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Upgrades Hardware

Building a Laptop Trickle Charger? 53

Posted by Cliff from the recharging-on-the-go dept.
chimpo13 asks: "In 18 months, I'm planning on riding around the world on a 1966 Ducati 250 single. I have some problems, but there's one that can hopefully be answered on Slashdot. I think my Powerbook G3 will take the vibration of the bike, but I'm trying to find out how to trickle charge the laptop battery on my bike. It's a 6 volt bike that will be converted to a 12 volt. Has anyone built a trickle charger for a laptop?"
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Building a Laptop Trickle Charger? More

Building a Laptop Trickle Charger?

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  • A likely story (Score:1, Offtopic)

    by L. VeGas ( 580015 )
    Trickle charge to your laptop, huh? I want to do this too. Computer? No, I don't need a computer.

  • Invert (Score:3, Informative)

    by Ledge ( 24267 ) on Friday March 21, 2003 @04:26PM (#5568629)
    Why not just hook an inverter up if you are going to convert it to 12 volts?

    • Re:Invert (Score:2, Informative)

      by cymen ( 8178 )
      In my experience inverters are very wasteful in terms of energy requirements and motorcycles are very fruagal in their providence of said energy. In other words, even modern bikes 700cc often have a hard time powering heating riding gear let alone inverters. This old bike probably won't have enough juice to power little more than the headlight.
      • Oh yeah, has the story poster considered a KLR-650? Not romantic like your current choice but it should get you there and back. /me goes off to motorcylce troll elsewhere
    • I agree, why not use an inverter? They can be small, cheap (less than $50), and simple. I don't know how much your time is worth, buy unless I could solve this problem is less than an hour, I would probably go down to the warehouse store and buy one off the shelf. regards, michael.
    • Kinda offtopic, but I love your sig. :)

      Model M's, the only keyboards you'll ever need... and the only ones I'll ever use.
    • Inverters are really inefficient. They suck a TON of juice.

  • Will it work? (Score:4, Informative)

    by TheSHAD0W ( 258774 ) on Friday March 21, 2003 @04:30PM (#5568684) Homepage
    I don't know if your notebook can be easily connected to trickle charge. Most laptops' DC in are designed for a full-current connection, and the charging circuitry won't function properly with a less-than-optimal supply.

    There are two possibilities I can see; one is, to remove your battery (or get a spare) and trickle-charge it outside of the laptop; or to trickle-charge an external battery and use that as a voltage input. I recommend the latter; I don't know what the Powerbook's battery terminals are like, but I suspect it'd be inconvenient to hook up to.
    • Thanks, this is EXACTLY what I'm looking for. It hadn't even occured to me that I might not be able to even trickle charge the laptop.

    • Re:Will it work? (Score:2, Informative)

      by GigsVT ( 208848 )
      I don't know what the Powerbook's battery terminals are like, but I suspect it'd be inconvenient to hook up to.

      If it's Lithium Ion, better be careful charging it. They can and will explode if not used with a proper charger setup. Other types of battery are much more tolerant of dumb chargers.
      • "trickle charging" the laptop itself will not likely be possible - Almost all laptops expect full current for charging. (Even when turned off, my dad's Dell Inspiron 8000 would overload and shut down our old inverter, which was too cheap and too small.)

        Trickling the batteries - Be VERY careful. Li-Ions cannot be constantly trickle charged. You SHOULD be safe giving the battery a low-current charge if you use a regulator set to 4.1 or 4.2v/cell (Depends on the exact battery chemistry, the type of electro
    • He could always hook up a 12 volt inverter to the new battery, then hook up a 12v trickle charger to the inverter

      Or I suppose just plug in the laptop to the inverter - how boring is that? ;)

  • HUH (Score:2, Informative)

    by mugnyte ( 203225 )
    this guy built one [qsl.net] and it seems rather trivial.

    I hit it on the first link of a yahoo search. So, for that, you get the big middle-finger-in-the-face award.

