Voltage resistor

[hughconley3]

If I use a resistor to change the voltage of a solar panel, do I lose power, and if so how much?

 

[JimB]

If I use a resistor to change the voltage of a solar panel,

Resistors do not just "change voltage", we really need to know how you are proposing to connect the resistor before we can give a sensible answer.

do I lose power,

Yes, when current flows through a resistor, power will be dissipated as heat.

and if so how much?

Impossible to say without knowing all the details of the circuit.

Sorry for the rather vague answer, but that is all I can tell you without details of your proposed circuit.

It may be better if you tell us what you are trying to do, rather than how you think it should be done, you will get better solutions that way.

JimB

 

[hughconley3]

Okay, I made a solar panel with 164 solar cells. Each solar cell is 1.75 watts and 0.55 volts. i can buy a charge controller that does that but at that high volts they're rather expensive and I thought I'd save some money by adding a resistor or resistors. I'd do it as long as I didn't lose more than a 2-3% power. The solar panel will go to a battery to charge it.

 

[Sceadwian]

What's the panel layout? You didn't use 164 cells in series did you? That's 90 volts.. generally speaking you would never wire that many panels in series unless thats' the voltage you wanted to deal with.
Typical solar panel setups are designed to charge lead acid battery banks so 12-24-36-48 volts are what you'll want to deal with, for the 300 watts your panel can put out 12 or 24 volts would be a more appropriate design voltage. You'd need to break the solar panel down into lower voltage chains in parallel.

Far more detail about what exactly you're trying to do would help your description so far is very vague.

 

[hughconley3]

Actually, I'd like to know how to wire them in parallel. That would be good.

 

[Reloadron]

I made a solar panel with 164 solar cells. Each solar cell is 1.75 watts and 0.55 volts.

What exactly are you trying to do? What output voltage and current are you looking to get from all this? You really need to give more details.

Ron

 

[hughconley3]

Wiring in paralel

Okay, if I was going to wire 42 cells in series. And I was going to do that 4 times. So I would have 4 panels. 42 cells is the correct number of cells? When I ask that question I want to know if when wiring a series of cells together in a panel and then planning on wiring those panels together in parallel to reduce the total volts would I start by making the first cell a positive cell and the last cell a negative cell?

 

[4pyros]

42 cells is the correct number of cells?

dont know, what voltage are you trying to make?

would I start by making the first cell a positive cell and the last cell a negative cell?

yes

You dont start with a bunch of cells, you start with a target voltage. most people charge batterys what are you doing?

 

[Sceadwian]

42 cells in series * 4 is 4 more cells than you have total and that would be only 23.1 volts per cell. So you'll need to buy more cells to start with an 23.1 volts is probably not going to be enough for a charge controller for a 24 volt charge controller. You need to design the panel with the specification of a charge controller in mind, you can't really start with just the panel in the first place.
For series wiring you would wire the + of each panel the previous panels - lead until you get the desired number of panels, then wire each series panel in parallel with the next to increase possible current..

You know one thing so far, you have 164 cells, based on the wattage of each cell you have a total possible output power of 250 watts, so look for 300-350 watt charge controllers for 12 or 24 volt battery systems, find out what their ideal running voltage is and design the series string to match that voltage then parallel for the remainder of cells, you'll probably have to buy a few more to get an even number of parallel strings which is why I recommend 300-350watt charge controller not a 250, besides in general it's a good idea to over buy a little. Given the wattage 12 or 24 volts systems are probably going to be pretty common and inexpensive.

Keep in mind again please that a 12 volt charge control system is going to need MORE than 12 volts, which is why you have to buy with a specific charge controller in mind with IT'S specs as the primary design parameter for your pane. Without a good matched charge controller those cells are useless.

 

[damkia]

Added info is that a 12V lead acid battery will need 14.6V or so to charge

You could do this with a bit of room to spare by using 3 x 54 cells to give a load voltage of about 29-30 volts which woulfd be satisfactory for charging a 24V lead acid battery.

By way of example most 12V solar panels sold for use for camping have a open circuit voltage of about 16-20V and a load voaltage of about 14.5V depending on available light and are usually not connected to anything other than a diode to prevent the panels loading the battery when the sun goes down.