Cheap boost converters to power things off 12v

[whiskthecat]

I was just posting this here in case anyone was unaware of these devices. They take in 12ish volts from your battery bank and output anywhere from 12v to 36v. I am currently using 2 to power my 40 inch LED TV and plan on adding another one to power my laptop. It sure beats having to run the inverter.

Inside my TV is a power supply board that takes in 120-240v and outputs 18v and 26v. I leave the cord unplugged and wired 2 of these boards up, one set at 18v and one at 26v and now the tv runs just fine off 12v battery power. Most laptop chargers are around 18v as well so it's just a matter of buying the connector or chopping the one you have and wiring to it.

[conachair]

+1

I use one to power my notebook, on a recent delivery it was on for days on end. Bearing in mind the output can only go down to within a Volt or so above the input. And sometimes they can be a bit rf noisy, though so far a capacitor on the in and out has sorted that out, though can't remember if that was specifically this unit, might have been a step down, I use a load of eBay dc-dc on the boat, really handy.

[travellerw]

Yup I use these all the time around the shop.. They can take a fair amount of punishment and drive pretty high loads.

I will second the RF noise though. THEY ARE SUPER NOISY and will probably affect VHF range. They are not only noisy on the output, but the input as well. I ended up having to put a Capacitor and Inductor on both input and output. Even then, if I brought it anywhere close to an AM radio it would interfere. A metal enclosure would be required to silence them completely.

[Sailorman Ed]

Whiskthecat - thanks , just bought 3 of them. Does the output stay steady even while the house voltage varies? ( low early in the morning and high during charging)

Do all modern TVs and monitors have these power supply boards that can be jumped?

[whiskthecat]

As conachair pointed out you can have some trouble near the thresholds of it's working range but you likely wouldn't even need to use one in that scenario. Like say something needed 14v and your batteries were above 14v. It doesn't really make sense to use a step-up/boost converter then since the voltages are already so close. But in my use case where I need 16v and 26v the batteries will always be below those voltages and the regulator will produce my required voltages regardless of variation in the input.

So the battery bank varying from 12v to 14v throughout the day won't make any difference to the converter. It will always output the correct voltage assuming the batteries are charged enough to provide power of course.

As for tv power supplies they can be somewhat diverse in their design and function. But most modern ones will have a one way diode feeding an output capacitor rated higher than the voltage the power supply is producing. So on my tv there are 2 different output capacitors, one rated at 35v and one rated at 25v. Upon attaching a volt meter to these I found my two operating voltages 16v and 26v. I then tuned my 2 boost converters using my volt meter and hooked them up to their respective capacitors and that's it, 12v tv on the cheap.

If you'd like I can probably find some time to pull the tv off the wall and take a few pictures of the inside. It could be a few weeks though. I've been meaning to reroute the A/V wiring back there anyways.

[Sailorman Ed]

If you'd like I can probably find some time to pull the tv off the wall and take a few pictures of the inside. It could be a few weeks though. I've been meaning to reroute the A/V wiring back there anyways.

That would be great. The first one will be to power up the netbook "boat computer" needing 19v

[whiskthecat]

That will be much easier than messing about with a TV power supply. Everyone should be using these things to power their laptops as opposed to bulky and much more inefficient AC inverters.

Take your voltmeter to the end of your laptops power cable and verify that the voltage is 19v and that the outside of the plug is ground (it almost always is but occasionally it is not).

Once you are sure of everything you can either order a cheapo chinese replacement charger for your laptop model and chop its plug off and wire to it. Or just chop your current chargers plug and wire to it if you don't intend to ever use it again on AC line power.

One more thing, often times these cables are coaxial so you might need a razor blade to shave off enough plastic insulation so you can have enough room to pull the ground shielding back and get to the inner conductor.

[jpstevens]

Originally Posted by whiskthecat

I was just posting this here in case anyone was unaware of these devices. They take in 12ish volts from your battery bank and output anywhere from 12v to 36v. I am currently using 2 to power my 40 inch LED TV and plan on adding another one to power my laptop. It sure beats having to run the inverter.

Inside my TV is a power supply board that takes in 120-240v and outputs 18v and 26v. I leave the cord unplugged and wired 2 of these boards up, one set at 18v and one at 26v and now the tv runs just fine off 12v battery power. Most laptop chargers are around 18v as well so it's just a matter of buying the connector or chopping the one you have and wiring to it.

Thanks Whiskthecat,- which of the many models do you recommend?

[conachair]

Youtube review of one here..

600W DC-DC Boost Converter Review and Play Around (This one's a keeper): http://youtu.be/cUpJs6Z41YM

[travellerw]

Just an FYI for anyone trying to use these on a Dell laptop.. Unfortunately they don't work as expected. Dell power supplies contain a 1 wire Eprom to verify that they are a legitimate power supply.

Although these boards will power a dell laptop, it will go into "limp" mode and allow the laptop to be powered, but not allow the battery to charge.

I ended up taking an old dell power supply apart and using part of the board (with the chip) to make it work.

[a64pilot]

My TV has a power brick that supplies 12V DC to the TV, I'm tempted to run it straight off the battery bank, but have ordered an adjustable step down converter, it has to have the input 1 V higher than output, so as long as my bank is 13 V I should be OK.
Has anyone else done this?

[whiskthecat]

If you are right on the threshold of being the same voltage and you just want regulation you can use a SEPIC converter. Step-up/Step-down in one unit.