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steve-b

Newbie

Joined: 07/09/2011
Location: Canada
Posts: 11

Posted: 01:05am 07 Sep 2011

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Hello all,
I'm new to the site, and am looking forward to learning as much as i can from fellow members.
I have recently built a wind turbine using a 72V Ametek motor.
My first question is... has anyone out their had any experience with this motor? and if so... has it been good?
My second question is... When using a charge controller, does the controller charge the batteries at whatever rate the motor is generating? or at the set high point...14.9 in my case. Does the controller switch to "dump" when the motor reaches 14.9, or only when the batteries reach 14.9?
Im new to all this stuff, and any help would be greatly appreciated.

Thanks,

Steve.
Edited by Gizmo 2011-09-08

Don B

Senior Member

Joined: 27/09/2008
Location: Australia
Posts: 190

Posted: 08:09am 10 Sep 2011

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Hi Steve,

I am not familiar with the Amtek motor that you are using as a generator, and can only guess about your charge controller, but a few general comments might help.

I assume that the Amtek 72V ls a 72 Volt motor, and you appear to be charging a 12 Volt battery with it. While this appears to be a major miss-match, it is capable of working, as the motor will only put out an open circuit voltage in proportion to the speed at which it is being rotated. This is presumably well below its rated speed as a motor with 72 Volts applied, and wind turbines turn fairly slowly anyway.

The problem is that a 72 Volt motor (if that's what it is) will have high resistance coils wound with many turns of small wire, and will not be capable of outputting much power at low speed. The current that it can output will also be more or less in proportion to the shaft speed. Despite this, it might possibly produce enough current to meet your needs if they are very modest.

With regards to the charge controller, these are designed to protect the battery from over-charging. With a discharged battery, they will ordinarily pass all of the current that the generator is capable of producing till the battery voltage rises to its maximum or "acceptance" value, which might be around 14.9 Volts, as you anticipate. At this point they will only pass a constant voltage through to the battery.

With the more advanced controllers, when the battery has been through its "acceptance" charge at fixed voltage for a long enough time for the charge current to drop to a low enough value, the controller will drop the battery voltage to a float charge value ordinarily about 1 Volt or so lower than the acceptance voltage value.

The point at which the controller begins to dump the rest of the generator output depends on the controller design, but ordinarily it would divert current into the dump load to avoid the generator voltage rising above the battery voltage. In your case, this would be at your quoted 14.9 Volts, or whatever lesser value your controller might be set up for as a float voltage. Please note though that, for the controller to dump power, it needs an actual load capable of dissipating or storing heat. If you don't have an actual load, or if it is inadequate, then the generator voltage just keeps rising, and the shaft keeps turning faster and faster.

With your set-up, it is unlikely that your 72 Volt motor (if that's what it is) is capable of putting much charge at all into a 12 V battery, so I doubt that you have any problem with excess current, unless your battery draw down is extremely low.

I hope that this helps.

Regards

Don B

steve-b

Newbie

Joined: 07/09/2011
Location: Canada
Posts: 11

Posted: 01:35pm 10 Sep 2011

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Thanks for the reply.

The motor is 72 volts. I have tested this motor with a load on it (12v) bulb. At about 280 rpm the light is very bright, and i am getting about 14 volts. It doesn't take allot to turn this motor.
You answered my question about the charge controller. It does "dump" when the battery hits 14.9, and then goes back to a charge state at 10.5v.
I have read that the Ameteck 72v is a good motor to use as a generator for charging a small bank of batteries, but i wanted to hear it from someone in the real world, with real experience.
Thanks again for the reply. If you know of a motor that is relatively easy to find, and that is proven to work good, i would love to know.

Steve.B

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