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Powering laptop etc in car from inverter?
I'm thinking of buying an 12V - 240V for the car, to enable me to
charge/run devices such as a laptop / mobile phone(s) / AA batteries for gameboys & camera etc etc while on the road (one at a time!); they seem to be as cheap as chips these days and this would enable me to use the standard mains chargers for all the above devices rather than buying separate low voltage kit to connect each of them up to the cigar lighter. Sounds good in theory, but are there any gotchas? Eg, safety? Does it run a car battery down more to power up a laptop via a 240V inverter than directly to the cigar lighter? etc etc Can't help feeling an inverter would be much better if wired or plugged into the car some other way than via the god-awful universal cigar-lighter plug... Thanks David |
Powering laptop etc in car from inverter?
"Lobster" wrote in message ... I'm thinking of buying an 12V - 240V for the car, to enable me to charge/run devices such as a laptop / mobile phone(s) / AA batteries for gameboys & camera etc etc while on the road (one at a time!); they seem to be as cheap as chips these days and this would enable me to use the standard mains chargers for all the above devices rather than buying separate low voltage kit to connect each of them up to the cigar lighter. Sounds good in theory, but are there any gotchas? Eg, safety? Does it run a car battery down more to power up a laptop via a 240V inverter than directly to the cigar lighter? etc etc Can't help feeling an inverter would be much better if wired or plugged into the car some other way than via the god-awful universal cigar-lighter plug... Thanks David i dont know about power usage on a laptop, but, i do know that 100w drawn from an inverter at 240v, will give you less than 1/2hours usage. one thing to remember if you get one, is that you have to make sure it is turned off with no power going into it whilst starting the car as to do so will damege the inverter. |
Powering laptop etc in car from inverter?
"Lobster" wrote in message ... I'm thinking of buying an 12V - 240V for the car, to enable me to charge/run devices such as a laptop / mobile phone(s) / AA batteries for gameboys & camera etc etc while on the road (one at a time!); they seem to be as cheap as chips these days and this would enable me to use the standard mains chargers for all the above devices rather than buying separate low voltage kit to connect each of them up to the cigar lighter. Sounds good in theory, but are there any gotchas? Eg, safety? Does it run a car battery down more to power up a laptop via a 240V inverter than directly to the cigar lighter? etc etc Can't help feeling an inverter would be much better if wired or plugged into the car some other way than via the god-awful universal cigar-lighter plug... Only thing I can think of is they do (or mine does) get rather (read heater in winter) warm in operation. I have never used mine without the engine running, but I suppose the main issue will be current drawn. mines only 150 watt, so I wouldn't put much more than a charger into mine. but it has already paid for itself in the amount I have saved buying car chargers for camera's, mobiles, etc etc. My only annoyance is its recommended not to plug anything else in to car socket at the same time as the inverter (no socket doublers/tripplers) so mines hardly used now I have a PDA sat nav always plugged in. loopy -- Posted via NewsDemon.com - Premium Uncensored Newsgroup Service -------http://www.NewsDemon.com------ Unlimited Access, Anonymous Accounts, Uncensored Broadband Access |
Powering laptop etc in car from inverter?
On Sun, 14 May 2006 10:23:38 GMT, Lobster
wrote: |I'm thinking of buying an 12V - 240V for the car, to enable me to |charge/run devices such as a laptop / mobile phone(s) / AA batteries for |gameboys & camera etc etc while on the road (one at a time!); they seem |to be as cheap as chips these days and this would enable me to use the |standard mains chargers for all the above devices rather than buying |separate low voltage kit to connect each of them up to the cigar lighter. | |Sounds good in theory, but are there any gotchas? Eg, safety? Does it |run a car battery down more to power up a laptop via a 240V inverter |than directly to the cigar lighter? etc etc Yes! assume your invertor is 80% efficient. |Can't help feeling an inverter would be much better if wired or plugged |into the car some other way than via the god-awful universal |cigar-lighter plug... Be careful that there is enough charge available to start the car. There are two sorts of invertor Modified sine wave output as below |---| --| |--| |-- |--| These are quite cheap but electronics do not like sharp edges anywhere near them. You should *check* that they will work *your* laptop. I was warned off using one of these with a TV Set Top Box by Bill Wright on uk.tech.digital-tv Others are pure(ish) sine wave which cost 3 times as much and should be OK. For myself I would buy a laptop which will run off 12V, which I did with the STB. -- Dave Fawthrop dave hyphenologist co uk Google Groups is IME the *worst* method of accessing usenet. GG subscribers would be well advised get a newsreader, say Agent, and a newsserver, say news.individual.net. These will allow them: to see only *new* posts, a killfile, and other goodies. |
Powering laptop etc in car from inverter?
