DC or AC Adaptors for Laptops?

Here's what I know. If I turn the switch on and no electricity comes out of the faucet, I call the man.

I think the man would say to take the inverter, and that cooling fan, out of the circuit.

GA for a great commonsense answer.

First, you have variables to remove. Usually when you power your laptop from an external source, you are also charging the internal battery. My simple solution to test efficiency is time. For both tests, first use the laptop battery til the laptop shuts down. Then make sure the external power pack is fully charged for both tests. Which unit automaticlly shuts down first? Measure the battery voltage, at the battery of the power pack, just prior to shut down. For example, when the AC inverter shuts down. That exact DC voltage at the battery will be the same point you'll conclude the test with the DC to DC converter. Which ran longer before reaching this voltage?

The more correct way to do this would be to plot a graph, measuring voltage and amperage during both cycles, (at the power pack's battery). Use the same time increments for measuring. Volts X Amps = Wattage. Average both graphs and you'll have a more scientific estimate.

A small but significant point about laptop batteries that many people never get told is that most modern laptop batteries have a finite number of charges before the capacity is affected. Good ones more, cheap ones less. Reckon with between 1000 and 3000 charges.....

It does not matter if the battery was full or empty when mains was applied to the unit......each connection is counted as a charge by the battery - sadly..

These laptop batteries are generally very expensive, its a good move to remove it when working on mains power.....

Even if you do get a few mains interrupts per year, provided you have set up your software to make backups every 5 minutes or so, you won't lose much.

Probably a better method (though I have never actually done it myself!) might be to have a lead acid battery on a charger, and connect the laptop with no battery to the LA battery via a car 12 volts to 18volts or whatever your laptop requires, unit.

That way you are safe if there is a mains interruption and you are not wearing out your laptop battery. The cost of a laptop battery replacement will more than pay for such a setup.......and have a longer run time if its a big LA battery.....

A similar setup could be a UPS from a good supplier - be careful, there is a lot of crap out there that hang your PC when the mains drops or returns........and they are far more expensive than the DIY version!!

Andy I found a thread on CR4 concerning aftermarket laptop batteries. Apparently DELL imbeds a chip in the battery pack so the laptop detects this grey market product and will not run. This is much the same as the cr*p Hewlett Packard did with their ink cartridges. If you run out of one color the whole cartridge has to be replaced. nora could you refill it, the chip was not reset and thus the printer said it was empty. the whole game seems to be to capture and hold customers to ransom so they are reluctant to change brands once they are stuck.

Good point Andy, and don't forget that more than one manufacturer has had recalls because the batteries start fires!

An important point that I completely forgot. Thanks for mentioning it.

Regards. It is the cycles life not only charges but Charge & Discharge cycles. However it is recommended to get the battery some 8-10 cycles on fully-charged & fully discharge by removing charger after it is charged fully. Modern batteries and Charging & Battery condition Monitoring in Laptops as well as in Battery Assemblies is to ensure a continuous connected to main will not make any difference on battery-life. As far as you suggested the indigenous arrangement I had been using it as in my country power failure and load shedding is so severe that I used 4X6.V batteries [24V] with all the required modifications to connect to input of laptop instead of adapter. It worked well but economically not feasible. The LeadAcid Sealed, Maintenance Free lasted only 6 months.

Hi,

firstly, modern laptop batteries do have a finite charge life, or number of charges....it is not easy to get details as its proprietary information that the Laptop manufacturers do not want to be generally known.....you are one of the majority that do not (did not!!) know it till now!!!

The life is planned that on average any long term guarantee will be finished before problems are noted.....

If a LA battery collapses in such a short time as you mentioned, assuming that it was not a Leisure type, its usually due to overcharging/Gassing and/or to discharging too deeply and leaving too long discharged. Too long can be an hour or so.

Also gassing loses water and dry plates quickly are useless....

The only other possibility was that the battery was of very poor quality.....

If you used one of those cheap chargers for cars, this will quickly ruin a battery as they are designed to give a quick boost so the car can start and then be disconnected. They are not designed to be left connected all the time....

A permanently connected charger needs to be setup to not ever charge to the gassing point, that just drives off the water.

On an SLA it just increases internal pressure till the gas vent opens on some. But its not a good idea to ever overcharge ANY battery of ANY chemistry....it just lowers the efficiency of the battery.....and often causes permanent damage....

The point by #2 reply is quite valid that a converter for your laptop adapter.

Try to use original laptop adapter as it may have some special circuit built-in [see the DC-plug of adapter] may have a thin center-pin which serves to control battery charging.

I found this yesterday, while downloading the new software available. Maybe a sticky thread would be more appropriate, including another for batteries.

Hope this adds something valuable.

http://www.powerint.com/en/pi-university

I measured both AC and DC power supply units. These are the results if it helps.

First I connected the Battery to an Inverter with volt and ampere meters from the battery. The inverter then went to the normal mains 240v adapter, which converts the power back to 18v DC. When the lap top was ON and had a letter on the screen but not using any program, just sitting there, The power from the battery was 12v 3.6 amps from the battery. 43.2 watts used. I measured the 18v dc side and only 16 watts went into the lap top. The inverter has a fan and the AC to DC box was very hot. I assume the loss was all in heat, 27.2 watts lost

Then I used a 12v to 18v Car adapter for the lap top, from the same battery on the same page on the lap top. This time 12v 1.4 amps, 16.8 watts only was used from the battery. This is much more efficient.