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External Power for ELPH 300HS

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Offline drillthrall

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External Power for ELPH 300HS
« on: 17 / January / 2014, 23:19:57 »
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This video shows how I disassembled two Canon CB-2LV/CB-2LVG NB-4L Li-ion Battery chargers to get twice the battery length by combining two NB-4L batteries to power my ELPH 300HS.  I tried to copy the method used by someone on youtube that did this same thing for his 3.7v Canon SX220.

Here is the video showing how I built it   Not a valid vimeo URL
It seems to power the ELPH 300 but I have yet to test its endurance compared to just one standard factory battery. It did turn off once when I was testing it but I think it was because one of my wires touched another one when I moved it. I'll put it all together as it's meant to be and test it in place on a tripod like I plan on using it and post the results in Part 2.
« Last Edit: 19 / January / 2014, 00:45:38 by drillthrall »
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Offline waterwingz

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Re: External Power for ELPH 300HS
« Reply #1 on: 17 / January / 2014, 23:41:31 »
tl;dw :  (too long, didn't watch) :  how to wire up two external batteries in parallel using hacked battery chargers as battery holders.

Nice job on the video - looks like you just doubled your picture taking capability !
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Offline drillthrall

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Re: External Power for ELPH 300HS
« Reply #2 on: 18 / January / 2014, 00:38:48 »
OK, tested its endurance today and it lasted exactly twice as long:  4 hours instead of 2.  I set CHDK like I have for my bird pics in the summer: MDFB with a forced flash power of 0.  I had it set up in the house with people and cats moving around and it took pictures with the flash for 4hrs before it stopped.

I'll post a video tomorrow showing what it looks like all put together.  The whole project cost about $45 to buiild.  I ordered the chargers that I cannibalized from eBay.  They were about $4 each.  I also found several Canon factory NB-4L batteries for cheap as well.

This process would be very similar if you were doing it for an S100 or S110.  I'm going to order parts and do the same thing for my S100.
« Last Edit: 19 / January / 2014, 00:38:22 by drillthrall »
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Offline drillthrall

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Re: External Power for ELPH 300HS
« Reply #3 on: 19 / January / 2014, 00:44:39 »
As mentioned in the original video above, my build puts out 4.10v so I tried it out on my used ELPH 300HS that I bought awhile back from Amazon for $60.  It didn't seem to mind the 4.10v for the 4 hour durations I got.  Nothing felt warm other than the flash.  I am getting one perhaps odd thing going on and that is when my dual battery build runs out of juice the lens doesn't retract like it does when the normal internal battery dies out.  It's not a big deal but it would be nice if the lens retracted like it usually does as I like to look out the porch to see if the lens is retracted to know when to go retrieve the cam.  Oh well.  Maybe someone has an idea why?
« Last Edit: 19 / January / 2014, 00:48:29 by drillthrall »
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Offline ahull

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Re: External Power for ELPH 300HS
« Reply #4 on: 19 / January / 2014, 05:18:27 »
Quote from: drillthrall on 19 / January / 2014, 00:44:39
As mentioned in the original video above, my build puts out 4.10v so I tried it out on my used ELPH 300HS that I bought awhile back from Amazon for $60.  It didn't seem to mind the 4.10v for the 4 hour durations I got.  Nothing felt warm other than the flash.  I am getting one perhaps odd thing going on and that is when my dual battery build runs out of juice the lens doesn't retract like it does when the normal internal battery dies out.  It's not a big deal but it would be nice if the lens retracted like it usually does as I like to look out the porch to see if the lens is retracted to know when to go retrieve the cam.  Oh well.  Maybe someone has an idea why?

I suspect the two batteries in parallel behave slightly differently from the single battery. It may be the case that they shut down at a voltage above the Canon's low battery threshold. Both cells will discharge with slightly different discharge curves. Perhaps when the first cell drops below its cutoff voltage, it receives a sudden surge of charge current from the remaining cell, causing that to drain very rapidly, or causing its over current protection to kick in, and thus it switches off very quickly.

