I'm working on a project where I have a chinese "GoPro" being powered by a battery pack via the camera's micro-USB port. The battery pack has three 2500 Ni-MH AA batteries (producing 3.8v under load) which are wired into a 5v step up booster. The booster sends 5v via USB to the camera. I am not using the camera's stock battery for this application.
I've ran into an issue where during photo capture and image saving the current demand (my estimates are somewhere between 300-500 mA) is too much for the booster. This is only about a 2 second period. I can see the voltage drop from 5v to 4.8 or 4.6, prompting the camera to turn off and the image file to be unsaved or corrupted.
I've tested third-party Ni-MH batteries and Eneloops to see if the batteries were the current bottle-neck. The booster is supposedly rated to 600mA - I doubt I've exceeded that unless the spike from saving to SD is the culprit. Regardless, the Eneloops performed only slightly better and still saw reduced/glitchy camera performance.
I need reliability here. Does it make sense to be more suspect of the booster than the batteries? I've ordered the boosters linked to below hoping they can better handle the current demand. Is this the right direction to go in? I need to be sure the camera can get a consistent 5v even during a long deployment as the battery pack voltage drops over time, and that the booster can reliability provide for current spikes up to 600mA in those conditions.
UPDATE: I didn't understand why the Eneloops wouldn't be able to provide enough current, so I made sure to give them another full charge last night. This morning with three Eneloops the camera appears to operate normally with those three batteries, but I think I can expect problems as the voltage of the batteries drops over time. This makes me think even more so that my problems reside in the booster itself, and that I'm demanding too much current from it.
Is my intuition here correct? Will a better booster rated for higher currents provide more consistent current as the voltage of the batteries drops?
I'm under the impression that Duracell's would have a far lower potential current output than the Eneloops. Is this correct? Also, I am confused why 2xAA would benefit me vs the 3xAA I'm currently using.
ted:
Measure that
Unfortunately until I find an adequate shunt resistor to measure the voltage drop, I won't be able to. My multimeter tops out at 200 mA. However I've found consistent documentation online for these cameras that puts the current when recording at about 300 - 400 mA. The spike when saving images is so short I don't think anyone is documenting it.
Most likely, the booster can't support the required input current.
For a voltage boost regulator, the input current rating is often more important that the output current rating. Pololu has a good selection, and they inform you about these details.
I can see the voltage drop from 5v to 4.8 or 4.6, prompting the camera to turn off and the image file to be unsaved or corrupted.
If the battery voltage doesn't drop, the battery is not the problem.
But the problem is... If the battery voltage drops a little, you still won't know if that's the real problem.
Most 5V "stuff" will run at 4.6 or 4.8V... But there could be some short-duration dips that your meter isn't picking-up.
There has to be some tolerance unless 5V is the bottom of the tolerance... The spec could say 5-10V, and then you couldn't complain if it flakes-out at 4.999V.
I'm under the impression that Duracell's would have a far lower potential current output than the Eneloops. Is this correct? Also, I am confused why 2xAA would benefit me vs the 3xAA I'm currently using.
Duracell are the strongest I know from practice, ok use 3 of them, energizer battery are also strong at least in commercials, i didn't use them.
You can consider 3.7V - 18650.
For testing you can use 10 ohm resistor.
AustinAnywhere:
I'm under the impression that Duracell's would have a far lower potential current output than the Eneloops. Is this correct? Also, I am confused why 2xAA would benefit me vs the 3xAA I'm currently using.
ted:
Duracell are the strongest I know from practice, ok use 3 of them, energizer battery are also strong at least in commercials, i didn't use them.
You can consider 3.7V - 18650.
For testing you can use 10 ohm resistor.
I know when I think of "Duracell" batteries, I think of alkaline ones - that's probably where the confusion lies here. I suspect Ted is recommending Duracell brand NiMH batteries as being stronger than other brands. Right Ted?
I was talking about this one, regarding Duracell rechargeable battery - never use them so I dont know how good they are, label and practice not always are the same.
Its just a single 18650 LI cell with a 5V booster in a small tin can.
Will run the Gopro for about 2 hours.
If you want a longer time , you can replace the internal cell with a Panasonic 18650GA which will give you about 3 hours.
Hi,
Did you measure the INPUT VOLTAGE to the booster when the problem occurs.
Don't forget power in will be higher than power out, and as you are going from 3.8V under load and expecting 5V out with current of 500mA.
Thats 5 * 0.5 = 2.5Watts out.
96% efficiency, they claim.... :o :o
2.5* (100/96) = 2.6W input power
InputCurrent = 2.6 / 3.8 = 0.684Amps
So probably 0.75A would be a possibility for input current considering its from "worldchips" china.
The other thing to consider is it built to manufactures suggested circuit, or to price?
0.9V input is a bit suspect for a start.
Have you tried putting a 1000uF 16V electro cap across the input to the booster?
@mauried suggestion is the best of all, I have quite a few of these for 5V supplies.
