ono3 - Pelican 1430 to S4 Portable VR Workstation
- Thread starter lhl
- Start date
For those following along, feel free to give feedback on anything that I might eventually miss or that's confusing. The idea is that DC post will bring together a bunch of disparate stuff - basic theory for doing power math, basic battery info on what's out there and why to pick something, and then a bunch of implementation specific details w/ LiPo batteries.
Hey, turns out there's a post limit, so continuing my DC discussion.
On to...
Connectors
Here are the connectors involved:
Depending on the battery charger, you may also need a banana plug to XT90 cable for charging your battery.
Battery Charging
Like for the batteries, I'll just give a recommendation. If you only need to charge a single battery at a time, I can recommend the Ultra Power UP300AC (CA shipping, China shipping) - it gives you great bang/buck w/ up to 300W/20A charging connected to AC. It has a touch screen, and has some data capabilities (I haven't used them). It also includes everything you need for monitoring, balancing, different battery types, cycling (charge/discharge) and with automatic safety cutoffs.
Here's a good 20 minute video that also steps through the basics:
When you charge the battery, do not charge above 1C. For safety, you probably want to have a safety bag/box and/or not charge the batteries unattended.
You should partially discharge the battery if you are going to put it into storage or not use it for a while (you'll also need to periodically recharge them in that case).
Battery Monitoring
Once you have everything connected up (be sure to test your wires w/ a multimeter for shorts) you're ready to plug it all in. I'll just assume it all works the first time (it did for me
. The one missing component is that you will want to have a battery alarm in the JST-XH plug. I'll link to some in the BOM, and below there's already discussion on if you wanted to connect that to report into your computer, blah blah blah. The alarm I'm using gives a disturbingly large alarm (they're built for drones mostly - you can gaff 'em to make them less annoying) if a cell goes below 3.3V. That should be fine.
On to...
Connectors
Here are the connectors involved:
- HDPLEX
- 7.4 x 5.0mm barrel connector - this is a pretty standard jack size, and in the Dell 330W and HP 350W power bricks use this (yay, no adapters)
- Multistar Battery
- XT90 - RC/drone batteries have tons of different connections for main power. The big multistars use XT90s. They look *just* like the XT60s in pictures, but they are bigger, so don't get them confused, even if searches for XT90s give you XT60 results.
- 6S JST-XH - this secondary plug is used for cell balancing/monitoring while charging (usually up to around 0.5A/cell for balancing). When in use, you will want to stick a voltage monitor or alarm on there. so you know when your charge is low
Depending on the battery charger, you may also need a banana plug to XT90 cable for charging your battery.
Battery Charging
Like for the batteries, I'll just give a recommendation. If you only need to charge a single battery at a time, I can recommend the Ultra Power UP300AC (CA shipping, China shipping) - it gives you great bang/buck w/ up to 300W/20A charging connected to AC. It has a touch screen, and has some data capabilities (I haven't used them). It also includes everything you need for monitoring, balancing, different battery types, cycling (charge/discharge) and with automatic safety cutoffs.
Here's a good 20 minute video that also steps through the basics:
When you charge the battery, do not charge above 1C. For safety, you probably want to have a safety bag/box and/or not charge the batteries unattended.
You should partially discharge the battery if you are going to put it into storage or not use it for a while (you'll also need to periodically recharge them in that case).
Battery Monitoring
Once you have everything connected up (be sure to test your wires w/ a multimeter for shorts) you're ready to plug it all in. I'll just assume it all works the first time (it did for me
. The one missing component is that you will want to have a battery alarm in the JST-XH plug. I'll link to some in the BOM, and below there's already discussion on if you wanted to connect that to report into your computer, blah blah blah. The alarm I'm using gives a disturbingly large alarm (they're built for drones mostly - you can gaff 'em to make them less annoying) if a cell goes below 3.3V. That should be fine.
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So are you planning on implementing some sort of battery management system that actually connects to the computer that can report its status to the OS so that it both knows it's running on battery power and what the charge level is and can adjust the power management appropriately?
Also how is the circuit going to be connected? is the PC essentially always running off the battery while the charger circuit can keep it topped off as needed while plugged in, or is it going to be switched where when plugged in, the pc is running directly off the mains along with the charger, and when unplugged switches over to battery power?
