Callibrating Universal DC Laptop Chargers

24-07-2013 9:09am #1

These things are eff'in dangerous. I very nearly fried my laptop for the 3rd time a few days ago.
If at all possible get a genuine charger supported by your laptop manufacturer. If like me your manufacturer (Acer) doesn't support them (because they're weapons in the wrong hands) then you may need to calibrate a universal one.

Before.JPG

When selecting one make sure you match the voltage exactly (don't trust the label you need to meter the output across the input voltage range) and the amperage within > 500mA or bad things will happen. Your laptop will have these figures listed on the power supply.
As well as this note the input voltage tolerance and stay within these confines eg. 12.0v < 16v.

A voltage regulator before one of these would be ideal but I reckon the conversion loss of two DC regulators will be the same as an inverter and an AC charger.

The one I use is 120watt. Which my laptop uses 90watts max.
So I opened up the cig. lighter plug and swapped the 10A fuse for a 7.5A
90watts / 12 volts = 7.5A
7.5A fuse.

Also it's very important to fuse the output which may be done internally in the charger but I bosched one together anyway.
Fuse the live output, check polarity with multimeter.

90watts / 19volts = 4.7A
5A DC fast blow fuse.

If you accidentally set the voltage too high on a one of these then your laptop will most likely die. I luckily knocked it too low and escaped lightly. My advice is lock the switch down so you can see it in the right position but that it will not move otherwise.

After.JPG
Fuses.JPG

24-07-2013 4:53pm

PS. I'd also advise using a real fuse holder...not like I did

25-01-2014 9:41pm

I thought I'd better append this.

Laptop motherboard #3 gave up the will to live today. :eek:

I've spent the day cobbling together an XP machine. Remember DOS? and device drivers? Before plug and play was a thing? ...great craic...that and a sticky delete key! :rolleyes:

It occurs to me that 12.0v is too shallow a threshold. Although I've been adamantly careful not to run my regulator with a battery voltage less than 12.0v it's likely that 12.0v at the battery terminals is closer to 11.6v circuit voltage with a 90watt load on.:(

Moral of the story folks; this is the one instance you want a voltmeter on the load carrying lines, or a power supply with a 10.5v to 16v input threshold, or another separate regulator if the first two are unfeasable...or a very good warranty.

moodrater · 26-01-2014 11:59pm

Sir Liamalot wrote: »

I thought I'd better append this.

Laptop motherboard #3 gave up the will to live today. :eek:

I've spent the day cobbling together an XP machine. Remember DOS? and device drivers? Before plug and play was a thing? ...great craic...that and a sticky delete key! :rolleyes:

It occurs to me that 12.0v is too shallow a threshold. Although I've been adamantly careful not to run my regulator with a battery voltage less than 12.0v it's likely that 12.0v at the battery terminals is closer to 11.6v circuit voltage with a 90watt load on.:(

Moral of the story folks; this is the one instance you want a voltmeter on the load carrying lines, or a power supply with a 10.5v to 16v input threshold, or another separate regulator if the first two are unfeasable...or a very good warranty.

Sure its psu related? When I see motherboards giving up at that rate is usually where the customers use them in bed or on their laps blocking the intake or exhaust vents the bgas eventually desolder themselves or crack a joint from overheating. If you want to use it in bed/on your lap either invest in a laptop cooler or at least stick a hardback book under it to keep the vents clear. If you've lost the rubber feet a few nice thick rubber feet from maplin or chop up a couple of rubber furniture pads to restore or improve the original clearance.

That or its a hp :eek:.

What psu are you using?

27-01-2014 12:25am

You could well be right. I'm watching two voltmeters at the moment and they're corresponding, I've only 0.4% drop on cable come to think of it. I did drive the bejaysus outtov it

.

The oversize graphics card was generally meeting the CPU shortfall.
I run speedfan to monitor the heat and generally it maxed about 80°C

.

I've used vented coolers, 3 inch elevation, removed the undercover etc.

PSU is a Maplins jobbie image in the above "before" image.

It's was an Acer and the 80 squid I spent on a 3 year "accidental" damage warranty was the best money I ever spent. Sadly that expired last year.

Oh well here we go again....maybe ever quad core this time :pac:

moodrater · 27-01-2014 8:59am

Look on ebay for a used named brand air/car charger that would fit the next one, some of the toshiba ones are rated as low as 8v, most are rated 10v. Sounds like you had a desktop replacement rather than a laptop. The tdp of some of those cpu/gpu combinations was ludicrous to put in a tiny plastic box. Unless you're plaing games, encoding video or something its totally unnecessary.