    • Re:HUH (Score:2, Insightful)

      by jargonCCNA ( 531779 )
      Actually, that's not quite what the article is looking for. Can that trickle charger interface with a Powerbook? Doesn't look like it.

      Calm down before you flip somebody off.

      • no mention of running the laptop while on the bike. in this case, a battery is what he's dealing with.

        the point is /. is not a search engine - that was just the first link from a cheapass search. this post looks suspiciously like there's no research behind it. there are quite a number of circuit design sites out there. yawn.

        • "...but I'm trying to find out how to trickle charge the laptop battery on my bike."

          You mean this didn't clue you into the fact that he's looking to recharge the laptop while on his bike? Funny, it seems to be explicitely saying just that.

          • Re:HUH (Score:2, Flamebait)

            by mugnyte ( 203225 )
            IS THE LAPTOP SUPPOSED TO BE ON OR JUST STORED?

            if he is keeping the laptop running and recharging ala as if we were plugged in, then this is a more complex problem. also, it seems kinda silly to me.

            if he is simply storing the laptop for the jaunt, then just pop out the batteries and put them in a simple trickle charger. 12vAC rectified to 12vDC transformed to 6vDC limited to %1 of max discharge mA.

            sheesh man, read MY post. Its not about a bike. Its about doing a SEARCH first
            • I have searched and I've been asking all sorts of people. I think part of the problem is, I'm not electrically minded.

              Common sense isn't something that's common. When you've done something a long time, you think everyone should know how to do it. For you, knowing what I should be trying is easy. How are you at rebuilding an engine? I'm not going to sit over you making fun of you when you ask questions trying to rebuilt one. Although finding out how to rebuild an engine is a lot easier to find out how

              • Good info. My suggestion: Sell the powerbook and Ducati and buy a bigger bike with a battery and a Palm along with you to read/write email.

                Seriously, if you are nowhere near a good source of electricity for this long, wouldn't a piece of paper and a pencil still be the easiest way to keep notes?

                If you are near a telephone to read/write email, there should be some sort of power source nearby. Especially if you are looking for petrol every X km. No vibrational damage either (save for the wrists and arse
                • I like small bikes. I'm not in a hurry and I want to see things. There's a lot more bikes that are better suited -- stuff like BMW 650 and KLR650s. But I want a small light unusual bike. I can work on it, so I'm not worried if it breaks down.

                  I figure with a laptop, I can have a place to store photos and do a site of my wacky shenanigans. Which I'm sure will say, "Day 83. Zanzibar. Man, my ass hurts." But I'll also be bringing paper and a pencil because I don't know if my laptop can survive the abuse
                  • in an airline magazine, and probably elsewhere, you can find a solar 12v car battery trickle charger, it is roughly 5x18" and maybe 3mm thick. they run about $100, and while you wouldn't be trickle charging the battery off of the engine any more, it would likely be more reliable overall. maybe that will help some. what website will you be posting your updates to?
                    • It'll be posted to rtw.nokilli.com but of course, I need to fix my cornputer at home. Part of todays plans...

                      If it's a car battery trickle charger, would it work on a laptop? I've been told that laptop batteries are picky about how they're charged.
                    • well you had mentioned that one of the major problems was getting a semi-steady power source, and that your motorcycle engine, over a wide range of revs, would produce different amounts of current, and whatnot. this should at least help you in the slightly more predictable current department (assuming a fairly sunny day each day). it might be worth it to invest in a second small 12v battery and charge the G3book off the battery that is being charged by the solar 12v trickle charger via a 12v adaptor for you

    • Re:HUH (Score:5, Informative)

      by chimpo13 ( 471212 ) <slashdot@nokilli.com> on Friday March 21, 2003 @04:47PM (#5568846) Homepage Journal
      That's dc to dc. The bike is ac. The alternator will probably put out about 100W. It also needs to run my headlight, my taillight, and my brakelight.

      I don't know much about electronics, but I'm learning now.

