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Is there an easy way to run a computer/laptop, almost directly from a car battery? Has anyone got some good ideas? Answered

This one has had us stumped for a while. I'm currently thinking along the lines of side-stepping the transformer.


I have an hp laptop input voltage is 19v and the current is 4.7ah.and laptop battery gives 10.8v and 55wh to laptop but I want to use a motorcycle battery for my laptop. Because motorcycle battery gives better backup time. Motorcycle battery voltage is 12v and the current is 7ah. I know how to convert 12v into 10.8v. but do not know how to convert 7ah current into 4.7ah current. Please help me.

Probably the simplest most efficient solution would be to use a DC-DC converter/regulator of some sort. In my personal experience for other similar projects I have found that buck converters are probably your most reliable solution where you will probably be getting approximately 95% efficiency stepping up the voltage from 12 to 18V (Probably more efficient than your AC charger). One thing I would recommend however is that if you are buying a cheap buck converter (off ebay perhaps) that you ensure that you either connect the outputs up to an oscilloscope to check for any large high frequency components to the output. If you don't have access to an oscilloscope I would recommend you also buy a fairly large electrolytic capacitor say ~200uF and put this in parallel between the positive and negative terminal, this should filter out most damaging high frequency DC voltage spike. Another thing to keep in mind is the power rating of the buck converter. Make sure its going to be able to power your laptop.

How about 12v battery Plus + 6v battery and connect them so they
make 18v current , I'm not really good in electricity and I want to ask
about the amperage , what if my battery is 60AH can I use transformer
to step up the voltage to 18 V or 14 V

It depends on what voltage the laptop requires. If you have a notebook that requires 12v, you probbly are in luck depending on the amperage, but if you have a laptop that demands 18v, you would need a transformer to step up the voltage and possibly the amperage. As stated below, and inverter isn't practical unless in is necesarry. You are simply going from 12v DC to 115v AC, back down to around 15v DC.

It seems like it would be a waste to use an inverted considering that you have a DC battery that you would run through an AC inverter in order to go to an AC to DC converter through your laptop charger. Maybe you could use an 18-volt linear regulator?

I have been studying this idea for some time because the power hungry laptops I have suck all the power out of a normal car battery and the inverter goes off much too soon. This method will not hurt the charger or plug. 1 Unplug the charger. 2 Cut off the output wire (about 1/2 way, i.e. in the middle) 3 Separate the two wires and bare the ends 4 plug in the charger and check the polarity (don't let them touch each other) 5 bare the wires of the other cord and note the color code for polarity 6 wire (3) 6 vdc batteries in series to get a total 16 vdc (+ to - to + to - to+ to -) 7 attach the + of the first battery and the - of the last battery to the computer 8 charge the batteries with a solar panel with an output of greater than 16 vdc The trick is to get total efficiency by eliminating any resistance factors using inverters or electronics. Use a voltmeter to monitor the voltage of the batteries. A vintage laptop should run for hours on this solar powered industrial grade setup. In fact, you can run your laptop directly without an internal battery so save money buying a new laptop battery.

Correction The total voltage of (3) 6 vdc batteries wired in series should be more than 18 vdc without a load and the laptop load should bring the voltage down to 14 - 16 vdc. The batteries should also be equal in size and quality to eliminate any imbalance. The solar panel should also be sized to keep the batteries charged but not overcharged.

Go to Jaycar or similar and lash out $44 on a voltage inverter.

there are many convertors that you can get on the web and in alot of shops, they come with a ciggarette adaptor for in the car but this could easily be taken off and put straight on the battery, then you just plug in your laptop!

There are a few ways to do this. If you have the car charger for it you can wire that to the battery and it will charge. Another way, you already suggested was to use the transformer. The last way you could do it would be to either step up or step down the voltage to what your computer would usually use. You can do this with some simple electronic components

One more for the just buy a cheap inverter, you can use it for any low power appliance, and a lot of them come with a usb port for charging gadgets. Though I would leave the inverter intact and buy a cigarette plug to clip adapter for 3 bucks. That and laptops are rather sensitive to the input voltage range, don't go frying your $$$laptop by being to cheap to buy an $$inverter.

Like others said, just get a car adapter for your laptop. Then cut off the car plug and wire it straight to your battery.

Type "laptop car adapter" into Google and go from there.

There are only two ways: 1. An inverter and the laptop's AC adapter (which uses a transformer). An inverter suitable for this can be had for $10-15. 2. A DC transformer that converts12v to whatever your laptop needs, in the correct amperage. I bought a generic one for the car for about $15 out of a clearance bin. There's no way to side-step a transformer. Period.

If you need lower voltage, all you really need is a suitable regulator chip and a few supporting components. This is pretty efficient. If you need higher voltage, you need a DC-to-DC converter. Transformers only work on pulsating/alternating current, so to step up voltage you need to put it thru an oscillator, run the output of that thru a transformer, then filter it back to to DC. This is less efficient, but more efficient than going all the way up to 110VAC and back down. However, the inverter-into-AC-adapter approach has the major advantage that it's all off-the-shelf parts. If you don't want to deal with circuitry and are willing to pay more for convenience and not being able to make a mistake, there's something to be said for simplicity. But as others have said, check the PC's specs from the manufacturer. It may be willing to run off the 10-12V the car will supply, at least in its low-power mode.

My bad, my electonics is a bit rusty... I knew that bit once but forgot. I think what the questioner is asking is "how can I plug this in without buying some parts" and the answer is, unless you're sitting on the parts... you can't. But there are plenty of car-adapters out there, and they tend to be a bit expensive... but a good shopper should be able to find a variable-voltage one like mine for less than $50. A great shopper should be able to find it for $20-30. I just got lucky.


9 years ago

If your willing to buy a laptop an eeepc 701 can take anywhere from 9 to 13 volts without any regulator or anything. you should just be able to hook it right up like you'd trickle charge a battery, but I could be wrong. be carefull. of coarse if you just want to charge the laptop off a car batter and don't need it to run while you charge there are sone great instructables about trickle charging.

Most laptops take 18Volts in - and the charger/transformer for your laptop has lots of regulators to keep voltage in check for the laptop, sometimes to prevent overcharging. I'd recommend getting a 12-volt universal-car-adapter for your laptop...but these are expensive. Personally I use an inverter- A box that converts 11-14vDC into 120vAC for the laptop's normal charger circuit.