27-01-2014 1:18pm

I searched high and low for a genuine manufacterer supported PSU and there was none to be had except a re-labelled Lavolta in Hong Kong. Much as the idea of two regulators appals me an Amperor could be a solution. Although looking at the larger picture I could stabilise the voltage with massive batteries for a greater return.

You're right about the atrocious ventilation in some machines but a desktop is an equally impractical solution for me.

27-01-2014 1:21pm

I'll try reflowing the solder on the board before I completely write it off. Cheers for the advise.

moodrater · 27-01-2014 2:01pm

Sir Liamalot wrote: »

You're right about the atrocious ventilation in some machines but a desktop is an equally impractical solution for me.

The problem is that 'desktop replacements' often use desktop processors running at high core voltages that have twice the dissipated power of the equivalent mobile processor.

When I say look for a name brand one I don't mean specifically the same, lots of laptops use the same/similar voltage and jack like 18.5v-19.5v and 2.5mm, 2.1mm, 1.65mm center pin. So you'll find that one from toshiba, hp, asus, ibm etc. may suit perfectly. Or get a dell pa-12 and a 7.4mm adapter

28-01-2014 12:24am

Fixt!

Sweating the solder worked a treat. Thanks for the pointer Moodrater.

moodrater · 28-01-2014 12:53am

Sir Liamalot wrote: »

Fixt!

Sweating the solder worked a treat. Thanks for the pointer Moodrater.

ghetto dude did you use the grill in the camper

back when bgas were all ceramic people used to reflow them with these: http://cpc.farnell.com/1/1/27949-electric-heat-gun-6966e-weller.html you had to cover everything with kaptan tape or the surrounding smd component would blow away :pac:

By the way if you have one of the problem acer models then it may be worth sticking in some decent thermal paste and a copper shim. I cut my own copper shims but found dx.com and tmart.com are selling them in vaious thicknesses precut in handy sizesso thats probably the route I'll got next.

If you google your model number and copper shim you'll probably find a guide.

Actually they seem to be all over ebay now too:
http://www.ebay.co.uk/itm/Acer-Copper-Shim-for-CPU-GPU-Heat-Sink-Thermal-Pad-0-8-mm-/201026305091?pt=UK_Computing_Other_Computing_Networking&hash=item2ece19fc43

http://www.ebay.co.uk/itm/Sony-Dell-Acer-HP-Compaq-Copper-Shim-for-GPU-CPU-Heat-Sink-Thermal-Pads-full-Kit-/261381529278?pt=UK_Computing_Other_Computing_Networking&hash=item3cdb8d9ebe

28-01-2014 1:05am

Nah that's preoccupied making victory cookies!

http://cpc.farnell.com/portasol/portasol-professional/soldering-kit-gas/dp/SD01455

28-01-2014 11:13am

moodrater wrote: »

By the way if you have one of the problem acer models then it may be worth sticking in some decent thermal paste and a copper shim.

Interesting thx.

holyhutzpa · 28-01-2014 12:26pm

I am still afraid of which charger to buy - my laptop is a macbook air so the penalty for failure is high!

So it was overheating that caused this ? (Should I be less afraid of which charger to buy?)

moodrater · 28-01-2014 1:07pm

holyhutzpa wrote: »

I am still afraid of which charger to buy - my laptop is a macbook air so the penalty for failure is high!

So it was overheating that caused this ? (Should I be less afraid of which charger to buy?)

Apple are idiots for not producing one, the old one even disable charging when using it. Of course they'll be more than delighted for you to use a third party one and not honour the warranty. I'd call stream solutions in cork and ask them what they recommend.

holyhutzpa · 28-01-2014 5:49pm

It's a PITA as they won't make one and won't licence out the Magsafe connector for anyone else to make third party versions. Am thinking of doing a mikegyver and soldering an old charger tail to one of the china chargers (as the "magsafe" connectors that come on them are usually pretty crap) http://www.mikegyver.com/Store/

moodrater · 28-01-2014 8:54pm

holyhutzpa wrote: »

It's a PITA as they won't make one and won't licence out the Magsafe connector for anyone else to make third party versions. Am thinking of doing a mikegyver and soldering an old charger tail to one of the china chargers (as the "magsafe" connectors that come on them are usually pretty crap) http://www.mikegyver.com/Store/

The lavolta ones on amazon would probably be a better bet than most of the chinese ones you'd be soldering it on to, still made in china but lavolta is a uk company - smart parts - and they claim its tested in the uk.
Hardly any reviews for it, most of the reviews under it are for the 240v versions which are listed together and some are complaining that its 'fake' even though the title and description and picture and shop name say lavolta :rolleyes:

holyhutzpa · 29-01-2014 12:35pm

I didn't realise Lavolta was a uk company, that sounds a bit better. I'm not very confident in the chinese ones...

