 sj |
||
|
||
Tech: Laptop and Car Battery?
|
|
|
Subject: Tech: Laptop and Car Battery? From: Geoff the Duck Date: 22 Oct 04 - 05:08 AM Just wondering if we would be able to take a laptop computer when we are in the caravan and run it from the spare 12 volt battery. Does anybody know anything about the practicality of such a thing. The laptop mains transformer input is higher than 12 volt (I think it's about 19v), so it would presumably need some sort of step-up transformer. Do they sell anything designed for the job. Thanks in advance for any useful comments. Quack! Geoff the Duck. |
|
Subject: RE: Tech: Laptop and Car Battery? From: Liz the Squeak Date: 22 Oct 04 - 05:11 AM Manitas has some contraption for this sort of thing, but I don't think it's a car battery. PM him and ask. He runs a fluoro strip off it when camping. My opinion is if you want to sit and read a book, there are perfectly good pubs for that! LTS |
|
Subject: RE: Tech: Laptop and Car Battery? From: Dave Bryant Date: 22 Oct 04 - 06:19 AM I often run my laptop in the caravan - how do you think that I print badges at events. It depends on what input voltage your laptop needs. Some will work straight from 12v - in which case you just need to make up a lead with the correct plugs on each end. If the voltage is higher than 12v (mine requires 14v), Maplin will sell you an adaptor for £19 - see here - my toshiba runs fine on the 15v setting. You can also buy adaptors which will reduce the voltage - but do make sure that it's a regulated one and can supply the neccessary current (you can find this out from the handbook or by reading the details on the mains adaptor/charger. Most adaptors come with a series of different plugs to fit most laptops, but check that you've got the polarity (+/-) the right way round. You could also use an inverter to convert 12v dc to mains voltage (240v ac) - these are useful if you want to run a printer which is mains only. Maplin sell these for about £30 - although they keep doing special offers on them - I've seen them at £19. Incidently if you wish to make up a lead to electrify your banjo, I suggest a 1/4 inch jack on the instrument end and a 13a three pin plug on the other. ;-) |
|
Subject: RE: Tech: Laptop and Car Battery? From: Dave Bryant Date: 22 Oct 04 - 06:42 AM Whoops - Having read your original post in more detail, I see that you need 19v - the adaptor which I've suggested should be fine. Incidently, you can't use a transformer with DC, inverters work by converting the DC to a rough AC sinewave and then using a step-up transformer. I'm not sure exactly how the Laptop Adaptors work, but I assume that it uses some sort of solid state bridging technique. Anyway the one I have works fine - it even seems quite happy running my little Canon printer as well. |
|
Subject: RE: Tech: Laptop and Car Battery? From: Paco Rabanne Date: 22 Oct 04 - 06:51 AM Power it by coal... oh... sorry... wrong thread! |
|
Subject: RE: Tech: Laptop and Car Battery? From: JohnInKansas Date: 22 Oct 04 - 07:22 AM The nearly universal method for running a laptop off an auto battery in the US - and the method recommended by the laptop manufacturers I've consulted, is to use your power converter that came with the laptop, plugged into 110v AC. You get the 110v AC from an "Inverter" that plugs into your accessory 12v DC socket (cig lighter) in the vehicle. A very few years ago, you almost had to go to a computer/electronics supply shop and pay $75 (US) or more for a decent small inverter, but they're now available at places like Walmart for around $30 in sizes appropriate for a laptop, or at truck stops on the highway in sizes large enough to run a refrigerator. You need a BIG battery for the larger ones. Most laptops here come with a power adapter, which takes care of getting the correct dc voltage and provides all the filtering necessary. Some, but not all of them, include a built in "reserve" that will even keep the computer alive during short power interruptions. The adapter supplied with the computer is supposed to handle all the variations seen on "mains" power that you plug into. It's now very easy here to find a variety of inexpensive Inverters that will plug into your car's 12V DC socket, and provide an adequate AC output to run your computer "on AC." I would expect that your local market should have similar inverters to provide the appropriate "mains" voltage and frequency for your stuff. With "AC Power" in your car, you can also run any number of other "household devices" - depending on the size of the inverter you get. I have seen some folk in a neighboring camp running a cocktail blender off one. Some of the larger campers have them built in for the TV, stereo console, and satellite dish converter, although these tend to be very large, and expensive, units. John |
|
