Battery Estimator

[Tom in NH]

It's been a long time since I posted here. Hello everyone. I've been playing with Java Script and have this little tool to estimate how many batteries one needs based on parameters you input. The thing is, I have no idea how accurate it is, and I hope maybe some of you would try it out and see if you agree with its estimation.

Here is the estimator. http://files.blog-city.com/files/M05/102402/b/batterycalc2.html

Thanks,

tom

[sPuDd]

"Number of no sun days"  per what? Month, week, year?

"Daily AC load" is usually in Kilo watt hours.

Other than that it showed the same results I got

for sizing my system by hand, so seems to work OK.

Could use a few more inputs & outputs. Maybe estimated

array size in watts? Maybe hours of light per day?

Once you start, you can't stop :-)

sPuDd..

[richhagen]

Welcome back Tom, sPuDd it looks like he is using it as a parameter to determine how long the batteries go between charging, the maximum amount of time that the batteries have to power the loads.  This would assume that you have a sizable array that could charge the batteries up relatively quickly when there was sun, so that you never started a period of no sun with half charged batteries, I would think.  Rich

[veewee77]

Run those numbers through my calculator and see how close it is. There are several companies on the web that do complete systems and I used their figures averaged to build my calculator. When I ran my house through it one time, it said my electric bill would be about $10 for that month, and the calculator calculated it at around $125 so it is pretty close.

Once you get to the calculator, go on to the bottom of the first page and click the Study It button, then scroll to the bottom of the second page and click the first Calculate It button.

At the top of that page, enter the total watt hours per day. Not kilowatt hours! This is actual watt hours.

The calculator will calculate the number of batteries required, but keep in mind, it is set up so that you never pull the battery bank below 80% (80% full, not 80% used) so as to keep them healthy for a long time. I adjusted it one time to do 50%, but that is a pretty deep discharge. I set it back to 80% and that will cover the few extreme situations that happen. For example, if you have your bank sized for a 2-no-sun-day size and you get 3 no-sun days once in a while. You're still ok, long as it don't happen a whole lot.

It also calculates the number of solar panels it would require to keep thos batteries charged and supply all the power needed.

Charging losses, inverter losses, temparature correction losses and etc. are all calculated in.

To try out the calculator, go to:

http://dsjscrd.gotdns.com/calc

Enjoy!

Doug

[veewee77]

REVISION!!!!!

My calculatos said my bill would be $120 per month, not $10. . .

Sorry. . .

Doug

[wpowokal]

Bottom line from some one living off grid, it is a sales pitch to say so many (usually 3 ) days with no imput. It is only relevent if you have a source of Re big enough to replace those 3 days plus what the fourth day's use is.

Otherwise you will need a back up generator and my advice would be to use that daily at your peak usage time, usually evening load. This is because you gain the most from your Re at lower battery volts (arguable I know) but if you are runing a generator let it run to meet a load without further loadng the batteries.

The further you run you batteries down the greater the harm for a given period of time, now it is all a compromise but......

allan down under

[Tom in NH]

Number of consecutive no sun days.

[Tom in NH]

Actually I should explain a little more. NASA's meteorology site has 10 year average data for the number of consecutive days without sun. http://eosweb.larc.nasa.gov/cgi-bin/sse/grid.cgi?uid=3030

They have a lot of other really good stuff too. But anyway the input value specifies how long the batteries have to work before the sun shines again (on average, of course)

I have another tool for estimating the number of panels needed for a given load and insolation value. That's at http://files.blog-city.com/files/M05/102402/b/solarcalc3.html if you're interested.

Thanks all, for the input and the suggested calculator from Doug.

Tom