Sorry if its not right but I was thinking of the following operation:

Where if I were to use a transistor as a switch to generate ON and OFF instead of having a manual ON or OFF switch.

Coz I thought when the switch is ON, the current will flow across the inductor and causes the current to increase? Then when the switch is OFF, the current will charge up the capacitor to a voltage higher than the input voltage?

Meaning, to have somekind auto charge and discharge of the capacitor thingy. Is this wrong? ops: Mind correcting me? :cry:

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If I can apply the attached circuitry, any advice regarding the following matters?

Thanks...

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Nice try .. but it seems like you are trying to get something from nothing .
i thought we allready decided that the best /simplist method to charge the battery with the solar pannel was a diode..!!!

 

Hi!

Yea, but I thought of getting a new solar panel that has the following characteristic:

Load voltage: 7.5V
Typical current at load voltage: 45mA
Output power: 0.3W

I'm trying to order this solar panel to run a test on it. However, at this stage, I'm allow to assume that this is the panel that I have for my project and develop a circuitry to implement this panel for charging. Since I will be charging a 12V battery, thought I'm suppose to first boost the voltage level to approximately 15V?

Hence, I come out with that circuit.

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By the way, I am now allowed to do the following:

I can ignore the solar panel I have bought and develop a charging circuit that assumes that I have the appropriate solar panel in hand for my project. As long as I manage to search for the datasheet for the appropriate solar panels.

Meaning, I was thinking to ignore using the previous solar panel that I've bought, the one with 133mW output and search for a better one to reduce the charging time for the 12V battery. (approximately 6400mAH)

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That sounds a far better idea, and for the purposes of the project will work just as well - simply simulate the solar panel using a variable power supply!.

I'll be interested to see how large a 6400mAH panel will be!.

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Hi, sorry as I don't quite understand what you mean here. About how large a 6400mAH panel will be, I thought it depends on the characteristic of the panel? As attached is two spec list, the first specification list is actually a single crystalline cell which has the ability to provide great output whereas the second specification sheet is a panel that shows the output as circled. (there is an error regarding the short circuit current, i think)

So you mean how large as in the size of the panel?

Attached Images

sp.jpg (151.4 KB, 281 views)

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Sorry, here is the other spec sheet...

Guess there is something wrong with the short circuit current. Is there a mis-print? Isn't it suppose to be higher?

Attached Images

sp2.jpg (47.6 KB, 276 views)

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By the way, just asking...not for the project. Just asking if the solar cell is available in the market, the attachment entitled SP. Issit possible to step-up the voltage to a level of 14-15V for battery charging purposes?

Through calculations, I get a value of Duty Ratio of 0.96. Is it possible to have a Duty Ratio of approx. 0.96 for the DC/DC boost converter?

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Looks like it to me!.

And yes, it was the physical size I was asking about, but I see the panel you've circled is only 330mW. I also don't see the relation between that spec sheet and the previous picture?.

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Yup, I posted two pieces of spec sheet actually. The first one is, entitled SP is a single crystalling solar cell which provides good outpput whereas the other spec sheet, SP2 (circled) is the regarding the solar panel which has the output of 0.3W. About the SP2 spec sheet, I will reconfirm with the distributor as soon as possible regarding the output short circuit current listed in the SP2. It states that the output short circuit current was 35mA, which is lower than the typical current and load voltage. Is this a mistake?

Regarding the physical size, I thought another aspect to look into would be the duration taken to fully charge the 12V battery?

Can I put it in this way? By just using one solar cell (spec sheet entitled SP, the dimension as stated in the spec sheet), I will be able to charge the 12V battery in approximately 1 and a half hour?

As for the other panel, (SP2 with one panel's output current at load voltage is 45mA) by using a total number of 5 units.
So => 45mA X 5 = 225mA
Thus => 6400mA / 225mA = approx. 29 hours

The size of a unit is => 150mm by 55mm. Thus, the size of a total of five units of this panel would be around => 150mm by 275mm.

Hope this is what you want.

But there are other solar panels that will provide a better output compare to the one circled in SP2. Just like the column, SA-03300, on the left of the SA-0640. In which this unit is approximately => 150mm by 110mm.

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Just asking...is this practical? I will try out as well. Thanks.

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how can i say this .?
NO it is not practical to use a DC/DC converter .
Forget you ever heard of a DC/DC converter.
Because you would be using up Your Limited CURRENT to boost the voltage.

 

Would like to ask a general question here. Nothing to do with project.

For an actual solar car:
From the solar panel, which will be used for charging a specific 12V battery. Is it true that the actual implementation of Boost DC/DC Converter is to step-up the voltage of the solar panel (assuming the voltage is lower than 12V battery)? Since we need a higher voltage from the charging circuit to charge the battery, a flow of current from high voltage to low? Is this right? Mind to comment?

Thanks a lot

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Yes, that's right - but don't forget, increasing the voltage with a DC/DC converter also decreases the current - so if you have 10V at 1A, and boost it to 20V, you will only have 500mA (actually more like 450mA, due to losses).

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