DC-DC Converters ... who has the best price?

LI-ghtcycle

LI-ghtcycle

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Oregon City Oregon
Hello, I'm looking to take roughly a 53V nominal battery down to 11 - 12v with a DC to DC converter, and I'm not looking to go cheap, but I would like to know who has one for the most reasonable price for a quality converter.

I see people talking about some on ebay for $5-$10, and I see one from ebikes.ca that is $55.

What's the main difference? Can I get away with a 48V DC - DC converter or do I need something higher rated to handle my 53V pack?

Thanks! :D

P.S. I will be using this converter to power my Magic Shine headlight, so I'm not sure the amp draw needed, but if I understand correctly, the MS usually runs on it's own battery pack of 7.4V 2.6AH Li-Ion, however it's a big plus if this converter also has a 3V- 4V conversion as well as the 12V, since I will be running my blinkers/tail light on 3V-4V.
 
Thats funny I was just looking for these for someone else...
405-001.jpg


Good for 50W each 12V output, plus has yer 3.3V too... Ya can find cheaper but I`d spend the little extra for Assembled-in-USA-peace-of-mind
Lock
 
LOL!! That is the exact unit I was just going to ask about that I just found on ebay, thanks Lock! :mrgreen: ... now my question is how many watts the Magic Shine light draws, I want to make sure the 50W 12V will be enough to power it?

I know that it uses a battery pack that is somewhere around 7.2V 2.6AH and I'm sure that if I was smarter I would be able to calculate the wattage it uses. :roll: :lol:

I found that DC - DC converter here for $33 shipped!
http://cgi.ebay.com/DC-to-DC-Conver...emQQptZLH_DefaultDomain_0?hash=item3354f3b639
 
However, if I can get away with just 12V 2.5A (30Watt) then I can get it from the same company for about $14 :shock: :mrgreen: :twisted:

Anyone know if this is enough for my Magic Shine light on high mode?
 
LI-ghtcycle said:
I know that it uses a battery pack that is somewhere around 7.2V 2.6AH and I'm sure that if I was smarter I would be able to calculate the wattage it uses. :roll: :lol:
Click to expand...
Hehe... let me try. 7.2V x 2.6Ah = only 18.72Wh... like, 18.72W for one hour... If this pack runs the light for one hour = 18.72W, two hour run time = 9.36W, three hr = 6.24W... all waaay less than 50W max... Ya could probably shave a few bux and go for the lower-rated converter at 30W max...
Lock
 
LI-ghtcycle said:
Can you tell me which connectors are for the Input? I would guess where it says Vin (voltage in?)
Click to expand...
No idea for sure, but I believe your guess is correct. It looks like these are surplus to mfg'ing requirements for these folks:
http://www.cdtechno.com/

So pretty sure yer not going to find a handy manual to explain all the connections. But there's smart folks on ES that'll know all about how these work. Kinda curious to know what the Synch In and Trim connections are about...
LoKc
 
The cheapy Hitron one you can get on ebay works a treat.

I've been dragging 40w out of mine for over a year I guess, despite the 30w max rating.


18-72v input, works fine with 74v.

Outputs:
3.3v 0.5A
6v 3A (I'm running 5 or 6 amps)
12v 1A

Ebay item number: 130353756516
 
Rather than run your light directly into the converter why not create a power strip? I did and I have a stella 200 light. Also a blinking red tail light. I intalled a cigarette lighter to charge my iphone or other things. There is room on the power bus for other toys. I am looking for a cool horn that is small.

ebent
 
The Trim pin is used with an external circuit to adjust the voltage of the outputs. I can't remember what Sync is for. Neither of them are particularly useful for our needs because none of the items we would be hooking this up to will require voltage accuracy.
LI-ghtcycle said:
Can you tell me which connectors are for the Input? I would guess where it says Vin (voltage in?)

Thanks! 8)
Click to expand...
I have a very similar one, but with two 12V outputs and one 5V output.
These will require you to short -V1 pin to the ON/OFF pin in order for them to be turned on.
It's also highly advisable to mount them to a heatsink of some kind or they won't last very long.

