21.5" Desktop PC - Powered By Cordless Drill Battery

No tricks... no sleight-of-hand. So, what's the point?...

My aging 17" laptop died, so I went searching for a replacement, (preferably one with a larger display because of my deteriorating vision, and I occasionally do CAD)... only to discover, 'Tain't no such animal. Disappointingly, and a bit restricted on cash, I visited my local pawn to haggle over a potential 'used' replacement, and be forced to spend even more on a larger monitor.  "The only 'puter I have with a larger display", he said, "is that 21.5" Lenovo desktop over there". When I spun it around and looked at the rear, low-n-behold, there was a 120V laptop power supply (a.k.a. brick) plugged in the back. Now that's interesting!  250 bucks poorer and I headed home with my replacement. Bare-in-mind, I'm on solar. The following images should speak for themself:

Advantages?

1.) 21.5" 1080p display (and up to 27" model is available)
2.) The detached keyboard allows me sit further from the display
3.) Low voltage powered so it melds with my solar storage without 120Vac

Specs;
2018 Lenovo IdeaCentre AIO 520 (AIO=All-In-One)

Consumes 18 Watts via 120V brick, and 14 Watts on battery.
So far, It drained my aging 3 YO, 18V Makita battery in about 1.3hrs (surfing the web)

Edit: Added image, so please tap your 'refresh' to view it.

Since you're that handy, I bet you could hook up two batteries paralel, so you could keep one or two charging and swap one at a time without shutting down. Is there a way to tell how much charge you have?

By the way, really cool project.

Awesome project Eugene!

Is that simply a direct wire onto the 18v battery?  If so, that is a simple, genius way to power a computer.

Eric

T Melville wrote:Since you're that handy, I bet you could hook up two batteries paralel, so you could keep one or two charging and swap one at a time without shutting down. Is there a way to tell how much charge you have?

I could, yes, but I'll pipe this one directly from my 48V solar bank via Dc-DC step-down converter so I'm not eating expensive Makita batteries. BTW.. you can use nearly any 18-20V cordless pack (Dewalt, Milwaukee, Ryobi, etc) to power many different laptops. Some batteries have a 'fuel' gauge (4 LED's), but my Makita's do not - but I do have a Fluke DMM.  

Eric Hanson wrote:Awesome project Eugene!

Is that simply a direct wire onto the 18v battery?

Eric

Yes.  Most laptop power supplies (brick) output 19.5-20Vdc. The Makita battery is 20Vdc fully charged so it's a perfect match.

Eugene,

Again, that's great!  Not to pick nits or anything, but my understanding is that all 18v/20v lithium ion batteries are actually 20v batteries just after being freshly topped off and then once put under a load for even a short time drop to about 18 volts which holds for the duration of the battery.  If this is the case, then your computer is actually running on about 18 volts which I think is fine.  How long have you run your computer in this setup?  Also, feel free to critique my understanding of the charge levels of the 18/20 volt batteries.

Again though, that is a simple, amazing setup for a computer.

Eric

Eric Hanson wrote:Eugene,

Again, that's great!  Not to pick nits or anything, but my understanding is that all 18v/20v lithium ion batteries are actually 20v batteries just after being freshly topped off and then once put under a load for even a short time drop to about 18 volts which holds for the duration of the battery.  If this is the case, then your computer is actually running on about 18 volts which I think is fine.  How long have you run your computer in this setup?  Also, feel free to critique my understanding of the charge levels of the 18/20 volt batteries.

Again though, that is a simple, amazing setup for a computer.

Eric

Many 18-20Vdc cordless lithium packs have five 4.2V (fully charged) cells connected in series = 21V.  Nominal (about 50% DOD) is 3.6-3.7v each cell, X 5 cells = is about 18.4V halve drained. So far, on a n aging 3yo pack, it's averaging about 1.3-1.7 hours. Bare-in-mind, this Lenovo has 2 SSD's and I'm on WIFI via an Alfa high power external adapter, so my power consumption could be even lower. Reducing screen brightness would also help.

Your spec's make sense.

I once saw a chart of Lithium Ion batteries voltage (for cordless power tools) and the drawdown from peak voltage.  From what I saw, basically any reputable manufacturer did have that 20 volt rating, but only until any load was put on it.  This was a pretty miniscule load, like drilling even a modest sized hole with a drill or making one cut with a circular saw.  At that point, the batteries were all at 18ish volts and stayed there.  The morale of the story was that all power tool batteries (in the given range) were 18 volt batteries and the 20 volt claims were basically a marketing pitch.

This is not to meant to in any way denigrate what you have done though.  I think your solution is simple and elegant--I love it.  

Nice work,

Eric

Correct polarity connections MUST be observed - if reversed, you'll likely kill the 'puter.

Perhaps add a fuse at the battery on the "+" side, in case of an accidental short? Always wise for an improvised setup IMO.

