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mid north Matt

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Joined: 06/01/2011
Location: Australia
Posts: 58

Posted: 11:34am 30 Jan 2011

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found a home made or mine made radio power supply 13.8v @14/25 amps with 3 trannies with double secondary winding's all wired parael/series with 4 2n3055 power transistor's, a voltage adjust pot,volt meter and a few over bits that i can't see,not bad for $4 at the dump shop.put the meter over the transformer's to check for shorts/open circuits and all was well so i wired a patch lead to it and measured to ac volts from the secondaries at 19.2 v with no heat gain after 10 mins and no signs of over heated winding's,because of damaged caps when it was thrown off a trailer i cant power up the dc side untill parts are replaced or replaced by a more modern regulation circuit like pete's and use some of what's there like the power transistor's/heatsink's.will it make a good 12v charger for my bp 570a/h cells?what do you guys think?

Pt Wakefield Matt

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Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 11:31am 31 Jan 2011

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Hi Matt

Sounds like a good starting point but the AC is a bit high to direct rectify, you will have to work out the circuit and get the voltage regulator going, refer to the adjustable power supply setup on forum front page, it also has current limiting.

All the best

Bob

Foolin Around

mid north Matt

Regular Member

Joined: 06/01/2011
Location: Australia
Posts: 58

Posted: 01:34pm 31 Jan 2011

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hi Bob
since each of the trannies is putting out 6.4v ac could i remove one of trannies to get the voltage down?if so will i keep the 25amps current?or use what ive got with Petes regulation circuit?

Pt Wakefield Matt

VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 03:07pm 31 Jan 2011

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Hi Matt

I think that the simpler the better as things electronic fail at the square of the number of components.
On your assumption with two trannies you would get 12. 8 volts, this put through a bridge rectifier should give you the 14.8 volts under load, required for charging a 12 volt battery, this however will depend on the load characteristics of the transformers, it's a case of suck it and see.

You could also use the other transformer on a separate circuit as a 6 volt charger to make it more versatile.

You may still require some form of current limiter to prevent overheating of the transformers.

All the best

Bob

Foolin Around

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