You can get the script to measure and log the voltage, and on subsequent runs, set a cutoff level just slightly higher than the minimum voltage you currently see the camera working reliably to. When the script sees we have reached this voltage, it shuts down cleanly. 
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Offline waterwingz

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Re: External Power for ELPH 300HS
« Reply #5 on: 19 / January / 2014, 09:49:02 »
Quote from: ahull on 19 / January / 2014, 05:18:27
I suspect the two batteries in parallel behave slightly differently from the single battery. It may be the case that they shut down at a voltage above the Canon's low battery threshold. Both cells will discharge with slightly different discharge curves. Perhaps when the first cell drops below its cutoff voltage, it receives a sudden surge of charge current from the remaining cell, causing that to drain very rapidly, or causing its over current protection to kick in, and thus it switches off very quickly.
I'd suggest putting a Schottky_diode diode in series with each battery's positive terminal to isolate it from the other battery.  A couple of 5A diodes should be less than $1 and will prevent the batteries from trying to charge each other if one decays faster than the other.
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Offline ahull

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Re: External Power for ELPH 300HS
« Reply #6 on: 19 / January / 2014, 10:22:58 »
This is by far and away the simplest method of doing this.

We are safe from actually damaging the battery using the setup as is, since we are using camera batteries, which have a built in protection circuit. If you were to try to run two unbalanced unprotected LiPo cells, there would be a risk of fire, but the schottky diode will avoid the reverse voltage issue to some degree, Due to the diode drop however, you may get slightly shorter running times.

If you want to be a little more power efficient, you could use a mosfet, but that will add a layer of complexity you may not want.  There is a good explanation of how to use a P-FET for reverse voltage protection here.
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Offline Microfunguy

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Re: External Power for ELPH 300HS
« Reply #7 on: 19 / January / 2014, 11:02:39 »
Quote from: ahull on 19 / January / 2014, 10:22:58
There is a good explanation of how to use a P-FET for reverse voltage protection here.

Excellent tutorial.
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Offline waterwingz

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Re: External Power for ELPH 300HS
« Reply #8 on: 19 / January / 2014, 11:25:48 »
Quote from: ahull on 19 / January / 2014, 10:22:58
There is a good explanation of how to use a P-FET for reverse voltage protection here.
Agreed - it's a great video.   

However, thinking about the P-FET circuit explanation,  its clear how it protects against reversed input voltage (from the battery on the left).  However,  if you have two batteries connected in parrallel via two P-FET circuits, both circuits will have their gates at a lower voltage than their source&drains so I think both will be biased "on".  Does this allow reverse current through the FET when one battery has a higher voltage than the other?
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Offline ahull

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Re: External Power for ELPH 300HS
« Reply #9 on: 19 / January / 2014, 11:40:12 »
Quote from: Microfunguy on 19 / January / 2014, 11:02:39
Quote from: ahull on 19 / January / 2014, 10:22:58
There is a good explanation of how to use a P-FET for reverse voltage protection here.

Excellent tutorial.

I can't take any credit for the tutorial, but all of the articles on that site are pretty good. His delivery style might not be to everyone's tastes, but I find it quite amusing.

There is also a good breakdown (pun intended) of reverse protection here which gives a pretty good explanation of the pro's and cons of most of the common methods of performing this particular trick. 

Most consumer grade equipment with a wall wart, generally use the cheapest solution, and that means a diode and fuse. The fuse is in line with the supply, and the diode is as per the example above.

This is not resettable, (most manufacturers of cheap consumer goods dont care if you blow them up with the wrong polarity, 'cos then you will need to buy another one). The method is cheap and relatively safe, since the currents involved with a wall wart are fairly low. I wouldn't like to see a high amperage circuit "protected" in this way, the resultant bang would send you flying. 

A reverse diode and fuse wouldn't work in our case, because we are know we are going to reverse the polarity, so if we decide the schottky diode isn't going to cut the mustard, then mosfets are the way to go.

The N-channel mosfet solution is probably the best, and you may recognise it from my NB-4L battery teardown. The DW-01G protection circuit uses two n-channel mosfets to do its magic, one of them is configured in a similar way to that described in the first tutorial, to protect against over discharge. 
« Last Edit: 19 / January / 2014, 11:45:54 by ahull »
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