Why do I need a switch for a solar battery/usb charger?

 I just browsed online and skimmed through other peoples' projects and failed to notice everyone using a switch. I then thought about it and my 4 solar cells where scavenged from lawn lights that used a light sensitive switch (can't think of the word at the moment). However I had already put my idea to work (without a switch) and I drained the batteries to around 1v a cell by charging my phone over night, and then I happily placed my charger out in the sun without anything hooked up via usb and when watching voltage it was going up at an ok rate. Well hours later I go back to check on it and the voltage dropped back down, now my cells are under 1v a cell. The solar panel is hooked up positive to the battery pack positive, there is a diode between, then after that connection a usb female connector is put in after that, and they are all grounded to the same line. I am confused as to where the batteries could have drained to, and why everything can't be in parallel, although I admit I am pretty newbish, but the logic still doesn't make sense to me.
Thank you for your time. (sorry the image looks like it was drawn b a 3 year old)

Picture of Why do I need a switch for a solar battery/usb charger?
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lemonie7 years ago
Can you post a circuit diagram, and the spec' of the cells, and the batteries?
It's hard to tell what you've really got here.

L
downgrade (author)  lemonie7 years ago
 Well the solar panels were stolen, they seem to each be 3v cells, but being in arizona when I have 2 in series they put out around 6.5v total. Which means I can't use a standard regulator.

Batteries I have 2 parallel sets of 4 NiMH AA cells rated at 2500mah. When I first put this together and put it in the sun I was charging at 5.03v, but I am guessing that was just the batteries

Sorry, as I said, I'm a newb at this and was trying to learn the hard way I guess, and now I am completely confused...
charger.gif
In that diagram your batteries are opposing each other - that ain't going to work.
Also NiMH should have controlled current & voltage, this is liable to damage them if it hasn't already.
For example if you search for "NiMH charger schematic"

L
jeff-o lemonie7 years ago
Yeah, why are your batteries opposing each other??  They must all face the same way!
downgrade (author)  jeff-o7 years ago
 I need a higher voltage, so thus they are in series. Otherwise I would be at around 1.2v

The idea is I have 3 chargers. A solar usb charger, a Batter usb charger, and a solar battery charger.

Here is a similar example, although like I said, they are using a switch that my newb mind thinks is pointless since all the power and ground wiring is all going the same direction...
Your diagram shows +[]--[]++[]--[]+
This isn't going to work, you'd need +[]-+[]-+[]-+[]-

L
downgrade (author)  lemonie7 years ago
 Any way, it's odd how I did it right with the solar cells but not the batteries...

I digress, I do have 4 NiCads... are those less picky about charge? From what I had read most people seemed to do ok with just getting an approximate charging voltage and off they went, doesn't make it right, but I figured after seeing it enough that maybe they knew what they were doing.

I am thinking about scrapping most of this and stealing someone else's idea of getting a kit to charge a small lithium pack and using a 5v step up. Failure isn't fun, but you can't just ignore it.
Getting something that works is a sound idea. Failure is fun when things explode...

L
downgrade (author)  lemonie7 years ago
 Sadly the batteries didn't even explode, oh well maybe I can salvage them in my store bought charger and reuse the cells for the next project. I still don't understand what didn't work with the circuit I made (not the one that I drew)... well I guess it could have been the nimhs are picky with their charging? I dunno.
downgrade (author)  lemonie7 years ago
 Hah, true, that was just me being an idiot, sorry, no the batteries are in a pack, so they are +-+-+-+- on both sides, sorry. brain fart. I expended much more thought on finding an app to draw it all for me than I did drawing it I guess.

My bad.
downgrade (author)  downgrade7 years ago
 PS I meant to say the solar panels were stolen from some lawn lamps...