[joecnc2006]

I was wondering if anyone has tried any, I have an Old Charger that is 120v, with 12v 2a, 12v 10a, and 50a starting mode, It is about 5 years old, and i wanted to see what the transformer looked like and what power it puts out, well depending on which leads you connect you get 120v, 98v, 33v, 21v, 1nd 11v as a quick test, now i was inperticlarly interested in the 33vac output which i tested for about 15 mins. with meter conected and it would switch between 32.9 and 33.0 even, being mostly on the 33.0vac side, now is i;m right this will yield a 46.66VDC +/- when connected to a rect. and a cap.

Anyone tried or used this trans out of a Car Battery charger before? and can you recomend a Rect. and caps to use?

Thanks, Joe

[Al_The_Man]

I don't see any reason why you cannot use it, just make sure the secondary you are using is isolated from the primary.
The size of the Caps will be decided what current you intend drawing, The bridge rect. can be 25~40 amp 100vw.
Al.

[NC Cams]

The 33 volts you measured for 15 min was that done loaded or unloaded, regular or "boost" mode??? Big difference in real life situation.

The widings are rated for a certain power level and if you were NOT pulling any current, essentially you weren't pulling any power thus wouldn't generate much heat.

There is usually a duty cycle chart on the device that outlines how long you can run any stage of the transformer at any power level - read and follow it or at least CONSIDER following it.

Essentially, a transformer is a transformer.

Auto battery chargers make real good, cheap sources of often overlooked high current transformers - and availability can be as close as your nearby K-mart!!! The model train guys have used them to make train P/S's for years.

If/when you do get it going, post up a wiring diagram and model info in "how to" fashion.

Gee, you never know when and if somebody just MIGHT need a P/S for a DIY CNC.

[joecnc2006]

no load, not is start mode, it was in 12v 10a charge setting, but disconnected from this switch to choose and meter connected straigh to transformer. I will strip it down and test again with 120v straight in and the 33v straight out from transformer so no other connections are present.

[NC Cams]

Keep in mind that current limiting in some transformers is done via the limitations of the wiring and/or the inductance factor or some other technobabble thing.

Just because you have 33 volts open circuit does NOT mean that you'll see the same under full load....

[Al_The_Man]

no load, not is start mode, it was in 12v 10a charge setting,

If you have a few different secondary connections, it may be worth disconnecting all of them and see if they are wound as separate windings (probabally not, probabally one continuous winding with taps).
Otherwise it will be easy to set up separate power sources of different voltage values.
Going by the apparent size of that core, I would think that is close to a 1kva, (not a bad size).
Al.

[One of Many]

Another thing to keep in mind is that battery chargers often use half wave rectifiers not full wave. What you see in AC will not give direct DC output ratings. I'd expect this will effectively reduce the transformer to a 10amp continuous output due to duty cycle and winding ratios at full wave rectification. At 14 volt(half wave) output the power may be 700 watts at 50 amps, but pushed to full voltage you will get the 700 watts in short bursts, but at far less than 20 amps for any useful duration.

DC

[joecnc2006]

I got a 50a rectifier for 10.00 local, hooked it up to the two leads as shown above and got 19.8vdc no good for me, i will test a little more, or maybe rewind what is there and see what i can get.

I still have a microwave transformer in which I used 14g shelded wire and got 24vac (not sure of the amps) from it but the space is full and can not take anymore wire, i can pull the second winding out that i put in and use other wire on it,

I just do not know what wire to use to get about 32v 20a or more amps, can someone enlighten me on a chart or what wire to use? Also I read somewhere that you can increase the amps by soldering two wires together at the emd then wind them together then solder the remaining ends.

Thanks, Joe

[vladdy]

I used a battery charger transformer here, it was from a 24v charger for a electric forkift...gave me about 34vdc after rectifier and filter caps..runs pretty cool in my setup.. the transformer was about 8x8x10" in size, and was fairly heavy, but the price was right..
I assume max current would be appx 40a, I only use maybe 6 to 8 amps top under worst case, but plenty of reserve..
I used the existing recifiers from the charger and a couple of 1000mfd caps, a bit undersized, but nothing fancy, been working probably two or three years now as is..

[Al_The_Man]

I just do not know what wire to use to get about 32v 20a or more amps, can someone enlighten me on a chart or what wire to use? Also I read somewhere that you can increase the amps by soldering two wires together at the emd then wind them together then solder the remaining ends.
Thanks, Joe

Buy some enamel wire from a motor winding shop, if you want 20a then use at least 12g.
Al.

[joecnc2006]

Buy some enamel wire from a motor winding shop, if you want 20a then use at least 12g.
Al.

What about the wire two wires in parrallel winding in it at the same time?

[NC Cams]

If you can wire ATX power supplies and or 2 12 volt car batteries in series to get 24 volts, you should also be able to wire the outputs off 2 charger transformers in series....

IF you are careful with grounding and phasing.

This, if you get 12vac out, you should get 24 in series with virtually no loss of rated current.

Effectively this is what is done with multiple wound trasformers on same core. With two separate transformers, you're probably going to use the same "mains" but the secondary sides are as isolated as if they were wound on common core - until they are linked in series. This is where the grounding and/or phasing become critical.

If you fear doing that, do full wave rectificaton and then connect the rectified DC in series and "cap" the summed voltage. It would still help to "match" the transformers and diode bridges just to make sure you don't over drive one with the other.

Still worried, fuse BETWEEN the DC bridges thus if something goes wrong (which it shouldn't) you'll break the link between the two current sources and they'll both "relax" to a non-current conducting state.

PS: The above works as I did it with batter chargers AND old slot racing transformers MANY times way back when Strombecker sold slot cars for home use in the first heyday of slots in the 60's. Laws of electricity haven't changed since.

[joecnc2006]

Yes i have wires three ATX in series, But what i was asking is feeding two wires in the rewinding of the transformer at the same time (parrallel), I thought i read it will increase the amps as well.

Beginning my soldering the two ends together then winding the two wiresz together in the transformer.

Joe

[Al_The_Man]

What you are refering to is bifilar winding, two windings wound together in parallel, you only need to do this if you have two lighter rated windings and require a higher current than either one, if you are creating the winding, then you can size the winding accordingly without going to the trouble of bifilar, as you will not gain anything.
Al.

[truman]

I often thought of using transformers out of ballests for hi intensity lighting some of those have high voltage I think

Rob

[Al_The_Man]

I often thought of using transformers out of ballests for hi intensity lighting some of those have high voltage I think

These are not isolated windings, they function in the auto transformer mode.
Plus they are usually dipped & sealed in a composition that makes modification virtually impossible.
Al.

[joecnc2006]

Here is the final output in 45VDC, I just do not know how i can test the amps.

[joecnc2006]

Hooked it up to my cnc machine and works I get 40.8vdc when hooked to the board and the same when jogging two motors.

So i guess that would be a load test??