Hi, based on this https://www.vata7.com/product-page/vata-pack-us-12volt
he claims to run 3V led strip over 7 hours on 3.7V 15,000mah battery.
i am looking to see if i can replicate a similar approach for a led project with same qty leds. and be visible in daylight.
Well, get LEDs that are bright enough, measure the current, scale your battery accordingly, and you're done.
What does this have to do with Arduinos?
they will eventually run of arduino!
cant find such leds
he claims to run 3V led strip
I can't see that claim on the link What I can see is that the LEDs are marked DC12V, and that they are in groups of 3. So it looks like the strip has three LEDs in series and is driven from 12V. If it has a 3V7 battery then there must be a boost regulator providing 12V from it.
So it looks like you should be looking for a red non addressable 12V strip.
It looks like a bog standard 12V LED strip to me on that photo. Arranged in groups of three, each with a resistor.
It might be a low power led strip, but the numbers seems to be for a normal led strip.
Suppose Lipo battery with average of 3.7V.
7 hours with a battery of 15 Ah = 2.1 amps.
Step up the voltage with a DC-DC converter with 80% efficiency to 12V = 2.1 * ( 3.7 / 12) * 0.80 = 0.5A @ 12V
A led strip could contain 30 leds per meter, with 20mA for each led. That is 0.6A per meter.
Is that about one meter led strip in the photo ? It could be. It's close.
A single cell Lipo battery of 15 Ah weighs about 0.3 kg. That is a big battery (compared to Lipo batteries in toys).
In the photo I see a battery in a blue wrap. Those can be found on Ebay, and they can be unreliable. They might bulge. They are the lowest possible quality. There could be a smaller battery inside and the rest is just foam or cardboard filler. Is that a certified charger ? I doubt it.
Grumpy_Mike:
I can't see that claim on the link What I can see is that the LEDs are marked DC12V, and that they are in groups of 3. So it looks like the strip has three LEDs in series and is driven from 12V. If it has a 3V7 battery then there must be a boost regulator providing 12V from it.So it looks like you should be looking for a red non addressable 12V strip.
Our 3 volt, SUPER bright LED lights are custom designed/made (NOT 12v) for very low current draw and longer hours of life, per charge. The LEDs are water proof and shock proof and have a 50,000 hour life span.
Our 3.7v battery has circuit board (PCB) protection to prevent over/under charging (VERY IMPORTANT), and come with a wall-plug, 120v charger. The battery life per charge with our VATA7-PACK is about 7 hours. One battery and one charger is included with each product purchase. Additional batteries and chargers can be purchased from our 'GEAR' page.
Koepel:
It might be a low power led strip, but the numbers seems to be for a normal led strip.Suppose Lipo battery with average of 3.7V.
7 hours with a battery of 15 Ah = 2.1 amps.
Step up the voltage with a DC-DC converter with 80% efficiency to 12V = 2.1 * ( 3.7 / 12) * 0.80 = 0.5A @ 12V
A led strip could contain 30 leds per meter, with 20mA for each led. That is 0.6A per meter.Is that about one meter led strip in the photo ? It could be. It's close.
A single cell Lipo battery of 15 Ah weighs about 0.3 kg. That is a big battery (compared to Lipo batteries in toys).
In the photo I see a battery in a blue wrap. Those can be found on Ebay, and they can be unreliable. They might bulge. They are the lowest possible quality. There could be a smaller battery inside and the rest is just foam or cardboard filler. Is that a certified charger ? I doubt it.
about 24 led per strip x2 and about 10 led for each of the yellow.
I was thinking to use the addressable 5V LED as they can be bright where i drive the std read at half brightness and brake on full brightness , possibly strobing if i can, tricking the eye to perceive .
destiny2008:
Hi, based on this https://www.vata7.com/product-page/vata-pack-us-12volthe claims to run 3V led strip over 7 hours on 3.7V 15,000mah battery.
i am looking to see if i can replicate a similar approach for a led project with same qty leds. and be visible in daylight.
I think you will have to research hi-intensity LEDs, the link does not saythe back pack is daylight visible.
In fact the main reason for such a back pack would be be nightime visible.
The LEDs are 12V strips.
When you get a battery pack, you will have to be sure its 15Ah.
The battery used has the back pack suppliers name on it, so I would assume it is a REAL 15Ah unit.
Its a great idea, using neopixels would be even more stunning.
Check out VATA on YouTube, they even have a video showing proof of battery life.
Tom... 
