Subject:
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Re: Pure Energy & the RCX
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 18 Nov 1999 22:21:16 GMT
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Viewed:
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669 times
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I don't know about other rechargables, but bad Ni-Cds can be identified.
The charger I use has a test mode which measures the battery's characteristics
(perhaps putting a load on it a observing the voltage discharge curve?) and
indicates its output voltage and if its bad. It's the Radio Shack 23-410
Charger/Conditioner and knows the diff between Ni-Cd and Ni-Mh. Ni-Cds are
drained before charging and put on trickle charge when full. It has kept
several sets of Ni-Cds working for me for quite a while: I have 6 that are at
least 5 years old and still running fine.
-Wes
I don't use Ni-Mh, so I can't comment on how well they endure.
Robert Munafo wrote:
>
> It's strange to see you describe the "how to find the bad cell" problem with
> reference to Alkaline cells, then go right on and suggest the use of Ni-Cad
> battery packs!
>
> Ni-Cad battery packs have the same problem that any other type of serial
> multi-cell battery pack has: there's no way to find or eliminate one bad cell.
>
> Ni-Cad batteries have to be discharged fully before recharging, for best
> results. (Unlike alkaline and lead-acid cells, Ni-Cads develop "memory"
> problems from being less-than-fully discharged). So, naturally, users of NiCad
> packs will try to use the pack until it's dead, before recharging it.
>
> When this is done, after 10 to 20 discharge cycles you reach the point where
> one cell in a 6-cell pack gets down to 0 volts while the other 5 cells are
> still at near-nominal voltage and still have a fair amount of stored energy.
> The result is that the weak cell will then begin to be *reverse* charged by the
> other 5 cells in the pack. Reverse charging is even worse than the memory
> effect.
>
> - Robert Munafo www.mrob.com
>
> (Note: A "cell" is a single enclosed chemical system, and a "battery" is a
> group of cells. Cells can be grouped in series, in parallel, or both.)
>
> In lugnet.robotics, Jack Gregory writes:
> > [...] managing a set of [rechargable alkaline cells] is fraught with peril.
> > [lacking] a "bad battery" tester. [...] Some freak battery that isn't
> > cutting it gets in your pack, and you can't find it. [...]
> >
> > [...] we could make [an external] 7-cell NiCd pack to replace
> > the 6 (8.4v vs 9.0) in the RCX [...] I am actually surprised
> > that more people don't discuss this [...]
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Message has 1 Reply:
 | | Re: Pure Energy & the RCX
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| No, you all missed the point. Jack was talking about the idea of LEGO(r) providing an external NiCad battery pack solution to certain perceived problem (the difficulty of taking a robot apart in order to change the batteries in an RCX, Scout, etc.). (...) (25 years ago, 19-Nov-99, to lugnet.robotics)
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Message is in Reply To:
| | Re: Pure Energy & the RCX
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| It's strange to see you describe the "how to find the bad cell" problem with reference to Alkaline cells, then go right on and suggest the use of Ni-Cad battery packs! Ni-Cad battery packs have the same problem that any other type of serial (...) (25 years ago, 18-Nov-99, to lugnet.robotics)
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