multivoltage battery charger with for 6v, 12v and 24v with galvanic isolation.

[amanzi]

hi guys..! I'm doing a project in my school and i need to design and to construct the battery charger which has got three output terminals for charging batteries of 6v, 12v and 24v and these terminals must be physically and electrically isolated from each other so that they can be protected from short circuit current that may flow during the operation of the facility. since i'm just the beginner in electronic field so i seek a help from any body who can help me in either way. plz help me guys.

 

[Diver300]

What you will end up with will be three separate battery chargers in one box.

To get isolation, you need a transformer. As, I assume, you will be powering this from mains electricity, you will need three separate transformers to get isolation as well as the three voltages that you need.

An idea how much current you are going to want the chargers to be capable of? I guess this is for lead-acid batteries.

A mass-produced product to that specification would probably use a custom-built transformer with multiple output windings. However I would not recommend that for a project, because building a custom transformer is a lot of work if you want it to be anywhere near as efficient and neat as a standard one.

 

[amanzi]

thanks for your advice mr Diver300. but i'm not so much sure with the amount of current that will pass through in each circuit out of the three i.e that of 6v 12v and 24v. can you please help me how can i know that?

in case of the batteries they can be in one box but for different uses that mean each battery will have its specified uses.

 

[Nigel Goodwin]

thanks for your advice mr Diver300. but i'm not so much sure with the amount of current that will pass through in each circuit out of the three i.e that of 6v 12v and 24v. can you please help me how can i know that?

You need to know EXACTLY what it will be used for - think of it as building a container, if you don't know what you want to fit in the container you don't know how big to build it. For battery charging you also need to know the type of batteries, as well as the required voltage and charging currents.

 

[bountyhunter]

Assuming you find out the actual specs:

charge voltage
charge current

It would be possible to get one BIG transformer with three separate output windings isolated from each other. You could connect each to a FWB and build a linear charger from each unregulated DC supply with the desired voltage and current.

 

[4pyros]

Yes, use one 24 volt transformer with a center tap.

 

[amanzi]

OK 4pyros, if i use single 24v transformer with a center tap the outputs will be isolated?

 

[amanzi]

yes Nigel i've got you. as i said earlier that i'm the beginner in this field of electronics so help me how can i be aware of the charging current if the charging voltages are 6v, 12v and 24v.

And in case of the battery type i'm going to charge is lead acid bateries.

 

[amanzi]

ok bountyhunter. are these transformers with three separate windings isolated from each other available in the market to suit my project?

 

[amanzi]

Nigel i've visited the link you have kept in your message and i've discovered that you can tell me the spcs of PIC chip to suit my project, so help me on that.

 

[Nigel Goodwin]

Nigel i've visited the link you have kept in your message and i've discovered that you can tell me the spcs of PIC chip to suit my project, so help me on that.

If you're wanting isolated supplies, and PIC control, you need a PIC for each one. I would also STRONGLY suggest separate transformers, separate windings isn't any where near as safe - aand centre tapped one isn't isolated at all.

 

[amanzi]

ok fine Nigel. so what spcs will direct me to decide the PIC micro controller chip needed in each circuit?

 

[Nigel Goodwin]

ok fine Nigel. so what spcs will direct me to decide the PIC micro controller chip needed in each circuit?

What do you want it to do?.

Analogue inputs and PWM are probably the main things?.

I'd suggest something like the 16F1827 (enhanced 16F series), it's cheap and very well specified.

 

[amanzi]

yes ofcourse the input is analogy (the main supply).

 

[bountyhunter]

OK 4pyros, if i use single 24v transformer with a center tap the outputs will be isolated?

NO

You have to have separate windings which are not connected

separate transformers is better

 

[4pyros]

Yes; The only way you can have "galvanic isolation" between the supplys is to have separate windings for each.
I was confused at first and thought the OP just needed the hole thing isolated.

 

[4pyros]

these terminals must be physically and electrically isolated from each other so that they can be protected from short circuit current that may flow during the operation of the facility.

What exactly is this about?
Are you going to be using more than one output at a time?

Nigel i've visited the link you have kept in your message and i've discovered that you can tell me the spcs of PIC chip to suit my project, so help me on that.

You realy dont need a PIC for a simple charger. Do you have any other special requirements?

 

[tcmtech]

Before you can get any further it is necessary to know what range of battery sizes and types you are going to intend to be charging. Charging a 6 volt 5 Ah gel cell over a period of several hours Vs charging a 6 volt 500+ Ah deep cycle in a hour or two are two completely different system designs despite both being 6 volt.

If you are doing multiple voltages with the requirement that each be isolated from each other it is by far the best to simply design three independent units opposed to putting all three systems in one unit single unit.

Commercial 6/12/24 multifunction battery chargers are already on the market and not that expensive which will likely make your design cost prohibitive to custom build in a practical comparison.

 

[amanzi]

my project supervisor dictated me to use pic in this that's why i'm inneed of it. but the main thing is also to control the over charging i.e. the charging process must end up outomatic once the batteries are fully charged.

 

[amanzi]

hi guys. pleaz guyz is there any body to give me a block diagram suitable for my project.