Batteries and chargers

[Oscar Spierenburg]

Originally the Elphel has 48v POE (power over ethernet), but it is possible ( Modifying the camera for 12-36v mobile applications - ElphelWiki )with a modified Elphel to use a power source within the 12v (9v-36v) range.
An important post on this by Sebastian:

Careful with the amps!

5W power consumption does not equal 5 Amps.

P (Watt) = U (Volts) * I (Ampere)
so I = P / U

Using a 12V battery as example:
I = 5W / 12V
I = 0.417A or 417mA

Battery capacity is rated in mAh (milli ampere hours).

So if in our example we have a fully charged 12V battery pack with
4000mAh we can estimate the camera (assuming 5W power consumption) to
last for around 9.5 hours.

This is a theoretical maximum value as you would have to consider DC-DC
losses, degree of efficiency, etc. as well.

Maybe the battery pack would last for 8 hours or less.

Regards Sebastian

5 Watt power consumption is not much at all. My EeePC draws around 15W
in idle mode and most laptops use up to 50 W.

5 W at say a battery

Right now, I've tested a 11.1v LiPo battery. It works well and they are extremely lightweight, but they are difficult to charge because they also need to be balanced so they require an expensive charger. Another issue is that you have to make your own housing with a small project box for example.

Alexandre from Elphel is testing this product which looks most promising so far: http://www.digipowersolutions.com/st...929b7124103a4d Here is an image with the camera: Hardware | Apertus Open Source Cinema It can be charged and used at the same time, has status LEDs on the side and also provides a 5v USB power.

[Andrey Filippov]

I would recommend to use 18-19V (as in most laptops), not the 12V. There are diode bridges (as required for PoE in IEEE802.3af) in the camera that waste around 1V or so. It is possible to bypass them but - but that requires soldering and makes camera vulnerable to wrong polarity.

Additionally - I'm working now on next model 373 camera (Elphel Development Blog Circuit design - 10373 ) - it uses TI DaVinci CPU that is more power hungry, some with GigE, faster FPGA and memory. 373 will have flexible power supply voltage (CPU core) and frequency tuning to balance performance/consumption, but still it would be nice to avoid additional limitations on the power cased by low voltage/high current input.

[Sebastian Pichelhofer]

More universal battery packs:

Portable lithium ion battery pack Battery Power Station weighs only 1 pound

http://www.bixnet.com/exnobapo80.html

[Oscar Spierenburg]

Hi everyone,

I'm looking at this external laptop battery to power the camera: PPU1619

Any comments on this? It seems a good solution and should be easy to integrate/mount on the camera rods support. Other suggestions are very welcome too!

[Oscar Spierenburg]

Another link: HyperMac External MacBook Power

There should be a lot of options out there. Please help us find all possible solutions. I really like some input on this issue.

[Steven Mingam]

Go the hobbyist way !
HobbyKing Online R/C Hobby Store : GENUINE A123 Systems 26650A LiFePo4 Cell w/ tabs $14.95

Get 5-6 of them, solder them serial and you've got the best priced LiPo battery pack around.
You can even build it with the form factor that suit you best...

Or because we just discharge at "1C" we don't even need ultra heavy duty battery : http://www.hobbycity.com/hobbycity/s...00mAh_5S1P_15C

[Oscar Spierenburg]

Hi Steven,

Thanks for the input. I've actually tried a similar Lipo Battery Pack | Apertus Open Source Cinema
The trouble is that not everyone who will be using the Apertus in the future is going to be a DIY guy. So for general purpose we need an out of the box solution. LiPo is difficult to charge and don't show how much power/time is left (only the LiPo saver LED showing when it's almost empty)

[Steven Mingam]

Well for the moment, they better be :P
(and quite frankly, they've got brain and it's not rocket science... the pre-made ones are enough.)

People using LiPo battery for their RC hobby encountered the same problems you had and solved them ages ago ;)

If you browse the "battery/charger" category of that same website, everything is in here (LCD displaying battery status & chargers)


You said "all possible solution" btw ;)

[Sebastian Pichelhofer]

Intersting Steve!

These parts battery + voltage monitor and security circuits could easily be assembled to build a custom and open battery pack as we originally dreamed about.

Perhaps this would even allow us to transmit the meassured results about remaining battery capacity to the DICTATOR interface to be displayed there and in ElphelVision!

[Oscar Spierenburg]

Hi Steven, didn't know about those battery status meters, good idea!

Originally Posted by Steven Mingam

Well for the moment, they better be :P
(and quite frankly, they've got brain and it's not rocket science... the pre-made ones are enough.)

Well, most mails we get through our website are: "when can I buy this camera?" or "Can I start filming with the Apertus system for my next project?"
That's why I'm looking for an out of the box solution (to begin with anyway)

There are also external chargers for laptop batteries. If we could have a status meter on that, it might also be an interesting idea.
Another thing we should consider: it would be preferable to be able to charge 'on camera' wile powering the camera at the same time. (like a laptop)