In uk.d-i-y Dave Fawthrop wrote:
On Sun, 14 May 2006 10:23:38 GMT, Lobster wrote: |I'm thinking of buying an 12V - 240V for the car, to enable me to |charge/run devices such as a laptop / mobile phone(s) / AA batteries for |gameboys & camera etc etc while on the road (one at a time!); they seem |to be as cheap as chips these days and this would enable me to use the |standard mains chargers for all the above devices rather than buying |separate low voltage kit to connect each of them up to the cigar lighter. | |Sounds good in theory, but are there any gotchas? Eg, safety? Does it |run a car battery down more to power up a laptop via a 240V inverter |than directly to the cigar lighter? etc etc Yes! assume your invertor is 80% efficient. |Can't help feeling an inverter would be much better if wired or plugged |into the car some other way than via the god-awful universal |cigar-lighter plug... Be careful that there is enough charge available to start the car. There are two sorts of invertor Modified sine wave output as below snip These are quite cheap but electronics do not like sharp edges anywhere near them. You should *check* that they will work *your* laptop. I was warned off using one of these with a TV Set Top Box by Bill Wright on uk.tech.digital-tv FWIW, I've never had a problem running any of ~12 power supplies on MSW inverters, including laptops, scopes, ... In practice, there is relatively little difference in stress between proper sine waves, and MSW inverters. The diodes typically get slightly hotter, but that's it. (IME) |
Powering laptop etc in car from inverter?
In uk.d-i-y aussie bongo wrote:
"Lobster" wrote in message ... I'm thinking of buying an 12V - 240V for the car, to enable me to charge/run devices such as a laptop / mobile phone(s) / AA batteries for gameboys & camera etc etc while on the road (one at a time!); they seem to be as cheap as chips these days and this would enable me to use the standard mains chargers for all the above devices rather than buying separate low voltage kit to connect each of them up to the cigar lighter. snip i dont know about power usage on a laptop, but, i do know that 100w drawn from an inverter at 240v, will give you less than 1/2hours usage. YLMV. And 100W can never give any meaningful amount of run time without specifying how long. My laptop - admittedly a subnote - uses about 40W when charging, and about 15W running normally. This runs on a standard car battery for around a day, from an inverter. |
Powering laptop etc in car from inverter?
In article ,
Lobster wrote: I'm thinking of buying an 12V - 240V for the car, to enable me to charge/run devices such as a laptop / mobile phone(s) / AA batteries for gameboys & camera etc etc while on the road (one at a time!); they seem to be as cheap as chips these days and this would enable me to use the standard mains chargers for all the above devices rather than buying separate low voltage kit to connect each of them up to the cigar lighter. Sounds good in theory, but are there any gotchas? Eg, safety? Does it run a car battery down more to power up a laptop via a 240V inverter than directly to the cigar lighter? etc etc I've got a 150W one from www.tlc-direct.co.uk and I've used it for a few years now. It's got a standard 13A socket on the side of it. It's supposed to cut-out if the input voltage goes bbelow 10.5V, but I've never had to test it... It produces a "modified sine wave" output, which does tend to make some battery chargers buzz a little and mayby run a little hotter than when on the mains at home, but otherwise I've not had a problem with it. I used to use it when out & about to test & install various wireless networking equipment. Not had much use for it recently though, but it's handy for charging various batteries which I don't have a separate adapter for. Can't help feeling an inverter would be much better if wired or plugged into the car some other way than via the god-awful universal cigar-lighter plug... Very probably - my last car had the socket powered at all times, but my current car needs the keys in & the ignition on to make it work )-: Gordon |
Powering laptop etc in car from inverter?
