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maaca
Newbie

Joined: 21/11/2006
Location: New Zealand
Posts: 22

Posted: 09:35am 27 Jul 2007

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Hi Guys I have been putting my first wind generator Ive made through some tests and wonder can some-one help with a couple of questions.Contoller or regulator is an Oatley k241 kitset.Seems to work ok,it certainly slows the windmill down when voltage gets up but it doesnt stop it.Can any one tell me if it should?. Also battery voltage raises to around 14.4volts and sometimes more.This is with nothing connected to the battery to draw off any load.The mill was built to run either a Cell phone repeater or Radio repeater which ever was ready first.At the moment its the radio and am wondering before I wire it all in if the battery voltage may be too high for it. It draws only 100m/a on stand by and 650m/a on transmitt at five second duration for each transmission. Does one need to build a 12volt regulator to be on the safe side to drive the repeater?.

davef
Guru

Joined: 14/05/2006
Location: New Zealand
Posts: 499

Posted: 10:48am 27 Jul 2007

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All radio repeater gear that we ever designed was rated to 16 Volts, so wouldn't worry about that. 16 Volts (max) is an industry standard for mobile based equipment.

Gill

Senior Member

Joined: 11/11/2006
Location: Australia
Posts: 669

Posted: 11:10am 27 Jul 2007

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G'day maaca,
Most all commercially manufactured 12v radio gear is actually made for a nominal 13.8v. This makes allowance for a low battery under no charge up to an almost full battery still under charge. View the spec sheet for your radio and you are likely to see something like: 10v - 16v DC, or 13.8v 15% ~ -20%.

In short, your radio will tolerate the fluctuations of charging the 12v battery, provided of course you have set the regulator to the recommended voltage.

From memory my battery when new would reach 15.2v under charge before the hydrometer bottomed out(fully charged). I run 5 different transceivers from this bank without concern. I currently have my Oatley K220 dumping load at 14.7V.

I know a little of the K241 circuit, and if it is slowing down the prop, there should be no charge being delivered to the battery.
Have you tested if this is so?
If you do not have a suitable Amp meter, then a volt meter will give you an indication by dropping slowly back from the 14.?v to 12.?v whilst the prop is in back EMF braking.

Hope this is of some assistace.

was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ

maaca
Newbie

Joined: 21/11/2006
Location: New Zealand
Posts: 22

Posted: 10:18pm 27 Jul 2007

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Thanks Guys yes you are right the manual says 10-16volts. Why on earth I didnt look there first I'll never know.Am I right in assuming this only a floating voltage that Im concerned about and that it would settle down a little with something connected and running?.I made a mistake with the transmitter current ,it should be 1.65amps not 650m/a. Gill the prop is definatly slowing down and Im sure the control gear is working but after measuring battery voltage I dropped the DMM and that was the end of it. This set-up is at my fishing batch which is almost four hors drive away.So I will certainly be armed and ready next trip to do the measurements. Thanks.Maaca.

Gill

Senior Member

Joined: 11/11/2006
Location: Australia
Posts: 669

Posted: 04:18am 28 Jul 2007

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On reflection I may be wrong with my statement of no current through the battery in back EMF braking mode. I was thinking of the blocking diode, but realise now that it and the battery are in parallel with the mosfets so whilst the bulls roar of current will pass through the mosfets, a little may still pass through the battery and so the battery voltage may not drop as I indicated.

The floating voltage you refer to sounds either like a reference to generator open circuit voltage as opposed to generator voltage under load (of charging the battery), or a reference to battery voltage under charge as opposed to battery open circuit voltage.

Gee it sounds complicated when I say it.

But wait, there's more! It could be battery open circuit voltage as opposed to battery voltage under load, or a combination of the above.

No wonder wise men choose to bypass such queries. It is complex.

Perhaps if I refer to power source and power load.
The generator is a source, the battery is a load.
The battery is a source, a starter motor is a load.
Note: battery is both source and load.
Source voltage must be higher than load and drops when it powers the load.

So:
Gen source - voltage is say 22v
Gen source connected to a (12.1v) battery load - voltage is say 14v
battery source - voltage is say 12.1v
battery source connected to (0v)starter motor load - voltage is say 9v
Gen source to battery load and also source to starter motor load - voltage is say 11.5v

I most cases voltage is measured at the battery hence it is necessary to know all the connections. You will in time establish a reference for all of your configurations.
Certainly the battery as both a source and load at the same time is the most complex.

I'm sure we're all confused now.

was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ

maaca
Newbie

Joined: 21/11/2006
Location: New Zealand
Posts: 22

Posted: 10:21pm 29 Jul 2007

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Thanks Gill,Yea a bit confusing but after reding it for a while and a couple of times it all makes sense.From what you and Davef have commented on I feel I can march on but will do the measurement tests you stated. Many thanks Maaca.

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