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Battery Power Question — Parallax Forums

Battery Power Question

BadgerBadger Posts: 184
edited 2009-10-21 20:12 in General Discussion
Hello

I have nicad batter here that is a 6 volt and says 1000 mah .. what does the 1000 mah translate into amps. and can i run a oem bs2 demo board from it


Badger

Comments

  • sylvie369sylvie369 Posts: 1,622
    edited 2009-10-14 16:51
    You cannot convert mah into amps. They are measures of two related but different things. Milliamp hours is a measure of the total capacity of the battery. It's similar to knowing how many gallons of gas your gas tank holds. Amps is more like a measure of how fast your car can go.

    In the documentation for the OEM board you will see that you can either supply 5 volts to the Vdd pin or 6-24 volts to the Vin pin. A 6v battery should work just fine. 1000 mah means that it will work for a long time before you have to recharge it. A standard 9V battery is only about 100-150 mah, which means it would run out more quickly than the battery you're talking about here.

    You may have to pay attention to the total current drain of the BS2 and the devices you have attached to it, but if you've only got one or two things and they're not motors, you should be fine.
  • BadgerBadger Posts: 184
    edited 2009-10-14 17:02
    Sylvie369

    thanks again for the dual answer you gave me. I just did not want to blow up my bs2 oem. I have 2 boe boards and one cpu . the cpu has went bad so i only have the bs2 oem and a home work board. that works ok. I also have a hydra that i dont use and another propeller board but i dont have a very good working knowledge of spin .. so if you know any body that would wish to do some trading please let me know.


    Badger
  • sylvie369sylvie369 Posts: 1,622
    edited 2009-10-14 21:29
    Download the Propeller manual and work your way through chapter 3. You'll be spinning like mad in no time.

    The Propeller is a bit intimidating at first, but once you spend a little time with it you'll find that you can do amazing things with it much more easily than you could with a Stamp and PBasic.
  • WBA ConsultingWBA Consulting Posts: 2,935
    edited 2009-10-14 23:16
    I use a 9.6 volt 600mAh radio control car pack from the WalMart clearance shelf ($4 for the pack and charger!) that's I've modified with a 2.1mm DC plug. It works great with my Propeller Demo Board. I am careful when it's fully charged, because the pack voltage can be ~9.8 volts. While in use with a small current draw, it drops down to 9.2 volts for an average usage time of 12 hours depending on what I am doing with the demo board.

    Regarding learning the propeller:
    I am a propeller newbie (started in June) and it has been a lot easier to learn than I originally thought. Certain things are so much easier than PBASIC that it is sickening. If you have a project in mind that needs the use of objects already available, you can create programs in no time. Here's a thread on my learning experience with figuring out SD card usage. All-in-all it was about 3 hours worth of playing, learning, coding, tweaking, etc. With the my BS2P40/VMusic USB drive datalogger project, it took me about 16 hours total just to get it all to work, and it was still messy (code and hardware).

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    Andrew Williams
    WBA Consulting
    WBA-TH1M Sensirion SHT11 Module
    Special Olympics Polar Bear Plunge, Mar 20, 2010
  • Carl HayesCarl Hayes Posts: 841
    edited 2009-10-16 00:50
    Just in case no one actually answered your question:

    (1) 1000 mah is 1000 milli-ampere-hours, and is equal to 1 ah, one ampere-hour. That means it can (theoretically) supply 1 ampere of current for an hour before going dead. But actually you'd be lucky to go 30 minutes at 1 ampere before needing to recharge. Figure 30 minutes at 1 ampere, or an hour at 1/2 ampere, or two hours at 1/4 ampere, and so forth.

    (2) While the battery lasts you can run your BS2 card from it, no problem.

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    · -- Carl, nn5i@arrl.net
  • tronsnavytronsnavy Posts: 70
    edited 2009-10-20 16:22
    Andrew Williams,
    I also purchased one of those 9.6 Volt rechargeable battery packs (from the clearance shelf at Wal-Mart).· I mounted the battery on my bot.· I knew that feeding a 5 volt regulator with 9.6 Volts would make the regulator hot.· In fact, I can only get about 60 seconds of use before I have to shut the bot down (the regulator on the protoboard is very hot after 60 seconds and I don't feel safe running it longer).· I am contemplating a small 7.5 volt switching regulator (to drive the 5 volt regulator), or just buying a 7.2 volt rechargeable battery.· Now, I understand that I am probably drawing more current than you (servos, sensors, ect). I am just curious... how hot does your regulator get?· How long do you run before shutting down (when fully charged)?· Did you purchase a switching regulator?· I will probably just buy a 7.2 volt battery (and charger).· Thanks and have a good one.
    Bob



  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2009-10-21 11:38
    One can use a series of rectifier diodes to drop the 9.6 volts down to a lower voltage. Each diode is a 0.7 voltage drop. About 4 in series should knock off 2.4-2.8volts and dump heat as well. Use 3 amp or higher rating (varies according to your maximum load).

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    Ain't gadetry a wonderful thing?

    aka G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
  • W9GFOW9GFO Posts: 4,010
    edited 2009-10-21 16:39
    My preference is to use a 5 cell, 2,000 mah+, sub C pack, it is a 7.2V RC car pack with one cell removed. The servos are happier and so is the regulator.

    Regarding the mah rating, to get the full mah out of a battery you need to draw it at 1/10C or 1/20C (or whatever rate they used to "rate" the capacity) and of course the cells need to be in good condition. I am happy when I get 80% of the rated capacity out of a pack when discharged at 1C but those cells are designed with high discharge rates in mind.

    Rich H

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    The Simple Servo Tester, a kit from Gadget Gangster.
  • tronsnavytronsnavy Posts: 70
    edited 2009-10-21 18:42
    W9GFO,
    It is·a real coincidence·that you would suggest the 7.2 volt, 2000 mah battery.· I just picked one up last night (and charger) at radio shack.· Yea, I know, I probably got ripped-off, but I don't mind paying a little more for something that I can have now.· Anyway, did you remove one of the cells yourself, or did you buy it with just 5 cells?· With only 5 cells, your total voltage is 6 volts; right? Also, do still charge for 5 hours? Thanks.
    Bob



  • W9GFOW9GFO Posts: 4,010
    edited 2009-10-21 20:12
    Yes, I remove a cell myself. I have a variety of charges that I use. Most of them will automatically detect the number of cells and charge accordingly. This is a popular charger, I have one of the older models.

    gpmm3153.jpg

    Rich H

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    The Simple Servo Tester, a kit from Gadget Gangster.
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