"Ian Stirling" wrote in message ... In uk.d-i-y aussie bongo wrote: "Lobster" wrote in message ... I'm thinking of buying an 12V - 240V for the car, to enable me to charge/run devices such as a laptop / mobile phone(s) / AA batteries for gameboys & camera etc etc while on the road (one at a time!); they seem to be as cheap as chips these days and this would enable me to use the standard mains chargers for all the above devices rather than buying separate low voltage kit to connect each of them up to the cigar lighter. snip i dont know about power usage on a laptop, but, i do know that 100w drawn from an inverter at 240v, will give you less than 1/2hours usage. YLMV. And 100W can never give any meaningful amount of run time without specifying how long. My laptop - admittedly a subnote - uses about 40W when charging, and about 15W running normally. This runs on a standard car battery for around a day, from an inverter. but is that 40w &15w at 240v or the normally 18v that most laptops use?? this makes a big differance |
Powering laptop etc in car from inverter?
Dave Fawthrop wrote:
On Sun, 14 May 2006 10:23:38 GMT, Lobster wrote: |I'm thinking of buying an 12V - 240V for the car, to enable me to |charge/run devices such as a laptop / mobile phone(s) / AA batteries for |gameboys & camera etc etc while on the road (one at a time!); they seem |to be as cheap as chips these days and this would enable me to use the |standard mains chargers for all the above devices rather than buying |separate low voltage kit to connect each of them up to the cigar lighter. | |Sounds good in theory, but are there any gotchas? Eg, safety? safety is ok, though you've got none of the protective devices found in houses, eg rcd, mcb. And you need to ensure you dont connect an output line firmly to earth, otherwise your car might end up live. Lower standards yes, but it seems to work ok in practice. Does it |run a car battery down more to power up a laptop via a 240V inverter |than directly to the cigar lighter? etc etc Yes! assume your invertor is 80% efficient. every conversion loses power, so yes. |Can't help feeling an inverter would be much better if wired or plugged |into the car some other way than via the god-awful universal |cigar-lighter plug... Battery clips are less convenient. A cig plug limits power throughput. Some cars have built in power connectors, though not many. Might be worth a look in the glovebox for a 2 pin socket. Be careful that there is enough charge available to start the car. yup! Or park on a hill. There are two sorts of invertor Modified sine wave output as below These are quite cheap but electronics do not like sharp edges anywhere near them. electronic SMPSU supplies will behave fine on square or msw waves. There is one type of supply that cant tolerate these waveforms, and thats a CR supply. CR supplies are only used for tiny power outputs with no external power connection, eg plugin timers, killawatt meters and so on. Laptops are always smpsu. For myself I would buy a laptop which will run off 12V, which I did with the STB. thats best, but if yours doesnt, it doesnt. NT |
Powering laptop etc in car from inverter?
In article ,
aussie bongo wrote: i dont know about power usage on a laptop, but, i do know that 100w drawn from an inverter at 240v, will give you less than 1/2hours usage. A reasonable sized car battery will be around 70 amp/hour at the 20 amp rate. 20 amps at 12 volts is 120 watts, so it would be reasonable to expect something like 3 hours use at 100 watts 240 volts. But a laptop will be nothing like 100 watts otherwise it wouldn't last for minutes on its internal batteries. -- *Who is this General Failure chap anyway - and why is he reading my HD? * Dave Plowman London SW To e-mail, change noise into sound. |
Powering laptop etc in car from inverter?
In article ,
Lobster wrote: Can't help feeling an inverter would be much better if wired or plugged into the car some other way than via the god-awful universal cigar-lighter plug... Only small ones work off the lighter socket - this is restricted to a max of 10 amps. Larger ones have crock clips for direct connection to the battery. But nothing to stop you using custom wiring and a suitable plug/socket for connection inside the car. TLC have rather good prices on modified sine wave invertors. You'll see the identical ones elsewhere at more than twice the price. -- *Husbands should come with instructions Dave Plowman London SW To e-mail, change noise into sound. |
Powering laptop etc in car from inverter?
