lead acid batery charger

[jmmendicoa]

I need to charge a 6volts 4amps lead acid batery ,it will be charging all the time and the circuit must operate with 120 vac ,the charger must not use  a transformer,any idea where to go for the squema.
Jose Mendicoa Valencia  Venezuela [email protected]


Thanks

 

[SM2GXN]

Hi jmmendicoa!

Why transformerless?
It sounds dangerous  ???

Bjorn

 

[ante1]

Hi jmmendicoa,

When you state that”it will be charging all the time” I suspect there are things running off this battery. If so, it must be completely insulated and touch protected! If you are not sure about this DO NOT use a transformerless supply!

 

[jmmendicoa]

transformerless because i want to make simple,just like an emergency lamp ,it does charge the batery 24 hours a day,with a very slow rate of charge,in case the power goes off,the batery will suply the 6 vdc for the circuit (it is not a lamp).
I know HOW to get a full charge ,it must give up 2.35 volts for cell= 2.35 x 3 = 7.05 volts
The problem is that i dont  know how to design a charger with a slow rate of 10 % of the total current of the batery (4 amps).
With a relay i will switch the batery in case the power goes off.
I hope you understoo my english.
Thanks Jose Mendicoa  Valencia Venezuela [email protected]

 

[ante1]

Hi Jose,

OK, I have got an example for you here: http://www3.telus.net/chemelec/Projects/Charger/110-chg.htm
This is for 12 Volts but can be changed to work for a 6V battery.
Be careful and please read the warnings! (Very nice site BTW)!

 

[ante1]

Hi Guys,

For continuous charging the cell voltage should not exceed 2.3V (2.29) or the battery starts loosing water. If the voltage is limited to (in this case) 6.88 V the current is not that important.

 

[ante1]

Hi tnk,

Zeners are somewhat old-fashioned don’t you think! Ever heard of the LM317? ;D ;D ;D

 

[ante1]

But on the other hand one can use a 6.2V Zener in series with a standard diode (reversed) and you get pretty close. Another benefit from this is very low drift, they kind of compensate for each other. I fact it wouldn’t be that bad after all!

I still prefer the LM317 though! 8)

 

[ante1]

Yes I know but the 6.2Z + the reversed standard diode I series will work fine I guess! With some effort one can find the exact match for 6.88V!  ;D

 

[ante1]

Hi again tnk,

Yes, when you read about diodes in a book they are 0.7V drop but in practice they are between 0.45 and 0.65 Volts. I can’t remember encountering a standard diode which was as high as 0.7 as the books says. Schottkys are sometimes even lower (about 0.4) and most fast recovery diodes are just below 0.6. However this is not a big deal, I just wanted to share this with you.  ;D

 

[jmmendicoa]

Finnily i will use a small transformer and with a LM-317 ,i will fixed the output for a 6.88 vdc (with out the batery).
Thanks to all the comunity for the answers .I  learned a lot off.
Thanks for all of you.(I will use the trikle method for chargin a ni-cad cell.

jose mendicoa al. venezuela [email protected]