Never is a long time ! :-)
Obtain sunshine hours per typical day on a typical month at your location from the superb gaisma insolation et al site here. As you are in NZ Ive chosen the Wellington page.
Th 4th graph down says the monthly mean insolation in kWh/m²/day Jan to Dec is as below. This is the equivalent full sunshine hours. Lowest is 1.4 hours/day in 6th entry = June
5.83
5.06
3.97
2.78
1.85
1.40
1.63
2.32
3.32
4.13
5.26
5.60
1.4 hours per day means over a 24 hour period you will get a mean solar Wattage per square metre of
- Watts = 1000 x 1.4/24 = 58 Watts per square meter of isolation
= 5.8% of full sun panel power
Solar panel efficiency = Zp typically ~ 13%.
Bird poop degradation factor = Kbp = depends on cleaning etc.
Say Kbp= 0.75.
Average Wellinton June day = 1.4 sunshine hour/day but some days Watts ~= 0
So D = days you want to run with NO solar input.
I'm going to stop naming K factors and lump them all into "Kother".
Kother is a degradation factor comprised of all the factors you can think of MULTIPLIED together.
Battery charge to discharge energy return - say 80% - depends on chemistry and several other factors.
Temperature - about 90%of rated at 25C as panel gets hot.
Panel matching to battery - addressed by eg MPPT controllers - Panel will be 18V oc for a 12V battery and energy loss without an MPPT controller will vary - say 80%.
SO
A Panel rated at say 100 Watts will power equipment run 24/7 in June in Wellington with a Wattage of
Below, Zp is allowed for by using the panel rated power.
ie a 100 Watt panel will run 3 Watts of equipment in Wellington in June IF days are typical. If you get super black dark and stormy and want to last say 3 days with about no sun you get 3/3 days =1 Watt 24/7 per 100 W of panel with 3 days holdup.
Pretty stunning !
Battery sizing = 1 Watt Hour per Watt of load x 24 hrs/day x D days holdup / Kbattery to load.
Say a 1 Watt load and 3 days holdup = 1 x 24 x 3 / 0.75 say = ~= 100 Watt hours.
E&OE !!!!!!!!!!! - the battery size and panel size don't seem quite correct. I may have dropped a figure somewhere there BUT the principle should be obvious and straight forwards A major aspect is getting the degradation factors correct.
Ask questions if interested.
A good first approximation would be to:
- Calculate the apparent power in VA. That's easy, just take the RMS voltage times the RMS current, in your case 10A * 230V.
- Divide that power by the battery voltage to get the battery current. Note that this assumes a perfect converter, which doesn't exist; remember, this is a first approximation.
- According to your question, you're done, but you may also be interested in maximum runtime. For that, divide the battery's capacity (150 amp-hours in your case) by the current that you got in step #2.
Okay, now that you have an unacheivable maximum performance figure, you can start accounting for inefficiencies, specifically:
- The converter isn't 100% efficient. Perhaps more like 80-90%. The other 10-20% represents extra current pulled from the battery and converted to heat.
- Battery capacity is not constant with load. It tends to decrease under heavy loads so that you may get 170-200 AH under a light load and closer to 100 AH under a heavy load. Exactly how much it changes depends on the specific battery.
Best Answer
Discharge is rated in "C" for example if your selected battery states 20C the maximum discharge is 20 * Battery capacity.
One of the reasons LiPo batteries are used in RC projects is the fact they can normally handle a high C rate (They can deliver a punch to the high-power motors).
If we look at the two options, you provided
Panasonic CG-320 - I've found a more detail breakdown of its specs here - LINK
The highest diagram they shown details a max discharge of 1C, they also mention in the handling guidelines to not let the battery voltage drop below 2.7V so you may need to do some voltage monitoring to be safe. Annoyingly thats the only mention I can find of discharging, so from that you could possibly assume the max discharge is 1C.
The 70mA Battery you linked has basically no technical documentation I'd recommend looking for a better documented version. Without a datasheet its impossible to know whats safe.
A better documented alternative would look like this Farnell LiPo this part has a datasheet with all the info you need here - Datasheet. I would recommend looking around the high end suppliers, Digikey, Farnell, RS & Mouser they generally require suppliers to provide proper technical documentation.