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Subject: 
Re: Rechargeable Batteries
Newsgroups: 
lugnet.robotics
Date: 
Mon, 6 Aug 2001 21:37:54 GMT
Original-From: 
Pink Tail <PINKMICE@BORG.COMspamless>
Viewed: 
556 times
  
I have been interested in what people have to say about
using 1.2v cells instead of 1.5v.

I don't think the RCX minds, but what is a problem to my mind
is that after the RCX motor drivers drop about a volt from the
already low 7.2v, you end up running the motors at ~6v instead
of their 9v design voltage. I like to get every last bit of umph from
my motors, so after you see how they can perform directly from
a 9v battery pack, it makes you need all the volts you can get.
That's why I went to the trouble to build an external MOSFET
motor driver amplifier thing. Of course if your not trying to build
big bots using non-Lego treads (deathly hush comes over the
crowd ;) it may not be quite so much of an issue.

John Barnes

In lugnet.robotics.rcx, Roger Glassey writes:
Jerry:
What is the problem with the NiMH batteries? the low voltage?  Or extra • $$ ?
Roger

In lugnet.robotics.rcx, Jerry Kalpin writes:

Frank, I would *not* use Nicads or NiMH rechargeables.  Their • full-charge
voltage is about 1.25V while alkaline batteries are about 1.55.  I have
Ray-O-Vac Rechargeable Alkaline batteries.  They last several hours of
operating time between charges, which for me is a few weeks (adequate
performance).  I have two sets of six and a charger, an investment of • about
CAN$60.

Roger, I believe the low voltage is more important.  A side issue is the
battery indicator that you access through NQC (or Robolab) set up in a • scale
of 0-9 volts.  Fully charged alkalines are 9+ and discharged ones are 6
volts.  With NiMH full charge would be 7.2 and discharged would be • somewhere
around 6.  The discharge curve is fairly flat.  You don't get much warning
when they are about to die.

I bet NiMH batteries would function OK in the RCX.  If you already have • NiMH
batteries, try them out and see.  I just believe rechargeable alkalines,
such as Ray-O-Vac Renewals are a better choice...!

Jerry




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