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October 2010

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Subject:
From:
Sonya Shaver <[log in to unmask]>
Reply To:
Sonya Shaver <[log in to unmask]>
Date:
Wed, 20 Oct 2010 23:55:47 -0400
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When you get a new rechargeable lithium battery pack, does anyone know how
long we should charge it the first time?

Thanks,
Sonya


On Wed, Oct 20, 2010 at 10:37 PM, Andy Traiger <[log in to unmask]> wrote:

>  Hey Jude,
>
>
>
> Be aware that alkaline batteries, which are the most common type of AA
> battery, may not be the best to use for your robot.  The reason is that the
> six alkaline batteries when fully charged will have a voltage of 9.6 Volts.
>  As youíre using the robot and the batteries discharge, the voltage will
> decrease fairly rapidly; even when the battery has a fair amount of capacity
> left the voltage can droop significantly.  The more they are discharged the
> lower the voltage gets.  Lithium batteries tend to hold their voltage more
> stable as the batteries discharge.  The Lithium batteries that are made for
> the NXT brick will be 8.4 volts when fully charged.  Comparing performance
> over the same amount of time, the voltage of the Lithium battery will stay
> stable while the alkaline voltage is drooping substantially.
>
>
>
> What does this mean to your robot performance?   If youíre using alkaline
> batteries, the motors will move faster than the Lithium when both are fully
> charged.  So, alkaline batteries can give your robot more power / speed when
> they are fresh.  However as the alkaline batteries discharge a bit the motor
> performance will slow down.  This will possibly lead to inconsistency in
> running your missions.  If the kids refined their missions when the voltage
> was low, the robot may perform completely differently when a new set of
> batteries is inserted.
>
>
>
> My team uses the Lego lithium battery pack.  The kids on my team
> periodically check the battery voltage as they are developing missions,
> especially if they start seeing their missions failing.   Use the NXT window
> to view this while the brick is connected to the computer if using NXT_G.
> Our team swaps the Lithium battery with a freshly charged one if the voltage
> drops to about 8.1 Volts.
>
>
>
> All that being said, besides Alkaline there are other types of AA batteries
> being sold (including even lithium batteries which are pretty expensive).
>  Each battery type will have different discharge characteristics.
>
>
>
> Andy
>
>
>  ------------------------------
>
> *From:* First Lego League in Virginia and DC [mailto:
> [log in to unmask]] *On Behalf Of *Jude Arulpragasam
> *Sent:* Wednesday, October 20, 2010 9:48 AM
>
> *To:* [log in to unmask]
> *Subject:* Re: [VADCFLL-L] NXT batery warning
>
>
>
> I would like to know if there is any advantage using re-chargeable battery
> pack over individual AA batteries'?
> I just bought new re-chargeable DC battery pack (NXT<http://www.legoeducation.us/store/detail.aspx?CategoryID=178&by=9&ID=1971&c=1&t=0&l=0>Rechargeable DC Battery (W979693)<http://www.legoeducation.us/store/detail.aspx?CategoryID=178&by=9&ID=1971&c=1&t=0&l=0> from
> Lego website.
>
> Please give me some pros and cons  on this
>
> Thanks
>
> Jude
>
>  ------------------------------
>
> Date: Tue, 19 Oct 2010 20:36:44 -0700
> From: [log in to unmask]
> Subject: Re: [VADCFLL-L] NXT batery warning
> To: [log in to unmask]
>
> Our team started using AA batteries instead of the rechargeable battery
> pack. But when they had to change the batteries, they had dismantle the
> robot to get to the battery compartment. I am worried that the kids will not
> put back the robot perfectly, if they have to do this just before the
> tournament to have fresh batteries in. Is that how it is normally done?
>
> thanks
> Gaja
>
>
>  ------------------------------
>
> *From:* Jerry Lorengo <[log in to unmask]>
> *To:* [log in to unmask]
> *Sent:* Fri, October 8, 2010 3:28:54 PM
> *Subject:* Re: [VADCFLL-L] NXT batery warning
>
> Agreed - always use fresh AAs.
>
>
>
> The recharchable batter has a goofy memory and the voltage drop will make
> reproducibility for missions almost impossible.
>
> Sent from my iPhone
>
>
> On Oct 8, 2010, at 12:48 PM, Lloyd O'Hara <[log in to unmask]> wrote:
>
>  We only use batteries and always make sure we have plenty on hand.
>
>
>
> Also, I'm sure why you would take 2 sets of four AA batteries, the nxt
> takes six AA..
>
>
>
> Lloyd
>
>  ----- Original Message -----
>
> *From:* Viquar Shaikh
>
> *To:* [log in to unmask]
>
> *Sent:* Friday, October 08, 2010 10:50 AM
>
> *Subject:* Re: [VADCFLL-L] NXT batery warning
>
>
>
> To add to this --- no matter what - we always carry 2 sets of four AA
> batteries - one is a new packed set. This is a good backup for these
> 'just-in-case' scenarios.
>
>
>
> Thanks
>
> Viquar
>
> On Fri, Oct 8, 2010 at 10:32 AM, Brandy bergenstock <[log in to unmask]>
> wrote:
>
> This came across the Ga FLL yahoo group adn I thought it was important for
> everyone to realize:
>
> The other day my team had taken one of their NXT bricks with them to a
> meeting.  When we got home, the battery was completely discharged. After
> recharging it, my  daughter discovered that the "Sleep" setting was at 60
> minutes. The brick had  accidentally turned on during transport and since
> the sleep setting was so long,  it ran the battery down. We discovered that
> the 60 minute setting is the default for both the 1.26 and 1.31 firmware
> update. That is WAY too long!
>
> If you have updated your firmware, you should check the sleep setting and
> change  it is a more reasonable time (perhaps in the 2-5 minute time frame).
> This way you won't accidentally run down your battery. I'd hate for someone
> to discover their battery was dead when they arrived at a competition.
>
> To access the sleep setting on the NXT brick, go to:
>
> Settings
> Sleep
> and then change the time with the arrow buttons
>
>
>  ------------------------------
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