recharging of 7volt battery by small wind turbine

[justchill.jun]

hii,
i need to know as to what size of wind turbines will i require to recharge series of 8 7volt batteries in 4 to 5 hours if the average wind flow is about 40km p/hr. i want to place 2 small wind turbines to recharge these 8 batteries. plz inform me and also suggest me regarding it!!
cheers.

[deleted-71712]

Hi justchill.jun,

Here are some questions you should be asking about the batteries and windmill to help answer this question:

What is the capacity of your batteries? What is the maximum voltage that can be applied during charging? The capacity is probably listed in milli-amp-hours (mAh). For example, if the capacity of a battery is 100 mAh, then it can output 10 mA (rate of current flow) for 10 hours, 2 mA for 50 h, etc. These values are nominal and subject to restrictions for safety and other reasons -- for example, a battery might not be capable of discharging faster than a certain rate, or it might become dangerously hot if it does so. The same current flow is required to charge a battery from a fully discharged state, and there are also probably safety/performance restrictions on the charge rate, which may not be the same as discharge ratings.

What are the current and voltage output capabilities of the windmill? If you are thinking of purchasing a wind turbine, it should have an output voltage and some kind of current output rating. This might be a max value under ideal conditions, might be given as a function of load (resistance of the batteries), wind speed, etc. If you are planning to build your own windmill... well, let us know.

How are you planning to connect the batteries? If you connect them all in one series to one turbine, you will need at least 56 V to fully charge them -- this sounds like a high number for a source to me, but look at the wind turbine's ratings. You could also connect them in parallel if the turbine's output is 7-8 V (8 V applied for charging is *probably* safe, but you want to check the batteries' ratings). If the turbine outputs 15 V, you could put four series-sets of two in parallel. Etc.

From this you should be able to estimate the time required to charge your batteries, with the significant approximation/assumption that the wind will remain a constant 40 kph. These threads should be of interest:
https://www.sciencebuddies.org/science- ... =29&t=3972
https://www.sciencebuddies.org/science- ... =29&t=3995

Amanda

[deleted-71588]

Amanda gave you some starting advice; however, you really need to get a data sheet for the batteries you are interested in recharging to see what the manufacturer recommends.

The mAhr rating is usually an over simplification that is valid only for a limited usage range typical of the intended application. This means that it is a good comparison for different batteries used in the same intended application but that is about the extent of its usefulness.

The published discharge mAhr simplification typically does NOT apply to recharging as the chemical processes involved have different characteristics in most cases. The data sheet will typically show several curves for various operating points that will give you more accurate answers.

There are often exothermic (heat producing reactions) and the potential for gas production if operated outside of the manufacturer's recomendations that can permanently damage the batteries and potentially cause fires and explosions and chemical leaks particularly with the recharging process.

[justchill.jun]

hii,
i need to run a motor of 10,000 rpm continuesly. and with battery. and recharge the battery with 2 small wind turbines.

so, plz suggest me the how many volts would be required to run this motor. and the how many volt generators would be required with assumption that there would be a wind flow of 40 kmp hr.

[deleted-71588]

i need to run a motor of 10,000 rpm continuesly. ... so, plz suggest me the how many volts would be required to run this motor.

YOU need to do some reading up on motors yourself to try and understand the physics involved or at least the vocabulary! The answers to all of your questions in this thread are indeterminant based on the information provided.

All electrical components have specifications that are specific properties of those specific components. In the case of electric motors, there are torque, voltage, current, RPM properties that are all interrelated and each different motor designs will have different tradeoffs that tailor the motor to certain applications. Coming up with a set of comonents that will work for a complete application is NOT a trivial problem. You can't just grab any motor and any battery and any generator and any fan/turbine and throw it together and expect it to work.

[justchill.jun]

hii, Thanks for being patient to such questions
.. the motor specifications are....3 phase AC induction motor with a with torque of 52 Nm at zero speed. The motors at a high speed of 8000 RPM.
can you now tel me what volts it would be required to run it for 5 hours.
Any approx ans will do!!! Actually i dont need to give exact technical details.
Again i have the ...battery to use is ....... eight 6 volts lead acid batteries to run the motor.

[deleted-71588]

the motor specifications are....3 phase AC induction motor with a with torque of 52 Nm at zero speed.

This is certainly outside the scope of a high school Science Fair project. What kind of a project are you actually trying to do?

1) AC motors won't run from batteries which produce DC current. You are going to need an inversion system to convert DC to AC at the correct frequency. The efficiency of these conversion systems will be a significant factor.
2) The motor specifications should also tell you their design voltage, locked rotor current, and frequency. The specifications should also tell you the designed rotational speed and the no-mechanical load current.

You need to do some basic research into electrical terms: voltage (electro motive force), current, and power. Your questions indicate that you are confusing "volts" (a force unit) with an energy or power question.

Since 1 HP is a power unit you should be able to look up a direct conversion into watts which is the electrical power unit, assume some inverter efficiency (say 50%) and come up with how many watts you need from the battery system.

I'm guessing that you will find a significant mis-match between the batteries you have and the motor you have. You might not have enough fully charged battery power to even start the motor.

I looked up a single phase 1 HP 220VAC 60 Hz 1450 RPM motor and it requires 7A full load run current (probably 4 times that in starting current for a few cycles). That would be 1540 watts * 2 for inverter inefficency = approximately 3080 watts DC. Series wire the 8 * 6 volts batteries to get 48 volts means 64 Amps. How long will your batteries supply that amount of current? A special deep cycle 12V marine battery will supply 25 Amps for 400 minutes so you aren't even close.

[justchill.jun]

hii, craig..

Actually i am preparing project report on mall wind mill and sub topic its uses. Now i require to present the conversion of wind energy to mechanical energy and i choose(suggested) the 3 phase motor that would run at around 8000 rpm consuming approx 220 volts.
Again i need battery(acid lead) to make the motor run continuesly for sometime assume 5 hrs. These batteries/y would be again charged by small wind turbine.
I hope idea is much clear to you! i just need to give a little information on this.
Dont go into extereme details about. just the reader should have an idea about the working.

Hey, i heartly thank you to take interest in this as my faculty also did not help me much..
Thanks. waiting 4 reply.

[deleted-71588]

You need to do some basic research into electrical terms: voltage (electro motive force), current, and power. Your questions indicate that you are confusing "volts" (a force unit) with an energy or power question.

Since 1 HP is a power unit you should be able to look up a direct conversion into watts which is the electrical power unit, assume some inverter efficiency (say 50%) and come up with how many watts you need from the battery system.

I gave you some hints at how to approach sizing things in my last post. It doesn't appear that you did any of the research yourself. You should be able to quickly use a search engine to find the constants or a calculator that knows the constant to convert your 1 HP into watts and then you can multiply it by 2 (the inefficiency factor) and then by 5 hours to get the watt-hours you need from your battery bank. Try it yourself.