Use UPS with solar panel?

Moderators: mdrjr, odroid

Use UPS with solar panel?

Unread postby magnum_pi » Sat Jul 19, 2014 2:06 am

Hi,

I've ordered a very small (3W, ~500mA) solar panel (from here) to experiment with. It doesn't have any voltage regulator, so I was wondering if I could use the Odroid UPS as a regulator/battery combo. I know that my panel isn't big enough to power a U3 (except maybe for short bursts), but I was thinking more along the lines of using it to power a USB I/O board or some Arduino-like hardware plus a few sensors. I reckon that the batteries and panel should let me run that 24/7 for most of the year.

If I'm reading the schematics right, there are two MAX8903c chip connected to the barrel connector that do the charging and two MAX8627 chips that step up the 3.7v from each battery to provide the 5v output. When I looked up the first chip, I found specs that say it can take anything from 4.1 to 16 volt input, which seems like it should work with the panel, which might output up to 10v in sunny conditions, but maybe less than 5v if it's not.

On the face of it, it looks like the UPS should handle the range of input voltages that the panel provides, but I wanted to check with you here first. The other thing that would be out of spec is the current that the panel provides. I'm only learning about this stuff, so I don't know if ~0.5A (or actually 0.25, since it has to charge two batteries) is enough to charge the batteries? If I knew that the voltage side of things was safe, I could test that and wire up two (or more) panels in parallel to give some more current if that's all it took.

Thanks :)
magnum_pi
 
Posts: 198
Joined: Tue Mar 05, 2013 6:37 am
languages_spoken: English, Japanese, French, Irish
ODROIDs: U2, X2, XU, U3

Re: Use UPS with solar panel?

Unread postby odroid » Sat Jul 19, 2014 10:54 am

Charger IC's input voltage is pretty wide.

But the input decoupling capacitors(10uF) on the charger IC(MAX8903C) have only 6.3Volt specification.
So don't connect the unregulated power source to the UPS board directly if its output can go higher than 6 volt.
User avatar
odroid
Site Admin
 
Posts: 28855
Joined: Fri Feb 22, 2013 11:14 pm
languages_spoken: English
ODROIDs: ODROID

Re: Use UPS with solar panel?

Unread postby magnum_pi » Sat Jul 19, 2014 11:51 pm

OK, thank you. Not the answer that I hoped, but at least I know what not to do now.
I have some LM317 linear regulators, but they appear to have a dropout voltage of around 1.6v at 25 degrees and 0.5A, so 5v5-1v6 won't supply enough input voltage to power the UPS :(
I guess I'll have to do some more investigating--maybe order a low-dropout regulator or buy or get parts for a switching regulator, or look for another charger/battery combo entirely. :(
Thanks again...
magnum_pi
 
Posts: 198
Joined: Tue Mar 05, 2013 6:37 am
languages_spoken: English, Japanese, French, Irish
ODROIDs: U2, X2, XU, U3


Return to UPS

Who is online

Users browsing this forum: No registered users and 1 guest