+Vin = pack voltage +
-Vin = pack voltage -

+V1 = 3.3V +
-V1 = 3.3V -
+V2 = 12V +
-V2 = 12V -
+V3 = 12V +
-V3 = 12V -

If you want a simple ignition setup use a keyswitch to toggle power from the battery pack to +Vin, or to short ON/OFF to -V1.
Then power the coil of a 12v contactor from one of the 12V outputs. The contactor when powered will complete the power circuit to the controller.
 
captainslug said:
The Trim pin is used with an external circuit to adjust the voltage of the outputs. I can't remember what Sync is for. Neither of them are particularly useful for our needs because none of the items we would be hooking this up to will require voltage accuracy.
LI-ghtcycle said:
Can you tell me which connectors are for the Input? I would guess where it says Vin (voltage in?)

Thanks! 8)
Click to expand...
I have a very similar one, but with two 12V outputs and one 5V output.
These will require you to short -V1 pin to the ON/OFF pin in order for them to be turned on.
It's also highly advisable to mount them to a heatsink of some kind or they won't last very long.

+Vin = pack voltage +
-Vin = pack voltage -

+V1 = 3.3V +
-V1 = 3.3V -
+V2 = 12V +
-V2 = 12V -
+V3 = 12V +
-V3 = 12V -

If you want a simple ignition setup use a keyswitch to toggle power from the battery pack to +Vin, or to short ON/OFF to -V1.
Then power the coil of a 12v contactor from one of the 12V outputs. The contactor when powered will complete the power circuit to the controller.
Click to expand...

Kewl! Thanks, but you lost me on the "contactor" part? What exactly is the contactor and what purpose does it serve?

And if I understand you correctly, I could just tie in the +Vin to my ignition switch and have the -Vin shorted to turn on and off the power to the DC- DC converter?
 
Tks captainslug! I'm thinking of picking up a few of these too... Dunno if they are a regular item for sale or not.
Re a heatsink, if going for the 50W-rated size, and if loads kept to maybe half this rated max, d'you think the sink still would be necessary? Guess they are normally installed in cabinets w/active cooling?
Lock
 
Lock said:
Tks captainslug! I'm thinking of picking up a few of these too... Dunno if they are a regular item for sale or not.
Re a heatsink, if going for the 50W-rated size, and if loads kept to maybe half this rated max, d'you think the sink still would be necessary? Guess they are normally installed in cabinets w/active cooling?
Lock
Click to expand...
It doesn't have to be much of a heatsink. Any heatsink will do, and even just bolting it onto the face of an aluminum L-channel should suffice for keeping it at a reasonable and safe temperature.
 
Thanks for the info Capt'n! :D

Now I can't WAIT to get this stuff in the mail, now I have no good way to even power my motor-computer, oh well, I'm sure it will all be here in the next few days. :mrgreen:
 
here's something @ http://www.ebikes.ca/store/store_accessories.php
scroll down to the bottom of the page
 
captainslug said:
Lock said:
Tks captainslug! I'm thinking of picking up a few of these too... Dunno if they are a regular item for sale or not.
Re a heatsink, if going for the 50W-rated size, and if loads kept to maybe half this rated max, d'you think the sink still would be necessary? Guess they are normally installed in cabinets w/active cooling?
Lock
Click to expand...
It doesn't have to be much of a heatsink. Any heatsink will do, and even just bolting it onto the face of an aluminum L-channel should suffice for keeping it at a reasonable and safe temperature.
Click to expand...

Pardon my asking, but help me out, it looks to me like this device is designed to operate at 104 F nominal? :? Here is the PDF for the unit:

http://www.part-datasheets.com/cds/vkp60.pdf

I also noticed that it has a rather large aluminum piece already attached at it's bottom. Does this still require some form of heat sink?

