DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius Sat)

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bsterne
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Joined: 07/14/2008
Points: 5

I have a Wilderness Energy BL 36 converted mountain bike. I would like to power a Sirius Satellite Radio receiver, mini amplified speakers, and some LED lights off of my 36v SLA batteries. The Sirius receiver takes in 5v 1.5A. My mini speakers take 4 AA batteries, so 6v. I'm sure I can find LED lights running at 5v or 6v. I think all of this should be able to run on 5v or 6v. I have a lighter-socket 12v to 5v DC-to-DC that came with the Sirius receiver so it can plug into a car's 12v which I can use. At some point I might upgrade my bike to 48v. So I am looking for a DC-to-DC converter that will handle 36v or 48v input, and output either 5v, 6v or 12v. Any reliable suppliers for such a converter?

Thanks!
- Brendan

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Dave-s
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Joined: 03/10/2008
Points: 58
Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius Sat)

You can also run the speakers off the 5v, so you will need only 1 DC-DC converter.
DC-DC converters are not cheap, so you might want to reconsider this solution.
Just run the radio,speakers and lights off rechargable Ni-mh AA batteries, and carry spare cells in your pack.

evDreamer
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Joined: 11/21/2007
Points: 36
Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius Sat)

For low amps like your application, 5v/6v voltage regulars are cheap and readily available for $1-2 dollars.

But input voltages as high as 48v are less available.
One way to get around this is to get 3 voltage regulators for each of the 12v batteries, and each regulator will take the 12 volt input and output 5/6 volts.

For $0.35, input at 35v max, Output current to 0.5A, Output voltage of 5v
http://www.goldmine-elec-products.com/prodinfo.asp?number=G13017
data sheet: http://www.st.com/stonline/products/literature/ds/2143/l7805c.pdf (look at the table for L7805)

For 6volts, get the 7806:
http://www.goldmine-elec-products.com/prodinfo.asp?number=A10483

For higher amps(claimed 3amps), use something like this:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G15674

bsterne
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Points: 5
Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius Sat)

I don't want a separate battery for accessories. I am willing to pay for the convenience of a single plug-in to recharge at night. I also don't want to tap the individual 12v batteries.

bsterne
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Joined: 07/14/2008
Points: 5
Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius Sat)

I have ordered one of these http://www.dimensionengineering.com/VHVBEC.htm, but I don't fully understand how to wire it. Any advice?

Model: VHVBEC
Specifications: Input voltage: 9V to 60V (3s-14s lithium, up to 40 cell NiMH)
Output current: 2.5A (~6 standard servos, 4 digital)
Weight: 17g/.6oz (including wires)
Universal connector fits all receivers

nasukaren
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Points: 188
Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius Sat)

What a great BEC and a good find. I'm not sure why you're having problems wiring it. You'd just want to tap a 48V powerline and feed it into he +/- feeds on the left side and use the receiver power on the right side for your 5V equipment.

Just remember that red is + and black is - and you should be just fine. Just don't wire it backwards!

Your local RC hobby store will have the appropriate connectors (prewired) if you don't trust your soldering skills.

Karen

p.s. I just bought this one: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250270816138
on ebay. It only went up to 40V but it's only about $15 w/ shipping. Since I plan on running my moped at 28.8V, 36V, or 38.4V (i.e., not above 40V), I should be OK.

__________________

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

slbaker
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Points: 59
Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius Sat)

Hi Karen,

Can you send me the schematic for the LM2576HVT-12-ND down-converter?
I have a 48V bicycle project and I would like to run some 12V accessories.

You can see a picture of my bike project here :-)

http://picasaweb.google.com/scott.l.baker/LongBikeProject#

Regards,
Scott

slbaker
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Points: 59
Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius Sat)

Here's a schematic for a very simple 20V-to-60V DC input to 12V DC output.
All the parts are available at digikey.com and the
parts cost is less than $10 (not counting the circuit board).
I may decide to make a circuit board if I can find some spare time ;-)
This same circuit can be used to make a 5V DC output regulator by just
changing the LM2576HV-12 to an LM2576HV-5 and a 6V regulator can be made
by adding a single resistor to the regulator's feedback path of the
5V regulator circuit.

http://mysite.verizon.net/sierracircuit/Free-Stuff/DC-DC-12V/schematic.pdf

Regards,
Scott

chas_stevenson
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Points: 1309
Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius Sat)

slbaker,

I was wondering about some additional specs. What is the max current at the 12v output? How many watts will this DC to DC converter handle?

Thanks,
Grandpa Chas S.

slbaker
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Points: 59
Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius Sat)

The LM2576HV-12 switching regulator is rated at 3A, but the coil that I
chose is rated at 2.5A continuous current. Even so, that's 30W.
I have not built one of these yet, so I don't know how hot
the coil or regulator would get when running continuous high current.
The LM2576HV's TO220-5 case allows for a heat sink if needed.

slbaker
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Points: 59
Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius ...

I found a supply of high current inductors at my favorite
surplus electronics place and I built the circuit.

I'll probably bolt on a chunk of Aluminum or copper as
a heatsink. Here's a pic.

http://mysite.verizon.net/sierracircuit/Free-Stuff/DC-DC-12V/12V-Conv.jpg

win32forth
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Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius ...

Yes, a heat sink would be a very good idea, since that little regulator needs to dissipate 144 watts with a 3 amp load and 60 volts input, or 96 watts with a 3 amp load and 48 volts input. I don't remember the specifics, but I would think you would need perhaps 10 square inches of aluminum surface area, and some air flow to dissipate the watts that the regulator will give off. Your total power consumption with a 3 amp load will be 180 watts with 60 volts input, which is a lot...

A more efficient method of regulation would be to buy a switching converter and use that. They aren't that expensive.

Tom

slbaker
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Points: 59
Re: DC-to-DC 36v/48v to 5v/6v/12v for Accessories (Sirius ...

The LM2576HV-12 is a switching regulator chip.
The 3A max rating is for the output current, so the max power is 3Ax12V=36W
I don't plan to run it anywhere near its max rating.

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