I wanted to build an led setup hooked to my battery but I am stuck at the voltage converter. I want to use bare 50w led's and later create some kind of enclosure for them. They require 32-35v, my pack is 25.9v nominal so I am looking at voltage converters. What I don't get is the input current. I see most state as 10 amp max input, does this mean that it can not be loaded with so many lights that it will draw more then 10amp from the battery or is there a max size the battery can be in ah?
Voltage converter
- Thread starter silviasol
- Start date
If you mean input current on the LEDs, that means you can't flow more than that thru them, or you'll damage them.
If you mean input current on the DC-DC converters, that means that's the max current it would ever be able to draw under normal operation (so you can size the input fuse correctly).
If you mean input current on the DC-DC converters, that means that's the max current it would ever be able to draw under normal operation (so you can size the input fuse correctly).
Drunkskunk
100 GW
Also, if the LEDs have a 10 amp spec listed, it means they don't have a driver, so you'll need to add one before you hook them up or they will blow.
Ok makes sense. I have been asking around on ebay for awhile but can never get a good answer. What I am trying to figure out now is what converter can I use with a battery. Seeing as how the voltage will drop will a converter hold the 32v-34v led power thru the entire battery cycle or will it lower along with the voltage of the battery?
dnmun
1 PW
how much power do the leds need? they only need a few volts to work.
Gregory
100 kW
He is talking about the "floodlight" style LED arrays with 33V 50W.
Use those ebay ones for proof of concept, but I would spend the money on proper Bridgelux units for actual use. At least they will output the lumens they claim, run cooler and live longer.
A DC-DC BOOST or STEP UP LED driver will hold the 33V that you set across the whole discharge of the battery.
Use those ebay ones for proof of concept, but I would spend the money on proper Bridgelux units for actual use. At least they will output the lumens they claim, run cooler and live longer.
A DC-DC BOOST or STEP UP LED driver will hold the 33V that you set across the whole discharge of the battery.
Good to know, thank you! Will look for bridgelux. Is 5000lm-8000lm led's overkill or illegal to use on the road? What do you really need for seeing enough going 20-30mph. I nearly took a dive on my scooter hitting some plastic car part on a bike path a few weeks ago.
If you mean the bare LEDs, then yes, that's how all LEDs work--they are current-driven devices, that also have a maximum voltage that can be across them (because they "short out" the rest of it, just like other diodes).
LED simply means Light Emitting Diode , so like other diodes they ahve a "forward voltage drop" (Vf), that is their voltage "requirement". If you don't have at least that voltage an LED won't light up properly, and if you have more htan that voltage you must have a resistor in series with the LED to "absorb" the excess.
Then they *also* have a maximum current thru them (like other diodes) before damaging them, and a minimum current to generate the light you want. The more current, the more light, up to the maximum current limit.
You can use just a resistor of sufficient wattage capability in series with an LED to limit it's current, but when you do that you must size the resistor so that a the maximum fully-charged battery voltage input it won't allow more current thru the LED than it can handle. And then as the battery voltage drops, the current thru the LED drops, and thus it's brightness too.
To figure out the resistor value you subtract the Vf (forward voltage drop) of the LED from the max battery voltage to get the voltage across the resistor. Then use the Vf and the desired current thru the LED (which will be the same as that thru the resistor) to calculate the needed resistance and wattage of the resistor, using Ohm's law.
Alternately, you can buy (or design/build) a driver board for the size/type of LED and battery voltage range you have, which will work better and be more efficient than the resistor method.
Some of the drivers also have brightness selection inputs too, or flashing modes, etc., which could be handy. For instance, you could have a "road/traffic" brightness that's a lot dimmer, and an "offroad/no traffic" brightness that is the full output that would otherwise blind oncoming traffic, but make it a lot easier to see in some situations.
(you can do that with resistors too but you have to have two different ones and a switch between them, or parallel two identical ones for Bright and disconnect one for Dim).
LED simply means Light Emitting Diode , so like other diodes they ahve a "forward voltage drop" (Vf), that is their voltage "requirement". If you don't have at least that voltage an LED won't light up properly, and if you have more htan that voltage you must have a resistor in series with the LED to "absorb" the excess.
