What is the absolute minimum power needed to turn on FW laptop without battery connected? (I tested and 65W seems to be enough, 18W not enough, so wondering what would be the exact value)
You mean a 12v → USB-PD? Or are you doing direct conversion to the 20v or whatever that it needs and somehow feed it it? If the latter, I’m quite interested out of curiousity. Otherwise, I do what you do, 12v → USB-PD for my trailer for working there on the road remote.
18W is not enough because running in BIOS consume about 18W so you need at least 18W to even POST, let alone boot up your computer.
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More or less what I thought. I’ve got a 100W one from Amazon, works well so far.
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Thanks for the replies, but I am looking for more of an exact value than recommended or safe or whatever. I know 65W will work and 18W won’t, because these I tired. I am expecting the value to be somewhere in 30-50W range.
The use case is a 10" tablet I have been struggling to design for quite some time. With battery and board layout as in a standard FW13, the surface area is too big. With battery rotated 180 degrees and over the mainboard, battery overheats. I need a smaller battery. So I am using a powerbank board and 4 lipo cells to try and power it, giving it roughly 40-45Wh and fitting the form factor.
For some reason I hoped 18W would be enough to power it, that the board would sense the max current and slow down the CPU accordingly (because I can get it to run at 15W when turned on), but it won’t run for more than 3 seconds. So I was wondering where is the minimum, then I would add a few watts just to be safe. But meanwhile I ordered a 100W powerbank module so this may not be a problem anymore.
Sounds like quite a jump up in power. Be careful not to exceed the safe discharge rate of your cells.
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