12 to 15V converter

[MyLady]

We've just bought a 'rechargeable stick vacuum' from Aldi. Haven't used it yet, but charging it, via the inverter, has compromised our power balance. The supplied 'wall wart' puts out 15V @ 200mA - 5W - but the inverter draws about 24W on stand-by, which dwarfs the required power.

 

What I want is a 'car charger' like the one that supplies 19V for my laptop which plugs into a 'cigar lighter' socket - and ideally has a the same size fitting as the Aldi docking station needs (2mm inside diameter, 5mm outside diameter co-ax plug). I haven't yet determined what the polarity is, but can easily do so - tomorrow. At a push, it wouldn't be hard, though a little messy, to chop the wires and connect the plug to the supply with a bit of terminal strip.

 

Searching on line for a suitable converter has been fruitless - lots of circuit diagrams and modules to plug into circuit boards and chargers for laptops by make and model, but nothing generic.

 

Can anyone point me in the right direction?

 

Thanks in advance,

 

Roger

[Robbo]

Maplin?

[Arthur Brown]

Hit the Maplin catalogue, there is one in there. I think it's in the "Truck" section

Edited September 17, 2014 by Arthur Brown

[1st ade]

I'll have a look tonight - I have a "Universal Laptop Supply" which takes 12v / 24v / 120V / 240V and gives out 5v (USB) and selectable 12, 15, 16, 17, 19, 20V at about 5A. It can also run off a standard airline seat socket and has a box of different "tips" for the end of the charging lead and an array of phone leads from USB. Don't know what the standby current is though.

[Alan de Enfield]

As per 1st Ade - I use one similar to this.

 

Input 11-14v, output 15,16,18,19,19.5,20, 22 & 24v

 

http://www.ebay.co.uk/itm/Ex-Pro-80w-Universal-Notebook-Laptop-Charger-11-14v-InCar-Adapter-Travel-Samsung-/390932864844?pt=UK_Computing_LaptopAccessories_PowerSupplies&hash=item5b056a1f4c

 

Under £9 delivered

[KJT]

Yes, Maplins do them. They do a range called 'Universal DC Power Supply'. If you take your appliances' power supply unit into Maplins they will supply the correct one with the correct 'tip' and polarity.

We use several onboard, the largest we use being 19v for a large laptop.

 

Ken

Edited September 17, 2014 by NB Ellisiana

[Robbo]

These should do...

http://www.maplin.co.uk/p/15-24v-laptop-car-adapter-85a-9-charging-tips-a33hu

http://www.maplin.co.uk/p/12v-auto-voltage-carair-laptop-adapter-with-1a-usb-socket-12-charging-tips-a83la

[MyLady]

Thanks everyone. I thought of Maplins this morning! We have one near home and are going tomorrow for blood tests, dentist & 'Dopler' circulation test, so will drive over and see what they say. All the ones suggested are way over spec, but that shouldn't be a problem, I think. At least they'll give me more data.

 

Thanks again,

 

Roger

[MyLady]

Looking at all those converters, they seem, as I said, well over spec. - and over price (except, maybe, the ebay one). They all can provide many tens of watts, but this charger only needs 3W: 1/5 of an amp @ 15V. The maplins ones cost 30 to nearly 40 quid, but the entire vacuum cleaner, including wall-wart, cost just under 40 quid. A suitable supply only needs a couple of relatively low power transistors, with a few cheap components to turn them int0 a multivibrator, plus a low current transformer and rectifier to produce DC.

 

Even 9 quid is too much if such a power supply were to be manufactured in any quantity. Surely someone must be doing so, though I accept that 9V offers a bigger market.

 

Does anyone know of such a product?

 

Roger

[phill]

http://www.ebay.co.uk/itm/321512253345

[Richard10002]

http://www.ebay.co.uk/itm/321512253345

Once you have added a box, diode, wires and connectors, I wonder how close this will be to £9?

[David Mack]

We've just bought a 'rechargeable stick vacuum' from Aldi. Haven't used it yet,

I would see whether it is any good before spending more money on an alternative charger.

[phill]

 

Once you have added a box, diode, wires and connectors, I wonder how close this will be to £9?

The connector is already there, as it's a fixed recharging point I'd screw it to the wall and hardwire it with a bit of the left over cable. Don't need a diode I checked polarity. Have I spent anything yet? Ah, 4 no4 screws and a bit of chocolate block (or whatever floats your 12v). No. Not £9.

 

what I get for the extra £5 is an ugly box I can't mount, 2m of cable I don't want a cheap switch to go wrong lots of useless tips to clutter up the place. And, the need for another 12v cigarette lighter socket and fitting.

 

I know which solution (does) suit me. I have a few similar running odd voltage stuff.

 

Being me, I'd also try whether it runs straight from the 12v

 

David Mack's advice is spot on.

Edited September 20, 2014 by phill

[MyLady]

The connector is already there, as it's a fixed recharging point I'd screw it to the wall and hardwire it with a bit of the left over cable. Don't need a diode I checked polarity. Have I spent anything yet? Ah, 4 no4 screws and a bit of chocolate block (or whatever floats your 12v). No. Not £9.

 

what I get for the extra £5 is an ugly box I can't mount, 2m of cable I don't want a cheap switch to go wrong lots of useless tips to clutter up the place. And, the need for another 12v cigarette lighter socket and fitting.

 

I know which solution (does) suit me. I have a few similar running odd voltage stuff.

 

Being me, I'd also try whether it runs straight from the 12v

 

David Mack's advice is spot on.

 

I finally got round to checking the wall-wart with my multi-meter: it showed an open circuit (except for the meter) voltage of 20.2V. putting it under load seems likely to drop that, but at least with this circuit board, checking that would be easy, but direct from the boat's "12V" seems doubtful (though not very, charging voltage is often 14V - and that's at a much higher current than the rated 200mA of the wall wart). Low input voltage seems to me likelytojust give longer charging times, but at 0.2A (less than 5AHrs per day) we could probably stand that. Best info (not measured) for the inverter plus wall wart is ten times as high! (And has seemed to cause power balance issues.) The vacuum cleaner itself seemed worth a 40 quid punt, throwing 4 quid more at powering it without taking too much from the batteries also seems worth a bet.

 

An in-line 500mA fuse would protect us from module faults, so I think this could be a proportionate cost solution...

 

Thanks phill and Dave!

 

Roger

Edited September 22, 2014 by MyLady

[MyLady]

The circuit board has arrived. I need to add a fuse and wire it in, but not back on board yet. Will report back.

 

Further to other replies/questions/reservations: the cleaner does work quite well: dirt & dust that never before was completely cleaned does get sucked up; so far it isn't a good solution, because, to avoid flattening the battery bank (marginal effect, on top of all other load) we've had to take it home to charge, with total cleaning time when back on the boat limited to 15 mins from a charge. With this c-board we hope to charge it on board.

 

An oddity is that when the charge light indicates fully charged, switching the mains supply off, then immediately on again leads to several hours more charging before the light indicates full again. My guess is that the wall-wart is too primitive, but it could be a high rate of self-discharge. I hope that is a function of having to take the whole kit and caboodle home to a mains supply, aiming to hit 100% SoC ready for the next visit to the boat... Once we can viably recharge on board, reaching 100% will no longer be an aim, enough to do some more cleaning will suffice because we can recharge straight away. DoD and battery life will remain a concern (no idea what the battery technology is), but at a price of 40 quid, plus 4 for the charger, we can afford to take that risk! In the meantime we can keep Milady cleaner than any hand brush can achieve...

 

Roger

Edited November 4, 2014 by MyLady