Then they *also* have a maximum current thru them (like other diodes) before damaging them, and a minimum current to generate the light you want. The more current, the more light, up to the maximum current limit.
You can use just a resistor of sufficient wattage capability in series with an LED to limit it's current, but when you do that you must size the resistor so that a the maximum fully-charged battery voltage input it won't allow more current thru the LED than it can handle. And then as the battery voltage drops, the current thru the LED drops, and thus it's brightness too.
To figure out the resistor value you subtract the Vf (forward voltage drop) of the LED from the max battery voltage to get the voltage across the resistor. Then use the Vf and the desired current thru the LED (which will be the same as that thru the resistor) to calculate the needed resistance and wattage of the resistor, using Ohm's law.
Alternately, you can buy (or design/build) a driver board for the size/type of LED and battery voltage range you have, which will work better and be more efficient than the resistor method.
Some of the drivers also have brightness selection inputs too, or flashing modes, etc., which could be handy. For instance, you could have a "road/traffic" brightness that's a lot dimmer, and an "offroad/no traffic" brightness that is the full output that would otherwise blind oncoming traffic, but make it a lot easier to see in some situations.
(you can do that with resistors too but you have to have two different ones and a switch between them, or parallel two identical ones for Bright and disconnect one for Dim).
Why must electronics be so confusing, lol. I suppose led, light emitting diode, should have rung a bell but I just don't think. Thanks for clearing it up I have more understanding now.
My 7 series Lipo 40ah pack is a great deal of amps for the the 1500ma requirement led's I have been looking at. Should I even be looking into using the onboard pack or make another smaller 5ah or so pack? I am going to do some research on the resistor, ohms law.... and hope it makes sense to me. Of course my pack being 29.6v fully charged I will need to step up the voltage as well to the 32-34v(on the cheaper chinese led's).
My 7 series Lipo 40ah pack is a great deal of amps for the the 1500ma requirement led's I have been looking at. Should I even be looking into using the onboard pack or make another smaller 5ah or so pack? I am going to do some research on the resistor, ohms law.... and hope it makes sense to me. Of course my pack being 29.6v fully charged I will need to step up the voltage as well to the 32-34v(on the cheaper chinese led's).
Gregory
100 kW
Lebowski
10 MW
what you actually need for driving LED's I think is a current source. Something that outputs 10 A independent of the voltage it is loaded with.
The LED's will then take the 10A and across them will be some arbitrary voltage that you're not interested in.... When the battery
voltage is higher than the LED voltage a buck converter with current control would do nicely. A few power parts, a u-Controller and a current sensor.
The LED's will then take the 10A and across them will be some arbitrary voltage that you're not interested in.... When the battery
voltage is higher than the LED voltage a buck converter with current control would do nicely. A few power parts, a u-Controller and a current sensor.
Lebowski said:
Most I see are 30v plus, I have a 29.6v full charge pack. Was thinking the bridgelux below with a converter like the previous posts listed. I will have to find some kind of heatsink for it also I guess. Also some way to adjust the brightness on the fly.
http://www.ebay.com/itm/1-PC-100w-Warm-White-3000-3500k-Led-Chip-Bridgelux-45-mil-led-light-DIY-/201072284326?pt=LH_DefaultDomain_0&hash=item2ed0d792a6
Assuming your meter simply uses a shunt between battery and controller, then yes--just put the converter on the controller side of the shunt, and it will measure the power used by the light/converter as well as the controller.
Turn off the controller to see what the light/converter uses by itself.
(and turn off the light but not the converter to see what the idle draw of the converter is).
If your meter is using the shunt of the controller to determine power usage, you'll have to add a wire inside the controller on the FET side of the shunt to go to the converter negative to see it's power draw.
Turn off the controller to see what the light/converter uses by itself.
(and turn off the light but not the converter to see what the idle draw of the converter is).
If your meter is using the shunt of the controller to determine power usage, you'll have to add a wire inside the controller on the FET side of the shunt to go to the converter negative to see it's power draw.