      Here's stuff I've heard from an electrical engineer who has old Ducatis:

      First, if you choose to implement a charger running off the bike, the charger will have a cord that plugs into the computer presumably through the carrying case. You'll have to plan in advance how long the cord needs to be, and you'll have to route it so it doesn't conflict with any moving parts.

      The AC configuration presents some special challenges. Batteries are DC creatures. A rectifier (a diode) handles the job of converting AC to DC nicely and cheaply.

      We like to design something called a full-wave rectifier, because that uses both positive and negative AC (alternating current) cycles. The trouble is, you need a reference contact to the center of the AC transformer, which in your case is the bike.

      The AC bike doesn't provide that. It can't be done because one side of the "transformer" is tied to the bike frame as a ground reference.

      That means all you can implement is a half-wave rectifier. So exactly half the time you're getting some voltage, and the other half of the time you're getting no voltage whatsoever. You have to average the two together, so some voltage averaged with no voltage equals significantly less than some voltage.

      Now we have DC voltage, but its pulsating DC. This isn't any good either. When the instantaneous DC voltage is above the voltage of the battery, the battery will charge. But when the DC pulse goes to zero volts during the unusable half-wave, of during the usable cycle when the DC voltage hasn't risen to the at least the same voltage as the battery, the battery will actually loose charge as it tries to send power to your charger!

      So now another diode is needed to limit current flow to the battery and prevent current flow away from the battery.

      Confused, I hope not. But there's more. We've got pulsating DC that's going from 0v to 10v DC. The 3.3 volt battery of the laptop might be destroyed by too high of a charging voltage. Now we need a special diode called a zener diode that regulates (not rectify) the voltage so we don't apply too much voltage to the battery.

      So now, by using a few diodes, we're shooting a tiny charge into your battery when the voltage is above your battery level, but not above the upper limit of battery charge. So for a few milliseconds of every cycle, as the pulse of DC rises and then again as it falls we get a tiny amount of charge into the battery. We can make up some ground by adding a capacitor to store some energy which we take when the DC pulse is too high a voltage for the battery level. But still, we can never make up for the fact that we can't use exactly half of the AC cycle.

      What I'm trying to get at here is that the constant 6 volts DC from a DC motorcycle can easily be regulated to the charging voltage of the batteries in order to supply a continuous recharge. The AC system would take some doing to make an effective charger for your laptop batteries.

      You need to see what your AC adapter or your car adapter say their output voltage is to the laptop. They should be the same. Maybe it will say something like 3.5 VDC, and it might even give a current specification, like 100 mA or 500 mA.

      You'll need a cord with the correct plug to mate with the laptop. I don't trust radio shack quality, but I'm not sure where else you can get the cord. If the car adapters are cheap enough, you can butcher one of those. They should have a higher quality cord.

      • Re:HUH (Score:4, Interesting)

        by BigBir3d ( 454486 ) on Friday March 21, 2003 @05:08PM (#5569102) Journal
        Considering Ducati's of that era have absolutely horrid electrical systems, I would use a seperate battery for the charger. At some point, you will most likely use it as a spare for the bike anyhow. I can not highly recommend enough going for a gel battery, no worries about loss of fluids during accidental tip overs, no boiling off in hot weather etc.

        I would like to post any pictures from your trip... www.yzedf.com
      • "The bike is ac."

        Well, um, pardon my ignorance, but... couldn't you just use a transformer, then, and, like, y'know--step it up from, oh, say 12VAC to 120VAC?

        Then you could, maybe, just plug in the laptop's regular ordinary PS into the xfmr. That would be suhweet.

        Am I missing something here? Like: needs of the powerbook exceeding the capabilities of the bike's altenator?
        • How would I step up the voltage?

          If I can get a 100W alternator (and that's a mighty big "if" I'm guessing 80W), the halogen headlight is probably 50W. I'm not sure of the tail light/brake light.

          Like I've said, I'm not good with electricity. Now I'm not even sure if a laptop trickle charge will cook the batteries.

