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Thread ID: 30356	2003-02-17 04:44:00	charging laptop battery	rugila (214)	Press F1

Post ID	Timestamp	Content	User
121885	2003-02-17 04:44:00	Currently I don't own a laptop (mobile computer) but need to buy one some time soon. I'll frequently be remote from mains electricity and will need to charge laptop (and other stuff) from a (nominal) 12volt solar panel (30watt), and 12v deep cycle battery(ies). (1) Are there commercial chargers available for laptops from 12 volt batteries like there are for cellphones etc? (2) What are the usual specs for laptop batteries (if I need to rig up my own charging setup)?. ie charging voltage, maximum amps they can take, etc.	rugila (214)
121886	2003-02-17 04:51:00	> Currently I don't own a laptop (mobile computer) but > need to buy one some time soon. > > I'll frequently be remote from mains electricity and > will need to charge laptop (and other stuff) from a > (nominal) 12volt solar panel (30watt), and 12v deep > cycle battery(ies). > > (1) Are there commercial chargers available for > laptops from 12 volt batteries like there are for > cellphones etc? Don't think so... generally laptops come with their own chargers. > (2) What are the usual specs for laptop batteries (if > I need to rig up my own charging setup)?. ie charging > voltage, maximum amps they can take, etc. Wouldn't it be dangerous to "rig up your own setup" ... get it wrong and you lose your laptop?? Like I say, laptops nowadays come standard with chargers. Lo.	Lohsing (219)
121887	2003-02-17 04:52:00	The laptops use a wide range of battery voltages: in the last week I've seen 10.5, 12, 17, 18V. I'd be inclined to add a 230V inverter to your solar installation, then use the standard power supply. :D Jaycar and DSE often have specials on them. 150W ones are between $85-$100.	Graham L (2)
121888	2003-02-17 04:52:00	D'oh!! Apologies... my mistake Rugila! Didn't read the "away from mains" comments... wouldn't have the foggiest of where to start! Lo.	Lohsing (219)
121889	2003-02-17 05:03:00	BTW, the newest ones have Lithium Ion batteries. I believe that the battery manufacturers won't sell the batteries on the retail market, because if they are not charged "correctly" they can explode. :D I've run my old laptop off ordinary 12V gel batteries because the NiCds died. The solar array will give up to about 20V open circuit, and the currect would be low enough to charge just about any laptop safely (except perhaps Li-Ion). But you'll probably feel safer (in dollar terms -- laptops cost lots ;-) ) using an inverter to give 230V ac.	Graham L (2)
121890	2003-02-17 08:02:00	> using an inverter to give 230V ac. You can get them to run off a car battery.	mikebartnz (21)
121891	2003-02-17 09:42:00	Thanks for suggestions. Couple of points though. I have plenty of background in electricity to work out a charging system that doesn't wreck a laptop (or indeed just about any other) battery if I know its specifications. Mainly wanted to know what the typical laptop specs are, but also if there are commercial chargers that will charge a laptop battery from a 12volt deep cycle or a 12volt car battery (not that I'm likely to have the latter where I want to use the laptop). Inverters have their goods (can use with other appliances) and bads (net power loss, one more piece of unnecessary equipment to carry, maintain care for, service if needed etc.). Somewhat goes against the grain to convert 12v to 230 and then back again when there's a direct way. MikeBartnz: deep cycle battery is different from a car battery - you'd soon wreck the latter with my use of it. Car batteries try to maximize CCA (cold cranking amps) and only work well and last for if they are kept fully charged. Deep cyclers are designed for supply of power over sustained periods and can be run down to 30% or less of charge regularly without doing them much harm. Try doing that to your car battery and you'll find yourself with a pretty hefty battery bill. And were you saying that it was the inverter that could be run off the car battery or were you saying there is a commercial laptop charger that runs directly off the car battery? It wasn't clear to me which one you meant.	rugila (214)
121892	2003-02-17 09:55:00	I appreciate the difference between a car battery and a deep cycle battery as I often look after a friends place which has alternative power (240V, Windmill, Solar panels and rarely a petrol gegerator) and I'm very impressed. >And were you saying that it was the inverter that could be run off the car battery or were you saying there is a commercial laptop charger that runs directly off the car battery? It wasn't clear to me which one you meant. I have definately heard of an inverter running off a car battery but I think I have also heard of a laptop charger. If the car battery inverters weren't too expensive you might find it cheaper to get one and then alter it for a deep cycle battery unless of course you have access to cheap goods,	mikebartnz (21)
121893	2003-02-18 03:02:00	When you get the laptop, you will find the battery specification on the battery label . There are so many different batteries used --- as there are for cell phones --- that a charger designed to be universal would be so complicated that it would be a farce (and very inefficient) . I wouldn't want to plug such a thing into a $X000 laptop, in case there were zappy transients I didn't know about . Charging a 12V battery from a "12V" battery doesn't work . You haven't got enough margin from the 12 . 75 full-charged deepcycle to supply a constant current charger . (My 12V NiCd packs takes 17V from the external charger) . You are going to have an inverter (even DC-DC) of some sort . It will be less efficient than a commercial 230V inverter (which are now well over 85%) followed by the standard supply of the laptop . These days, the only reason for designing and building a battery charger is the desire to build a battery charger . (Or rather, two battery chargers --- things like that are like software: you plan to throw the first one away, because with the first one you learn how not to do it) . Life is too short	Graham L (2)
121894	2003-02-18 03:53:00	Graham L. Your comments appreciated. Couple of points however. From your first paragraph I take it your answer to my question about commercial chargers is no they don't exist. OK. That's one thing I wanted. After that you lose me a bit though. I don't think many people try to charge 12 volt batteries from 12 volt batteries. I didn't know that laptops used 12volts, so was asking their voltage so I could design a system if that would be the best approach. I have an excellent solar charger and charge controller that charges 12volt batteries just fine, cutout voltage at present set at 14.1v but can be changed as needed. To charge 12 volt battery from 12 volt batteries you might try two in series (24 volts) and use a voltage regulator to set voltage as needed. No problem whatever. Have you had problems doing this? It's just not correct that "You are going to have an inverter". While I might might conceive of situations where an inverter might be useful, any answer depends on careful investigations rather than unsupported allegations to that effect. I'd aim to design an optimal system to suit my specific needs and circumstances, just don't see any problem with doing that - do you? These days (any other days as far as I know) the only reason for designing and building a battery charger is to charge batteries - maybe your car battery has never gone flat but mine has, also my nicads and a variety of other battery powered appliances (excludes laptops so far). Some of the commercial chargers are really pretty bad, and it's a good idea to know what one is doing ...	rugila (214)
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