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The strip uses .5-2A and 5 volts. I'm using four AA batteries, so the voltage becomes 6. What do I do to reduce the voltage, and get the right current? Will the strip itself just draw the current in it's own way since it's remote controlled? I read online something that said something like the equation for the extra volts is you take the original volts, and subtract it by the end voltage you want. Then you take the difference and put it in a ratio to the end voltage. Like 6-5=1. 1:5, meaning you use two resistors, the second of which being 5 times the first resistor. Is that correct? And if so, what about the current?

Edit: What if I used 4 rechargeable AA batteries. Each is like 1.2 volts, 4 of them would make 4.8 volts. Online it says that the internal resistance is about 30mΩ-100mΩ. That means .03Ω-.1Ω right? Using ohms law to find the current, V/R=I, and the max resistance, that should be 1.2/.1=12. So a single rechargeable AA battery can pump out 12 amps? Correct me if I'm wrong

EmeraldVolts
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  • *** I have no experience with LED strips, never used one of them. So don't take my words guaranteed. Wait for someone to answer. *** What you read is called as a voltage divider. It is not an effective way of lowering voltage when the load needs considerable amount of current, so ti is ok to use this kind of a voltage divider for signal voltages, but not for something like you plan to do. You can try adding one more AAA battery and using LM7805 or similar 5V constant voltage regulator to get 5 Volts. By the way, I don't think triple A batteries will be capable of delivering 2A of current. – muyustan Jun 06 '20 at 15:14
  • Also: https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings – brhans Jun 06 '20 at 15:31
  • and https://electronics.stackexchange.com/questions/75448/how-to-reduce-dc-voltage-using-resistors – brhans Jun 06 '20 at 15:32
  • .5 to 2 A and AAA batteries **isn't a good idea**, that is too much current for AAA batteries. I suggest that you **just try 3 AAA batteries** and see what happens. If the light output is enough then you're done. If not then use 4 batteries in series with a resistor, start with 10 ohms and see how that goes. Measure across the LED strip, if it has less than 5 V use a lower value resistor. Again, if light output is OK you can keep it 10 ohm. And again: AAA batteries might be depleted very quickly, AA batteries might be more cost effective. – Bimpelrekkie Jun 06 '20 at 15:49
  • @Muyustan Sorry, I mean AA batteries, not AAA, I sometimes confuse them by accident. – EmeraldVolts Jun 06 '20 at 17:51
  • @Bimpelrekkie Sorry, I meant AA batteries, not AAA, I sometimes confuse them by accident. Would AA make it better? – EmeraldVolts Jun 06 '20 at 17:52
  • I found this online "At room temperature an AA has about 0.15 to .3 ohms internal resistance when fresh. I=1.5volts / 0.15 or 0.3 = 5 to 10 amps! But not for a long while! Practically considering that at lower temperatures and after the battery has been used some then the internal resistance is higher, the actual useful amps would be 1 or 2 amps." Does "the actual useful amps" mean like the lowest when the battery is almost done, or like the general amps? – EmeraldVolts Jun 06 '20 at 18:01
  • What if I used 4 rechargeable AA batteries. Each is like 1.2 volts, 4 of them would make 4.8 volts. Online it says that the internal resistance is about 30mΩ-100mΩ. That means .03Ω-.1Ω right? Using ohms law to find the current, V/R=I, and the max resistance, that should be 1.2/.1=12. So a single rechargeable AA battery can pump out 12 amps? Correct me if I'm wrong – EmeraldVolts Jun 06 '20 at 23:55
  • @EmeraldVolts If all things perfect, a 2600 mAh AA battery will provide 2.6 Amps for 1 hour. But it's not. The voltage will drop off sooner than 1 hour. Look at an energizer data sheet. https://data.energizer.com/pdfs/hr6-2650_eu.pdf Useful amps means 2 amps for about 40 minutes before the voltage starts dropping down rapidly. – Passerby Jun 07 '20 at 00:04
  • To summarize everything, you can drop the voltage of 4 AA alkaline using a 1n400x diode for a ~0.7V drop. You could draw 2 amps for about 40 minutes before you start seeing significant brightness drop. But you are unlikely to see 2 amp draw unless the RGB led strip is at full white the entire time. – Passerby Jun 07 '20 at 00:07
  • @Passerby Where did that sheet mention 1 hour? And for the most part I'd be fine? – EmeraldVolts Jun 07 '20 at 00:32
  • Look at the graph of Typical Discharge, Voltage vs Hours. The colors list a Current draw. And you can extrapolate other draws from there. – Passerby Jun 07 '20 at 00:50
  • @Passerby Overall, I should be fine? – EmeraldVolts Jun 07 '20 at 01:17
  • Overall, yes. Frankly, you can avoid most of this by just using a USB power bank. Many allow for 2 Amps at 5V, built in low voltage cutoff, high current cut off, etc, and with a typical 4800 mAh pack, you will get realistic 1.5 hours or more at 2A (due to conversion efficiencies and other factors). More if you get those 11000 mAh or bigger packs. – Passerby Jun 07 '20 at 02:18
  • @Passerby Is there any circuit in them that I could just buy? – EmeraldVolts Jun 07 '20 at 15:24
  • @Passerby I'm just gonna go with straight AA batteries, rechargeable, or alkaline. – EmeraldVolts Jun 07 '20 at 17:54