          But anyway, now I have new info to give to James, the Ducati-minded EE, and hopefully James can figure something out.
      • Are ye all retarded? If the bike supplies AC current, use a transformer to raise the voltage, and sent that into the laptop's existing power adapter!
      • If that were the case, your bike battery wouldn't recharge. Your generator produces AC, the it is regulated and rectified down to ~12v DC.

        You have a 12v DC system that will have a tendency to fluctuate within a couple volts of 12. So, high RPMs will give you ~13-14v (depending on the regulator) and low will hopefully not drop below 10.

        Considering you have a 1cyl bike, that means relatively low rpms (unlike my 4 cyl sport bike, which redlines at 14k), so hopefully the cycles won't be as bad as that.

        I woul

  • Consider a few things... (Score:4, Interesting)

    by heldlikesound ( 132717 ) on Friday March 21, 2003 @04:44PM (#5568822) Homepage
    1. In 18 months time handhelds will be even more capable than they are now, not to mention more energy effecient and easier to get online. Plus becuase they use different power schemes, you have more options for recharging the units via the sun, or your bike, etc... Plus, it makes sense to bring a cell phone. A blown tire, or God forbid, a wipe out, could leave you in a tight spot if you have no way to contact somebody. Why not combine your computer and your cell phone in a handheld? NO there are not really great examples of these devices right now, but there WILL be in 18 months!

    2. I assume your trip is similar to backpacking in which we think about every ounce as basically "costing" us carrying energy and the ability to bring something. In this case, taking a computer like a Powerbook G3 (like the Walstreet, Pismo, or Lombard) is pretty expensive weight-wise, if HAVE to take a computer, bring a 12" iBook.

    3. If you choose to go the PDA route, think about using the weight you save to bring a really nice SLR digital camera, instead of a little canon Elph or something... Also, GPS would be nice, but by that time i imagine it will be in the PDA that i describe above.

    Mind you, i am putting a bit of faith in the steady progression of handheld devices, but i don't think that is unreasonable given the inevetiable convergence of cell phones and PDA's...

    Now a question for you....

    How did you get off work for that long!!!?!?!?!?!??!

    Good luck!
    • I'll see what they have in 18 months, and hopefully something better and cheaper will come out. Right now it's a powerbook, because that's what I have. Money will be an issue though. I'm selling off all my stuff on eBay before the trip.

      I'll use a solar recharger for my digital camera batteries.

      The laptop is just for keeping a blog. I'm not in any rush on the trip. It'll probably take me 3 years. Since I'm on a bike, I can't use it while I'm riding. It's a small bike that doesn't put out much power.
      • I did a road trip on my TL1000 a couple years ago, and ran into a similiar problem, wanting to power my Nomad Jukebox. What I wound up doing was installing a cigarette lighter plug in the (small) compartment under the pillion. Using a six foot extender, I ran the wiring through my chassis from the rear end, to pop up under the front lip of my seat.

        I lopped the end off and attached a quick disconnect connector set at that point, even going so far as to cut off the plastic retention clip so it wouldn't snag
      • The laptop is just for keeping a blog.

        My recommendation would be to see if you can use a handheld with external keyboard - you'll save weight and space and without a hard drive and such, it should hold up better to driving. Also the battery charging issue should be moot, provided you can get batteries easily. I get several weeks, maybe a couple of months, from a pair of AAA's in my Palm III. Even for a three-year trip, I suppose you could carry enough batteries with you and still be talking about less wei

  • One additional question: (Score:3, Funny)

    by cybermace5 ( 446439 ) <g.ryan@macetech.com> on Friday March 21, 2003 @04:51PM (#5568891) Homepage Journal
    Circumnavigation is best done with a ship. Do you plan on rafting the Ducati over the oceans, or driving on the sea floor?