Chargers are a bit of a contentious issue for mac users, they cost a bloody fortune, and often die just outside the 12month warranty (largely due to people destroying the cable by tightly wrapping it around the charger, but ...)

moodrater · 29-01-2014 2:38pm

holyhutzpa wrote: »

I didn't realise Lavolta was a uk company, that sounds a bit better. I'm not very confident in the chinese ones...

Chargers are a bit of a contentious issue for mac users, they cost a bloody fortune, and often die just outside the 12month warranty (largely due to people destroying the cable by tightly wrapping it around the charger, but ...)

lavolta = smart parts = Cubetag Ltd. CRN:6606067

Still chinese crap I'm sure and I doubt much testing goes on other that it works and if you're lucky a voltmeter but at least its a uk company with a reputation to protect and probably buy enough of them for the supplier to give a crap about shafting them.

The main thing I'd be concerned about is the 11.5v spec, lots of cigarette sockets have weedy cables that would drop a significant amount at 90w.

Everything is a contentious issue with apple, support staffs primary role is to sell you an annual support subscription, the only time I've seen them admit fault with know issues is where it can be fixed with a software update or it gets major media attention. Don't talk to me about wrapping up wires I just soldered a new cable on my wifes dell for the same reason. Same with the hairdryer a few months ago and the iron last year.

29-01-2014 3:19pm

holyhutzpa wrote: »

So it was overheating that caused this ?

Yeah looks that way.

Check out my latest invention. 12v fan power on a barrel plug with USB charging point.

MacGyver away. Warranties are for the weak of heart.

I did a better job reassembling my lapper than them Acer service techs did. Gobsh1tes lost screws, paid no attention to thread depth and left my hard-disk unsecured.

What concerns me about Lavolta is there isn't an awful lot of space or a grille for ventilation on their models. A 90watt 12v PSU is a fairly power intensive piece of kit.

My barrel plug outlet is ran in on 14mm² cable over about 5m and that's the only way I can get away with such a low threshold. Even a 2% drop on this would equate to 0.25v drop.

I wouldn't use any charger without verifying it's within spec first; loaded and unloaded across the battery voltage range.

I haven't figured out how to test the output while it's plugged into the laptop yet without splicing the wiring...not all the good practices I recommend do I actually do myself though :rolleyes:

holyhutzpa · 29-01-2014 7:06pm

Looks pretty good Liam! I might be making a few of those for my trip to Spain in July/ August

(to stop me melting, not the laptop) I presume it's actually running on 12v(ish?), not the 5v of the usb socket

I've ordered one of the Lavolta yokes from Amazon (mine's actually a 45W laptop, but I ordered a 60W charger, which I'm told is ok). I am gonna set up a voltmeter display somewhere so I have a fair idea of what the battery's at, I wouldn't want to take it down to 11.5V. I'm still getting used to this leisure battery yoke, and not 100% convinced that it holds a charge!
I reckon I'll put a cigarette socket somewhere closer to the leisure battery too, on nice big cables. Primarily if I ever need to use an inverter, but it makes sense to do several hour charging duties from it too.

Yeah, testing it without a load (laptop) on is easy, testing with the laptop connected would be quite difficult...

29-01-2014 8:58pm

holyhutzpa wrote: »

Looks pretty good Liam! I might be making a few of those for my trip to Spain in July/ August (to stop me melting, not the laptop) I presume it's actually running on 12v(ish?), not the 5v of the usb socket

Aye, soldered to the back of the barrel pins before the 5 reg. PCB.
Yellow fan wire not needed that's just PWM control.

holyhutzpa wrote: »

I've ordered one of the Lavolta yokes from Amazon (mine's actually a 45W laptop, but I ordered a 60W charger, which I'm told is ok).

60watt is better it'll handle heat better. Chunkier leckytronics.

holyhutzpa wrote: »

I am gonna set up a voltmeter display somewhere so I have a fair idea of what the battery's at, I wouldn't want to take it down to 11.5V.

The intention isn't to drop the batteries to 11.5v it's to allow for voltage drop on cabling, voltmeter inaccuracy and in the event of inadvertent over-discharge of the battery (or say a low battery and a compressor fridge kicking in) that the laptop is not destroyed in the proceedings.

holyhutzpa wrote: »

I'm still getting used to this leisure battery yoke, and not 100% convinced that it holds a charge!

