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Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
I'm needing to design a small step-up converter for a 14Cell Hydrogen fuel cell stack for a Renewable Energy Fair, at which my Institute will attend to. I already have the specifications (power curve etc) of the stack and it puts out 25W @ 6-7V, with 30W peaks. The question is: since most laptop power supplyes/chargers have a rating of 70-100W will 25W be sufficient to maintain the laptop, or will it refuse to charge?
Registered Member #1819
Joined: Thu Nov 20 2008, 04:05PM
Location:
Posts: 137
If you plan to just charge the battery, then 25W should be enough power. Computers don't draw too much power when idling. Unfortunately, this means no Halo . Keeping the laptop closed should help, and if that doesn't work, put the computer on standby.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
Laptops won't like being underpowered, I would recommend simply getting a lower powered laptop. You can get something like an eeepc 701 for under $200 on ebay, that even under full processor load and charging the battery won't draw more than 22w. You can also add a real keyboard/mouse, and maybe a small backlit LCD if you find the internal screen isn't enough.
But if you want to stick with the laptop idea, I would expect it to work if the laptop is fully charged, but I doubt that it will be ok charging the battery with only 30w. You might be able to get away with turning off the laptop completly and letting it only charge the battery, but I think most laptops will do the bulk of the charging at over 30w.
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
Your power conversion stage is also likely to be 90% efficient at best given the low input voltage. This further reduces the output power that is available to the laptop.
If you need it to work with a particular laptop, then I would try to characterise its power requirements first. A few quick experiments with a variable voltage supply and an ammeter will give you the I-V curves you need. Then you will be able to tell whether your theoretical power source will meet the appliance's requirements.
Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
THe mini-laptop idea seems good. Eventually i will go this route. Underpowering a normal-sized laptop can do some damage? (che duty cycle will be limited to don't allow the stack to go below 6V , so no damage to the cell)
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25W LapTop Pc power source
. Keeping the laptop closed should help, and if that doesn't work, put the computer on standby.
