What's the max I can load off my 1.5kw system?

[Twistit]

We have 1.5kw solar panels that are pared to 4x200amp 12v lead acid batteries, inverted to 220v, sun 80% of the time and a generator that charges them 10hrs a day through the night. At the moment we have a combined max load of 400w, would it be possible to run a chest freezer of say 400w off the panels and battery as well? Where's somewhere I can find the formulas for this?
Thanks!

[Mike90250]

While the generator is running, or the sun is shining, you can most likely run the freezer.

Look here:

http://www.solarpaneltalk.com/forumdisplay.php?28-Off-grid-solar-panel-systems

for the stickie topics with the formulas for sizing arrays, batteries and systems.

I can see that by your needing to run a generator for 10 hours a night, something is very much out of balance in your system, and the battery bank is too small.

I believe for your loads you need to go up to a 24V system and maybe even larger batteries.

parallel batteries are to be avoided - see http://www.smartgauge.co.uk/batt_con.html

Battery bank sizes:
yours: 12V 800ah = 9600wh
24v 400ah = 9600wh
48v 200ah = 9600wh
Just a simple rewire of existing batteries (if they are any good) could reduce your losses in the copper wires and increase the system capacity.

You can us about 50% of your battery, any more and you reduce battery life too much.BatteryServiceLife.jpg

[Twistit]

While the generator is running, or the sun is shining, you can most likely run the freezer.

Look here:

http://www.solarpaneltalk.com/forumdisplay.php?28-Off-grid-solar-panel-systems

for the stickie topics with the formulas for sizing arrays, batteries and systems.

I can see that by your needing to run a generator for 10 hours a night, something is very much out of balance in your system, and the battery bank is too small.

I believe for your loads you need to go up to a 24V system and maybe even larger batteries.

parallel batteries are to be avoided - see http://www.smartgauge.co.uk/batt_con.html

Battery bank sizes:
yours: 12V 800ah = 9600wh
24v 400ah = 9600wh
48v 200ah = 9600wh
Just a simple rewire of existing batteries (if they are any good) could reduce your losses in the copper wires and increase the system capacity.

You can us about 50% of your battery, any more and you reduce battery life too much.[ATTACH=CONFIG]4211[/ATTACH]

The generators used to power hundreds of lights and rooms that otherwise have no power during the day.
As for the battery's, they're wired parallel, but I've been meaning to change the first connectors to spread charge like in your link.
I've been searching the stickies but I still can't find a formula or the like to work out max power output with and without sun..?
Thanks

[Mike90250]

.......I've been searching the stickies but I still can't find a formula or the like to work out max power output with and without sun..? Thanks

The general plan is to start with LOADS first, and build the system. Starting with panels, there are many blind alleys you can run into.

1) figure the reasonable discharge rate for your battery bank, it's marketed at the C-20 rate (20 hours). If you hit the batteries with too heavy of load, they sag and the inverter shuts off.

2) w & w/o sun. All depends on how low the batteries are.

[Sunking]

The generators used to power hundreds of lights and rooms that otherwise have no power during the day.
As for the battery's, they're wired parallel, but I've been meaning to change the first connectors to spread charge like in your link.
I've been searching the stickies but I still can't find a formula or the like to work out max power output with and without sun..?
Thanks

Please tell me you are not using a 12 volt system. If you are you have a major problem on your hands. With 1500 watts of panels requires 125 amp charge controller which none exist. A 80 amp MPPT charger can only handle roughly 1000 watt input on a 12 volt battery system. Only way to do 1500 watts at 12 volts is with two 60 amp MPPT charge controllers. With 1500 watts minimum required battery voltage is 24 volts. So please tell me you are not running twelve volt battery

As for what size inverter you can use is pretty easy. No larger than panel wattage assuming the batteries are sized correctly. Unfortunately your batteries cannot quite handle a 1500 watt inverter, 1200 watts max. FlA Batteries can only supply a maximum of a C/8 discharge current where C = the battery AH capacity. You have 4 12 volt batteries in parallel so you have 800 AH. So C/8 = 800 AH / 8 H = 100 amps. So 12 volts x 100 amps = 1200 watts.

Last comment if you are running 12 volt battery, 4 in parallel is a really bad idea and design which will significantly shorten you battery life. If I were you I would reconfigure for 48 volt battery, and with a 80 amp MPPT controller you can grow the panel wattage up to about 5000 watts. If you are having to run a genny everyday indicates your system is grossly undersized.