DIY Battery pack for camera, Voltage Question

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Old 09-19-12, 05:53 PM
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DIY Battery pack for camera, Voltage Question

Hello all! This is my first post and im looking for help on a new project!

Im attempting to make a external battery pack for a digital camera of mine, Ive got the adapter made but before hooking it up and potentially frying my camera ive got a few questions!?

The stock battery is a 3.7v lithium rechargable battery.
Ide like to have the option to use AAA or AA batteries as they are easier found on the fly. Most rechargable AA's are 3.7v would stacking 4 of them in a holder be to much for the camera? common sense says yes.

Do I need to buy some sort of capacitor or insulator inbetween the battery pack and camera?

Ive only basic electrical knowledge and would love some guidance!
 
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Old 09-19-12, 07:12 PM
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AA batteries are not 3.7v, they are 1.5v. NiCd and NiMH rechargeables are 1.2, but most devices work just fine on them. Four of them in a standard 'series' battery holder outputs 6v, which will probably fry the camera - and going by your screen name it won't be a cheap repair.

I have a feeling you are talking about Lithium-Iron Phosphate (LiFePO4) rechargeable AA's, which are 3.6v per cell. These are NOT direct replacements for AA's, they are designed to be used in conjunction with 'dummy cells' (an empty battery-shaped cartridge which has its + and - ends connected together so that it simply passes power through) to create the correct voltage for an AA powered device. For example a device that requires 2xAA batteries (3v) would use one LiFePO4 AA and one 'dummy cell'. A device which requires 4xAA (6v) would use two LiFePO4 AA's and two dummy cells. You can not use LiFePO4 batteries in any application where it would be replacing an odd number of standard AA cells. You also need a special charger for LiFePO4's. A standard charger for NiCd or NiMH will not charge them.

In your case 4 LiFePO4 batteries in a standard series case would output 14.4v, which would DEFINITELY cause you expensive problems. What you propose IS doable, and it would make a nice pack that would last at least a couple times longer than the stock battery, but you need to make it so that the AA cells are wired in PARALLEL (+ to + to + to +, and - to - to - to -). This will give you 3.6v output with roughly 4,000mAh capacity. Camera batteries are usually in the 700-1000mAh range, and LiFePO4 cells are in the 900-1000mAh range per cell.

So basically what it comes down to is AS LONG AS THE LiFePO4 BATTERIES ARE CONNECTED IN PARALLEL, they will meet the voltage requirements of your camera and you will not need any additional circuitry between the holder and the camera. You CAN NOT use a standard 4-cell holder from Radio shack or similar because they put the batteries in SERIES, which adds up the voltage of each cell.

If you are looking to make this work off standard alkaline AA's, then things work different. There is no easy or efficient way to do it.. You can do 3xAA/C/D in series to give you 4.5v, then use a simple transistor/zener regulator to shave it down to 3.7ish, but that is actually going to waste the excess power as heat - and it will get hot enough to burn you.. That heat = wasted power from the batteries, so it won't last very long.

So you'd probably be better off going with the LiFePO4 method and keeping a spare set charged and ready to go. LiFePO4's have very slow self-discharge, so they'll stay fully charged in storage for quite a while.
 

Last edited by JerseyMatt; 09-19-12 at 07:33 PM.
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Old 09-19-12, 07:24 PM
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What make and model is your camera?
 
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Old 09-20-12, 06:38 AM
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Welcome to the forum.

Make and model of your camera would be a good start.
There might already be a aftermarket battery pack for your camera. They tend to cost a bit more then a DIY setup, but when you are out in the field, messing around with a DIY system can be a real pain.
Also consider looking at an aftermarket spare rechargeable battery. I've picked up spare batteries for my DSLR cameras as well as my rugged P&S cameras from places like amazon.com. The $60 battery for my rugged camera was about $15 there.
Spare batteries are so much easier to handle in the field, take up less space, and have less of a failure rate then an external pack.

I only ever used an external pack on my DSLR cameras when doing long studio photo shoots. I've since moved to spare internal batteries as they are easier to deal with.

If you really want to go with an external DIY setup, A quick inline resistor would be the simplest and cheapest method. Current draw would not be all that high.
 
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Old 09-20-12, 06:48 AM
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Long ago I used an extended grip for my DSLR which also housed an additional battery to extend shooting time. While studio and portrait photographers love them because of the extra grip and shutter button when holding the camera sideways it just did not work out well for my out in the field wildlife photos. It was big & heavy and like Northern Mike said. It's just easier to swap out the battery for another.
 
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Old 09-20-12, 01:13 PM
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I'm going out on a limb here but the OP's screen name is "Leica-Devin".. I would say the camera in question is a Leica. Considering you can't touch a Leica for under a thousand dollars and most are in the several thousand dollar area (which is why I wouldn't even suggest gambling with crude voltage regulation), and even 'cheap' extra batteries are over $100 apiece, I'd have to assume that is playing into the OP's motives.. Just sayin..
 
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Old 09-20-12, 01:27 PM
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I'm going out on a limb here but the OP's screen name is "Leica-Devin".. I would say the camera in question is a Leica. Considering you can't touch a Leica for under a thousand dollars, and even 'cheap' extra batteries are over $100 apiece, I'd have to assume that is playing into the OP's motives.. Just sayin..
Based on the info in the OP, I did a quick search of amazon and found a dozen or so 3.7V Leica batteries all about $75 or less.
Definately more expensive then my DSLR batteries or my rugged camera batteries, but as expected, pretty cheap.

An external pack is do able, but I know from experience, it can and will be a PITA. Specially if you have issues with the DIY craftsmanship.
More then likely, and external unit will not be a nice and clean setup like my external portrait grip I have for my DSLR cameras, it'll be piece with a cable going to the camera. A DIY probably can be cheaper (based on my search without knowing what model of camera it is) but is the couple $$ worth the headakes in the field?
 
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Old 09-23-12, 09:27 AM
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Thanks for the great info! Exactly what I was looking for, how to wire the batteries to maintain 3.7v.

The camera in question is in fact a Leica, a D-Lux 4 to be exact.
The batteries, even new, do not last a whole day of shooting.
My intention of a battery pack is to add to my shooting time and to the size of the camera itself.
The camera takes wonderful photo's but much to small to feel comfortable in my hands, even with a custom grip.
 
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