DIY external battery

C

Carlos_E._Martinez

Well-known member
As I recently bought a BMPCC Pocket camera, along with a 7" Lilliput battery, I am considering using an external battery to power them both.

For the Pocket I did buy an external supply, by Indipro, but I was thinking of powering it all, along with the external audio recorder and perhaps an external video recorder. All supported on the 15mm rods.

So I'm considering a DIY project that might let me power all things together.

Two problems to consider:

1) Finding a 14v battery with enough amperage.

2) Finding an intelligent li-ion or nimh charger for it.

For the first item I have already found an option:

http://www.aliexpress.com/item/1680...velmate-2300-TM3000-4000-4010/1333915585.html

For the charger nothing for now.

I would further need a good box to hold the battery and connectors, but that is not that difficult.

What would you suggest for the project or think of the idea?
 
For BMPCC I would either build the battery pack using 18650 cells or use some batteries for heavy duty power tools (i. e. from Bosch or Makita). You can choose between several voltages and capacities as well as between LiIon and NiMh (even NiCd are still relatively easy to get). Chargers are also readily available and these batteries are much better mechanically than laptop packs.

I use Bosch LiIon 14.4 pack that came with power drill/screwdriver to power my on-camera light (with a switching power supply to get 7.2V). The only issue was making a suitable plate with contacts, but I have milled that from a piece of polyamide I found in our workshop and it works fine.
 
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The problem with 18650 and other separate cells is that you can't charge them together reliably. You have to separate them and charge them individually.

Nicads are certainly out, due to charging memory issues and environmental pollution. NiMhs might be an option if I can find them in 14.4v packages.

Those Bosch are probably sturdy, but look hard to box-in. As I said, there are not that many 14.4v batteries to pick for that are relatively small to be packaged and charged.
 
power tool batteries are also what i'm about to start tinkering with. i've narrowed it down to bosch and milwaukee, as they have a good variety and reliability.

warthog, have you just used the 14v, or have you tried the 12v stuff as well?
 
Paul F said:
If the Ali express battery has enough power for you, consider using the Sony NP batteries. There are 6600mah batteries available. Two of those can mount in this battery pinch and provide you the various voltages you might need. The problem is they don't publish the output capacity.

http://www.ebay.com/itm/DSLR-15mm-R...708?pt=LH_DefaultDomain_0&hash=item3f31af3184
Click to expand...

Yes, I had seen that supply somewhere, and it does look interesting. Unfortunately maximum voltage is 12v, which is a bit low for the Pocket.

That Tekkeon looks very interesting.
 
carlmart said:
How would you interface tool batteries and how would you box them? They seem difficult to.
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Easily. Just make a base plate that accepts these batteries (copy the bottom end of the power tool they come from) and can be installed on standard 15 mm rods. You do not need to box the battteries, just use them in their original enclosure.

I do not have my base plate here, but I will ask a colleague of mine to make a picture and send it.
 
They would probably work - their voltage is typically well above 12 V under small loads and considering the camera's internal battery is only 7.4 V, it will probably tolerate somewhat lower voltage on the external power input. And you could always use step-up converter. But of course 14.4 V batteries can be used as they are.
 
Warthog said:
They would probably work - their voltage is typically well above 12 V under small loads and considering the camera's internal battery is only 7.4 V, it will probably tolerate somewhat lower voltage on the external power input. And you could always use step-up converter. But of course 14.4 V batteries can be used as they are.
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No, apparently the Pocket doesn't tolerate 12v external supplies. I have read reports on the BMPCC forum telling about this issue. The camera loses frames and other errors.

As far as I can see it, there must be an internal DC-DC converter that boosts the internal 7.4v voltage to higher values. I was also confused at first, as I didn't get why some of the external supplies used two 7.4v batteries instead of one. If you want to use one 7.4v battery you will need a DC booster.
 
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