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Discussion Starter #1 (Edited)
I'm working on a little hobby project.
essentially I want to power a set of LED lights that are typically run off a 12v DC (automotive), to be run off a much smaller portable battery instead.
Id considered a 9v battery hookup but I'm not sure that will have very much power to run the lights for very long. Are the lights likely to be about 25% dimmer running on 9v than 12v as well?

the other idea I have is, to run them off one of those little rechargeable cell phone battery boosters you can buy now for about $5. but I'm not sure how to wire that up to power the lights due to the USB or mini usb port connection. any thoughts?
something like this, but I'm flexible
https://www.walmart.com/ip/2600mAh-Portable-Mobile-USB-Power-Bank-External-Battery-Charger-for-Cell-Phone-backup-Blue/42556861?variantFieldId=actual_color
the setup has to be pretty durable as well as resistant to heat.
I guess the other question should be, will this provide more power than a 9v batt as I'm just assuming it does?
Edit: the portable batt pack may not be feasible as it appears to be running closer to 3.7v....so back to the 9v batt I guess
 

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You need to find out the power consumption of the LED set, usually milliamps (mA).
Then, the battery will be rated in AH or mAH (amp-hours or milliamp hours).
There are fairly small SLA (sealed lead-acid) batteries now that may be a good compromise between the capacity of automotive and the portability of common disposable batteries.
 

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IMG_0994.JPG
You need to find out the power consumption of the LED set, usually milliamps (mA).
Then, the battery will be rated in AH or mAH (amp-hours or milliamp hours).
There are fairly small SLA (sealed lead-acid) batteries now that may be a good compromise between the capacity of automotive and the portability of common disposable batteries.
You can find everything you need in downtown Miami...
 

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9v will power the strip but not at full brightness. All you need to do with the usb thing is figure out which 2 wires are positive and negative. Cut all the others. Pos to Pos neg to neg and you're good to go. Seen videos on YouTube on how to make your own external battery with a USB cable.
 
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9v may not light it up at all, depending on how it's wired.

You can buy 12V versions of the USB power banks, usually designed as a battery booster, or to store power from a solar panel. I saw an infomercial for one the other day that would start five cars.

Motorcyclists have the neatest stuff.

You can also get a DC to DC convertor to go from 5, 6 or 9V to 12V. These can be very noisy.

Two of those USB chargers wired in the right way would give you 10V.

8 AA rechargable batteries would give you 12V or more, but I'm not sure for how long,

How many ma are the lights?

These are $50 in Canada, but $15 in the USA.

Talentcell Rechargeable 6000mAh Li-Ion Battery Pack For LED Strip And CCTV Camera,12V DC Portable Lithium Ion Battery Bank With Charger,Black: Amazon.ca: Camera & Photo
 

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I don't think the light will be dim; rather, it will flicker on and off as the LED closes, and opens, and closes again. That is assuming the 9V gives enough voltage to cross the forward voltage threshold.

The LED's themselves won't be much higher than 3 volts, and may be as low as 1.5V. For a twelve volt application, they will have a properly sized resistor in series to give a three volt power drop across the diodes. To properly drive them from a nine volt, you will need to change the resistor value (reduce it). V=IR, so the resistance would just have to drop by about a quarter of its original value to go from 12V to 9V.

A fairly non-technical write-up is here --> www.baldengineer.com/led-basics.html/amp
 

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I don't know your physical parameters but two of these 6 volt flashlight batteries, in series, would give you the required voltage and enough capacity (AmpHours) to run it for a long time. I get these at the dollar store for about $3 (just the battery).

upload_2017-5-4_9-55-0.jpeg
 

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How about 11.1V LiPo batteries for RC applications. Just make sure you have and know how to use the correct chargers. LiPos can be dangerous.
 

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Discussion Starter #9
Thanks guys.
I did a test of the lights with the 9v batt...it does seem to work normally. I'll have to do a side by side beside a 12v to see if theres a drop in brightness.
I'll have to dig up some info on power consumption of the lights. their just cheap led strip lights from ebay (china).
 

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You will definitely see a drop in brightness at 9v, anything less than about 6 volts and you will start to flicker or maybe even shut down. What size led's are in the strip? There are about 6 different sizes at least and they all have their own milliamp requirements. 3528, 5050, 5630 to name a few.
 
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