Subject: RE: Tech: Laptop and Car Battery? From: pavane Date: 22 Oct 04 - 07:46 AM I use a car battery and an inverter myself. In the UK, Maplins keep a range, as noted above. A car battery will do up to 12 hours, maybe more, depending on how much you plug into it. Simple calculation: 60W means about 5 amps from a 12v battery. A fully charged battery will provide 5 amps for only about 12 hours, probably less because the inverters have a low-voltage cutout, intended to stop you from completely flattening your car battery. I also have a couple of 'power units' with 7 amp-hour batteries. These last less than 2 hours. I have just bought a UPS which should have a similar capacity. This contains a built-in battery and inverter, and can be used at home in its intended role as well. In order to save power, I have my working files on a USB memory stick, which means that the hard drive is not used too often. Another possibility - Makro are currently selling 650W generators for £45 plus VAT. These will run for 8 hours on a 5L fill. |
|
Subject: RE: Tech: Laptop and Car Battery? From: pavane Date: 22 Oct 04 - 07:50 AM Also - when you have got your inverter, you can use it to run lighting. The low-power bulbs which you can now get will give much better light than a typical caravan unit. I run 5 20W bulbs from an inverter in my stable. |
|
Subject: RE: Tech: Laptop and Car Battery? From: Dave Bryant Date: 22 Oct 04 - 08:10 AM If you just want to run a laptop, though, the device which I've suggested is much smaller and lighter than an inverter - I keep it in the case with my laptop. I actually have a 300w inverter in the caravan, but only tend to use it for specific applications. I would expect that the efficiency of using an inverter to knock 12v dc up to mains and then using your laptop power unit to knock it back down again would be less than the single adaptor - when I checked it out of curiosity, the input current was only very slightly higher than the input - about what you'd expect for 13.2v (a typical battery voltage) to 15. If you want to drive a printer as well then perhaps the best bet is an inverter - I would recommend a 300w one at least. Luckily my little cannon printer will run directly on 15v the same as my laptop. |
|
Subject: RE: Tech: Laptop and Car Battery? From: IanC Date: 22 Oct 04 - 08:19 AM Geoff We used to set up and test computers for a charity which had projects in 26 African countries. Some of them used 12v car batteries with their solar power systems and wanted to run their laptops off these. After some investigation and trials, we found that 240v battery to mains converters actually worked very well and quite efficiently. Attaching them directly to a battery (or via the cigarette lighter attachment, though they mostly didn't want this) was very straightforward. We supplied about 20-30 of them in all, over a period of about 5 years, and there was never a problem, so I'd be inclined to recommend this method. :-) Ian |
|
Subject: RE: Tech: Laptop and Car Battery? From: harpgirl Date: 22 Oct 04 - 11:17 AM I just bought an inverter for $15.99 which I am hoping to use a small coffee maker with at tonight's MagFest! My question is, do you need to have your car engine running and if not how fast does it drain your car battery? Guess I'll find out tomorrow morning when I make coffee! |
|
Subject: RE: Tech: Laptop and Car Battery? From: Gervase Date: 22 Oct 04 - 11:41 AM Careful how much drain you put on the inverter. The cheaper ones will only cope with a couple of hundred watts, which may not be enough for the heating coil on a coffee maker. Before you buy, take a look at the maximum wattage and make sure it's up to the job. My beloved tried running a hairdryer from an inverter at Sidmouth and blew the fuse on the car! |
|
Subject: RE: Tech: Laptop and Car Battery? From: JohnInKansas Date: 22 Oct 04 - 02:03 PM The cig lighter on most US cars has a 20A fuse. 20A*12V = 240 watts. You probably shouldn't exceed about 80% of rated, so the lighter socket may be only good for about 180 or 190 watts. My home coffee pot shows a "nameplate" rating of 1,050 watts, so likelihood of successful use off the cig lighter socket would be quite low. Most of the commonly available small inverters I've seen are in the 60W, 90W, 150W range. You'd likely need to look for a 1,500W inverter to handle my pot. Clipped direct to battery terminals, you could pull the (1500/12 = 125A rated, 1,050/12 = 88A needed) current safely - for a few minutes, but probably not long enough to brew coffee. Even with the engine running, most alternators are only rated at 35 or 40A on the small cars, (but up to 125A on some of the gas guzzlers). You might be able to run a large enough inverter, with the engine running, long enough to get coffee from a smaller pot - but don't shut the engine off before the battery is back up to starting level. Multiply the volts by the amps, shown on the baseplate of your coffee maker. That gives you Watts. Your inverter should show how many watts it can put out. If the inverter output is less than what the pot needs, chances of successful operation are minimal. You can get "warmers" with 50W or so ratings, AC or 12V dc - whichever you find, to heat a cup at a time - and use instant coffee (yeah, I know...). John |
|
Subject: RE: Tech: Laptop and Car Battery? From: open mike Date: 22 Oct 04 - 04:06 PM i amjust now searching on e-bay for just such a transformer.. try www.ebay.com. My Gateway laptop takes a 19 volt plug as well, and there are quite a few avaialbe. some models require a specific one to provide their power...many diff. brands and voltages ara available. try here: http://computers.listings.ebay.com/Laptop-Parts-Accessories_Adapters-Chargers-for-Laptops_W0QQfromZR11QQsacategoryZ31510QQsocmdZListingItemListQQsocolumnlayoutZ3QQsocustoverrideZ1 oh my looks like a long URL..jsut go to e-bay and search computers - laptops - accessories...charges, adapters... |
