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Forum Index : Other Stuff : PMDC generator choice? 12VDC vs. 130VDC
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stevet47 Newbie  Joined: 12/09/2008 Location: United StatesPosts: 7 |
I have built a wind turbine before using a 90VDC tredmill motor, but now I need to build 2 electricity-generating bikes. For low RPM applications like wind, a higher voltage motor is desired, but is this still the case for a high RPM application like a bicycle? I am using 2 bikes to charge a 12VDC deep cycle marine battery which will be hooked to an inverter powering a LCD projector and speakers. Also an iPod will be charged off the battery. These devices must work continuously (no peddle for a hour to power it for 20minute kind of deals). Should I be looking at 12V PMDC motors, or a higher voltage motor such as http://www.surpluscenter.com/item.asp? UID=2008091019412299&item=10-1783-A&catname= My concern is that each bike will likely be producing more than 12V, and I am unsure as to whether putting say 30V into a 12V battery will harm it. I heard one person say that the battery will self-regulate the incoming power to ~12V and just up the amps, but that sounds incorrect to me. Also, what is a safe amperage rating to charge with? As you can tell, I need a little help! THANKS! |
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CraziestOzzy Senior Member  Joined: 11/07/2008 Location: AustraliaPosts: 135 |
G'day. Without getting a headache (I have had only one coffee and need two to get me going for the day)....I found some links you might want to look into: 1) General overview of deep-cycle batteries 2) Information rich site on pedal power-check out the internal links too I think you will need to quantify the total output of your powered devices (such as bar fridge, inverter, the television etc) and compare your consumption to the output voltage/amperage and capacity of your one battery...having done that, working out the ideal generator should be a piece of cake. Better to leave the more complicated stuff to those fellas who have had their two cups of coffee, their answers may be better and more correct than mine! ...but do check that link out on pedal power here from their FAQ's and check their other FAQ's out further on down the page that should answer your questions about using a battery as a "buffer" to pedal power. http://cr4.globalspec.com/member?u=25757 http://www.instructables.com/member/OzzyRoo/ |
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| stevet47 Newbie Joined: 12/09/2008 Location: United StatesPosts: 7 |
The last link you posted says this... "...Perhaps a better way to look at this is to look at a comparison plot of how fast you would have to pedal for each PM Motor to maintain a constant 12 Volt output while varying the Wattage Load from 0 to 150. The graph below shows this simulated data. By looking at this graph, you can see that at little or no Wattage load, you will have to pedal much faster on the 12 Volt Rated PM Motor than on the 180 Volt PM rated Motor. But at ~ 30 Watts, the tables turn and both bicycle generator PM motors will have about the same output at 1,700 RPMs. Note that at loads higher than 30 Watts you will need to pedal faster with the 180 Volt PM motor. So again, the conclusion is the PM Motor rated at 180 Volts DC is better for small loads, like a 5 Inch television that kids can power with a smaller bike using a voltage regulator / charge controller. But for Wattage Loads in the higher range, the PM motor rated for 12 Volts is better." I understand that, but would charging a 12VDC marine battery be considered a small load or a high load? And is the load always the same, or does the load increase as more power is drawn from the battery? |
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| CraziestOzzy Senior Member Joined: 11/07/2008 Location: AustraliaPosts: 135 |
"would charging a 12VDC marine battery be considered a small load or a high load?"...it is my uneducated guess that the value of a high or low load is relative, your main constraint (I think) would be the specification values of charging any given battery as set by the manufacturer. This would mean you would have an ideal optimum "trickle" charge and of course the other end of the spectrum with an optimum "fast charge" of higher voltage and amperage relative to the trickle charge. 1) If your optimum charge input into the battery is relatively lower than than your consumed output from the battery using devices such as television etc, it would obviously mean you would be draining the battery. But you mention that you wish to use the batteries to power your units while not pedaling away for periods of around 20 minutes, so this is a non-issue. 2) Battery power consumption would of course be influenced (reduced?) with the use of an inverter...but the total wattage consumption of your output devices would need to be determined to see if you have positive gain while charging the battery, if you decide to use the battery entirely as a source of power to your devices. 3) You would need (I think) to construct a control unit that regulates the power supply to your battery output from your generator for the purpose of charging and then rig up another control to regulate your output direct to your devices, if you decide to have dual output...and possibly have a useful dump for excess power generated during pedaling. "is the load always the same, or does the load increase as more power is drawn from the battery?"...assuming you have only a single output for power directly from your batteries, your charge load would increase to compensate for the loss caused by power consumption of your devices...I would be using a voltage regulator to limit the input charge to your battery from the generator to manufacturer's specifications...as the idea of pumping 30+ volts at a currently unknown amperage into a 12 volt battery is asking for some interesting and dangerous side effects. You mention using two bikes...I think two 12 volt generators in parallel would be ideal and would not require anything larger such as the generator you question of purchasing, assuming you have two 12 volt generators that are capable of producing the correct amperage draw required by your consumption devices (LCD etc). I believe your choice of generator would ultimately be determined by how fast you wish to pedal. http://cr4.globalspec.com/member?u=25757 http://www.instructables.com/member/OzzyRoo/ |
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