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replacing AA's with lithium? Answered

 Hey I have a cheap camcorder that runs on AA's but I want to put it on a lithium battery. What I want to use is just the standard battery out of an old phone 3.2v, I'd like to use these because I have a huge surplus of them. I have pretty much no knowledge of electrical circuits and so I need of bit of help. I know two AA's is 3v and any lithium battery is 3.2v, how could I step the battery down to 3v?

Tags:Lithium

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hughperman (author)2010-06-04

Hey there, I've been looking at a lot of battery specs recently for a project, and they are more variable than I thought! Lithium batteries have a range of 4.2V (fully charged) down to 3.2V (when they stop working), and work for most of their charge lifetime around 3.7V in the middle. 2 AAs would be between 3V (fully charged) - 1.8V (when they stop working). The camera's electronics are therefore probably working between 1.8V - 3.3V. This means that your lithium battery would probably exceed max design spec for the camera and possibly fry some of the electronics. If you put a couple of silicone diodes in series before the battery, they would each give you a voltage drop of 0.7V meaning your battery would be providing 2.8V - 1.8V, which would be perfect for the camera.

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problems (author)hughperman2010-06-07

hey thanks for the info on lithium, didn't know it was so variable. I'b be sure to use some silicone diodes to step it down.

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problems (author)2010-05-29

 Hey guys thanks for all the responses. I know this was a really stupid question, I just wanted to make sure I didn't do anything bad. After a quick look at the phone battery it's actually 3.7v and 1000MaH, I just assumed it was 3.2 as every battery in portable electronics I'v ever seen was 3.2v. A difference of .7v should be fine though right?

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lemonie (author)problems2010-05-31

If the machine takes a standardised battery-format (AA) the manufacturer will expect someone to put different types of AA in it. Check the manual / user guide - if it doesn't say not to use rechargeable AAs get some of them.
Trying to use the phone batteries just because you've got them is not a very practical idea, how would you charge them?

L

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killerjackalope (author)2010-05-29

Check out the Mah rating of the phone battery, typically they're not that high, todays big ones are at most 1300mah, a set of rechargeable  NiCads have a combined of 3000mah and jessops cheapest camera rechargeables are 2800mah per battery. 

The difference in capacity would really shorten battery life...

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lemonie (author)2010-05-29

0.2V isn't likely to make much difference.
The current-rating & capacity might though - what is the spec' of the phone battery?
You could just buy rechargeable AAs, they're not that expensive.

L

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killerjackalope (author)lemonie2010-05-29

Depending on the kind of AA some would add up to 3.2 and some sit at 2.8 the leeway's there for it... 

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aeromancy (author)2010-05-29

As Lemonie said, .2V will not make very much difference. If you're that concerned, you can go to your local electronics store and pick up some resistors, and look up Ohms law (I would tell you, but you didn't mention the specs of your battery). You could also purchase a germanium diode. The voltage drop with a germanium diode should be a steady .3V.

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