12V SLA Float Charger

[letsrelaythat]

Hi All,

I'm looking to design a simple backup battery charging system, will be connected indefinately, so I have found a circuit using the LM317T.

Problem is I read about how the input voltage must be a few volts (about 4) to combat the voltage drop from the regulator. The only supply I have access to above the 12v, 15v, then goes to 24v.

Will this be ok, or will I need to adjust my 240ohm and 2k resistors on the output? I am using an LED as the minimum current draw requirement as recommended by another topic here.

Also I don't have access to a IN5400 diode, only IN5404. Will this do?

Thanks all,

Tim. :wink:

 

[Russlk]

The long term current draw will be low, so power dissapation is not a problem. The LM317T is internally current limited and has over temperature protection in case the float charger tries to re-charge a dead battery, so use the 24 volt source to be sure there is enuf head room.

The 1N5404 is a higher voltage version of the 1N5400, so it is good to use.

 

[letsrelaythat]

Awesome!

Cheers for your help