Question re a 12V universal DC power supply

[AlistairHowie]

Hello

Can I use this product  http://www.maplin.co.uk/p/12v-3a-universal-dc-power-supply-with-6-power-tips-a92jh to power my USB hub using my Tracer lipo?

Specifically, what I'm asking is whether it will tolerate an input voltage of less than 12V .... say 11.5V or 11V which my lipo outputs as it discharges ... and still be happy outputtng the necessary 5V for the USB hub?  I know it won't be able to output 12V if the input is less than that, but for those of you who know how these things work, will be be OK outputting 5V?

Many thanks

[Merlin66]

Alistair,

Good question!

I've been using one of these for the past six years to power my USB hub from the 12V gel cell batteries I use.

(I also a similar convertor 12V>15V for the NEQ6 mount)

I don't monitor the battery voltage so I can't confirm 100%, but - touch wood - I haven't experienced any issues so far......

[AlistairHowie]

But your 12V gel cell will be outputing more than my lipos 11.5V, won't it?

[Mick J]

I have seen these things suggested before, you will need a bit of diy,

http://www.ebay.co.uk/itm/180669621759?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

http://www.ebay.co.uk/itm/TURNIGY-3A-UBEC-w-Noise-Reduction-Output-UK-SALE-/180773848790?pt=UK_ToysGames_RadioControlled_JN&hash=item2a16f606d6

Usual disclaimers, may be worth a look...........

[Skipper Billy]

The Turnigy ones that MickJ linked to re a much better bet - I use several of them for my 'other hobby' to power video transmitters and they are cheap, clean and reliable - I use one to power my USB hub. Faultless.

[AlistairHowie]

Thanks for the suggestion, Mick.

I already have the 12V Universal DC supply and have been using it fine with my LiFePO4 battery, but that outputs about 12.5V across almost all of it's discharge curve.  I'm reconfiguring things now and seeing if I can run my hub using a my lipo battery at 11.5V.  I suspect it'll all be fine, but just looking for input from someone in the know.

Those BECs are interesting, though.  Far less bulky than my clunking great universal power supply so now you've got me thinking and a quick Google search returned this ...

http://www.ebay.co.uk/itm/New-Waterproof-DC-Converter-12V-Step-Down-to-5V-3A-15W-Power-Supply-Module-/301379142651?_trksid=p2054897.l4275

Looks like all I would need to do would be to put a cigarette lighter plug on one end, and a 1.7mm power tip on the other (actually, I have no tools or ability to do that, but I'll worry about that later!!).  Input voltage is 8-23V, so that would work just fine with my lipo.  So I have three questions then ...

1.  What is the functional difference between this small converter, and my larger converter?  Why the great size difference, do they operate in different ways?  I know my converter offers switchable output, but that can't be the sole reason for teh size difference ... or is it?

2.  My existing DC DC converter is fused, and I guess this little box is not.  Is that an issue, or do I just put on a fused cigar plug?

3.  The description on the above item says it is non isolated.  What does that mean, is it an issue?

All advice gratefully appreciated.  Many thanks.

[Mick J]

Sorry Alistair, I am on my limits, obviously these things are designed to work with RC equipment, planes/cars, they control the voltage to the receiver another take off from the battery controls the motor/speed.  Modern RC has Lipo & LiFe, I know lipo - each cell is 3.7 volts, we use 2 cells in cars =7.4 volts (just over 8 off the charger) 3 cells give over 11 volts that you have.  Not very helpful and I am sure others will be along, Skipper Billy may know more.

If you do go this way you must make sure you get the positives & negatives correct.

[Skipper Billy]

Hi Alistair

1. It works in a completely different way to the old transformers - you can find the technicalities on Google but in essence it just works, produces nice clean power and is very efficient. (low losses). Some of these little chaps have adjustable output voltage.

2. If you are putting a cigarette lighter plug on one end it will be fused - in reality if you massively overpower it or short the output side it just lets the 'magic smoke' out - its highly unlikely to damage anything. (Although you will have to replace it!!)

3. I dont know what they mean by non-isolated - I suspect its  translation/Chinglish thing.

A 3 cell lipo is nominally 11.1 volts but hot off the charger will be more like 12 - 12.5, a freshly charged 12 volt car battery is nearer to 13.2 so there is some latitude there.

If you are worried about low voltage why not use a 4 cell lipo (14.8 volts) and the Turnigy chappie to drop it??

If you need help pulling it together if you get the parts together and post them to me I will gladly solder them up and heat shrink them for you and post them back. Just PM me for my address.

[Skipper Billy]

Quick update - I just tried a Turnigy voltage dropper on a 2 cell (7.4v) lipo and it still puts out 5v.

HTH

[AlistairHowie]

Billy

That's really helpful, thanks for the reply.  i already have my Tracer Lipo http://www.deben.com/tracer-battery-packs/12v-10ah-lithium-polymer-battery-pack.html  which is all nicely packaged, protected from over charge, discharge, shorts, etc and has it's own power guage.  So I feel safter using it rather than a Turnigy lipo.  I used to have Turnigy lipos when I was into RC helicopters but they were kept in a lipo bag when not in use and sometimes in an ammo box as well!  I don't take such precautions with my Deben battery (maybe I should!) so I'll stick with that one.  And as you point out, the slightly lower voltage isn't an issue when outputting 5V.

Thanks so much for the offer to do the DIY for me, that's very kind.  I wouldn't know where to start with a soldering iron, even if I had one.  I got away with crimped Anderson Powerpoles in the RC world!

I'll source all lthe parts and take you up on your offer.  I'll be in touch,  Thanks again.

Man .... I LOVE this forum!!

[Skipper Billy]

No problem - just PM me when you are ready.