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Re: PF train motor
by Dave Sterling
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In lugnet.trains, Eric Albrecht wrote:
> In lugnet.trains, Dave Sterling wrote:
>>> Paul
>>
>> I just noticed the new PF Lithium Polymer Battery Box output is 7.4V. Am I
>> missing something here? Did they drop it from 9V since most people only run
>> their train controllers at the 4th or 5th 'hash mark' equating to about 7.4V
>> maximum? Is this going to pose an issue with longer/heavier trains?
>>
>> Just thinking...
>
>
> They made it 7.4V because all lithium polymer battery cells are 3.6 - 3.8V.
> Since this is a pack with 2 cells in series, you get 7.4V. A 3 cell pack is
> typically 11.2V. As you can see, keeping the old 9V system was not really an
> option if using Lithium power. LEGO could have used Nickel Metal Hydride
> (NiMH), but the batteries would have weighed a lot more and had a lot less
> capacity. 1150 mAh is pretty substantial when you consider that a car battery
> may only be 20x this.
>
> Regarding the motors, I would assume that the new motors were designed to have
> adequate power at 7.4V. There's no reason they couldn't have the same power at
> 7.4V as the old motors did at 9V, they would simply draw more current.
>
> Eric Albrecht
Eric:
Thanks for the awesome explanation! I learned new stuff today...does that mean
I can go home now? :-) I'm excited to see how the new motor and battery box
pull. I think the new PF trains could add a lot of functionality to existing 9V
layouts. I'm planning to incorporate PF into my layout for BW for sure.
Thanks again for the electrical information. I'm an electrical doofus. ;-)
Best Regards,
Dave
ToT-LUG
> In lugnet.trains, Dave Sterling wrote:
>>> Paul
>>
>> I just noticed the new PF Lithium Polymer Battery Box output is 7.4V. Am I
>> missing something here? Did they drop it from 9V since most people only run
>> their train controllers at the 4th or 5th 'hash mark' equating to about 7.4V
>> maximum? Is this going to pose an issue with longer/heavier trains?
>>
>> Just thinking...
>
>
> They made it 7.4V because all lithium polymer battery cells are 3.6 - 3.8V.
> Since this is a pack with 2 cells in series, you get 7.4V. A 3 cell pack is
> typically 11.2V. As you can see, keeping the old 9V system was not really an
> option if using Lithium power. LEGO could have used Nickel Metal Hydride
> (NiMH), but the batteries would have weighed a lot more and had a lot less
> capacity. 1150 mAh is pretty substantial when you consider that a car battery
> may only be 20x this.
>
> Regarding the motors, I would assume that the new motors were designed to have
> adequate power at 7.4V. There's no reason they couldn't have the same power at
> 7.4V as the old motors did at 9V, they would simply draw more current.
>
> Eric Albrecht
Eric:
Thanks for the awesome explanation! I learned new stuff today...does that mean
I can go home now? :-) I'm excited to see how the new motor and battery box
pull. I think the new PF trains could add a lot of functionality to existing 9V
layouts. I'm planning to incorporate PF into my layout for BW for sure.
Thanks again for the electrical information. I'm an electrical doofus. ;-)
Best Regards,
Dave
ToT-LUG
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