In article .com,
wrote: Be careful that there is enough charge available to start the car. yup! Or park on a hill. But mine's an auto... -- *Husband and cat lost -- reward for cat Dave Plowman London SW To e-mail, change noise into sound. |
Powering laptop etc in car from inverter?
"aussie bongo" wrote in message ... "Ian Stirling" wrote in message ... In uk.d-i-y aussie bongo wrote: "Lobster" wrote in message ... I'm thinking of buying an 12V - 240V for the car, to enable me to charge/run devices such as a laptop / mobile phone(s) / AA batteries for gameboys & camera etc etc while on the road (one at a time!); they seem to be as cheap as chips these days and this would enable me to use the standard mains chargers for all the above devices rather than buying separate low voltage kit to connect each of them up to the cigar lighter. snip i dont know about power usage on a laptop, but, i do know that 100w drawn from an inverter at 240v, will give you less than 1/2hours usage. YLMV. And 100W can never give any meaningful amount of run time without specifying how long. My laptop - admittedly a subnote - uses about 40W when charging, and about 15W running normally. This runs on a standard car battery for around a day, from an inverter. but is that 40w &15w at 240v or the normally 18v that most laptops use?? this makes a big differance 40W is 40W whether its at 1nV or 306MV P(WATTS) = VOLTS x AMPS 40W from an 12V battery = 3.3A 40W from 240V rms supply = 0.167A rms Average car battery = 35Ah, assuming 100% conversion efficiency = 10hrs |
Powering laptop etc in car from inverter?
In uk.d-i-y aussie bongo wrote:
"Ian Stirling" wrote in message ... In uk.d-i-y aussie bongo wrote: "Lobster" wrote in message ... I'm thinking of buying an 12V - 240V for the car, to enable me to charge/run devices such as a laptop / mobile phone(s) / AA batteries for gameboys & camera etc etc while on the road (one at a time!); they seem to be as cheap as chips these days and this would enable me to use the standard mains chargers for all the above devices rather than buying separate low voltage kit to connect each of them up to the cigar lighter. snip My laptop - admittedly a subnote - uses about 40W when charging, and about 15W running normally. This runs on a standard car battery for around a day, from an inverter. but is that 40w &15w at 240v or the normally 18v that most laptops use?? this makes a big differance About the wattage at teh plug. The figures from 15V are 2A (sticker - I've never seen it past 1.5A) and about 12W. |
Powering laptop etc in car from inverter?
"Dave Plowman (News)" wrote in message ... In article , aussie bongo wrote: i dont know about power usage on a laptop, but, i do know that 100w drawn from an inverter at 240v, will give you less than 1/2hours usage. A reasonable sized car battery will be around 70 amp/hour at the 20 amp rate. ? where did 20A come from? 20 amps at 12 volts is 120 watts, Not when I went to skool so it would be reasonable to expect something like 3 hours use at 100 watts 240 volts. WTF? But a laptop will be nothing like 100 watts otherwise it wouldn't last for minutes on its internal batteries. I'll give that a tick -- *Who is this General Failure chap anyway - and why is he reading my HD? * Dave Plowman London SW To e-mail, change noise into sound. |
Powering laptop etc in car from inverter?
In uk.rec.cars.maintenance Slurp wrote:
"Dave Plowman (News)" wrote in message ... In article , aussie bongo wrote: i dont know about power usage on a laptop, but, i do know that 100w drawn from an inverter at 240v, will give you less than 1/2hours usage. A reasonable sized car battery will be around 70 amp/hour at the 20 amp rate. ? where did 20A come from? He means 20 hour. Battery capacity is typically expressed as how much current it can supply when discharged in 20 hours. Discharge it faster, and you get less out. snip so it would be reasonable to expect something like 3 hours use at 100 watts 240 volts. WTF? 100W/12 = 8A from battery. Say 10A, due to inefficiencies. A 70Ah battery will supply 10A for slightly less than 7h. |
Powering laptop etc in car from inverter?
