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| Posted: Mon Feb 16th, 2015 07:43 am |
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| Posted: Mon Feb 16th, 2015 10:56 am |
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pipopak
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I am not an electrician, but I know you can't create energy. A higher voltage (plus whatever current the module uses) means shorter battery charge life. But I am curious about the matter anyway. Jose.
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| Posted: Mon Feb 16th, 2015 02:37 pm |
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3rd Post |
Herb Kephart
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Correct Jose.
Watts, the correct measure of power available or consumed, are calculated as volts X amps.
The converter cannot be 100% efficient.
So the total available power has to be less.
But-- the converter is smaller than an additional cell if you want/need more voltage, A single, large as possible cell (misnamed battery, as a battery is a group of cells) eliminates the need for balance charging, if that is thought necessary
The linked converter has a led readout, the purpose for which isn't mentioned--I have to suspect that it reads output volts, and if so is something not needed for our purposes. In our needs, the voltage can be set by what performance is desired. I have seen on Fleabay converters that do not have the readout, which has to mean a smaller overall size, and less cost.
Herb
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| Posted: Mon Feb 16th, 2015 06:25 pm |
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| Posted: Mon Feb 16th, 2015 09:34 pm |
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Tramcar Trev
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Dave H wrote:
I have just bought some of these......
http://www.technobotsonline.com/pololu-step-up-voltage-regulator-1.5a-max-i-p-12v-output.html
.....to play with in OO gauge.
I'll let you know how they go! See how small they are 0.32" x 0.515"
They look the bees knees exacary what I wanted 12V from 6.6V I'll have to do some practical measurement and see If I can get away with 1.4A draw...
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I perceive with regret that I am
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in predestinate groves
I'm not a Bus, I'm a tram
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| Posted: Mon Feb 16th, 2015 09:44 pm |
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6th Post |
| Posted: Tue Feb 17th, 2015 06:10 am |
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7th Post |
fallen
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Herb is right, there is no free lunch. If you double the output voltage you at least double the input current, so you need fewer cells but they each need bigger capacity. You do have more flexibility on the voltage supplied though.
However there is another advantage. If you have a big single cell it is easy to charge. If you have two smaller cells you need to provide for balance charging of the two cells which is slightly more complicated. This can make the installation easier.
FrankLast edited on Tue Feb 17th, 2015 06:12 am by fallen
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| Posted: Tue Feb 17th, 2015 02:09 pm |
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8th Post |
bobquincy
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I have been using the Pololu converters to step up 2xAA to 3.7 V. One of the smaller ones (1.2 A input) got overloaded with a motor pulling about 700 mA and would shut down until I closed the throttle for a short time. No damage done though.
Most of these are rated for input current which is the output current times the ratio of output voltage/input voltage divided by the efficiency: in my case 700 mA * (3.7/2.4) /0.8 = 1.35 A input current. I switched to one of the 2A converters and it can handle the 700 mA output.
One of the benefits is that the output voltage stays constant until the battery is really exhausted.
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Monorail modelers have a one track mind.
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| Posted: Tue Feb 17th, 2015 05:23 pm |
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9th Post |
Herb Kephart
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The 80 - 90% efficiency means that 10 - 20% of the supplied current is dissipated as heat. Some of the ads you will notice offer ''heat sinks''. These keep the chip cooler and in marginal cases may eliminate thermal shut down.
You don't need to buy their aluminum finned extrusion, as it takes up considerable space. Any piece of thin aluminum will help, and of course the larger the better. A coat of flat black helps to shed the heat also. Be sure to put some heat conducting paste between the chip and the aluminum, what ever size you use, Beer and soda cans are a good source, and can be cut with scissors once the can is disassembled to a size dictated by the space available. Sand both sides of the metal (the inside has a clear coating) before painting with the flat black, and leave the section that will contact the chip bare, excepy for the heat compound.
http://www.ebay.com.au/itm/Gold-CPU-processor-heat-conducting-paste-gt-3-8WmK-PC-Thermal-Heat-sink-cooling-/281307590991?pt=LH_DefaultDomain_15&hash=item417f3d314f
Various size quantities, this is the smallest (and cheapest) at the present time on Ebay
Strictly speaking this isn't necessary, but a cool chip is a happy chip.
Herb
____________________
Fix it again, Mr Gates--it still works!"
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| Posted: Tue Feb 17th, 2015 07:10 pm |
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10th Post |
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