If I put 50v on a 2.5 v led but restrict the amps to the Leds specification say 20 ma, this Led will run all year on a 50v supply.

Try it.

Buy a red 2.4v 20ma led light. Lets forget the voltage.

You have a 24v pack reads 28v fully charged.

Find the resistance need to run 20ma at 28v.

So 28v/.020A=1400 ohms The entire circuit we will design can not exceed or be less than 1400 ohms

Buy a red 2.4v 20ma led light. Find its on resistance,

2.4v/.02 amps= 100 ohms.

Now subtract 100 ohms for 1400 ohms and you have 1300 ohms. Write this 1300 ohm number down.

Now we need to find the watt resistor needed We do this easy because we know our led is 2.4v so let us do this one easy.

The resistor will make a voltage drop and divide the volts so the led doesn't get too much volts or amps so we subtract the volts we have with the led from the battery input.

28v-2.4v= 25.6v@20ma The resistor will drop 25.6v

Watts = VXI=W 25.6v *20ma =.51 watts. You will need more than a half watt resistor to handle the heat the resistor need to dissipate to make the voltage drop.

Buy a 1300 ohm 1 watts resistor and connect it to the battery in a series circuit with the led and the led will run nice.

The same applies with digital current regulation but this is much better. If the circuit sees a 8v or 4v input it will not allow anymore current to the led than 1 amp and the led will not go bright or dim.

This is better than a resistor as your pack will run out and the resistor becomes too high.

Current follower circuits do just this. They can run single devices on many voltages without any voltage regulation all based upon what current the device needs.

We can do this whole math not knowing the voltage requirements or the Led too. Enough for now.

This is an analogue current follower.

The equasion is 1.25v/I= the resistor you need

This calculator makes it easier as it tells you watts you need too..

http://www.reuk.co.uk/LM317-Current-Calculator.htmSo say you want one amp to pass this circuit. 1.25/1=1.25ohms

See the resistor there you need a 1.25 resistor for this to work 1 amps..

You can then put a 39v to 5v supply on a 2.4v led and the led will run perfectly through the LM317t.

Very easy to do.

So really your question has now become one of current not voltages.

**Buy your led lights and measure how much current it used by each light at 6v and mark it on the lights so you don't get mixed up.**

We an work from there and make you lights run in perfect balance in series at 12v..