In uk.rec.cars.maintenance Slurp wrote:
"aussie bongo" wrote in message ... snip myu comment but is that 40w &15w at 240v or the normally 18v that most laptops use?? this makes a big differance 40W is 40W whether its at 1nV or 306MV P(WATTS) = VOLTS x AMPS 40W from an 12V battery = 3.3A 40W from 240V rms supply = 0.167A rms Average car battery = 35Ah, assuming 100% conversion efficiency = 10hrs Err, no. If it's measured at 240V, you've then got to addin the efficiency of the inverter. If it's measured at 12V, you don't. |
Powering laptop etc in car from inverter?
HI Dave
On Sun, 14 May 2006 13:29:36 +0100, "Dave Plowman (News)" wrote: In article , aussie bongo wrote: i dont know about power usage on a laptop, but, i do know that 100w drawn from an inverter at 240v, will give you less than 1/2hours usage. A reasonable sized car battery will be around 70 amp/hour at the 20 amp rate. 20 amps at 12 volts is 120 watts, so it would be reasonable to expect something like 3 hours use at 100 watts 240 volts. But isn't there something about car batteries being designed for delivering lots of current for a very short period of time ..? You might get this sort of duration from a 'leisure' battery - as they're designed for lower current over a longer period. Years ago, when I was young and foolish, I tried providing lights for several tents in our scout troop - using a car battery and car sidelights. Load would have been in the region of 60watts or so - lasted about 15 minutes before the battery died. Just as well really - it was before I knew about fuses g - and were it not for the fact that the wiring was really weedy I might have toasted the entire troop ! You live & learn g.... But a laptop will be nothing like 100 watts otherwise it wouldn't last for minutes on its internal batteries. True.... Don't know how efficient modern inverters are - I guess it's be fairly easy to find out with the aid of a multimeter and a mains light bulb.... Regards Adrian ======return email munged================= take out the papers and the trash to reply |
Powering laptop etc in car from inverter?
Dave Plowman (News) wrote:
In article .com, wrote: Be careful that there is enough charge available to start the car. yup! Or park on a hill. But mine's an auto... I tried starting one I once had with the crank handle, coudnt get it to turn tho, nor could anyone else. Most disappointed. NT |
Powering laptop etc in car from inverter?
"Ian Stirling" wrote in message ... In uk.rec.cars.maintenance Slurp wrote: "aussie bongo" wrote in message ... snip myu comment but is that 40w &15w at 240v or the normally 18v that most laptops use?? this makes a big differance 40W is 40W whether its at 1nV or 306MV P(WATTS) = VOLTS x AMPS 40W from an 12V battery = 3.3A 40W from 240V rms supply = 0.167A rms Average car battery = 35Ah, assuming 100% conversion efficiency = 10hrs Err, no. If it's measured at 240V, you've then got to addin the efficiency of the inverter. Err, no you have to add in the INefficiency, ie if 80% efficient then add in 20% If it's measured at 12V, you don't. ????? The extra current due to the inefficiency of the conversion has to be supplied from 12V!!!! |
Powering laptop etc in car from inverter?
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Powering laptop etc in car from inverter?
"Lobster" wrote in message ... I'm thinking of buying an 12V - 240V for the car, to enable me to charge/run devices such as a laptop / mobile phone(s) / AA batteries for gameboys & camera etc etc while on the road (one at a time!); they seem to be as cheap as chips these days and this would enable me to use the standard mains chargers for all the above devices rather than buying separate low voltage kit to connect each of them up to the cigar lighter. Sounds good in theory, but are there any gotchas? Eg, safety? Does it run a car battery down more to power up a laptop via a 240V inverter than directly to the cigar lighter? etc etc Can't help feeling an inverter would be much better if wired or plugged into the car some other way than via the god-awful universal cigar-lighter plug... Thanks David I did with a dell lt, not again, i didnt like the feel of the laptop power module(230 to 18) it got very very hot compaired to warm on full fat mains power. |
Powering laptop etc in car from inverter?
