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AA Rechargeable Nimh Batteries — Parallax Forums

AA Rechargeable Nimh Batteries

jbodjbod Posts: 46
edited 2008-02-22 23:09 in Robotics
Is it ok to run these in the Boe-Bot?

Comments

  • FranklinFranklin Posts: 4,747
    edited 2008-02-19 00:21
    Yes but you should use 5 of them.

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    - Stephen
  • UghaUgha Posts: 543
    edited 2008-02-19 01:02
    Parallax sells a nice item for this called the Boe-Boost Module. It basicly clips into the existing BoeBot battery
    pack and lets you put in a 5th AA-sized battery.

    The item number is 30078
    You can find it by doing a search on the Parallax site for the above number.

    In addition... If you've got a single battery holder already, you can just put them in series with the main holder... that would
    most likely require soldering though.
  • jbodjbod Posts: 46
    edited 2008-02-19 01:06
    Can you run 6? Or is the 7.2v to much for the servos on the Boe-Bot?
  • UghaUgha Posts: 543
    edited 2008-02-19 01:12
    If you have the servo jumper on the BOE set to VDD mode instead of VIN... the servos should be fine.
  • allanlane5allanlane5 Posts: 3,815
    edited 2008-02-19 02:29
    The issue is, NiMh are 1.2 volts per battery. Alkalines are 1.5 volts.

    Thus, 4 alkalines give you 6 volts -- 7.5 if you use 5 of them.

    4 NiMh give you 4.8 volts -- which is too close to the brown-out voltage value. 5 gives you 6 volts.

    7.5 volts isn't going to help you much, it'll just increase the amount of heat disappated in the voltage regulator.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2008-02-22 07:43
    The disappointing thing about NiMh and NiCad batteries is that the battery manufacturers seem to want make them last less than 50% as long as the Alkaline. No matter what you do, you will have to change batteries more often.

    I find it very interesting that you can NEVER find an Alkaline battery with an mAmp/Hour rating attached.

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  • dandreaedandreae Posts: 1,375
    edited 2008-02-22 15:04
    Here is an informative link regarding batteries and mah:· www.starbatteries.com/batteryfaqs.html.· Alkaline batteries typically have a rating of 2500 mah rating.· We have found that the Kirkland batteries last just as long as the Duracell batteries if not longer and are cheaper.·



    Dave

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    Dave Andreae

    Parallax Tech Support·
  • WhitWhit Posts: 4,191
    edited 2008-02-22 23:09
    jbod,

    Bean (Hitt Consulting) has some 5 AA holders for sale (which are very hard to find). They are also a good solution.

    See here http://www.hittconsulting.com/miscforsale.html·- they fit perfectly under the BoeBot.

    The Boe-Boost is nice too. I have both so I could check it out for myself.·smilewinkgrin.gif

    Five regular Alkaline batteries are supposed to discharge more fully than four. Five also lets you use the rechargeables too!

    Have fun!

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

    Post Edited (Whit) : 2/22/2008 11:22:54 PM GMT
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