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Li-ion for Arri S & Bolex motors


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#1 bexley

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Posted 30 September 2012 - 08:38 AM

After deciding to ditch my massive 12v 7Ah SLA and find a more portable battery that I can easily fly with, I read a bunch of the threads on this subject and settled on RC battery packs: 8.4v for my Arri variable speed & single-frame motor and a 12v for the Bolex motor w/intervalometer. Then I found this:

http://www.ebay.de/i...a-/170901647118

Hmm, Lithium-ion got cheap. Admittedly, this seems to be one of the best deals out there and maybe the cel is crap, but I'm surprised at not being able to find discussions online about li-ion's suitability for film cameras. Cost used to be a reason for this, but now that it's not, are there others? Between the trouble flying with SLA's and NiMH's problems in the cold, I'm looking for reasons not to go with a lithium pack.

They're light, require the least maintenance, live longer than NiMH, can be packed in carry-on, and work in the cold. Voltage is more consistent too.

That 6800mAh pack would be more than enough. Were I to stick with lead acid, I'd go from the 7Ah I had to a 2-3Ah--even with the SLA's quick voltage drop-off, I never came close to needing a charge since I rarely shoot more than 500' in a day.

Please, ridicule this idea if I'm missing something.

If I'm not, I also found a reason to convert the Arri's variable and torque motors to 12v.

Edited by bexley, 30 September 2012 - 08:40 AM.

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#2 Hal Smith

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Posted 30 September 2012 - 08:51 AM

The seller's 96.2% feedback is a huge warning sign. Buyers who get screwed often try to return the merchandise they bought for credit. Or if not too much money, they just crawl away wounded. They don't post negative feedback to avoid first getting the seller angry. When a seller has a feedback rating that low, it usually means they've got a lot of unhappy customers.

Quality Li-Ion cells are expensive but worth it in the long run. Figure out what you need and deal with reputable dealers...only!
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#3 bexley

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Posted 30 September 2012 - 08:54 AM

Here are some auctions in English, from China:

http://www.ebay.com/...=item1c28d78083

http://www.ebay.com/...=item1c28d78083

$30 for 9800mAh is cheaper than SLA. Seems too good to be true even if they have a high failure rate. As long as they don't explode, I guess.
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#4 bexley

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Posted 30 September 2012 - 09:00 AM

The seller's 96.2% feedback is a huge warning sign. Buyers who get screwed often try to return the merchandise they bought for credit. Or if not too much money, they just crawl away wounded. They don't post negative feedback to avoid getting the seller angry. When a seller has a feedback rating that low it usually means they've got a lot of unhappy customers.

Quality LiIon cells are expensive but worth it in the long run. Figure out what you need and deal with reputable dealers...only!


Thanks, Hal. It sounds like I underestimated the issue of quality. If price is any indication, it looks like eBay only has the disreputable dealers, so I'm worried that the cost from a reseller in Germany may force me to look back to SLA and NiMH.
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#5 bexley

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Posted 30 September 2012 - 09:03 AM

.

Edited by bexley, 30 September 2012 - 09:06 AM.

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#6 Hal Smith

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Posted 30 September 2012 - 09:21 AM

.

There are reasonable prices on eBay for high volume production LI-Ion batteries for things like motorcycles and tools.

Personally I'd take a chance on something like that but I've got a shop and YEARS of experience building "One-Off" pieces of equipment.

An example of what's probably not a bad deal is:

eBay motorcycle battery

PS: Look at the last photo...notice where it's made?
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#7 bexley

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Posted 30 September 2012 - 09:44 AM

I see. At that price, I'd continue to put up with the SLA. I'm sure I can find a compromise without going to the peddlers of Chinese li-ion on eBay.

What about LiPo batteries? Conrad is a reputable electronics shop in Germany and sells a self-branded line, so I assume this would be of acceptable quality. If 2500mAh is enough to drive the camera, I'd be fine with switching batteries every few 100' loads.

http://www.conrad.de...earchDetail=005

Or?

http://www.conrad.de...earchDetail=005
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#8 bexley

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Posted 30 September 2012 - 10:12 AM

Sorry, I'm posting too quickly. I meant to ask if the 11.1v pack, more common and cheaper than 12v, could suffice for my uses. The Arri variable motor would work, left at 8v or converted to 12v, but I'm not sure about the Bolex motor.

The second link is indeed more expensive than what you showed, but I think I could find a lower capacity and more competitive price for that battery.

And forgive the barrage of product links. Germany has more than its share of batteries and I'm trying to figure out what my options are locally.

Also, should I consider building a pack with some affordable 3v li-ion Varta cels?
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#9 Hal Smith

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Posted 30 September 2012 - 10:13 AM

What about LiPo batteries?


I don't have any personal experience with them, I'd be guessing if I offered an opinion.
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Media Blackout - Custom Cables and AKS