Subject:
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Re: rechargeable 9V battery packs for RCX/JCX and Legos motors
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 10 Sep 2001 13:52:54 GMT
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Viewed:
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816 times
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> > We're thinking of college labs where they will have 12 or 20 JCX systems
> > and where feeding them alkalines is just not practical or cost effective.
> > Charging 120 AA cells gets awkward too, so some sort of self-contained
> > rechargeable pack seems a good idea.
I would like to follow up on this. The school I volunteer at to teach
LEGO Robotics now has 4 RIS 1.5 and 4 RIS 2.0 and batteries are a real
problem. Disassembling kids robots to change batteries is a pain!
I have been using 1800MAh NiMh AA cells in digital cameras, GPS etc
with great success. BUT they are easy to physically swap the batteries.
Here's what I plan to to experiment with, and I would like any
suggestions or collaborative efforts from you LugNuts:
1. Install 6 AA NiMh cells in an RCX with no external power connector.
2. Connect a thin two-wire cable internally to the RCX + and - points
and route it securely to the outside.
3. Externally recharge the battery pack with a suitable charger.
Here are my current questions and concerns:
A. What is a 'suitable charger'? (6 cell chargers are unusual...)
- Easiest is a 1/10 C (Say 150Ma) constant current charger overnight.
How about cheap 12V wall wart with series resistor ??
- There are available fast chargers but they are more expensive. (See
http://www.mahaenergy.com/products/radios/amateur/chargers/mhc777.htm
for an example. Expensive, but maybe OK for a school/lab )
B. What is a suitable connector?? The problem is that BOTH the battery
connection and the charger connection are 'live' and can short out
against a metal object, so the typical "source is Female and load is
Male" doesn't work. Need some small, simple, cheap hermaphroditic
connector. I am leaning toward a simple .100 dual socket with one
inserted pin (result, one male, one female, no shorts).
**Sorry for all this sex discussion; I know we have kids here :-)
I'll do a little more research; I have the NiMh specs available..
Any suggestions and/or comments welcome!
Terry King ...In The Woods In Vermont
...associated :) with:
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