battery charging?

Question

I need to find a way to charge 18 12 volt batteries wired in series. Is it possible to use a bridge rectifier on mains voltage as when the batteries are fully charged the voltage will be 240 volts so they wont be over charged

Thanks for your answers. Some of the wind turbines I sell are 240volt and use a controller to charge the batteries and then an inverter to convert to ac. The problem is when there is no wind I need a charging system to charge the batteries from a generator

Answer 1

Yikes! This is not a good way to do it. One bad cell out of 108, and all of a sudden nothing gets charged, or (if bad cell is shorted) everything else gets overcharged.

If you must do it this way, you really need some serious individual battery monitoring.

For lead-acid batteries, the full-charge terminal voltage is about 14.6 volts. This is the kind of voltage you need to push a charge onto the batteries (263 volts).

A full-wave rectifier on 240VAC mains would yield about 340 volts DC. This is too much for your string. You would still need a voltage AND current regulator -- not just a bridge rectifier.

As long as you need a voltage and current regulator anyway, why not buy a commercial unit made for just your purpose?

.

.

Answer 2

A bridge rectifier is normally the term given to the type of rectifier that is used in modern cars. They are 3ph devices. You can of course get a rectifier to work at 240 volts. You will also have to make sure it can deliver quite a large charging current. This is going to be a very large expensive piece of equipment. It will probably have to me manufactured as a one off. On top of that I am not sure what you need 240V dc for. If you want to run normal 240 volt domestic equipment. You will also need an inverter. If this is the case then It will be far cheaper to arrange the connection. of your battery's to form 50 or 110V . This will still be a very expensive system to set up.
You will also need to arrange to isolate the mains supply with a change over switch. before you can use your battery back up.


So you know the Output of your windmill in current and voltage. You need to buy a generator with the same output or
You buy a ac generator 240V and a rectifier that will give the same out put as your wind mill. You will need to match the generators power output with the rectifiers power out put.
You can of course select a generator with a lower ac voltage
It just depends on the cost of your rectifier. In puts and outputs have to be able to delver the required power. The only other considerations are the time taken to charge your battery's and as long as your Output voltage of the rectifier does not exceed the fully charged battery voltage the system will be self regulating..

Answer 3

It sounds like you are trying to achieve a powr supply for a 240v piece of equipment? If this is so you wont achieve anything by using batteries. Bridge rectification will give you a ripple dc- the sort found in battery chargers but you must remember that any plug in 240v appliances are ac not dc.