Lobster presented the following explanation :
Sounds good in theory, but are there any gotchas? Eg, safety? Does it run a car battery down more to power up a laptop via a 240V inverter than directly to the cigar lighter? etc etc A switch mode PSU (which is basically what an inverter is) has an efficiency of between 70 and 90%. Powering a laptops own PSU from one means that you would have two steps in voltage conversion, each with losses. A better way would be a purpose designed inverter which directly replaces the laptop PSU with one which takes in 12v and outputs whatever the laptops needs. Maplin do such an item with various output voltage settings, various plugs and at 3amps. Can't help feeling an inverter would be much better if wired or plugged into the car some other way than via the god-awful universal cigar-lighter plug... Agreed, but it is the 12v socket commonly fitted to most cars. -- Regards, Harry (M1BYT) (L) http://www.ukradioamateur.co.uk |
Powering laptop etc in car from inverter?
In article ,
Slurp wrote: A reasonable sized car battery will be around 70 amp/hour at the 20 amp rate. ? where did 20A come from? 20 amps at 12 volts is 120 watts, Not when I went to skool so it would be reasonable to expect something like 3 hours use at 100 watts 240 volts. WTF? Remind me not to post while on the phone. ;-) I meant the 20 hour rate, which would be around 3.5 amps discharge. A 150 watt invertor takes approx 12.5 amps, and the higher discharge rate means the battery won't deliver quite its full capacity. But 3 hours from a 70 amp/hour battery driving a 150 watt invertor at max isn't a million miles out. ;-) Although theory says nearer 6. Sorry for the rubbish post. -- *I'm not being rude. You're just insignificant Dave Plowman London SW To e-mail, change noise into sound. |
Powering laptop etc in car from inverter?
|
Powering laptop etc in car from inverter?
"Slurp" wrote in message ... "Ian Stirling" wrote in message ... In uk.rec.cars.maintenance Slurp wrote: "aussie bongo" wrote in message ... snip myu comment but is that 40w &15w at 240v or the normally 18v that most laptops use?? this makes a big differance 40W is 40W whether its at 1nV or 306MV P(WATTS) = VOLTS x AMPS 40W from an 12V battery = 3.3A 40W from 240V rms supply = 0.167A rms Average car battery = 35Ah, assuming 100% conversion efficiency = 10hrs Err, no. If it's measured at 240V, you've then got to addin the efficiency of the inverter. Err, no you have to add in the INefficiency, ie if 80% efficient then add in 20% If it's measured at 12V, you don't. ????? The extra current due to the inefficiency of the conversion has to be supplied from 12V!!!! That's just what Ian said. -- Malc "When I say 'Run like ufck and commit assault on a police officer several times,' run like ufck and commit assault on a police officer several times." - Channon Transmetropolitan |
Powering laptop etc in car from inverter?
On Sun, 14 May 2006 11:48:36 +0100, Dave Fawthrop
wrote: On Sun, 14 May 2006 10:23:38 GMT, Lobster wrote: |I'm thinking of buying an 12V - 240V for the car, to enable me to |charge/run devices such as a laptop / mobile phone(s) / AA batteries for |gameboys & camera etc etc while on the road (one at a time!); they seem |to be as cheap as chips these days and this would enable me to use the |standard mains chargers for all the above devices rather than buying |separate low voltage kit to connect each of them up to the cigar lighter. | |Sounds good in theory, but are there any gotchas? Eg, safety? Does it |run a car battery down more to power up a laptop via a 240V inverter |than directly to the cigar lighter? etc etc Yes! assume your invertor is 80% efficient. |Can't help feeling an inverter would be much better if wired or plugged |into the car some other way than via the god-awful universal |cigar-lighter plug... Be careful that there is enough charge available to start the car. There are two sorts of invertor Modified sine wave output as below |---| --| |--| |-- |--| These are quite cheap but electronics do not like sharp edges anywhere near them. You should *check* that they will work *your* laptop. I was warned off using one of these with a TV Set Top Box by Bill Wright on uk.tech.digital-tv Others are pure(ish) sine wave which cost 3 times as much and should be OK. For myself I would buy a laptop which will run off 12V, which I did with the STB. Laptop PSUs (unless youve got one from the 80s) are quite happy with any of the inverters. However the direct converters from Maplin are cheaper & more effecient. |
Powering laptop etc in car from inverter?