    Oh...and your G3 will be dead in 18 months. And if the vibration doesn't kill it, nothing will. And...just get an inverter and run 12volts to the saddlebag. You don't have to leave it plugged in all the time.
  • ..if that bike runs it's electrical on a magneto I can guarantee you don't want to hook it directly up. Spike city. Your best bet is to get a 12 VDC car adapter, charge the batts separate,out of the laptop somehow, or let them recharge from your bike batt when it's stopped. Don't try to run the laptop with the motor running in other words. You can also get a flexible solar PV panel you can strap on top of your gear, so it will get some juice while you are driving and stopped. Unisolar makes them, different
  • You say that you are going on a world tour on your bike. This is Slashdot, anything mentioned here must have a website associated with it. So where is your website and photos of your bike?

  • Few options... (Score:4, Informative)

    by stienman ( 51024 ) <adavis@@@ubasics...com> on Friday March 21, 2003 @05:14PM (#5569184) Homepage Journal
    There are probably 6v to 120vAC power inverters which should do the job just fine, and will be the easiest and fastest way to go. Just plug your power adaptor into it and then into the laptop and you're done.

    I suspect they are rather expensive though.

    The other alternative is to make an adaptor that goes directly from the battery to the powerbook. Since you didn't give any specs on the power requirements of the laptop you're talking about (and yes, the different powerbooks and ibooks have different power adaptors) then I can only give some general suggestions.

    Unless you are an EE (or aspiring to be one) then don't get involved with switching regulator design and go with the option above. If you must, then go to National Semiconductor [nationalse...ductor.com], Linear Technology [linear-tech.com] or Maxim [maxim-ic.com] and look at their parametric guides to the power regulators. What you need is a switching boost regulator. If you are exceptionally lucky, you'll find just the part you need with the exact application note for input voltage, output voltage, and supply current. I doubt it though. Then you'll need to buy the parts and assemble it. Getting all those tiny surface mount parts on a bread board is only half the fun, though you can still get many parts in through hole.

    Of course, neither of the above two methods result in a 'trickle' charge. It'll still suck power from your bike while charging, which leaves the last option:

    Charging the battery directly. Just don't. If you don't know enough that you must ask slashdot (of all the places...? Why not sci.electronics.design or something? Egad...) Sorry, uh... Yeah, like I said, if you think the best place to find out is slashdot, then you don't know nearly enough to properly charge your battery directly without damaging it. Plus you still have the problems of building a step up switching regulator on top of the charger, since the battery will need a higher voltage than your 6v motorcycle cell.

    However, I will give you a general overview: Battery charging is essentially a current (not voltage) operation. You force a certian amount of current in for a period of time, and the battery releases some as heat and stores the rest. Lithium Ion batteries are very finicky when it comes to charging. You will reduce your batteries capacity by 10% or more each time you charge it incorrectly. If a battery costs you $100, then it's worth doing it right, and in your case I think the only 'right' way is to use an inverter and the laptop's internal charger. Furthermore, Lithium Ion batteries do not like being trickle charged. When done properly it doesn't hurt them, but it doesn't give them a good full charge, either. Lastly, LiIon batteries are well known for their inability to take many charges. Early cells couldn't handle more than 500 charge cycles without losing most of their useful capacity. State of the art cells now don't go over 800. Trickle charging excacerbates this issue.

    If you can get NiMH batteries for your laptop then I'd say you have a good chance, since you can go to your local hobby shop can get a charger from them, but they still take 12v so we're back to square one. If your LiIon is only 10.8v then you can get LiIon chargers from the model airplace community, but those are also usually 12v or 120vAC.

    So, in closing, I'm still strongly advocating usage of a regular inverter with the laptop's own power brick.

    Good luck on your trip!

    -Adam

    Yet another reason I loathe Apple (not the products, the company): they don't have power specifications on their website about the laptops. The have the input specs to the power brick, but not its output or the laptops input and current requirements, nevermind the battery V and I. I know they have to dumb things down for the average user, but at least put some real technical specs on the technical specs page instead of the fluff they currently have there.
    • I have a 500MHz PowerPC G3. I'll have to look into what sort of batteries I can use but I don't know if there's much of a choice.

      I don't know much about electronics, you sure have that right.

