I am doing a science fair project on solar panels, and I need four solar panels to conduct the experiment. I would only need the solar panels for a week. What type of solar panel should I get?
Your USB power booster may be fragile and is likely expensive, so possibly you should get your 5 volts some other way. 3.7 volts plus a .2 volts D cell is 4.9 volts which is likely close enough for charging most anything with a USB charging cable. If bright sunlight is falling on your solar panel the battery voltage will go to about 5. volts charging at 700 MA, which is also likely acceptable, and will generally be less as part of the 700 ma is being used to charge something else. Also 300 ma may be more typical output of your solar panel even when the sun looks like it is bright. Over charging is unlikely unless the lithium cell has a lower amp-hour = AH rating than the Ni-cad (or nickel metal hydride NiMH 4 AH) D cell, but perhaps you should disconnect the solar panel, if it has been more than one bright sunny day since you charged something with a USB cable. If your battery reads over 5 volts with the solar panel unlighted or disconnected, you are likely to over charge either the lithium cell or the D cell. The PCB protected may complicate adding the D cell (probably not) so you may want to follow your original plan. Your solar panel may send as much as 9 volts to your PCB protection board, when the lithium cell does not need charging: Can the protection board tolerate 9 volts? Probably. If in doubt you can put either a .5 volt or .2 volt rechargeable D cell in series with the solar panel which reduces the input to your PCB protection by about .5 volts. That D cell will over charge, unless you replace it weekly, perhaps oftener. I think your PCB protection prevents over charging and cuts off the load if the lithium cell is discharged to an unsafe level or the load is demanding excessive current. Only the last is a possible problem = one of your USB cords may demand an amount of current that the PCB protection considers excessive. Your USB booster needs about twice as much current as the usb cord is supplying. You don't get the extra voltage by magic. Neil
It okorder /... More info is needed about your experiment to help decide what you need.
If okorder / for some ideas.
