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Question about DIY Laptops...

S

starhawk

[H]F Junkie
Joined
Oct 4, 2004
Messages
8,908
Hey, putting this here because it's more "modding" than "mobile" -- yes, it involves a laptop, specifically the homebuilt variety, but it's more a "how do you do this" than it is anything else. This could sorta maybe also go in "Electronics" but I'd prefer buying over building (see below -- the soldering skills are weak in me, old man!) so that's really not a good fit.

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I'm thinking of building a DIY laptop, and what I keep tripping over is the battery issue. I know the runtime will be short, not what I'm worried about. HOW do I run the system off battery, and let it be charged at the same time, like a normal laptop? I do not want the user to have to flip a switch (=power off, flip switch, boot back up) to change between battery and wall power, as that's not terribly idiot proof, nor is it user-friendly. I can probably rig up a battery meter (like on Mart Karts -- a little bargraph LED sorta thing) to tell the user when the battery is getting low, but I don't want a hard switch doing the job. Pulling the battery out to charge it is really awkward, so I'd like to avoid that as well.

I've seen this, but it's rather a bit over my operating budget. There are no eBay knockoffs that I can find (must not be popular, then!). I would want something fairly similar in terms of functionality, but I'd rather not hack apart a real UPS to do it (I have one, but it's insanely heavy and the battery is basically vestigial at this point -- and I could buy the linked PicoUPS for the same price as a new battery!) TBH, I may try to email or call this Mini-Box company and see if they offer open box stuff at a discount -- it doesn't look like it on their site, but it never hurts to ask...

Worth noting: I can solder, but not super-well, so if someone has a circuit for me with no SMT parts, then I can (probably) build it, although I'm a little skittish of that idea. Mouser Electronics won't tell me how much shipping is, ahead of time -- and I'm not about to call them and say "If my order costs more than $x.yz to ship, cancel it!" because I'm not like that. So I'd either have to keep costs of the parts below $15 and the weight below a pound, or I'd have to build it from available-in-the-store Radio Shack parts (ouch). The good news on the RS front is that the local RS stocks every electronics part that the company will let them -- so if it's not marked "Web Only" on the website, I can get it if it's in stock.

Because I'm fairly poor, I'm trying to use parts I can trade for here on [H] or that I already have... I have a discretionary income of about $40/mo. and I can spend half that on this, at most. I know that's a fairly constricting budget, but I'd like to try and stick within it if at all possible. Again, I'd prefer to spend $20 on a prebuilt device if I can at all, rather than $15 for parts and $5 to get them here, and then have to risk ironing a component (which would cost quite a bit to replace, relatively speaking).

Let me know what you guys come up with. Don't fail me, [H]!
 
I'm gonna bump this. If I need a tl;dr section, tell me and I'll see what I can do, OK? I do tend to be a bit of a windbag sometimes ;)
 
Bumping again. Gonna give up and save for the mini-box part if I don't hear an alternative soon.
 
I always thought making your own laptop is a no go unless you wanted to make somthing thicker than a laptop you could buy. But if you do manage to make your own keep up posted i would like to know more :) good luck
 
I don't care about size. I can carry 10lbs without (much) trouble so weight is less of a concern as well.

I'll be using desktop components so it will be a LOT thicker than a "regular" (buy in a store) laptop. It will also have a shorter battery life by plenty... I'm estimating an hour MAX for this -- and that's if I can get ahold of a nice SLA. If I gotta use NIMH that's gonna cut it in half.

Mind you LiIon batteries are not really available for consumers in standard sizes of any kind. LiPoly batts are but (a) they like to do nasty things during (re)charging, and (b) they take some *really* special charging requirements. We're talking "afterschool Christmas special" special here ;)

There's that LiFePo stuff too but I don't trust it at all -- IIRC it's just another kind of LiPoly, so: no please.
 
I don't understand why you would need the UPS part. You could connect everything in series and not need it, only downside is the whole thing stops working if your battery goes bad.

AC Power source (removable power brick)->Charging Circuit->Battery->PicoPSU->Laptop

This simplifies things a bit, provided your AC power source provides more power than what the system can draw so it can charge while still being used.
 
I'd ideally like to be able to do one of three things here...

(1) run off AC while charging battery.
(2) run off battery without AC.
(3) run off AC without battery (in case of the battery going belly-up)

Can't do that without circuitry -- or at least a switch or two. Switches aren't terribly user-friendly here ;) Besides, that particular device goes nicely with SLA batteries, and it eliminates me building (or finding) a switch-mode regulator that would handle ~80w. Those PicoPSUs do say that you need a regulator to use 'em with a battery ;)
 
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