I'm planning on attaching this to an ABS plastic base with the same packing plastic that the pins were pushed into to protect it in shipping. it appears to be cool to the touch while in operation, but if needed I can fab up a small square of 1/4inch aluminum to be at the bottom.

Thanks!

8)
 
Yeah that's what it looks like it says ... 40 degrees CENTIGRADE nominal = 104 degrees farenheit.
Looks like it also depends on how many watts your load draws thru it. See in the table under "Thermal Inpedance" and "Case to Ambient". It says for ever watt that you use the case temp will be 8.2 higher than ambient temperature.

LI-ghtcycle said:
Pardon my asking, but help me out, it looks to me like this device is designed to operate at 104 F nominal? :? Here is the PDF for the unit:

http://www.part-datasheets.com/cds/vkp60.pdf

I also noticed that it has a rather large aluminum piece already attached at it's bottom. Does this still require some form of heat sink?

I'm planning on attaching this to an ABS plastic base with the same packing plastic that the pins were pushed into to protect it in shipping. it appears to be cool to the touch while in operation, but if needed I can fab up a small square of 1/4inch aluminum to be at the bottom.

Thanks!

8)
Click to expand...
 
Sacman said:
Yeah that's what it looks like it says ... 40 degrees CENTIGRADE nominal = 104 degrees farenheit.
Looks like it also depends on how many watts your load draws thru it. See in the table under "Thermal Inpedance" and "Case to Ambient". It says for ever watt that you use the case temp will be 8.2 higher than ambient temperature.

LI-ghtcycle said:
Pardon my asking, but help me out, it looks to me like this device is designed to operate at 104 F nominal? :? Here is the PDF for the unit:

http://www.part-datasheets.com/cds/vkp60.pdf

I also noticed that it has a rather large aluminum piece already attached at it's bottom. Does this still require some form of heat sink?

I'm planning on attaching this to an ABS plastic base with the same packing plastic that the pins were pushed into to protect it in shipping. it appears to be cool to the touch while in operation, but if needed I can fab up a small square of 1/4inch aluminum to be at the bottom.

Thanks!

8)
Click to expand...
Click to expand...

Hmmm I'm sure I'm not quite understanding you correctly Sacman, but it appears that what you are saying is that if I calculate the watts of power generated by this converter, which I come up with 119.4 watts total, and I'm sure that I can't multiply 119.4 x 8.2 F to get the temperature generated? (that's V1= 3.3V @ 18A, V2= 12V @ 2.5A and V3 = another 12V @ 2.5A terminal)

I'm just trying to make sure I don't burn it up, but I admit I am being a bit lazy, since replacing the frame, adding blinkers and head & tail lights is taking a lot of time, and I'm wanting to ride to my brother's house with it all finished tonight. :wink:
 
Sorry I didn’t mean to confuse you. I’m only pointing out things on the spec sheet that are relevant to your question of how hot this DC-DC converter gets. I’m only interpreting the things on the spec sheet that I think are helpful to answering your question. But I’m no expert on these things so don’t take what I say as absolute.

Okay now with that said… what I have noticed on the spec sheet are these 3 important parameters:
1) All the Output Specifications Tables say that “Total Combined O/P Power = 60 Watts Max”. So you can’t just add all the outputs together and come up with 119.4 watts. You’re limited to only 60 watts max.
2) In the “Common Specifications, All Models” , under “Operation/Specification” it says max operation temperature is 100 degrees Centigrade
3) In the “Common Specifications, All Models” , under “Thermal Impedance” it says the case temperature rises 8.2 degrees Centigrade (above ambient temp) for every watt.
So those are your 3 parameters… The one that gives the lowest temp is going to control. Now since 60 x 8.2 = 492 degrees C. That means the one that controls is 100 degrees Centigrade. That’s really how hot thing can get. Isn’t that enough to melt your ABS plastic base?

But you can also get a better idea of how hot this gets under the load you’re going to put thru it. Try to compute how many watts your blinkers, headlight, & tail lights are going to draw and multiply it by 8.2. That’s how hot (above ambient temp) it should run.

