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Boe-Bot Robot with new Ultrafire Rechargeable 3.7V 900mAh 14500 Lithium Battery — Parallax Forums

Boe-Bot Robot with new Ultrafire Rechargeable 3.7V 900mAh 14500 Lithium Battery

bamccallaubamccallau Posts: 1
edited 2008-10-15 14:19 in Robotics
Boe-Bot Robot with new Ultrafire Rechargeable 3.7V 900mAh 14500 Lithium Battery.

Ultrafire 3.7V 900mAh 14500 Lithium Battery Rechargeable·is same AA battery cell size.

Boe-Bot Robot AA Battery Holder· is up to 6 Volt for four Standard battery 1.5V is waste money.

4x 14500 Lithium Battery and total 14.8Volt and down to 5V in Board of Education

Notice: Ultrafire 3.7V 900mAh 14500 Lithium Battery Rechargeable is required purchase Ultrafire 3.7V chargeable unit at Hong Kong eBay for Ultrafire Flashlight Torch selling.

Anyone interestidea.gif
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Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2008-10-15 04:17
    Actually, this is not a good choice for power. At the very least, you would need a switching regulator to take the 14.8V and drop it to 6V for the servos and the BOE's 5V regulator. If you just use the BOE's regulator, all the extra voltage will be dissipated as heat (a lot of heat) and you'll need to run the servos off the BOE's regulator rather than directly off the battery supply. If you want to add something extra like a PING))) and the servo bracket, you'll be getting close to the 1A current limit of the regulator and exceeding it under any kind of heavy mechanical load. In addition, you need a Lithium battery recharger for the 4 series cells.

    I think you're better off with a 5 cell NiMH battery pack and 2300mAh or 2500mAh AA cells which are readily available. 4 of these can fit in the normal battery holder and you can add a single cell holder from RadioShack or Parallax which is glued to the top of the aluminum platform over the skid ball. Although fast chargers made for NiMH batteries are best, you can charge the 5 cell pack just using a current limiting resistor to provide a maximum charge current of 1/10 capacity (or about 230mA) and charging for 12 to 16 hours.
  • SRLMSRLM Posts: 5,045
    edited 2008-10-15 05:35
    Also, Lithium batteries can be explosively damaged by dropping too low in voltage...
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2008-10-15 05:36
    Parallax also carries the BOE-Boost, which simply snaps into the undercarriage battery holder to add a fifth AA cell in series with the other four.

    -Phil
  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2008-10-15 14:19
    SRLM said...
    Also, Lithium batteries can be explosively damaged by dropping too low in voltage...

    That is probably why they are called "Ultra Fire" and a good reason to avoid them.

    There are some advantages to the Lithium packs but when you factor in how dangerous they can be (anyone remember the laptop recalls or exploding cell phones) it just doesn't seem to be a good choice for Hobby projects. As I recall safely charging them is a bit tricky as well.

    Robert
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