heavy duty battery charger

[tony Ben]

pls can any one help me on chager circuit that can deliver up to 20A @ 12v . i did one base on a linear regulator and a pass board transistor but
d xsistor gets too hot , i need a better design pls.

 

[Nigel Goodwin]

pls can any one help me on chager circuit that can deliver up to 20A @ 12v . i did one base on a linear regulator and a pass board transistor but
d xsistor gets too hot , i need a better design pls.

With a linear supply for that sort of power you would really need multiple output transistors, and large heatsinks - with possibly fan cooling.

A switchmode PSU would run far cooler, but is more complicated. Have you considered using a PC PSU - there are quite a few projects on the net for using PC PSU's as high power switch-mode PSU's. Although I'm not sure what the 12V output is normally rated at.

What do you need the PSU for?, linear ones are often used for radio transmitters due to their lower susceptibility to strong RF fields.

 

[TheOne]

What is the charger for? If for car batteries you can make a charger with the secondary of your transformer containing a controlled rectifier, using a SCR (Thyristor) I once made a 30A charger this way with current limit, over voltage etc. I used a small current transformer to sense the max AC current and another nifty circuit to terminate the SCR conduction mid-cycle for better control.

 

[Nigel Goodwin]

I rather missed the fact he was wanting a charger, and not a PSU - having already built a linear regulator confused me!.

You don't need a regulated supply for a charger, as TheOne always said, a thyristor charger is all you need - there are plenty of suitable designs all over the net.

If all you are looking for is a crude charger, which you need to manually look after and turn off to avoid overcharging, all you need is a transformer, a rectifier, and a current limiting resistor (a very BIG (high wattage) one. This is all that standard battery chargers contain - often they don't even have a resistor at all, the transformer is designed to give the current limiting.

 

[bryan1]

Hi Tony Ben,
Siliconchip currently have a project for a 16 amp deep cycle battery charger, I don't know if you want to charge deep cycle batteries or nimh/nicad batteries. If you can be a bit more specific on what type of charger you need then I can be more helpfull but make sure you check out www.siliconchip.com.au and check out the range of battery chargers they have produced over the years.


cheers Bryan1

 

[lombardp]

If someone is interested, I and two my colleagues have just opened a website (http://www.seven-segments.com) related to electronics for hobby and rc models. We have designed and built several original projects and now we want to make them available on the net.

All documentation, from schematic and PCB to PIC source code is free to be downloaded. Since we have just started producing detailed documentation, at present only PIC-based battery chargers are fully documented (it's the reason why I'm posting in this thread). Other projects... coming soon. :wink: