Raspberry Pi + Pico Projector on a Lipo Battery?

Thanks for the response! I did end up having to use multiple batteries, but I didn't use any capacitors (other than maybe the ones on the SBEC circuits.) All my batteries have protection circuits to hopefully elimate any danger.

The projector I was using was an Optoma PK102. It has HDMI and VGA, but I was using a composite video connection.

I did eventually finish the project and wrote a lengthy blog post about it. If you have the time, check it out! I'd be curious to get your advice on what I could have done differently.

Mini Raspberry Pi Controlled R2D2

http://www.langleycreations.com/blog/?p=17

Hi Andrew, I'll try to give you some elements of answer with your problem.

The "Amps" as say Nate isn't the only thing you expect from a power supply. You first expect stability of your output voltage. You can even use a 30A power supply, if you haven't stability you'll just have a *** voltage... . So I would first check the size of the output capacitor, and add capacitors on that 5V for all the subsequent DC/DC power supplies to have a stable input.

If your Pico Projector isn't charging, that could be due to the instability of the voltage. Another reason can be as simple as the wiring of the cable you're using. I have no idea of the kind of cable provided with your projector, and I assume it's a USB cable.

I've had some troubles with charging phones from a home made power supply, only because the phone detects it's "own charger" and refuse to charge with any other charger. This is achieved by short-circuiting the 2 data lines of the USB cable inside the charger itself. I just had to do the same wiring and voilà! my phone was charging .

I'm interested in your project. Keep in mind that LiPo batteries need to be managed, and you MUST use a security interface to switch off if the batteries get low (risk of fire).

Which Pico Projector are you using ? Is is an HDMI/VGA or a USB projector ?

Good luck ;-)

You probably are getting a little charge but eventually the batteries are coming to a balance and no charge is being passed.  I don't know if charging a battery with another is good for them.  As I haven't really tested this I couldn't tell you.

No, it's the other way around. Sorry, I know it's confusing. Let me summarize:

I have a 11.1v LiPo battery with a 5v 5amp SBEC circuit. I wanted to run the projector off this battery along with the Raspberry Pi, so I tried two things:

1. Take the internal 3.3v Lithium ion battery out of the projector and run it off a wired power connection to the LiPo battery, essentially replacing the projector's 5v power supply with my LiPo battery. This did not work, probably because it was drawing too much current.

2. Keep the 3.3v internal battery inside the projector, and when the projector isn't on, connect the 11.1v Lipo battery (again, regulated at 5v) to the projector in hopes that it would charge the battery enough to run it for short intervals when the projector was switched on. However, then I connect the LiPo battery to the projector with the goal of charging the 3.3v Lithium ion battery inside the projector itself, it doesn't actually charge the battery at all.

Hopefully that clears things up. I only tried option 2 because I couldn't get option 1 to work, even though it seems to me like it should have.

let me make sure i understand what you are doing correctly.  So you are trying to charge the lipo battery with the battery from the projector correct?  if that is the case like you stated above the lipo battery is 11.1v the max output on the projector battery is 3.3v.  Since the projector battery is 3.3v which is less than 11.1v  then the flow would go the opposite way of what you want.

And just to clarify, the internal battery for the projector is 3.3v, but the AC adapter to charge or operate the projector is 5v.

Thanks for the reply, although I'm not sure that makes any sense to me. The 11.1v battery is running through a 5v switching BEC circuit, so it seems to me that this would create the same conditions that the projector would run off if it were simply plugged into a 5v AC adapter like it is normally.

Even in terms of amps it seems to be the same to me. The SBEC circuit allows a maximum of 5 amps, approximately 2 of which are needed to run (or charge) the projector. The remaining amps seem more than enough to power the Pi.

I know I'm missing something obvious here, but I'm just not seeing it.

If the battery on the projector is lets say  3.3v but you are trying to charge the lipo battery back thats 11.1v the voltages are different.  It would act like water and the charge would move from the higher voltage(Lipo) to the lower voltage(projector) which is opposite of what you want.  Hope this helps.

For the projector battery? I'm not sure exactly. It's a 3.3v battery, but the AC adapter for the projector that charges the battery is 5v at 2 amps

You are correct in that it doesnt have enough amps to support all the devices.  What is the charging voltage for the battery?