Battery Charger Transformers

[jammeejoe]

I am wanting to build a power supply for an amplifier and was wondering if a transformer out of a large battery charger would work. Transformers are so high when you can find them that it is not practical to buy them. I am wanting to build the amp and power supply in one box. You can buy them at Sams for less than $100.00. They are rated at more than 100 amps. If anyone has had any experience with them let me know. Thanks in advance

 

[rlnthndr]

Keep in mind a battery doesnt like to be charged to fast. Therefore the transformers used in alot of the battery chargers do not do for excessive extended amounts of current being pulled.

The larger battery chargers I have seen are good for usually 50A continuos pull, and peak at 100A or so but that is not to say that the transformer is a 100A transformer just that it can sustain a heavy current load for a short amount of time before heating up to a point at which its performance will degrade.

I have looked at the idea before and build some smaller supplies out of scrap chargers they will do just be weary of the ratings. Also you will want to filter the output to reduce the amount of ac ripple you will get as well as it is advisable to use bridges that can be mounted to a heatsink.

Hope this helps some back to my hiding place.......

 

[jammeejoe]

The charger I am talking about is rated at 225 amps. It weighs about 28 lbs. A huge transformer. The output wires are about 10 guage solid wire-very stiff. You can buy them at Sam's for 87.99 + tax. You answered my question about the output amps. It was just something I was thinking about. Thanks

 

[unit_399]

If you're looking for a transformer to build a high current - low voltage supply, get a junk microwave and strip out the transformer. Remove the high-voltage winding (you'll probably have to use a chisel) and install a new low-voltage winding. For high current use # 8 or 10 insulated wire (Home Depot has #8 with teflon insulation), and rewind the transformer for the voltage you want. A good rule of thumb is one turn per volt with a 110 volt primary. When you get the voltage you want, pack the new winding in as tight as possible and glue it in place using something like Weldwood Contact Cement (also available at Home Depot). Many late model microwaves will do 1200 watts, so the primary side of these transformers will handle a lot of power. About 10 years ago, I built a 15 volt - 80 amp supply using a transformer like this and it's always worked perfectly.

- 399