Ian Stirling wrote: In uk.rec.cars.maintenance Slurp wrote: "aussie bongo" wrote in message ... snip myu comment but is that 40w &15w at 240v or the normally 18v that most laptops use?? this makes a big differance 40W is 40W whether its at 1nV or 306MV P(WATTS) = VOLTS x AMPS 40W from an 12V battery = 3.3A 40W from 240V rms supply = 0.167A rms Average car battery = 35Ah, assuming 100% conversion efficiency = 10hrs Err, no. If it's measured at 240V, you've then got to addin the efficiency of the He did. Which bit of "assuming 100% conversion efficiency" don't you understand? It might not be a valid assumption but the method is perfectly clear. MBQ |
Powering laptop etc in car from inverter?
Lobster wrote: I'm thinking of buying an 12V - 240V for the car, to enable me to charge/run devices such as a laptop / mobile phone(s) / AA batteries for gameboys & camera etc etc while on the road (one at a time!); they seem to be as cheap as chips these days and this would enable me to use the standard mains chargers for all the above devices rather than buying separate low voltage kit to connect each of them up to the cigar lighter. Sounds good in theory, but are there any gotchas? Eg, safety? Does it run a car battery down more to power up a laptop via a 240V inverter than directly to the cigar lighter? etc etc A lot of laptops need more than 12V so you would still need a DC-DC converter to run from the cigar lighter. It then depends on the relative efficiencies of the inverter and the DC-DC converter. By "on the road" do you actually mean driving? If parked then just be careful your battery can withstand being discharged repeatedly. MBQ |
Powering laptop etc in car from inverter?
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Powering laptop etc in car from inverter?
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Powering laptop etc in car from inverter?
"aussie bongo" wrote in message ... "Ian Stirling" wrote in message ... In uk.d-i-y wrote: Ian Stirling wrote: In uk.rec.cars.maintenance Slurp wrote: "aussie bongo" wrote in message ... snip myu comment but is that 40w &15w at 240v or the normally 18v that most laptops use?? this makes a big differance 40W is 40W whether its at 1nV or 306MV P(WATTS) = VOLTS x AMPS 40W from an 12V battery = 3.3A 40W from 240V rms supply = 0.167A rms Average car battery = 35Ah, assuming 100% conversion efficiency = 10hrs Err, no. If it's measured at 240V, you've then got to addin the efficiency of the He did. Which bit of "assuming 100% conversion efficiency" don't you understand? It might not be a valid assumption but the method is perfectly clear. Indeed, and my point that he completely missed the point that asking "Was it 40W at 18V or 240V", is obviously referring to the conversion efficiency. the current drawn at 40w on 18v is around 2.222222222222-amps // but 40w at 240v is about 6-amps this do not include the extra power that the inverter needs just to run its self, also if you draw 40w at 18v then the inverter will need more than 6-amps input sorry the 6-amps should read 0.6-amps (puts head under jumper in shame) |
Powering laptop etc in car from inverter?
In article . com,
wrote: By "on the road" do you actually mean driving? If parked then just be careful your battery can withstand being discharged repeatedly. What do you reckon the capacity of the laptop's internal battery is? -- *Very funny Scotty, now beam down my clothes. Dave Plowman London SW To e-mail, change noise into sound. |
Powering laptop etc in car from inverter?
In article ,
aussie bongo wrote: the current drawn at 40w on 18v is around 2.222222222222-amps // but 40w at 240v is about 6-amps watts amps = ----- volts So 40w at 18 volts is as you say 2.2. But watts are sort of an absolute measurement of power, so increase the voltage and the current goes down, so 40 at 240 volts is 0.17 amps. Thus the wattage drawn by the invertor will be the same as its load, but increased by the efficiency figure of the invertor. So if that's say 80%, the load of 40 watts will draw 50 watts from the battery. -- *I used to have an open mind but my brains kept falling out * Dave Plowman London SW To e-mail, change noise into sound. |
Powering laptop etc in car from inverter?
