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Subject: 
Re: ni-cads in parallel
Newsgroups: 
lugnet.robotics.handyboard
Date: 
Mon, 6 May 1996 22:38:30 GMT
Original-From: 
Fred G. Martin <[fredm@media.]saynotospam[mit.edu]>
Viewed: 
1636 times
  
Don't do this.  First off, you won't get more current, nicads already
can deliver gobs of current, enough to be dangerous.  You want more
amp-hours, not more instantaneous amperage.

Secondly you will have problems with cells charging each other.  I
don't know exactly how it will work out, but my bet is both packs end
up discharging the other.  Remember, even innocent-looking AA nicads
can deliver tens of amperes if there is not a load of some kind
preventing them.  If one pack is at a lightly lower voltage than the
other, current will flow, and lots of it.  (AA alkaline batteries
can't deliver nearly the current that AA nicads can.)

Use separate power supplies to run your servo and your HB.  The HB
will run on as little as 6.2v (got to overcome the 1.2v characteristic
drop of the 7805 regulator).  You could probably get away with 6v.

-Fred




Does anyone know anything about connecting Ni-Cad packs in parallel
to get more current?  I'm trying to connect two 6V packs in parallel for
driving my motors and sonar, and I also need to make a 4.8 tap to drive a
servo.  I'm not sure how Ni-Cads in parallel behave, since once might charge
the other, etc.  Also, I'm guessing that I'll have to make a 4.8 tap on
_both_ of the battery packs, and then connect the taps together as well, to
avoid having one of the 6V packs being discharged faster than the other.  Is
this sound reasoning?  I want to avoid blowing up my robot before I've had a
chance to mess with it!  :-)




Message has 1 Reply:
  Re: ni-cads in parallel
 
(...) Yes. My problem is that my motors draw somewhere around 2 amps average, and the AA pack I have is rated at 600mAh. This isn't much fun, I'm tempted to leave the thing plugged in instead of charging it every few minutes! It's really not tooo (...) (29 years ago, 7-May-96, to lugnet.robotics.handyboard)

Message is in Reply To:
  ni-cads in parallel
 
Does anyone know anything about connecting Ni-Cad packs in parallel to get more current? I'm trying to connect two 6V packs in parallel for driving my motors and sonar, and I also need to make a 4.8 tap to drive a servo. I'm not sure how Ni-Cads in (...) (29 years ago, 6-May-96, to lugnet.robotics.handyboard)

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