# Need a custom battery rig for project--Will pay!! $$



## MikeGoob (Apr 19, 2011)

Trying to get a series of cells to power a decorative project. Think low output, extended life.
I know numbers needed but don't get Cell Chemistry or all the nuances that goes into it. I need an expert!

Please help--will pay! 
Thanks guys!


----------



## Lego995743 (Apr 19, 2011)

any numbers that i can have to work with


----------



## MikeGoob (Apr 19, 2011)

This is to power a series of small LED diodes. Output 12v 3amps or 5amps, 8 hour life. 
Im imagining a series of cells end to end, can be 2" diameter, 24" long, this is for a light project, not a handheld light. Something stable that can run for 8 hours, charge in 5-8 hours.


----------



## Lego995743 (Apr 19, 2011)

I will try


----------



## bbawkon (May 20, 2011)

12V * 3 Amps = 36Watts, 36 Watts * 8 Hours = 288 Watt Hours Add 20% for Efficiency Losses = 345.6 Watt Hours.

If you do 3.7V Cells, You'll Need a total of 93 Amp Hours (93,000 mAH) of batteries. An 18650 is roughly 2400 mAH (on a REALLY REALLY good day), so if you were to use those, you would need about 40 of them).

For 5 Amps, it's worse.. 155 Amp Hours or about 65 18650 Lithium Cells.

This all assumes a switching power supply with 80% + efficiency.

Ben


----------



## Ken_McE (May 23, 2011)

bbawkon said:


> ...If you do 3.7V Cells, You'll Need a total of 93 Amp Hours .. For 5 Amps, it's worse.. 155 Amp Hours ....



This puts him into the region of car batteries. *MikeGoob*, can you run a line to a couple of car batteries sitting off to the side somewhere?


----------



## Ken_McE (May 23, 2011)

MikeGoob said:


> This is to power a series of small LED diodes. Output 12v 3amps ...



You're running around 35 watts worth of LEDs? Mind if I ask what they are?


----------

