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Of battery packs... Does amp rate make a difference?


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#1 Sir Alvin Ekarma

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Posted 01 May 2006 - 08:48 AM

I've seen over-the-shoulder battery packs on Ebay that are listed as being 12V/12Amp for very cheep and I've seen camera places that sell 12V/5amp at around 30-40% more. Is the 12v/12amp battery belt a better deal or will I wreck things up if I use it? I've been told that the amp rate just determines how long it'll hold a charge. What sez you all?
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#2 Stephen Williams

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Posted 01 May 2006 - 09:13 AM

I've seen over-the-shoulder battery packs on Ebay that are listed as being 12V/12Amp for very cheep and I've seen camera places that sell 12V/5amp at around 30-40% more. Is the 12v/12amp battery belt a better deal or will I wreck things up if I use it? I've been told that the amp rate just determines how long it'll hold a charge. What sez you all?


Hi,

The cheap ones are probably sealed lead acid. They are cheaper than other rechargable batteries. Also don't fully discharge them or they will die quickly. I often use sealed lead acid batteries without any problems.

Stephen
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#3 Laurent Andrieux

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Posted 01 May 2006 - 09:15 AM

I've been told that the amp rate just determines how long it'll hold a charge


Yes. It's not an amperage, but a charge in amp.hour. for instance a 5 A.Hour battery can deliver 5 A during an hour, or 1 A during 5 hours etc.

So a 12 A.H battery will last more than twice as much the 5 A.H one will.

Also, it would hold better a high intensity for a short time if needed. If it's a video camera you are feeding it doesn't matter much, but for a film camera, it may happen that you need a stronger battery (esp. with high speed work for instance)
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#4 John Pytlak RIP

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Posted 01 May 2006 - 12:24 PM

The voltage is the key parameter for compatibility. But the battery needs to maintain its nominal rated voltage as it discharges, so "Ampere-Hours" is a measure of the total energy that can be delivered by the battery before its voltage drops below a usable level.

Also, some batteries may not have the current delivery capability required for high-load devices, so you need to be sure it can deliver the "Amps" needed without a significant voltage drop.
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#5 Sir Alvin Ekarma

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Posted 01 May 2006 - 05:22 PM

Thanks for the info everybody!

Sir Al
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#6 Nick Mulder

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Posted 02 May 2006 - 01:23 AM

lead acid - cheaper, also heavier
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#7 Mike Welle

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Posted 02 May 2006 - 10:25 AM

Just a practical observation...When I used my Eclair ACL back in 2000 I had a 12 Volt 7AH battery pack (from Du-All Camera--where I got my camera from) that I wore over my shoulder. I never had any problem with flickering in the films I shot. I got tired of wearing the pack over my shoulder so I sold the 7AH battery and upgraded (or should I say downgraded) to a 12 Volt 5AH battery pack (Du All has this one up on their website). I can only recall one shot where I saw some flickering with this pack. I used it in 2002 in New Orleans. Then I decided I wanted some on-board batteries so I sold the "superfluous" 5AH pack and got a couple of 12 Volt 1.2AH on board batteries specifically designed for the ACL (this is 2003-2004). I get an occassional flicker with this design. I've decided that I will accept the occasional flicker for the convenience of not having to wear the battery over my shoulder or on my belt. I think the more amperage you have the less chance you have of getting flickers--and I am saying that from practical experience.

Mike Welle
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#8 Dan Goulder

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Posted 02 May 2006 - 10:41 AM

The condition of your camera and mags will also affect the current draw. Extra resistance will draw more current to maintain speed, thus the importance of keeping all moving parts well serviced and lubed.
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#9 Evan Kubota

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Posted 02 May 2006 - 04:15 PM

The current draw varies by camera, but I use a 12v 5Ah SLA with my Kinor and it works well. A little heavy at 4.5 lbs or so but in the shoulder rig it's fine. I get the subjective impression that it's more than powerful enough to run the camera (and the camera in the worst case will probably not draw more than 1.5-2 A, so it's good for at least 2 hours of film time) - about half a feature if you maintain a low ratio. Another good thing about film cameras - almost no battery drain unless the motor's running ;)

I have a recelled 300mAh internal NiCd for my Scoopic (grey) that is fine for that camera but it doesn't give enough juice to power the Kinor. Same for a 300mAh wallwart (although stated output is always inflated on cheap stuff).
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#10 Sir Alvin Ekarma

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Posted 03 May 2006 - 09:32 AM

Is there a way to determine how much power your camera draws? Or is there a technical reference you can go to? (I have a bolex EBM btw).
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#11 Laurent Andrieux

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Posted 03 May 2006 - 09:52 AM

Waht you can do is to have an ampermeter on the line whilst the camera is running and see how many amps it uses while working. Let's say it's 500 mA, then a 5 AH battery would then last 10 hours
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#12 Sir Alvin Ekarma

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Posted 03 May 2006 - 09:37 PM

Waht you can do is to have an ampermeter on the line whilst the camera is running and see how many amps it uses while working. Let's say it's 500 mA, then a 5 AH battery would then last 10 hours


Thanks!
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