Re: Battery type detection
- From: MooseFET <kensmith@xxxxxxxxx>
- Date: Sat, 15 Dec 2007 07:46:18 -0800 (PST)
On Dec 14, 9:12 pm, Robert Baer <robertb...@xxxxxxxxxxxx> wrote:
Dave wrote:
I'm designing a radio that can take dry cells or rechargeable cells. I want
the radio to have a charging point but don't know how to detect that the
batteries it may have in it are not rechargeable and so shouldn't be
charged.
Is there a simple way to do this or do I just put a disclaimer on the radio
not to try to recharge dry cells?
Thanks for your comments.
Dave
Nope!
First, no assumption can be made as to the condition / charge of the
battery, so a simple unloaded voltage measurement will do.
*IF* one knew the battery was fresh, a Leckance cell measures about
1.55V open circuit, and different (fresh) rechargeables measure
different voltages depending on the type, but the majority of themseem
th be in the 1.25V region.
Oh, yes...attempting to re-charge an unknown battery could lead to
disastor.
There is less risk than it first appears with standard shaped cells.
This assumes that you have a temerature rise detector on the cells:
A Lithium produces way more voltage than a nicad or zinc-carbon. If a
Lithium is down that low, it is junk. Refusing to attempt to take a
battery from less than 1.6V as a Lithium protects the charger against
trying to do a Lithium charge on a nicad.
If a completely dead Lithium has a current applied that stops before
the cell gets above 1.6V nothing very interesting will happen.
A nicad charger that limits the voltage won't do anything bad to a
good zinc carbon cell. Zinc carbon cells that are really messed up
heat up when you connect 1.2V onto them but if you stop on detecting
the rise, nothing comes of it.
.
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- From: Dave
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- From: Robert Baer
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