In uk.d-i-y "Dave Plowman (News)" wrote:
In article , aussie bongo wrote: the current drawn at 40w on 18v is around 2.222222222222-amps // but 40w at 240v is about 6-amps snip So 40w at 18 volts is as you say 2.2. But watts are sort of an absolute measurement of power, so increase the voltage and the current goes down, so 40 at 240 volts is 0.17 amps. Thus the wattage drawn by the invertor will be the same as its load, but increased by the efficiency figure of the invertor. So if that's say 80%, the load of 40 watts will draw 50 watts from the battery. Plus the inefficiency of the laptop power supply, which may be another 20%, or maybe 60-65W |
Powering laptop etc in car from inverter?
In article .com,
wrote: Dave Plowman (News) wrote: In article . com, wrote: By "on the road" do you actually mean driving? If parked then just be careful your battery can withstand being discharged repeatedly. What do you reckon the capacity of the laptop's internal battery is? Why is that relevant? Because it's likely to be be tiny compared to the car battery. The OP wants to power the laptop from a car battery. In the past I seem to have buggered a car battery by allowing it to discharge to much (courtesy light left on for a few hours). Most courtesy lights don't draw much current - or those that do often switch themselves off after a time. Maybe it was on it's last legs anyway. Sounds rather like it. -- *Errors have been made. Others will be blamed. Dave Plowman London SW To e-mail, change noise into sound. |
Powering laptop etc in car from inverter?
In uk.rec.cars.maintenance "Dave Plowman (News)" wrote:
In article .com, wrote: Dave Plowman (News) wrote: In article . com, wrote: By "on the road" do you actually mean driving? If parked then just be careful your battery can withstand being discharged repeatedly. What do you reckon the capacity of the laptop's internal battery is? Why is that relevant? Because it's likely to be be tiny compared to the car battery. Smaller, but not tiny. Many laptop batteries are 10% of the capacity energy-wise of the car battery. 7Ah@12V or so (9 Li-ion cells, for example). |
Powering laptop etc in car from inverter?
In article ,
Ian Stirling wrote: Thus the wattage drawn by the invertor will be the same as its load, but increased by the efficiency figure of the invertor. So if that's say 80%, the load of 40 watts will draw 50 watts from the battery. Plus the inefficiency of the laptop power supply, which may be another 20%, or maybe 60-65W The 40 watts was just following on from ab's post - not meant to be an actual figure for a laptop. 60-65 watts might be closer when it's charging the laptop battery - the actual running current will be very much less. -- *Any connection between your reality and mine is purely coincidental Dave Plowman London SW To e-mail, change noise into sound. |
Powering laptop etc in car from inverter?
aussie bongo wrote:
"Lobster" wrote in message ... I'm thinking of buying an 12V - 240V for the car, to enable me to charge/run devices such as a laptop / mobile phone(s) / AA batteries for gameboys & camera etc etc while on the road (one at a time!); they seem to be as cheap as chips these days and this would enable me to use the standard mains chargers for all the above devices rather than buying separate low voltage kit to connect each of them up to the cigar lighter. Sounds good in theory, but are there any gotchas? Eg, safety? Does it run a car battery down more to power up a laptop via a 240V inverter than directly to the cigar lighter? etc etc Can't help feeling an inverter would be much better if wired or plugged into the car some other way than via the god-awful universal cigar-lighter plug... Thanks David i dont know about power usage on a laptop, but, i do know that 100w drawn from an inverter at 240v, will give you less than 1/2hours usage. Car bateries are 40-70Ah, and at a nominal 12v, that is 480-840Wh. Giving and expected uptime at npominal 80% eficiency of say 4-8hrs roughly. one thing to remember if you get one, is that you have to make sure it is turned off with no power going into it whilst starting the car as to do so will damege the inverter. Total ******** as well. |
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