Update
Caution:
Do Not try this at home, with a cell phone you like.
I am a trained professional, with a cell phone I hate.
Today, busy watching engine oil drain.
Grab a couple solar assemblies I never really tinkered with.
AND the cell phone is almost totally dead.
Poor solar day. Hazy. Heavy cloud cover. some patches worse than other patches.
10 x 1/2A cells paralleled with 10 more.
Voc =~ 6.5V.
Hmmm... straight into the cell phone's micro-USB port?
Yup. That works fine.
Wind kicks up, leaves on the "assembly", still works fine.
This is with NO external regulation whatsoever.
Another "Hmmm" moment?
How about all 20 cells in series, to a Lighter-to-USB-switcher thingie?
Again, no issues... until I added a lot of leaves on the array... which caused the cell phone's "Poor charger connection!" warning on the phone.
I found the "Poor charger connection!" warning a bit strange, since I could not force it to happen without the USB switcher.
I have no explaination for that.
Also, once the phone's "Poor charger connection!" warning went off, it seemed that the charger needed unplugged from the phone before it would 'reset'. The input voltage to the regulator indicated the PVs were operating at over Vmpp (basically unloaded).
The Good Stuff (if that wasn't good enough):
This is all for 20 cells. Series for 10Vmpp, or parallel for 5Vmpp.
- The 5Vmpp array was operating at between 4.6 and 5.8V.
It seemed to swing with the available solar intensity. More clouds was less Vinput. This was a smooth voltage fluctuation.
The phone was happy the whole time.
- The PVout / Vin at the Lighter-to-USB-switcher thingie varied a LOT more.
PV tended to run about 7.8V, sometimes >8.3V. It didn't seem to matter so much with the solar strength, which implies a fairly substantial load to the system.
BUT, every so often, the PV voltage would jump up to >12V, even >13V, for a few seconds, which would imply Voc on the array. Guessing that was related to the phone somehow, and the phone was taking '0' power from the charger.
- A few notable things:
1) Grid charging to 'full' at the condition the phone started takes about 3~4 hours (best guess) with the factory OEM parts supplied with the phone.
2) Solar/USB/Direct took about 2.5 hours until 'full'.
3) Part of the time the phone was charging, I was talking using the phone via USB headset, which I would expect would use a lot more power than if the phone was doing nothing. But it still charged faster than via the OEM supplied grid charger (and no "battery is over-temperature" warning like was common this summer even when the phone was not charging).
4A) I have far less money in this entire charging system (PVs, adapters, S&H, etc), than the cell company charges for a simple car charger (>$30 with tax where I got my phone).
4B) Phantom loads are always an issue. More so on tiny RE systems.
Seems like something like this would eliminate phantom loads, inefficiencies, battery costs...
Nothing ground shattering.
It is fun.
G-