Hmm, well I have other problems now. I hooked it up to my 6s lipo pack, a large spark at the dean connector happens(and anytime I connect it), I get the green led light (cut off indicator) and no constant current led. The out voltage on the converter is just under the in voltage. The led will come on but adjusting the current does nothing. I try to adjust the cut off voltage dial and am not able to get it to boost the power or turn the led to red(I guess that means it is on and not in cut off mode).
Gregory
100 kW
So the first step is with the LED array disconnected you set the DCDC to output approx 33 to 34V. But that's not working and your're only seeing 22V?
PS thats an array that claims to be assembled using Bridgelux dies. Not an actual Bridgelux end product, hope it works OK.
PS thats an array that claims to be assembled using Bridgelux dies. Not an actual Bridgelux end product, hope it works OK.
Found this video which helped. He is using the same converter. Seems to be working ok I just had the dials wrong. I just maxed out the voltage cut off so it was at 34v, then mess with the current dial until it reaches max brightness however I am only getting 30v, hopefully my 7s pack I will hook up to will get me to the 32v. It is bright as hell though 
https://www.youtube.com/watch?v=tcWyIEBGJMU
After more messing with it.....
low to max brightness
https://www.youtube.com/watch?v=MKeAODu-c5o&feature=youtu.be
I set the voltage with the led not connected to 34v, when I connect the led it drops the voltage.
https://www.youtube.com/watch?v=DW5BOG0RNsc&feature=youtu.be
Now when I raise the current the voltage goes up?
https://www.youtube.com/watch?v=XjqaihRqVnw&feature=youtu.be
https://www.youtube.com/watch?v=tcWyIEBGJMU
After more messing with it.....
low to max brightness
https://www.youtube.com/watch?v=MKeAODu-c5o&feature=youtu.be
I set the voltage with the led not connected to 34v, when I connect the led it drops the voltage.
https://www.youtube.com/watch?v=DW5BOG0RNsc&feature=youtu.be
Now when I raise the current the voltage goes up?
https://www.youtube.com/watch?v=XjqaihRqVnw&feature=youtu.be
Alan B
100 GW
On LEDs the current is what is important. The voltage will change with temperature and current. Regulating the current is the primary goal, the voltage will do what it needs to.
Car headlights are nominally about 1000-1500 lumens each, and they have a specific pattern (especially for low beam) to keep light out of oncoming driver's eyes.
Floodlights are good for offroad use but are not safe for onroad lighting (due to blinding oncoming drivers and pedestrians) and would be illegal on any type of licensed vehicle, they are required to have SAE/DOT approved lights (in most places).
Car headlights are nominally about 1000-1500 lumens each, and they have a specific pattern (especially for low beam) to keep light out of oncoming driver's eyes.
Floodlights are good for offroad use but are not safe for onroad lighting (due to blinding oncoming drivers and pedestrians) and would be illegal on any type of licensed vehicle, they are required to have SAE/DOT approved lights (in most places).
Alan B said:
Yes I will have a different light used for normal riding then a switch for this led. In the future I plan on adding a second board to control the brightness like amberwolf stated in the previous post. Just need to mount it to my scooter now with some kind of heat sink I guess.
I bought these led's to use with these cool little nimh batteries I pulled out of a battery pack. The led's are rated at 240 to 300mah at 3-3.4v. 3s of the batteries is about 4v fully charged and 360mah. Will they blow if I do it at that voltage/current or will they be alright until they get down to nominal voltage?
http://www.ebay.com/itm/191315131246?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
http://www.ebay.com/itm/191315131246?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
John in CR
100 TW
Thanks for the link. I didn't realize high power 1W LEDs could now be had so cheap. I'm looking at that voltage drop range and thinking how perfect it would be to use with 1s of Lifepo4. Some of those replying in the other thread seem to be a bit tangled up in their previous experiences with LEDs and having to come up with fancy controls for their LEDs because the voltage drop of the LED didn't match their power source, and forgetting about how ohms law can make driving them so simple.