You want daytime visible, you light translucent diffusers from behind same as brake lights on cars.
Light milky plastic from behind. The glowing plastic will contrast to surroundings except perhaps bright sky.
using neopixels would be even more stunning.
Except that showing anything other than a red light to the rear of a vehicle is illegal. An orange / amber light is permitted if it is intermittent and used for directional indication.
Our 3 volt, SUPER bright LED lights are custom designed/made (NOT 12v)
Those LEDs are 12V, it is just that you have three in series that allows you to use 12V to power them. That new link with new information is a sales puff piece written by an non technical person. That company may have the strips made but you can bet your life that the actual LEDs are manufactured by some one else.
It is not possible, due to the laws of physics, to have a red LED with a forward voltage of 3V.
I agree with Grumpy_Mike, it is a normal 12V led strip.
This is with "daylight" in the beginning of the video : VATA7 - DAY - EVENING - NIGHT RIDES! - YouTube. Look at the lights of the cars, that is not daylight, that is dusk.
Despite all the comments we make, the idea is excellent.
Grumpy_Mike:
Those LEDs are 12V, it is just that you have three in series that allows you to use 12V to power them.
I was surprised to see three resistors in each group of three LEDs. One resistor per LED. If those LEDs are in series, a single resistor should do - provided it can handle the heat of course.
Also with a single red LED taking about 1.8V drop, that'd be less than half the 12V supplied - and would mean half the provided energy is lost in the resistors. That's a serious waste.
Wouldn't it be much more efficient to use constant current drivers for those LEDs? Then you would be able to put 5 LEDs in series, drop 9-10V over them, and have 2-3V left for the driver. If you have LEDs that drop 1.6-1.7V you may even do a sixth LED in the same circuit and get double the light for the same amount of power provided.
When you light a led with a resistor for current control, the voltage not dropped across the leds needs to be more than a small fraction of the total to work well.
I can guess at reasons but you don't want to use 11 of 12 volts and attempt to regulate through the 1 left. It's probably not going to work the same as you thought.
The cool part about 12V through 3 leds is that the same current flow lights them all. Current needed is per group, not per led.
I think the best would be to go through the 5V Led addressable strip vs 12V strip RGB red.
this way DC-DC boost from 3.7V to 5V , make sense?
I know - simple resistors won't work for 1V out of 12V but wouldn't a constant current controller like this work?
33R resistor for 20 mA, and a simple BC547 should indeed be able to handle the power (20 mA, 3V drop = 60 mW of heat).
Try and see how bright those look in daytime.
You can get addressable leds in other forms than strips. I've seen 10mm RGB WS-whatever leds with leads for reasonable prices.
You need a light diffuser to make an RGB led look like anything but a pinpoint of color. From close up you can see the junctions as little bits of red, green, blue, unlike leds with colored/diffusing led bulbs that glow all over.
wvmarle:
I know - simple resistors won't work for 1V out of 12V but wouldn't a constant current controller like this work?
33R resistor for 20 mA, and a simple BC547 should indeed be able to handle the power (20 mA, 3V drop = 60 mW of heat).
Well yeah. I understand that there are leds powerful enough to warrant constant current circuits. My little laser modules have tiny little CC boards even!
Thinking of leds, their resistance goes down as they warm, don't they? That leftover V gets bigger while the resistor does not...
Yeah not stacking up leds to get 11V of forward drop is just the price of cheaping out on current control.
I think I found a led
1.8V x 2 ~ 3.7V series Parallel configuration 20ma each
what do you guys think?
2x1.8 = 3.6V
Current regulator as suggested above:
20 mA at 33 Ohm = 660 mV
Transistor minimum voltage drop = about 200 mV
Total just under 1V
So that's 3.6 + 1 V = 4.6V mimimum to drive two 1.8V LEDs. Won't work. Even not at full charge when the voltage reaches 4.3V, let alone when discharging and the voltage drops.
Much more efficient would indeed be to use a boost converter to produce 12V, then six such LEDs in series (total drop 10.8V) and a constant current regulator for each set (those resistors and transistors are dirt cheap - resistors can be had for as little as USD 1-2 for a bag of 1,000 and the BC547 about USD 0.50 for 100 pcs, it's just a bit of soldering to do). About 80% efficiency for the converter (good ones may reach 85%), 90% for the LED/constant current controller (10.8/12 = 0.9), total about 72%.
Resistor based: 3x LED = 5.4V for 5.4/12 = 45%, add in the converter and you're at 38% efficiency in converting battery power to LED power.
