Can you replace a power adapter with batteries?

[Stephen Tashiro]

If you have a small DC powered device like a digital camera that can be run by an external DC power supply ( a "power adapter" ) could you wire up some batteries and hook it to the camera where the adapter plugs in? Specifically, I'm wondering whether I could use D or C cell batteries in a portable stand to hold a camera for use on a worktable. I'd think the bigger batteries would last longer than the smaller ones that fit inside the camera.

[mickey cassiba]

Back in the day we used PRC77 batteries to power all of our cassette decks and shavers. Not sure why it couldn't work, but there are a lot of smarter folks here that will prolly give you more details.

[Dave Gaul]

As long as the you give the device the correct amount of voltage, it should work fine.

[Dan Friedrichs]

Sure. Check the label on the power adapter to see what voltage you need to supply, and if it's a multiple of 1.5V, you can series together batteries and connect them to the camera.

Some adapters might produce AC output, but as long as yours produces DC, you can replace it with batteries. D's will last longer than C's will last longer than AA's..... (but all produce the same voltage)

[Stephen Tashiro]

It's interesting to me that the battery voltage listed for the DC adapter of a product like a digital camera rarely matches exactly the voltage that you can get from the batteries you put inside it.

[Rich Engelhardt]

If you have a small DC powered device like a digital camera that can be run by an external DC power supply ( a "power adapter" ) could you wire up some batteries and hook it to the camera where the adapter plugs in? Specifically, I'm wondering whether I could use D or C cell batteries in a portable stand to hold a camera for use on a worktable. I'd think the bigger batteries would last longer than the smaller ones that fit inside the camera.


C or D cells may or may not last any longer.
It depends on what the cells are made from.
Most electronic equipment (digital camera/laptpop/cell phone, etc) requires Lithium batteries.
Lithium holds a steady voltage as it discharges.
Alkaline is only fair in that regard.

Way back when - like 20 years ago - the 286/386 computers used a Lithium battery to power the CMOS (setup). A lot of repair places tried to slide by on the cheap by using an Alkline battery (The Li ran about $20.00 compared to a buck or so for the Alkaline). It didn't work out well at all. The Li would last for a year or better. The Alkaline would only last a few weeks - @ best.

My "kitchen table analogy":
I'm a lot larger than the late great Bing Crosby. We can both sing the same note @ the same volume. I can only do it for 10 seconds. Bing could hold the note & volume for 60 seconds.

Bottom line here is that while a C or D may work, it may discharge to the point of not being able to supply the required voltage faster.
If you move up to Lithium C or D cells, they get expensive real fast.

HTH & I didn't just add to the confusion.

[John Coloccia]

re: why voltages don't match

There are a number of reasons. Electronics have tolerances that they will work within. For example, a 24V device may run just fine on anything from 20V to 30V. As a designer, what you would do is match up what you can easily get with batteries to what you can easily get with DC adapters.

The other thing is that they normally go through different paths as well. Batteries are VERY clean power. Line power is going to have all sorts of ugliness on it, such as ripple. This has to be filtered. It will also probably be protected with some diodes from accidentally reversing polarity, and things like this. All of this causes losses which will have to be made up for.

There are other reasons as well.

[David G Baker]

I have purchased 4 amp hour nicads batteries from Radio Shack in the past and built containers for them that made it easy to remove the batteries and charge them in a Radio Shack charger designed for the batteries. I used the batteries as an external power supply for a 200 watt second electronic flash unit. If you do it, make sure you match to polarity of the unit you are trying to power with the polarity of the battery pack.
I have also done the opposite. Powering items that were battery operated with small transformers.

[Tom Esh]

It's interesting to me that the battery voltage listed for the DC adapter of a product like a digital camera rarely matches exactly the voltage that you can get from the batteries you put inside it.

That's because they're often unregulated. The higher the load, the more the voltage "pulls down". For example it would not be unusual for a 5V 200ma adapter to produce 7 or 8V under no load. If battery charging is involved or the device is particular about voltage, regulation is done within the device.

[Dan Hintz]

Also be aware that rechargeables (such as NiCads) are typically outputting 1.2V compared to a standard alkaline at 1.5V... makes a difference in the final stackup when you have multiples in series.

[Mike Cutler]

Stephen

Yes it can be done, but I wouldn't do it with C and D cells. You would need to arrange enough of them in a series parallel arrangemnent to meet the voltage and current requirement of a camera. The current requirements are actually significant for a camera.

We use 12 volts gel cells with 7 amp hours each and make a voltage divider to match the voltage. Be very careful of the polarity or you'll destroy the camera.

[Trevor Howard]

Also check the polarity of the jack you connect up, some are center pin positive and some are center pin negative. But like others say, no reason why it would not work.