If it's a new battery and fails a discharge test bring it back under warranty. If it's an old one solar should keep that in check. Older batteries often won't hold charge until lower in the range. My starter battery tells me 12.4v is the new 12.8v, works fine.

holyhutzpa wrote: »

I reckon I'll put a cigarette socket somewhere closer to the leisure battery too, on nice big cables. Primarily if I ever need to use an inverter, but it makes sense to do several hour charging duties from it too.

I might be misreading you but it'd be better run separate cable for the inverter and cig. sockets.
Close to the batteries will save you some expense on copper but really thicker cable and closer to where you want to use it would be more ideal.

holyhutzpa wrote: »

Yeah, testing it without a load (laptop) on is easy, testing with the laptop connected would be quite difficult...

You'd have to splice it or otherwise strip the positive out to get the meter probe in there, easily done before you heat-shrink it seeing as you're going to McGyver it.

Curiosity got the better of me, I dropped my batteries to 11.5v (don't do this at home kids!...or well do if you want but not because I said it was a good idea) and metered my DC PSU unloaded and it was a steady 19.4v all the way. So go figure...

Oh and regarding the laptop warranty just don't tell them you are using a DC power supply, they'll never guess, it's external.
Most of the warranty centers even request you don't include the battery and power leads when you send the laptop for repair because they can't guarantee their competence to not lose them.
Just play dumb and say it doesn't work, you don't know why!

:pac:

29-01-2014 11:28pm

Sir Liamalot wrote: »

When selecting one make sure you match the voltage exactly (don't trust the label you need to meter the output across the input voltage range) and the amperage within > 500mA or bad things will happen. Your laptop will have these figures listed on the power supply.
As well as this note the input voltage tolerance and stay within these confines eg. 12.0v < 16v.

Time to correct myself again! (did someone say visible learning curve? :pac:)
The charger can exceed the device amperage/wattage as much as you want just don't go under the rating. The appliance will just pull what it requires to run. Going too high only minutely increases the idle consumption but may give a longer service life.
The voltage is crucial though.

30-01-2014 12:32pm

I've another unsubstantiated caveat about these things. I've a toasted alternator regulator kicking out >15v in storage (good for winter use

) which I believe is a direct result of using this contraption.

When you look at the laptop dry cell battery charge profile from the >80% charge absorption cycle the laptop starts to use a pulse charging cycle. This I think wrecks havoc with the alternator field control wires and wears out the alternator reg. duty cycling at a rate it was never designed for.

There's three solutions to this I use;
Don't charge the battery, take it out and run it without the battery.
Charge the laptop battery from solar or a resting battery (and pay 2-3 times the energy in charging a battery from a battery).
Don't charge it from the auto-electrics cigarette lighter socket in the front of the vehicle. Use one in the back from the leisure batteries. The cable distance and buffer provided by leisure batteries in turn buffered by the starter battery will do a lot to dampen the effects.

moodrater · 30-01-2014 1:53pm

Sir Liamalot wrote: »

This I think wrecks havoc with the alternator field control wires and wears out the alternator reg. duty cycling at a rate it was never designed for.

There is always r/c filtering on the input of the regulator comparator. There is usually a simple reason for failure. In a modern vehicle the ecu can drop the voltage / increase the engine rpm to deal with a heavy load. In yours it would probably maxed out the field to try to maintain voltage that would be life threatening especially at idle speed when the fan is providing the least cooling

There are loads of pulsing loads in a modern vehicle, indicators, hazards 8A, radiator/ac/oil cooler fans, injectors, a/c demister, autobox solenoids, abs solenoids etc.

30-01-2014 9:40pm

Yeah, it could be unrelated.
The reason I'm suspicious is that my alternator regs. stopped going bad when I stopped using the dash socket (2 batteries a day some days).
Looking at the laptop charge with an AH counter on the lead acids shows a lot of ripple, there's also interference with some LEDs I use; they pulse in time.
There's nothing detrimental to the alternator temperature, it's only a 4.5Ah battery (9A bulk rate).
I always leave the upper 40% of my alternator capability well enough alone, apart from the danger of damaging the alternator, the wiring loom from the alternator is much too small for a constant high current load.

16-03-2015 5:58pm

Just did a bittov Spring cleaning.

moodrater wrote: »

...it may be worth sticking in some decent thermal paste and a copper shim.

+ cleared out the heat sink fins.

30°C > 40°C lower operating temp. with GPU + dual CPU maxed. :cool:

28-03-2015 8:37pm

Seeing as I bought this thread back from the dead it's worth mentioning I'd recommend changing the plug for a DIN type. Those cig. lighter connections are fires waiting to happen I don't use them for any more than 30 watts these days.

DIN%20plug_zps35xaggm1.jpg?t=1427484777

Callibrating Universal DC Laptop Chargers

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