Discussion in 'Electronic Design' started by Danny, Dec 8, 2003.

1. ### DannyGuest

Hi

If i am charging a 12v rated lead acid battery must i use a voltage
greater than 12v, because a lower voltage would theoretically cause the
battery to discharge into the charging device.

Danny

2. ### DboweyGuest

If the battery has a load, you can "float" charge it at 2.17 Volts per cell.

If it has no load, 2.2 Volts per cell is reasonable.

You can use higher charge voltage, but then you need to monitor the battery
temperature, and avoid trappping the gas given off during the charge.

Also, it's good to measure the current during the charge so you can get a clue
that a cell may have a short and causing too much current through the battery.

Don

3. ### DannyGuest

I'm not too sure how many cells this battery has, so any more help?

4. ### John WoodgateGuest

I read in sci.electronics.design that Danny <>
A 12 V lead-acid battery has six cells.

5. ### James BeckGuest

The "12V" Lead Acid batteries we use have the data printed on the side.

13.5VDC - 13.8VDC float charge
14.4VDC Overcharge.

The float charger IC we use on one of our products goes through the
following charging states:

If the battery is below 8.0VDC trickle charge at 50mA until battery gets
above 8.0VDC (protects against trying to bulk charge a shorted battery).

If battery is above trickle charge point (8.0VDC) go into bulk charge,
in our case .75A.

When bulk charge reaches over charge voltage go into float mode.

Overcharge and float voltage are temperature compensated by an on chip
reference.

If the voltage drops below 10% of the float voltage the units resets to
bulk mode.

Removing battery resets unit to the start.