Hi All,
I've been going trough my old electronics drawer, to see if I can re-use some.
I hooked 4 small solar panels in series , and am measuring about 300 mA - 400 mA current at 5,95 - 6.3 V (in full sun at 13:00).
I'm looking to use these panels to charge one 18650 2.5Ah cell.
A)
I want to kindly ask you if I am thinking in the correct way, and if the charge controller has enough juice to charge a 18650 OK:
- Assuming that the buck conversion from solar 5.9V to ~3V (during CC charging) will loose about 20% of power, then :
solar panel power = ~1.8W
1.8W - 20% = 1,44W - power available to charge the battery?
1,44W/ 3V = 480mA - max charge current during CC mode?
1,44W / 4.2V = 340mA - max charge current during CV mode?
- This math can't be that simple , can it? Please could you tell me if my general / ball-park-figure thinking is wrong?
- Will the 6V solar panel voltage be enough for the buck/PMIC in charge controller to operate well switching down to 3.0V ~ 4.2 V?
- When I read datasheets of 18650 batteries I struggle to find the minimum charge current. I read somewhere "charge cut off = 65mA", but I imagine this will only keep the charge level, not increase it.
- In your experience, what is the minimum charge current on 18650s at which they start to gain some reasonable charge?
The project idea I'm playing with is to power 6x 48BYJ-28 motors with a single 18650 (2.5Ah or 3.0Ah ) , this is for window blinds, so max 30 sec operation at a time, couple of times per day; low torque as there is a reduction worm gear in the fixture, so also can disconnect the servo in Arduino sketch not to consume power when idle. FYI.
B)
These solar panels are from an old power bank, but the battery bulged up and so it was safer to dispose of the battery safely before it blows up.
The power bank was using a YLN-135V board - I am not sure if it works well, I cannot remember if it was charging well on USB power in before I took the battery out, and I forgot what type of battery it was using and how it was connected - I thought board is well annotated but I cannot get it to charge no matter what I connect to B+ B- or even if I connect USB power in. Now, the charging LED are switching OK and showing charging / full charge, the LED torch lights turn on OK with button press.
- Each of the panels has connection for Vout and Vin to connect in series on the side of panel market with minus "-" and another Vout on the side of the panel marked with plus "+".
-
Why are there two separate Vout on one panel and how to use them?
-
The separate Vout on the "+" side is the final load connection?
- The power bank board, when connected to 4 panels in series via S+ S-, gives voltage on battery pins (B+, B-) fluctuating between 5.0V - 5.4V @ 300mA - 450mA
I tried to charge power bank by connecting it's micro USB charging port directly to B+ B-but off course no charge.
-
I imagine minimum current to start charging via micro USB is 500 mA ?
-
What battery uses 5.0V - 5.4V to charge, would it be 2S Lipo battery ?
I'm quite rusty with my EE , I would appreciate greatly your lesson.
I'm trying to see what junk I can use that I already have lingering about, instead of buying new stuff all the time, but it's good opportunity learn why it wont work, and what I need instead and why.
All the best to you all.