minimum is C/12, and maximum is C/8. Ideally C/10 is perfect.

All that means is where C = the battery rated Amp Hour capacity divided by Hours. So your 200 AH batteries need a minimum of 200 AH / 12 Hours = 16.6 Amps or 17 is close enough. Maximum is 200 AH / 8 Hours = 25 amps. Ideal is C/10 or 20 amps. With a MPPT controller if you know the battery voltage and current it is real easy to find the wattage required to generate a given current. Watts = Charge Amps x Battery Voltage.

Armed with that then you know you need at least 17 amps x 24 volts = 408 watts or just call it 400 Watts minimum. The highest panel wattage is 25 amps x 24 volts = 600 watts. So there you go you need a panel of at least 400 watts and maximum of 600 watts. 500 watts and 20 is a perfect C/10.

So your friend said you needed 10 units of 150 watts panels. That is 1500 watts. He also said you needed a 30 amp controller. Two huge problems with that advice. That is roughly 300% more power than your batteries can absorb. Second problem is with 1500 watts into a 24 volt battery would require a 1500 watts / 24 volts = 62.5 Amp MPPT controller. Tell your friend he has no clue what he is talking about.

Your friend also said to use 150 watt panels. That would be a low voltage battery panels made for 12 volts. Granted it would work providing you use enough of them, but is a horrible ideal and just plain foolish. Battery panels are low voltage, low wattage, and very expensive. The whole point of using a MPPT controller is it allows you to use much higher voltage panels called Grid Tied Panels. GT panels cost 1/2 to 1/4 what a battery panel cost. They make GT panels from 200 to 300 watts and higher. For you that means you only need two of them connected in SERIES.

Like I said tell your friend is clueless.