Age old question -- One or Two batteries.

Comments

• dandreae Posts: 1,375

  2005-06-24 21:41 edited 2005-06-24 21:41

  On the Hexcrawler we used a 9v transistor battery for the board and a Panasonic 7.2v 3000 ultra metal hydried NI-MH battery pack.· It runs great with this power set up.
  
  
  
  Dave
  
  
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  Post Edited (Dave Andreae (Parallax)) : 6/24/2005 10:13:49 PM GMT
• Dobermann (Black Dog Systems, LLC) Posts: 71

  2005-06-24 22:07 edited 2005-06-24 22:07

  Dave,
  
  Thanks for your reply, I was kind of leaning in the two battery direction. I'm trying to be careful with weight/load considerations. My last robotic project was grossly overweight, so heavy in fact, that it could barely move a few feet without problems (I won't discuss my first robotics project, it was a total FAILURE). It also placed a really high current demand on the single battery arrangement. So much so that it was causing the BS-II to brown-out and reset. I figured that this time around I'd be less frugal and allow for the extra volts/mAh. Thanks again for your input!
  
  Respectfully,
  Michael G. Jessat
• KenM Posts: 657

  2005-06-25 03:43 edited 2005-06-25 03:43

  Obvious to some, but not all.....
  
  If you run two batteries and you are NOT using opto isolators on all I/O pins, you must tie together the grounds of the two batteries.
  
  Ken
• Tricky Nekro Posts: 218

  2005-06-25 09:16 edited 2005-06-25 09:16

  Yes, but this is optional, right
  
  How many motors (servos) do you use?
  
  
  
  Provas
  
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• Dobermann (Black Dog Systems, LLC) Posts: 71

  2005-06-25 13:31 edited 2005-06-25 13:31

  Ken and Provas,
  
  Thank you for your replies. I was aware of taking all grounds to a common point. But, its a good point to bring up, as many people just starting out don't realise this. I have read various postings that seem to indicate this fact. As far as servos are concerned, I am using two HITEC HS-805BB's for the main drive. These have been modified for full rotation with the electronics left intact. I am planning on running them on at least 7.2VDC with a 3000mAh NiMH battery pack. Hitec claims that these servos can take up to 8.4VDC, and will only become slightly warm to the touch. At 12VDC, the electronics become toast within minutes. I also am looking at a pan and tilt turret for my CMU camera. I am going to use two Hitec HS-425BB's (unmodified) for this. I'm planning on using the MINI SSC II to provide the servo's with the necessary pulses to drive them. That way the stamp would be free to do other things. I'm also looking to use at least two PING))) sensors, several IR distance detectors, CDS light detectors, and some form of edge detection sensors. Maybe a serial LCD display (Scott Edwards 2X16), since it could provide some debug information during testing, or possibly just use LED's to indicate what is happening. So, the current demands are going to be fairly high, that is why I am looking at using two instead of one battery. But, having said that, weight is a primary concern. I'm trying my hardest to keep it under 3 pounds, since my past projects have been grossly overweight. Was looking at maybe Li-Poly instead of NiMH, but they seem to have alot of potential for problems. From what I have read, Li-Poly can catch fire very easily if not closely monitored during the recharge cycle. Or if they are pushed too hard (high current demands) for any amount of time they can catch on fire. I certainly don't want another 'flaming' robotics project, yes, I've had one of those already. So, I'm still in the middle of the road with the battery issues.
  
  
  Thanks for your replies!
  
  Respectfully,
  Michael G. Jessat
  
  Post Edited (Dobermann (Black Dog Systems, LLC)) : 6/25/2005 1:36:03 PM GMT