If you supply those LEDs with 3.0-3.4V that voltage drop highlights the internal resistance of the LED itself, and in that range of supply voltage the LED itself will regulate the current itself. That's why I'm so intrigued with them, because that's the prime voltage range of LiFePo4 cells under light loads. I will be able to set a single cell solar charge cutoff voltage of a nice conservative 3.5V, and after dark the voltage will drop a bit, and there will be some voltage drop in the wiring to get to the LEDs. That means I could direct connect those LEDs to a 1s Lifepo4 battery using only a switch in between. Just to be conservative I'll probably put a low value resistor in line just to be safe, as well as not drive the LED at full power.
Since your voltage won't be as precise, the easy way would be to just look up a LED resistor calculator and put that in line with your LEDs. As an alternative there are some really cheap devices on Ebay with variable current and voltage settings and tune in exactly what your want. Then put LEDs in series to best match the total pack voltage. I picked up some for under $3/ea that could handle in input voltage from under 10V up to 36V, and output from 3V-30V. I doesn't need a heat sink unless you go above 1A, so just one of those units would be fine driving 3 of your LEDs in parallel up to 8 or 9 in series. 24 or 27 of your 1W LEDs would make an awesomely bright light. You could use 2 of those units and a 3-way switch (one for high beam, one low, and the other off) and tune each for different amounts of light output using the same LEDs. Since it's all so cheap, then going conservative and using 3 separate drivers, each with only 1p string of 8 series LEDs would be even better. 1 ON is low, and the other ON lights all 3. That improves safety, since a single LED burning out won't quickly kill the another 2 in parallel and leave you with no lights high or low.
Getting LEDs lit is simple, and your more difficult task will be in controlling where all that light goes. You want a nice bright light, but shining primarily on the road to not blind oncoming traffic but still give you plenty of light to see. You also don't want things lit too much, especially close to you, because that can significantly reduce your ability to see things in the darker areas you haven't lit as well. That's a common mistake of those running very bright LEDs that are especially bright in a relatively small area of the beam. What may show up in the camera photo might not be what they can really see, because the camera won't capture the incredibly bright spot in the center that causes our own irises to close and see poorly at the periphery.
John
If you supply those LEDs with 3.0-3.4V that voltage drop highlights the internal resistance of the LED itself, and in that range of supply voltage the LED itself will regulate the current itself. That's why I'm so intrigued with them, because that's the prime voltage range of LiFePo4 cells under light loads. I will be able to set a single cell solar charge cutoff voltage of a nice conservative 3.5V, and after dark the voltage will drop a bit, and there will be some voltage drop in the wiring to get to the LEDs. That means I could direct connect those LEDs to a 1s Lifepo4 battery using only a switch in between. Just to be conservative I'll probably put a low value resistor in line just to be safe, as well as not drive the LED at full power.
Since your voltage won't be as precise, the easy way would be to just look up a LED resistor calculator and put that in line with your LEDs. As an alternative there are some really cheap devices on Ebay with variable current and voltage settings and tune in exactly what your want. Then put LEDs in series to best match the total pack voltage. I picked up some for under $3/ea that could handle in input voltage from under 10V up to 36V, and output from 3V-30V. I doesn't need a heat sink unless you go above 1A, so just one of those units would be fine driving 3 of your LEDs in parallel up to 8 or 9 in series. 24 or 27 of your 1W LEDs would make an awesomely bright light. You could use 2 of those units and a 3-way switch (one for high beam, one low, and the other off) and tune each for different amounts of light output using the same LEDs. Since it's all so cheap, then going conservative and using 3 separate drivers, each with only 1p string of 8 series LEDs would be even better. 1 ON is low, and the other ON lights all 3. That improves safety, since a single LED burning out won't quickly kill the another 2 in parallel and leave you with no lights high or low.
Getting LEDs lit is simple, and your more difficult task will be in controlling where all that light goes. You want a nice bright light, but shining primarily on the road to not blind oncoming traffic but still give you plenty of light to see. You also don't want things lit too much, especially close to you, because that can significantly reduce your ability to see things in the darker areas you haven't lit as well. That's a common mistake of those running very bright LEDs that are especially bright in a relatively small area of the beam. What may show up in the camera photo might not be what they can really see, because the camera won't capture the incredibly bright spot in the center that causes our own irises to close and see poorly at the periphery.
John
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