LI-ghtcycle said:
Sacman said:
Yeah that's what it looks like it says ... 40 degrees CENTIGRADE nominal = 104 degrees farenheit.
Looks like it also depends on how many watts your load draws thru it. See in the table under "Thermal Inpedance" and "Case to Ambient". It says for ever watt that you use the case temp will be 8.2 higher than ambient temperature.

LI-ghtcycle said:
Pardon my asking, but help me out, it looks to me like this device is designed to operate at 104 F nominal? :? Here is the PDF for the unit:

http://www.part-datasheets.com/cds/vkp60.pdf

I also noticed that it has a rather large aluminum piece already attached at it's bottom. Does this still require some form of heat sink?

I'm planning on attaching this to an ABS plastic base with the same packing plastic that the pins were pushed into to protect it in shipping. it appears to be cool to the touch while in operation, but if needed I can fab up a small square of 1/4inch aluminum to be at the bottom.

Thanks!

8)
Click to expand...
Click to expand...

Hmmm I'm sure I'm not quite understanding you correctly Sacman, but it appears that what you are saying is that if I calculate the watts of power generated by this converter, which I come up with 119.4 watts total, and I'm sure that I can't multiply 119.4 x 8.2 F to get the temperature generated? (that's V1= 3.3V @ 18A, V2= 12V @ 2.5A and V3 = another 12V @ 2.5A terminal)

I'm just trying to make sure I don't burn it up, but I admit I am being a bit lazy, since replacing the frame, adding blinkers and head & tail lights is taking a lot of time, and I'm wanting to ride to my brother's house with it all finished tonight. :wink:
Click to expand...
 
LI-ghtcycle said:
captainslug said:
Lock said:
Tks captainslug! I'm thinking of picking up a few of these too... Dunno if they are a regular item for sale or not.
Re a heatsink, if going for the 50W-rated size, and if loads kept to maybe half this rated max, d'you think the sink still would be necessary? Guess they are normally installed in cabinets w/active cooling?
Lock
Click to expand...
It doesn't have to be much of a heatsink. Any heatsink will do, and even just bolting it onto the face of an aluminum L-channel should suffice for keeping it at a reasonable and safe temperature.
Click to expand...

Pardon my asking, but help me out, it looks to me like this device is designed to operate at 104 F nominal? :? Here is the PDF for the unit:

http://www.part-datasheets.com/cds/vkp60.pdf

I also noticed that it has a rather large aluminum piece already attached at it's bottom. Does this still require some form of heat sink?

I'm planning on attaching this to an ABS plastic base with the same packing plastic that the pins were pushed into to protect it in shipping. it appears to be cool to the touch while in operation, but if needed I can fab up a small square of 1/4inch aluminum to be at the bottom.

Thanks!

8)
Click to expand...
If it is cool to the touch under the load you intend to use it at then you should be good. You could space it out from the ABS with some washers/nuts at the screw holes to future proof it in case you add more load later and it gets a bit warmer.
 
Hey ya'll I just wanted to point out that thunder struck motors has one that comes in a small metal case and is prewired for $35. It's rated at 10amps!



Also I had a question about calculating the drain on these.


Say I had a 50w halogen bulb. 50w/12v=4amps, but if I'm running the convertor through with 3 12v 14ah sla batteries how would you calculate run time? I was thinking it'd be like (3x14ah)/4amps=10.5 hour run time. Does that sound correct?
 
If the inexpensive DC-DC converter has an 85% efficiency and exactly a 12V output then your 12V/50W light will draw roughly 59W from your main pack or about 1.6A using a nominal 36V. If that's the only load on the battery then those 14Ah batteries may deliver 90% of rated capacity for close to an 8 hour run time.

A 50W halogen however is waaaaaaaaaay overkill for a bike so try to find a lower wattage replacement lamp. A 10W-20W halogen is probably all you'll need especially if you over-volt it.

Still with all of the efficient LED lights now available they are becoming the bike light of choice for many.

-R
 
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