I need Help In a solar Battery Question

[(unknown)]

A 12 V, 36 cell, 60 W module has a Vmp of 17.6, an Isc of 3.8 A, and a Voc of 22 V. Plot the characteristic curve for this module for 1 full sun, 3/4 sun, 1/2 sun and for 1/4 sun. On

the same graph plot the curve for a cell temperature of 50°C assuming that the derating factor is -0.0022 V/cell/°C.

  If the module of the previous question is used to charge a battery at 14.4 V:

a) What would be the charging current for 100% sun, 50% sun and 25% sun?

b) Calculate the power delivered to the battery in each case in (a).

c) Explain why the power delivered to the battery at full sun not Mpp?

[bob g]

dang dude!!

up late doing homework? thought maybe you would cheat a little?

good luck with that buddy

bob g

[ghurd]

A)  Full sun, about 3.45A.  (slightly more than 60W/17.6V, and slightly less than Isc)

Half the sun, half the amps.  Quarter the sun, quarter the amps.

B)  Full sun = 3.45A x 14.4V = 49.7W

Half is half, 1/4 is 1/4.

C)  Power = Watts = Volts x Amps.

Power at Mpp requires a 17.6V battery.  

The voltage Mpp changes with temperature, so if you had a 17.6V battery it really would not do much good.  If the temps are high, it may not charge at all.

"Plot the characteristic curve for this module"?

Amps?  It is close to a straight line from Isc until about 16V, where it starts over a rounded cliff, then is nearly linear down to 0A and 22V.

Is this homework, planning a homemade panel, or just whipping up a simple MPPT?

G-

[tanner0441]

Hi

I have 3 20W panels giving me 60W in total. On a good summer day I can see 4.5+ A average summer to good winter I see between 2 and 3.5A cloudy day I am happy if I see 0.5A.  I have several controlers the one I prefere is a three step PWM unit that you can see the current throttling back as the batteries reach full charge.

Your looking for finite figures when everything is a variable, my meter will vary from hour to hour albeit at times very slight, when my eyes see no change in the light at all. Slight haze or light mist can make a large difference in the reading, changes in battery state, there are so many things that will affect your readings. I do not track the sun but I do alter the angle of my panel monthly, which is facing south.

Hope this helps.

[ghurd]

What do the stickers say for Isc, Imp, and Vmp?

G-