# 10w ebay LEDs, questions on power



## mackinthebox (Oct 29, 2011)

I know that LEDs require a constant current source
the specs on the LEDs I purchased are 9 to 11 volts and 1A or 1000ma
I purchased 4 of them as well as 4 1000ma constant current drivers for them

connecting the 4 with the equipment I have is a no brainer

what Im wondering now is for my future build

the LEDs are going to be used for a DIY aquarium light
the aquarium currently has fish only and no plants but the second project will be a 55 gallon tank with plants and fish

my plan for that tank will be 10 cool white 10w leds and 10 blue 10w leds
I would rather power them all off of 1 power supply

from what Ive read if I wire the LEDs up in series I would need about a 90 volt DC power supply that supplies 1A for each set of 10 LEDs
I would need a constant current DC-DC regulator (unless I can find a sufficiently powerful constant current power supply)

I thought about wiring them in parallel but if I had a single LED fry on me the rest would wind up with way too much current and fry as well

can someone confirm for me if Ive done the math correctly and if I am right in my assumptions?


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## deadrx7conv (Oct 29, 2011)

They are not sets of 10 if you wire all 30 in series. Its a single set of 30. 
If you are using 3v LEDs, and not the earlier 10v, then all you have to do is find a driver that can output in that 90-100v range with the current that you need. 3w * 30 is a driver of at least 90w. They are out there if you go the single driver route. 

The other option is to use a separate driver for each string of 10. If a driver burns out, you still have the other 2 independent strings. Would you want your aquarium out of ALL light while you wait for a new driver to come in the mail? IMO, I'd run multiple drivers unless installation space was an issue.


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## mackinthebox (Nov 2, 2011)

thanks for the info
so my assumption was correct, that I add the voltage together for the total voltage from the supply and the current remains the same?

so 10 LEDs at a rated 9v each (theyre the 10w LEDs with 9 smaller LEDs integrated into a single light) with a rated 900ma would need a 90V 900ma driver?

I will have more than one string, right now Im just trying to make sure I understand how to power them correctly
I will probably have 3 strings of 5, so 3 drivers at 45V and 900ma which would be about 40W per driver


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## evilc66 (Nov 2, 2011)

Your setup seems excessive for a 55g freshwater planted tank. I don't see a need for so many blue LEDs either. A 1:1 ratio of blue to white is typically reserved for reef setups which normally require a much higher color temperature than the typical 5000K-8000K, and require a lot more blue light for growth. I understand that blue LEDs do make certain fish color pop, but 10 10W LEDs seems really excessive. If you do want to use blue LEDs, I would advise using a dimmable driver on those to allow you to dial in/out the amount of blue that you want.

On the whites, I don't think you would need 10, unless you are going with a very high light setup. You could probably cut the number of LEDs in half (or close to it), and still have a good setup for a tank of that size. What color temperature white LED were you looking at using?


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## blasterman (Nov 2, 2011)

> so 10 LEDs at a rated 9v each (theyre the 10w LEDs with 9 smaller LEDs integrated into a single light) with a rated 900ma would need a 90V 900ma driver?



Correct. Voltage is cumulative in series while current is cumulative in parallel. The problem though is that LED drivers over 48 or 54 volts are almost impossible to find. 

The 10watt LED's you mention are basically an array of 3x3 1watt LED's. If they are blue or white Chinese LED's you can assume the forward voltage is around 3.5~3.6 at 350mA. At 9v they will be very dim (3v each). My experience with using many of these is that 900mA is a good maximum current for long term use and forward voltage total is around ~10.5. You can drive them at an amp, but you'll notice some degree of dimming after 10k hours or so. 

Given that most fixed LED drivers come in either 700mA or 1000mA flavors you have a choice of either under driving a bit or over driving a bit (unless you get into dimmable . You are also correct that parallel runs are a bit dangerous given that if a single run becomes disconnected all the current flows to the remaining run and will likely kill the LEDs. Although counter intuitive, more parallel runs are safer than fewer given that if you had, for example, four parallel runs and you lost one string the remaining runs wouldn't get hit as hard as having two runs and one fails. I hope that makes sense.

My more basic advice *is to not use the 10watt Chinese LEDs - at all.* That is, unless you live in some weird alternate universe where you can only get products from Ebay. For instance, a 800 lumen Cool-White Bridgelux 802 runs at an even 700mA and costs $8.25 from a reputable company like Newark or Farnell. Unlike the Chinese LED the Bridgelux has reliable specs, better color, is also more efficient, likely brighter, and you have some limited choices of optic. In many cases they are actually cheaper per lumen than the 10watt junk pimped on E-bay.

You can drive three 802's in series with a $17 Mean Well LPC-35-700, and that's a fully regulated and common AC based driver. I haven't figured out the exact PAR requirements for freswater given I mostly build lights for salt, but I have set up Bridgelux based lights on a few freshwater tanks, and they look incredible. Cool white Cree's or Bridgelux look awesome on freshwater tanks and the light looks natural while pulling out great colors from fish. For a 55gallon you'll want at least half a dozen 802's. Cree XP-Gs work fine as well, although two of them are required to match a 802 and this costs a bit more. You save power though (25-33%) using the Crees.


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## blasterman (Nov 2, 2011)

> I understand that blue LEDs do make certain fish color pop, but 10 10W LEDs seems really excessive.



If I told you what I thought of blue LEDs on freswater tanks I'd get banned from Candlepower 

Regular cool-white LED's on freshwater look incredible. The guppy breeder I set up for a friend rivaled anything in the salt water world. I'm just not as familiar with PAR requirements for FW plants, although we both know it's a lot less than for acropora.


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## mackinthebox (Nov 2, 2011)

To respond to some of the questions, I was using the numbers for ease of multiplication and to ensure i had my math right
I was planning on using 10 of each color, white and blue, on the tank but for now Ive only ordered 4, as a test

I probably would overdo it on the blue so I might just make it half and half with blue/red and wire in some dimmers as advised

when it comes to planted tank there usually is no such thing as too much light 
I might decide later to reduce the number of LEDs used once Ive tested the 4 i have on order now

thanks for the info blasterman
in total for the 4 LEDs, heatsinks, and drivers ive spent around 50 bucks and had free shipping
for now Im just using the 4 on a breeding/grow out tank that is bare
the questions were to ensure i had done my research correctly and will be for a 55 gallon I plan to plant in a couple months

thanks again for all the info 
I will post some pics when i get the leds set up


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## evilc66 (Nov 3, 2011)

mackinthebox said:


> when it comes to planted tank there usually is no such thing as too much light
> I might decide later to reduce the number of LEDs used once Ive tested the 4 i have on order now



Don't know about that. The higher the light intensity, the more you have to add CO2 and fertilizers, to the point where if you screw up, or miss a day or two, then algae can take hold really easily. I think you will find on some of the forums like plantedtank.net that most people would prefer to run lower light with higher CO2 and fert concentrations to acheive the growth you want. With that setup, it's a lot harder for algae to start becoming a problem.


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