2 Answers2

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LED strips designed for 5V will typically work with a power supply voltage from 3.5 to 5.5V. So there is a fair chance that with 6V (with new batteries it could even be as high as 6.6V), you could destroy the LED strip. A voltage divider as the one you describe, will not work, since the current through the resistors would have to be much too high. Even a solution with a simple series resistor would not work because the operating current is not constant. Next idea could be to use a Zener diode with a series resistor, but again, the current through the diode would cause a lot of power dissipation.

A series diode (e.g. 1N5404) would reduce the voltage from 6V to about 5.3V (or at 2A rather 5V). However, battery voltage will decrease rapidly with time and at the end of the battery life time, the battery voltage will only be approximately 4V and the series diode would reduce that to about 3.3V. So you would loose a little bit of your battery capacity.

A low dropout voltage regulator could be another choice. However, it must be rated for the maximum operating current of the LED strip and the dropout should be well below 1V. Furthermore, a linear regulator will have a maximum dissipation power of about 2W.

Although it is technically possible to get 2A from a AA battery, the initial internal resistance is between 0.15 and 0.3 ohms per cell, which would lead to a voltage drop of 1.2 to 2.4V. In addition, the battery capacity at these currents is significantly less than 1Ah and, consequently, the battery would be empty very quickly. Therefore, it does not seem to be a sensible choice. I would recommend to use C (or D) batteries.