|
Subject: RE: Tech: Laptop and Car Battery? From: GUEST Date: 22 Oct 04 - 08:36 PM you can also now get mini ITX motherboards that can run on a 12v supply direct http://www.itx-warehouse.co.uk/ |
|
Subject: RE: Tech: Laptop and Car Battery? From: Geoff the Duck Date: 23 Oct 04 - 05:02 AM Thanks for the information so far. In the UK our mains electricity is 240 volt, so the US mains info isn't relevant to my setup, but I'm sure it will be useful for other readers. Transforming (inverting or whatever) all the way up to 240 volts then taking it back down sounds like it would be energy inefficient and more than is needed to just do the job I need. Best bet (for us) so far sounds like the Maplins gizmo mentioned by Dave Bryant. We'll probably go for that option and test the laptop on our caravan's spare battery to see what sort of performance and duration we can get doing the heavy load tasks such as playing DVDs. I know that caravan batteries are more heavy duty than a standard car job, but don't know by how much. I'll report back with any useful additional data. Quack! GtD. |
|
Subject: RE: Tech: Laptop and Car Battery? From: GUEST Date: 23 Oct 04 - 07:10 AM |
|
Subject: RE: Tech: Laptop and Car Battery? From: The Fooles Troupe Date: 23 Oct 04 - 11:00 AM Tech: threads have traditionally been above the line - whether our anonymous GUEST 'Mudcat Thread Policeman' thinks they are BS or not... so GUEST is either very new here, or has just not been paying attention... |
|
Subject: RE: Tech: Laptop and Car Battery? From: pavane Date: 23 Oct 04 - 04:33 PM Caravan batteries are not more heavy duty, they are just built to cope with deep discharge cycles. Car batteries don't like being fully discharged many times. |
|
Subject: RE: Tech: Laptop and Car Battery? From: JohnInKansas Date: 23 Oct 04 - 05:11 PM GtD - It would be assumed that the inverters available in your area would produce the appropriate "mains voltage" for the area where they're sold. They may, of course, be less easily available in your market than in mine, although Dave indicated no problem finding them. The "laptop power converters" described by Dave are not commonly available - that I've seen - in the US market. Other kinds of DC/DC converters are fairly common, but they're seldom advertised as being suitable for laptops. The laptop makers here seem pretty fussy about having people use only their power supply with their computer, and in fairness to this attitude it should be admitted that the usual units that they supply do include quite a lot of heavy duty filtering. They also tend to cost $100 to $200 (US) each. An auto battery should be a very stable and noise-free source, but the charging systems on most automobiles are, by "electronic" standards, extremely noisy. The alternators commonly used actually produce AC currents internally that frequently run into the hundred (or hundreds) volt range. The "spikes" are sent pretty much direct to the battery, where they're supposed to be swamped by the large capacity of the battery, but aren't always. The automakers tend also to use the minimum amount of copper to get by, so any other things that click on and off can cause a lot of trash on the line. Using the laptop maker's own AC to DC converter gives some assurance that the laptop gets "clean" power - and even using the AC to DC unit off a rather "dirty mains line," a.k.a inverter output, isn't likely to do any harm to the computer. (And you can blame the laptop maker if his device isn't clean enough.) I don't have any argument with anyone who knowledgably uses another kind of device, but that puts the burden on the user to assess whether the regulation and stability of the device is suited to the laptop application. The inverter/converter route lets even dummies be safe, and doesn't really cause much in watt-hour losses in practice. And, as Dave said, it gives you a way to run your printer too, if you've got a large enough inverter. John |
|
Subject: RE: Tech: Laptop and Car Battery? From: The Fooles Troupe Date: 23 Oct 04 - 08:05 PM 1) If you want to run any electrical device for any period of time from a non-mains source, you should do the necessary calculations on power/endurance, or get a techie oriented friend to do it - the life of car batteries - or even laptop batteries is surprisingly short, especially when under heavy drain. 2) If you want to cook/heat food/make coffee etc in a remote or camping site - you would be better off forgetting electrical devices unless you have a portable generator - and use some chemical form of stove/burner - gas or liquid if you can't get access to a campfire. |
|
Subject: RE: Tech: Laptop and Car Battery? From: John J Date: 24 Oct 04 - 08:12 AM Hi Geoff, You and others are quite correct regarding the ineffiencies in using an inverter to get to 230vAC, then a separate power supply to get 19v. Points worth noting: 1) Your existing plug-in adaptor is probably not a step down transformer, but is far more likely to be a switch mode power supply. These really are quite efficient, small and lightweight. 2)If your existing power supply is 19v it may well be worth buying a 6v (motorcycle?) battery and wiring that in series with your car / caravan battery. 12v+6v=18v, but... 3) When you consider that fully charged lead-acid batteries actually supply more than 12v, you'll probably find the actual output of this 2 battery arrangement is nearer 20v. Good luck! John |