I'm a little worried about brownout on your 'puter as the voltage drops. This might have repercussions.

Douglas Alpenstock wrote:Perhaps add a fuse at the battery on the "+" side, in case of an accidental short? Always wise for an improvised setup IMO.

Yes, I agree. This started as a simple test to observe loads WO/power supply, and to get up and running ASAP, since my main 'puter was DOA.

Douglas Alpenstock wrote:I'm a little worried about brownout on your 'puter as the voltage drops. This might have repercussions.

I did run this as pictured to completely deplete an older battery - it suddenly shut-off (black-out) at around 10.2V - no negative impacts.

Eugene Kenny wrote:I did run this as pictured to completely deplete an older battery - it suddenly shut-off (black-out) at around 10.2V - no negative impacts.

Eugene, with all respect, that power brick you bypassed is pretty impressive, moving heaven and earth to protect the delicate "downstream" circuitry of your PC. Yup, it's your system, and it's fun to mess with things to see if/when they blow up. I do it all the time, after shopping at the dump. When will it fail? gotta push the limits! But: I do not do this, ever, with a system I need to rely on. At the very least, please back up all files you don't want to lose.

Douglas Alpenstock wrote:

Eugene Kenny wrote:I did run this as pictured to completely deplete an older battery - it suddenly shut-off (black-out) at around 10.2V - no negative impacts.

Eugene, with all respect, that power brick you bypassed is pretty impressive, moving heaven and earth to protect the delicate "downstream" circuitry of your PC. Yup, it's your system, and it's fun to mess with things to see if/when they blow up. I do it all the time, after shopping at the dump. When will it fail? gotta push the limits! But: I do not do this, ever, with a system I need to rely on. At the very least, please back up all files you don't want to lose.

Hi Douglas,
I do sincerely appreciate your concerns, unfortunately, we're not in complete agreement.
I remain dubious that a AC power supply connected to a vulnerable and unreliable 'grid'
is more protecting than an completely isolated DC source. More than once, I've lost
sensitive electronics via AC>DC 'bricks'... especially during lightening storms.

But again, thank you for your concerns.  

Eugene Kenny wrote:

Douglas Alpenstock wrote:

Eugene Kenny wrote:I did run this as pictured to completely deplete an older battery - it suddenly shut-off (black-out) at around 10.2V - no negative impacts.

Eugene, with all respect, that power brick you bypassed is pretty impressive, moving heaven and earth to protect the delicate "downstream" circuitry of your PC. Yup, it's your system, and it's fun to mess with things to see if/when they blow up. I do it all the time, after shopping at the dump. When will it fail? gotta push the limits! But: I do not do this, ever, with a system I need to rely on. At the very least, please back up all files you don't want to lose.

Hi Douglas,
I do sincerely appreciate your concerns, unfortunately, we're not in complete agreement.
I remain dubious that a AC power supply connected to a vulnerable and unreliable 'grid'
is more protecting than an completely isolated DC source. More than once, I've lost
sensitive electronics via AC>DC 'bricks'... especially during lightening storms.

But again, thank you for your concerns.  

IMO, most of what that brick does is about conversion, and the protection is mostly about.. things that happen on the other side of that conversion.

A battery is a very stable voltage source compared to a PSU. Low voltage is the only likely oddness that the puter will see... and that will likely not ever happen once connected to the step-down converter...

I wouldn't be enthused about feeding the thing from the powertool battery long term without some sort of low voltage disconnect at a more reasonable level... but the step-down converter is a better option anyhow.

Well it seems I accidentally muddied the waters. Not what I was aiming to do, so that's my bad.

It may be that the hardware is much more tolerant of voltages bouncing around, including brownout as the battery voltage drops and the system crashes. I suspect it's not sustainable, but the only way to really know is to experiment.

I've always liked old laptops for this sort of stuff. An old battery pack provides a buffer for power oddities, even if it only has five minutes' run time left in it.

Douglas Alpenstock wrote:Well it seems I accidentally muddied the waters. Not what I was aiming to do, so that's my bad.

It may be that the hardware is much more tolerant of voltages bouncing around, including brownout as the battery voltage drops and the system crashes. I suspect it's not sustainable, but the only way to really know is to experiment.

I've always liked old laptops for this sort of stuff. An old battery pack provides a buffer for power oddities, even if it only has five minutes' run time left in it.

Hi Douglas I think it was touched on earlier. I use a step down dc to dc voltage transformer to run my ryobi tools directly which is within that 18 to 20 volt window. It was fairly cheap. That was a step down from 24 volts. They also offered  step up from 12 volts... not sure step down from 48 is available but definitely an option...
Cheers,  David

Fair enough -- I'm losing track -- too many quotes within quotes. (Tsk! C'mon Doug, try to keep up, will ya?