Subject:
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Re: New Press Release about Power Function Trains
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Newsgroups:
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lugnet.trains
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Date:
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Wed, 26 Mar 2008 18:26:21 GMT
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Viewed:
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9836 times
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In lugnet.trains, Eric Kingsley wrote:
> In lugnet.trains, Steven Barile wrote:
> > BTW the batt box is 4 bricks high, not studs.
> I found the real news in this release was the battery box. What I am waiting to
> hear is some real tests in terms of battery life before a charge is needed and
> how long it takes to charge. (How many batteries are we going to need to do a
> show without having a long period waiting on batteries).
>
> Ideally I want a battery that can pull a standard 6 wide train with 10 average
> cars for at least an hour and a recharge time of less than an hour**. If we get
> that minimum standard or more I will make the switch. If not I may be stuck
> nursing my old 9v stuff for the foreseeable future.
Here are some rough calculations to estimate the longevity of the announced
battery.
Li-poly technology offers 300Wh per litre[1]. The battery box will be 4x8x5 lu
(4 bricks high=5 studs) = 32*64*40mm3 Assuming 2mm thick walls, that leaves
28*60*36 = 60ml for the cells so we get about 18Wh to use. Capacity would be
23Wh with 0.5mm thick walls. Of course, leave room for the power jack and any
recharge/protection circuitry that may be inside the housing as well.
I found no info on the power draw of the RC train motor but the 9V motor draws
up to 950mA[2] (stall current, 9W) when pulling a long, heavy load. Shorter,
lighter trains such as the retail RC trains would probably draw closer to 3W.
Given the above assumptions, this battery box should run a typical retail sized
train about 6 hours non-stop and an AFOL train about 2 hours (the kind where
having a second motor helps but is not required.) I am likely off on both power
available and required, have neglected efficiency and maximum drain level but
this should still last at least one hour under worst case conditions.
Recharge time could be about an hour if an external charger is used. All bets
are off if the recharge circuitry is embedded in the battery box. For reference,
the NXT Lithium Ion battery has embedded recharge circuitry and takes about 4
hours to recharge although this is slightly different technology. The standard
LEGO 9V transformer supplies 7W@12V so we are probably looking at a 4 hour
recharge time here as well.
Doug
[1]http://en.wikipedia.org/wiki/Lithium-polymer
[2]http://www.philohome.com/motors/motorcomp.htm
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Message has 1 Reply:
 | | Re: New Press Release about Power Function Trains
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| (...) past, would it be possible to have a 4 stud wide footprint on the bottom and the have the rest of the side recessed similar to the headlight brick configuration.This will give the ability to build 6 wide hood units by providing a 4 x 8 plate (...) (16 years ago, 28-Mar-08, to lugnet.trains)
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Message is in Reply To:
| | Re: New Press Release about Power Function Trains
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| (...) Thats funny, I read it as 4 bricks. I didn't even notice the 4 studs until you pointed it out. I have to say I am intrigued. The battery box seems to be a decent compromise. I would have prefered it either a couple of studs narrower or a (...) (16 years ago, 26-Mar-08, to lugnet.trains)
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