|
Subject: RE: Tech: Laptop and Car Battery? From: The Fooles Troupe Date: 24 Oct 04 - 06:42 PM And the practical reality of what happens to 2 so widely differing battery types in series means that it is not necessarily the best option. Unfortunately 'theoretical' options aren't always that simple in practice***... Then again, if you only use it occasionally, it may work well enough. *** for example the small m/c battery will be of a lesser amp hour capability, and a different internal resistance, and it will flatten first, so you will then find you end up reverse charging it and damage it... |
|
Subject: RE: Tech: Laptop and Car Battery? From: JohnInKansas Date: 24 Oct 04 - 07:42 PM You guys had to keep talking about this until you forced me to go look at my user's manual.... I note that the AC Adapter that came with my Dell laptop is rated for input of 90 to 135 VAC and 164 to 264 VAC, at 47 to 63 Hz with no modification, and not even any switches to flip. Just snap on a "socket adaptor" and plug in almost anywhere in the world. Regardless of what you put in, you get 20V DC out. Not too bad for a $50 (US) power adjuster/regulator. IF YOURS IS THE SAME, you don't have to worry about whether you've got a US (120V 60 Hz) inverter or a euro (230V 50Hz) inverter - just plug in and go. I did come across some comments that may be worth noting. I found a rather disturbing batch of complaints about laptop external power sockets in general. It seems that many of these are connected directly to the motherboard so if you damage the socket you replace the board. Expensive. It also appears that it's common that the board is the only (or at least the primary) physical support for the socket, so some of them are very fragile - at least compared to what you'd expect in a "portable" device. Some manufacturers seem to assume that if you're on AC power you're at a desk, and recommend that you unplug all external devices before you even slide the computer around on the desktop. I don't think I care much for that attitude, but it appears that many laptops are designed and built so that one should "observe the warnings." John |
|
Subject: RE: Tech: Laptop and Car Battery? From: Dave Bryant Date: 25 Oct 04 - 05:11 AM The only trouble with most cheaper inverters is that they don't tend to produce a "clean" sine-wave output - usually nearer a saw-tooth. Most laptop power supplies usually rectify (convert to DC) and smooth the output voltage, so this shouldn't really matter. I do reckon though that my laptop's mains power supply does seem to run hotter on an inverter than on the mains, so it might be putting more strain on the transformer and smoothing capacitor. Harpgirl, most of the cheaper inverters over here in the UK seem to be rated at 150w. At full power this would be probably be drawing at least 13a from your car battery - it's about the same load as full main beams and emergency rear fog lamps turned on together. I would definitely suggest keeping your engine running. Incidently, I would expect even a small coffee pot to have greater power requirements than 150w. Heating devices tend to require quite a lot of power and 12v batteries are not the best source. There are small 12v drink heater available, but I'd still tend to keep the engine running if I was using one of these. Finally, cigarette lighter style sockets are officially rated at 10a, and will usually be fused accordingly. If you do want to take heavier currents from one, not only do you need to fit a higher value fuse, you must also make sure that the supply cables to it from the battery can handle the increased current. When my boat was surveyed for it's safety certificate, the examiner, made me replace a 16a fuse with a 10a for that reason - even though my wiring could handle 18a. |
|
Subject: RE: Tech: Laptop and Car Battery? From: Gurney Date: 25 Oct 04 - 05:33 AM As Parvane said, if you are going to deep-cycle a battery, use a deep-cycle battery, such as is sold for boats and caravans/trailers. They cost more, but will handle that emptying-recharging treatment better. An ordinary car battery will have a shortened life with that treatment. |
|
Subject: RE: Tech: Laptop and Car Battery? From: Dave Bryant Date: 25 Oct 04 - 07:41 AM Running my laptop on the relatively small (car) battery which I had in the old caravan, didn't seem to cause any problems - even with the printer, it never drew much current. The new caravan has a fairly new, very large, deep-cycle leisure battery, so I don't have any worries there. The main current draw will probably be charging up the laptop battery if it needs it. |
|
Subject: RE: Tech: Laptop and Car Battery? From: pavane Date: 25 Oct 04 - 07:53 AM I see the note above about the power socket being attached directly to the motherboard. That was the case with my Sony, and I had to perform major surgery to solder in a bypass wire (flexible) when the connection failed. (That patch has lasted a couple of years now). So be careful when inserting or removing the adaptor plug! |
| Share Thread: |