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Re: Batteries

On Sun, Jan 16, 2000 at 10:01:06PM -0500, Cindy Wong wrote:
> Okay, I don't know if I'm not doing the math right, or whether I should

What?  A girl do math wrong?  Bah!  Not possible!!!!

<ducking and running>

> Before I give you my analysis, let me tell you what my temporary
> conclusion is.  I think we're better off buying alkaline batteries. 

I agree.

> Also, the mAh for the Alkaline is an approximate because the shopping site
> did not show the specs.  I had to look in a manufacturer's site and it may
> vary with brands, I presume.

My understanding is that it does not vary very much with different
brands.  Of familiar name brands, I trust information I've been told
that Energiser is slightly better than most others, Duracell next, and
almost everything else being equal.  Even those two are not very
different.  How the battery responds to different types of usage
--- regular, infrequent, sudden current drains, etc. --- does vary a
little bit more from brand-to-brand, I understand.  Still not enough
to worry me.

> So, what do you think?  =)  I may look at Canadian Tire to see what their
> prices are like, but I think Alkaline is probably the way to go.  Please

You may be able (ie. will be able) to find Alkaline batteries
cheaper from sources other than Canadian Tire.

What about: - recharging method?  Are NiCD and NiMH equally easy to
            - Obviously alkaline can't be recharged.  You haven't
              considered the possible necessity to repurchase
              alkaline batteries after test runs of our robot.  Or
              would it be acceptable to plug our robot into the
              wall with a trailing umbilical cord during tests?
              We will want to test him in real-life fights against
              other robots.
[Yes, I am serious about doing testing by plugging the bot into an AC
 power source and then only doing a bare minimum testing to ensure it
 all still works with DC batters [caveat: I haven't defined "bare
 minimum"] ... I can outline my ideas on how to do this, if requested].
            - You probably recall I have a stash of 30 Duracell AAs :)
              I may still be able to get more of them for $5 for 18 if
              you so desire...
            - We could try to earn brownie points by considering the
              effect of battery disposal on the environment.  :)

> reply and give feedback.  Since rechargeable batteries were suggested (by
> whom?), I'm wondering whether I'm just missing something here.

By fourth years on my floor.  His argument was that you'll end-up
recharging the batteries so many times that they will pay for
themselves.  He may be correct if one assumes that we do not use an AC
power source for any of the testing.

What are the different voltage levels we need?  I can construct
circuit to supply your choice of DC voltage from an AC source for
probably a price cheaper than even purchasing alkaline batteries....

Sensors may respond ever so slightly differently to noise when working
from such a constructed power supply vs. working from batteries.  I
may be able to design a circuit sufficiently noise-free (from a supply
perspective) that this will be inconsequential.  Love'em op-amps.

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