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RETRO XP i3 400lm - Technical Details

RETRO XP - Light Level Usage

When you are on a multi-day trip Mode 1 - still provides a perfectly adequate amount of light, so you can now consider dumping the carbide or spare batteries as you can easily achieve +80 hours (for mixed power mode usage with predominately Mode 1 output) lamp run time from a standard Oldham battery.

For normal activities Mode 2 is perfect and more than enough at 185 lumens! This is almost 4 times the light output of a standard Oldham 3W bulb, however due to the light output being closer to 'day light' and having a wider flood angle the perception of brightness is enhanced.

If you require an extra amount of light then Mode 3 gives that extra illumination.

RETRO XP - Run Times

If you have a battery pack or cell combination that is not listed below it is possible to calculate the estimated battery run time, see: RETRO XP - Input Voltage / Current Curves.

The table below lists estimated lamp run times for various battery packs. Light output is in Lumens (lm).

 

RETRO XP RunTimes In Hours

Battery

Mode 1 - 70 lm

Mode 2 - 185 lm

Mode 3 - 400 lm

       

Oldham Lead Acid 4V 16Ahr

90.0

42.0

19.0

FX2 7Ahr

20.0

9.0

3.8

FX3 7Ahr

35.0

16.0

7.4

Li-Ion 3.7V, 2.6Ahr

13.5

6.3

2.8

Li-Ion 3.7V, 5.2Ahr

27.1

12.5

5.7

Li-Ion 3.7V, 10.4Ahr

54.2

25.0

11.3

3 x AA 3.6V, 2.8Ahr

14.0

6.5

3.0

4 x AA 4.8V, 2.8Ahr

19.0

8.9

4.1

3 x C 3.6V, 5Ahr

25.4

11.6

5.3

4 x C 4.8V, 5Ahr

33.7

15.8

7.2

3 x D 3.6V, 9.5Ahr

48.0

22.1

10.1

4 x D 4.8V, 9.5Ahr

64.0

30.1

13.8


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RETRO XP - Input Voltage / Current Curves

The switch mode power supply keeps a constant power level to the LED's over a varying input voltage. As the input voltage falls the input current rises. From the curves below it is possible see the current that will be drawn for a particular input voltage. This can be used to estimate the lamp run time on a particular battery pack.

If a 3 cell NiCAD battery pack with a capacity of 6.5Ah is used to power the RETRO XP, then the total input voltage is 3.6V, this corresponds to a input current of 0.900A at 400lm, 0.408A at 185lm and 0.187A at 70lm, dividing the battery pack capacity by the input current and multiplying the result by 0.9 will give an estimation of the run time for a particular setting - 400lm = (6.5 / 0.900) x 0.9 = 6.5 hours run time, 185lm = (6.5 / 0.408) x 0.9 = 14.3 hours run time and 70lm = (6.5 / 0.187) x 0.9 = 31.3 hours.


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RETRO XP - Efficiency Curves

Using a switch mode power supply to drive LED's is more efficient than limiting the current with a resistor especially at higher powers (a resistor can only be used if the forward voltage of the LED's is lower than the batteries - in this case with two 1W LED's the forward voltage is around 6V). Where possible it is better to use a higher number of cells (higher input voltage) to keep efficiencies high and power loss to the minimum. Efficiencies over the whole power range (0.46 - 2.6W) for different cell combinations are: 2 cell battery pack (2.4V) 64 - 70% efficiency, 3 cell battery (3.6V) pack 69 - 81% efficiency, Li-Ion battery (3.7V) pack 69 - 81% efficiency, 4 cell battery (4.8V) pack 70 - 84% and a 5 cell battery (6.0V) pack 82 - 87% efficiency.


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RETRO XP - Light Output

Due to the power supply light output remains constant as the battery pack drains. The LED's will still give out light when a normal bulb would not even glow.


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