Hufi
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  • So 3 AAA batteries (4.5) would work, but what do I do about the current? – EmeraldVolts Jun 06 '20 at 17:28
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    Most LED strips have an internal current control loop, so you usually do not have to worry about this – Hufi Jun 06 '20 at 17:37
  • But you said that getting 2A from 4 AAA batteries isn't good. – EmeraldVolts Jun 06 '20 at 17:46
  • Sorry, I mean AA Batteries. Most people are saying that drawing 2A from these batteries isn't good. – EmeraldVolts Jun 06 '20 at 17:51
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    Sorry, I misunderstood your question. Indeed, AAA batteries would be a bad choice, but you could try 3 C (or D) batteries. – Hufi Jun 06 '20 at 17:52
  • I'm trying to use batteries I commonly use so I don't have to go out of the way and buy batteries for only this. – EmeraldVolts Jun 06 '20 at 17:55
  • I found this online "At room temperature an AA has about 0.15 to .3 ohms internal resistance when fresh. I=1.5volts / 0.15 or 0.3 = 5 to 10 amps! But not for a long while! Practically considering that at lower temperatures and after the battery has been used some then the internal resistance is higher, the actual useful amps would be 1 or 2 amps." Does "the actual useful amps" mean like the lowest when the battery is almost done, or like the general amps? – EmeraldVolts Jun 06 '20 at 18:03
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    Usually AA alkaline batteries are only specified up to an output current of 1A. In practice, they can delivery more then 1A, but at 2A, they will only last about 30 minutes and they could get rather hot. Furthermore, the internal resistance of a fresh cell is between 0.15 and 0.3 ohms, thus with three cells, this would give a voltage drop between 0.9 and 1.8V. You could try, but I doubt whether this is a good solution. – Hufi Jun 06 '20 at 18:20
  • So 1 can do 1A, so why can't 4 do 2? – EmeraldVolts Jun 06 '20 at 21:15
  • What if I used 4 rechargeable AA batteries. Each is like 1.2 volts, 4 of them would make 4.8 volts. Online it says that the internal resistance is about 30mΩ-100mΩ. That means .03Ω-.1Ω right? Using ohms law to find the current, V/R=I, and the max resistance, that should be 1.2/.1=12. So a single rechargeable AA battery can pump out 12 amps? Correct me if I'm wrong. – EmeraldVolts Jun 06 '20 at 23:54
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There's some good info on the internal circuitry of LED strips here. You will see that any practical LED strip design will include internal current limiting (usually just a series resistor) such that a 20% overvoltage shouldn't be a problem.

But you should also Google for "AAA battery voltage vs current" and read some of the references, so you'll understand better the realities of battery application.

You will see that 2A is far beyond the maximum current a AAA battery can supply, especially for any practical amount of time. You will also see that the output voltage of a battery depends on the current you draw from it, because the battery itself has internal resistance, that battery voltage declines with discharge for most types, and that even the initial voltages are only nominal.

A "1.5" Nickel-metal-hydride battery's actual voltage is only about 1.2V, a perfectly justifiable falsehood because the voltage of an alkaline "1.5V" battery will fall continuously throughout its life, and any circuitry properly designed to run off them will be designed to work even when they're down to less than 1.0 volts.

The output of a nominal "1.5V" lithium battery such as the Energizer L92 (Google its product datasheet) will be 1.8V when new, drop quickly to 1.7V if lightly loaded, or to 1.5V if you draw 100 mA from it, and will steadily decline to about 1.3V at end-of-life (where you've drawn about 1300 milliampere-hours from it). Trying to draw 2A continuous current from an L92 would probably cause it to explode and start a very nasty fire.

It's really important to get and read battery datasheets, especially for any heavy-load application. A bomb is in essence a container of chemicals whose total potential reaction energy is released in a short time. A battery is a container of chemicals designed with the assumption that their total potential reaction energy will be released in a controlled way over some extended period of time. Overloading or short-circuiting a battery turns it into a bomb. (The same applies to any energy-storage device.)

user254583
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  • Sorry, I meant AA batteries. Does that change anything though? – EmeraldVolts Jun 06 '20 at 17:56
  • I found this online "At room temperature an AA has about 0.15 to .3 ohms internal resistance when fresh. I=1.5volts / 0.15 or 0.3 = 5 to 10 amps! But not for a long while! Practically considering that at lower temperatures and after the battery has been used some then the internal resistance is higher, the actual useful amps would be 1 or 2 amps." Does "the actual useful amps" mean like the lowest when the battery is almost done, or like the general amps? – EmeraldVolts Jun 06 '20 at 18:03
  • What if I used 4 rechargeable AA batteries. Each is like 1.2 volts, 4 of them would make 4.8 volts. Online it says that the internal resistance is about 30mΩ-100mΩ. That means .03Ω-.1Ω right? Using ohms law to find the current, V/R=I, and the max resistance, that should be 1.2/.1=12. So a single rechargeable AA battery can pump out 12 amps? Correct me if I'm wrong – EmeraldVolts Jun 06 '20 at 23:55