Watts in to watts out

Plucka

I have 12 volt solar input via 60amp mppt controller to 360 amp/hr lithium batteries then 240 volts output via a 3000 pure sine inverter.The question is "To get 1.5 kilowatts output at 240 volts over 24 hours how much input in watts do i need i.e 10% or 20% more etc?

Photowhit

Plucka said:

I have 12 volt solar input via 60amp mppt controller to 360 amp/hr lithium batteries then 240 volts output via a 3000 pure sine inverter. The question is "To get 1.5 kilowatts output at 240 volts how much input in watts do i need i.e 10% or 20% more etc?

You can get that purely as battery reserve power and never will a 60 amp charge controller produce 1500 watts at 12 volts out put.

If you are asking what solar input to replace an hour of 1.5 KWh Output, Then it's a bit of a math problem. I'll use some ball park figures, we don't know how efficient, your inverter, charge controller or batteries are, but You can use figures which should be close. Inverter 12 v 3000 watt pure sine will likely be about 85% efficient, MPPT Charge controller at 12 volt output around 95% (I'm including loses with very good wiring!), and lithium batteries are about 95%.

So you your hour of output at 1.5 KWh, will draw about 1500 watthours ÷ .85= 1765 watthours from the batteries.

Replacing 1765 watthours will require 1765 watthours ÷ .95 = 1858 watthours

To get 1858 watthours to the battery bank 1858 ÷ .95= 1955 watthours.

Unfortunately a 60 amp output 12 volt charge controller can only output 60 amps at 12 volts (or whatever the charging voltage of the lithium battery bank is) so 60 amps at 12 volts 60 x 12 = 720 watts per hour maximum.

Please also be aware that solar panels produce about 75% of their panels rating under normal opertating conditions, so a 100 watt panel will only produce 75 watts.

mike95490

With a 12V battery system, you run a excellent chance of FIRE.

3,000 w @  12V @ 85% effic = 290A in your DC cable.   That's going to take a lot of copper cable

For 1500 watts output, half that 145A  Still ready to start a fire.    You should be looking at a 48V system if you expect loads of 1,500watts

Plucka

Sorry -I didn't explain my question properly-1.5 kw is over 24 hours usage.How much input is needed over 24 hours?

mike95490

>  1.5 kw is over 24 hours usage.How much input is needed over 24 hours

Assume a 3 hour solar day in winter (maybe more, maybe less)

1500wh x fudge factor of 2 = 3000wh harvest needed

1000w /hr required  1300w of panels installed

battery voltage

12V you need 2, 60A controllers, or 1, 100A controller [ see PT-100 ]

24V you need 1, 60A controller

battery wh required : 1500 x 5 = 7500wh battery   That would be 8,

L-16 batteries for about $2,500, wired as 12, 24, or 48V

  Smaller battery pack would discharge deeper and not last as long.

Estragon

There's no simple answer, but @Photowhit numbers are likely in the ballpark. With lithiums, you'll need to produces ~2kwh - ish pv output for 1.5kwh AC usage. Lots of assumptions in that estimate though. For lead acid, it might be closer to 3kwh, depending on a bunch of factors.

Photowhit

Plucka said:

Sorry -I didn't explain my question properly-1.5 kw is over 24 hours usage.How much input is needed over 24 hours?

You can pretty much use the "1955 watthours" figure, So on a average day with 4 hours of direct sun light, you would need about 500 watts at the charge controller for 4 hours, which about a 670 watt array would produce.

Photowhit

Estragon said:

There's no simple answer, but @Photowhit numbers are likely in the ballpark. With lithiums, you'll need to produces ~2kwh - ish pv output for 1.5kwh AC usage. Lots of assumptions in that estimate though. For lead acid, it might be closer to 3kwh, depending on a bunch of factors.

Lithium's high efficiency is great, but 12 volt requires a lot of pretty heavy wire not to have significant lose in transmission. Glad you are saying 1.5 KWhs in a day rather than a momentary load!

Plucka

Thanks-It's winter here with panels on a flat roof and I now know why I have to run the generator through a lithium charger to catch up battery storage