      I would just like a way of charging my laptop from a small bike. Maybe I should put you in touch with the EE who's been helping me. He knows a lot about old Ducatis and you seem to me like you know laptop batteries.
    • Okay, more words from my Duc EE guy:

      I haven't read that guys answers all the way through, but from the little I've read so far he seems well informed.

      The power brick he speaks of is not an option for you though.

      Why?

      Reason number one is they just don' make them. Since no one has made 6V automotive systems for so many years that there is no demand.

      Secondly, remember that website you sent me for the 12Vcd car adapter plug? The commercial 12v power converters for you model of Apple are made to run the co
      • Ok, you can find a 5V to 12V DC to DC converter at MPJA [mpja.com] but it only supports 1A of current.

        You might give it a try, though, since the laptop in charging mode should consume less than one amp. I doubt you'll have any issues with putting 6v in instead of 5v, but buy a few (they're cheap) and find out.

        Get a car adaptor (cigarette lighter type) that powers your laptop in a car and hook it up to the DC to DC converter. In a pinch, if you need more current, your friend can use two or more converters with
  • When I do my motorcycle touring, I usually use the credit-card-camping technique (restraunts and motels). Motels provide a simple place to plug in the laptop overnight, and even in a restraunt you can get an hour or so of charging time while you eat.

    I get the impression that you will be roughing it more than I do. But if you aren't using the laptop much, you won't need much charging time. So you may be able to get away with finding somewhere to plug it in every few days, and not worry about overloading
    • ... It's probably bad karma to reply to my own post, but what the heck!

      I used the word "rectifier" without much of an explaination of what it is. This is mostly because I'm not an EE, and I don't know in great details what it does. In general terms, however, it's part of the system that takes the power from your alternator, and smoothes, polishes, and munges it into a form that's suitable for charging your bike's battery and powering your bike's electrical system. It normally generates heat (perhaps tha

  • Ask Greg Frazier (Score:2, Informative)

    by gmhowell ( 26755 )
    Ask Greg Frazier. He writes many stories for Rider magazine on circumnavigations via motorcycle. I believe he was wired with laptop for his latest jaunt.

    As far as charging, I'd look into some of the solar rechargers. Don't think a vintage Ducati's charging system could keep up.

    I found this address with a quick google search: gregfrazier@yahoo.com

  • I know it isn't specifically what you asked for, but you can buy a:

    Solar powered 12V trickle charger (about $40) [batteries.com] to run into the bike's battery, then get a auto/air adapter for the powerbook [macmall.com]($80), and a lighter/accessory outlet (about $5, with cable at Radio Shack or your local auto parts store) if you need one. This way, the alternator is feeing the charging usually, and the solar panel is 'topping off' the bike's battery, whether or not the bike is running -- handy to have for a trip around the world, e
  • Lind Electronics [lindelectronics.com] sells adapters for a variety of laptops. Check the "Auto Air Adapters" section.

    I've been installing Lind power supplies for the last 3 years to power mobile-mounted, Panasonic Toughbooks. Out of hundreds installed I've only had one go bad and it was jump-started by an idiot. I've had a higher failure rate on the Toughbooks. As far as the laptops are concerned, they think they're hooked to their normal AC adapter.

    The adapters we've been buying are completely potted with rubber inside and
  • if you're riding a '66 ducati 250 you'll be their enough that you won't even need a battery.
    leave it at home.
    unless you plan on riding and geeking out at the same time.
    or did you want to sit out in the fields of flowers and compose love sonnets and haiku to your jelly tanked moto bolognese.

  • If your bike is being converted to 12v, see MCE Tech [mcetech.com]'s Auto power adapters [powerbook1.com], which run about $30.

    I'd have to recommend doing a 12v conversion just for your sanity of finding parts on the road. You probably already know that it's not a question of if but when it will break, so try to make it easy on yourself to repair. Maybe even get a list of repair shops along your route before you set out.

    The full power adapter requiment of 45 watts is designed to be enough to run the PowerBook and a few Firewire/USB p

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