Hello,

Looking for a bit of advice on designing/buying a battery pack to power some UVa light strips. The project is a custom picture frame with UV strips mounted behind the glass but in front of the artwork along the inside edges of the frame. So it will be a glass>LED>artwork sandwich.

The LED strips I plan on putting on a momentary switch to show some "hidden" UV features of the piece when it is switched on.
These are the lights I plan on using: https://store.waveformlighting.com/...Specification_Sheet.pdf?v=2156247376753912624

Because they are on a momentary switch, I think it would be really cool to power this with a battery hidden behind the picture mount as I will not be using a ton of capacity.

My dilemma:
It seems to be difficult to source an ultra slim battery pack that would be able to power the 12v strip. Lots of 9V options, but strip LEDs are almost all 12V, espeically the UVa ones I am looking for.

These are the two that I have found:
https://www.revrobotics.com/rev-31-1302/
http://tinyurl.com/yyazypzz

The Amazon pack is ideal in size, although sparce on the specs.

Can I just make my own NiMh pack with a series of 10X AAA batteries?

 

Welcome to AAC.

A NiMH battery would certainly work. The question is run time. That will depend on the current consumption of the LED strips. According to the specifications, the strip draws 400mA/ft. Most decent quality NiMH AAA sized cells will provide about 850mAh at some discharge rate (see the cell’s datasheet).

So let’s say you use 4ft of LEDs. That would use 1.6A of current. Assuming you could get the entire 850mAh of capacity at that discharge rate, you‘d get about 30 minutes per charge—not much.

The same idea—though more complicated to build—would use LiPo pouch cells. Those could be very flat but also with a lot of surface area. The larger cells which can be thinner than a NiMH AAA cell, can have a capacity of ~3000mAH or more. Assuming the 3000mAh number, you could possibly get as much as 2 hours run time.

Of course you have to put real numbers into that. If your frame is very large, things get “worse”. This is all doable, and building the LiPo battery isn’t hard, but you will need to include protection and a charger.

 

Welcome to AAC.

A NiMH battery would certainly work. The question is run time. That will depend on the current consumption of the LED strips. According to the specifications, the strip draws 400mA/ft. Most decent quality NiMH AAA sized cells will provide about 850mAh at some discharge rate (see the cell’s datasheet).

So let’s say you use 4ft of LEDs. That would use 1.6A of current. Assuming you could get the entire 850mAh of capacity at that discharge rate, you‘d get about 30 minutes per charge—not much.

The same idea—though more complicated to build—would use LiPo pouch cells. Those could be very flat but also with a lot of surface area. The larger cells which can be thinner than a NiMH AAA cell, can have a capacity of ~3000mAH or more. Assuming the 3000mAh number, you could possibly get as much as 2 hours run time.

Of course you have to put real numbers into that. If your frame is very large, things get “worse”. This is all doable, and building the LiPo battery isn’t hard, but you will need to include protection and a charger.

Hmm, ok those are good points on runtime. I was initially leaning toward the AAA batteries because I could in theory make them replaceable (rather than dealing with the charging of a LiPo pack). But with my frame size I'd be likely looking at 15minutes of run time, conservatively.

This might be enough though. I expect that since it's on a momentary switch that it will likely only be "on" 5-15 seconds at a time. There's a chance I'm significantly overlighting the picture too- I may be able to get away with ~3ft of LEDs if I break the strand up. That would help the cost as well!

And thank you for the thoughtful advice!!