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I've never had plans for any sort of mobile PC, but I have always wanted to be able to internalize a UPS by separating the AC-DC converter and DC-DC converter subsystems (which is the bog standard PicoPSU route) and putting a battery subsystem between them and to have it actually report its status to the OS like a laptop battery or external UPS would, but, while I understand enough to be able to install a battery, and properly charge and discharge it it, I am at a loss how to make the management circuitry that reports to the PC or even where to find a pre-built solution.
Also how is the circuit going to be connected? is the PC essentially always running off the battery while the charger circuit can keep it topped off as needed while plugged in, or is it going to be switched where when plugged in, the pc is running directly off the mains along with the charger, and when unplugged switches over to battery power?
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I've never had plans for any sort of mobile PC, but I have always wanted to be able to internalize a UPS by separating the AC-DC converter and DC-DC converter subsystems (which is the bog standard PicoPSU route) and putting a battery subsystem between them and to have it actually report its status to the OS like a laptop battery or external UPS would, but, while I understand enough to be able to install a battery, and properly charge and discharge it it, I am at a loss how to make the management circuitry that reports to the PC or even where to find a pre-built solution.
Very interesting material, keep it coming ! Are you trying to recreate the laptop battery system so it has an easy accessible charge port while keeping the system running or are you going for replaceable battery packs with possibly a hot-swap function ? You're probably going to answer this in a following write-up, if so I'll wait until then
There are multiple components. The actual voltage measurement into GPIO is fairly trivial and well documented (for those interested):
- http://raspi.tv/2015/raspio-duino-as-a-lipo-monitor
- http://www.rcgroups.com/forums/showthread.php?t=2032914
- https://www.sparkfun.com/products/10617
- http://www.instructables.com/id/Arduino-Voltmeter/
- https://automationandrobotics.wordpress.com/2014/08/01/arduino-lipo-cell-monitor/
- http://forum.mysensors.org/topic/18...gulator-but-connect-directly-to-the-batteries
- https://github.com/rlogiacco/BatterySense
All that being said, it's a lot of additional complexity that could be solved just as easily by a $2 external battery alarm, so as of now, no I'm not planning on reporting the status into the computer.
No, if you are using RC batteries you should absolutely *not* do this (at the risk of explosion/fire) unless you have balancing and charging circuitry. If anyone has questions like this, I would recommend that they not build this kind of system without better understanding the safety risks.
There are some micro-UPS boards available (aimed at industrial/embedded use) and they typically report/interface with traditional UPS management systems like NUTS. That kind of stuff is above and beyond the scope of the project I'm publishing, but if you read the links I've posted so far you should get a pretty good idea of how to build one yourself if you wanted to.
Very interesting material, keep it coming ! Are you trying to recreate the laptop battery system so it has an easy accessible charge port while keeping the system running or are you going for replaceable battery packs with possibly a hot-swap function ? You're probably going to answer this in a following write-up, if so I'll wait until then
I think my response to @BirdofPrey pretty much covers this. If anything I'd go for a hotswap system. The electronics and weight required for high amperage battery charging + power system is non-trivial (somewhat expensive, heavy, and of course would make the system tethered, which defeats the purpose).
I feel bad, because this is such an awesome project and thread that I want to participate in constructively... and yet, all of it is so far above and beyond my abilities that I simply can't
Are you an electromechanical engineer, or someone who's been trained in this stuff? Seriously, this is just ridiculous.
Are you an electromechanical engineer, or someone who's been trained in this stuff? Seriously, this is just ridiculous.
I have a fine arts degree.
Before I switched I took enough CECS to get to EE102, but that's all very vague - pretty much all my working electronics knowledge is picking things up mostly online over the past 10 years or so, starting with simple micro-controller work (Adafruit and Sparkfun have good tutorials, Tom Igoe's Physical Computing is the classic practical guide). Dealing with power systems, robotics, fabrication, etc is mostly a result of building some pretty crazy projects for my own company the past 5 years or so (including building a waterproof outdoor solar-powered shoot-forever camera system, among other things).
There aren't a lot of very good guides for battery-powering PCs, so I think this thread in particular is good because it brings together a lot of disparate topics that would otherwise take a long time for someone getting started to figure out.
OK, deadline finished, so lets polish off the rest of this DC guide.
Here's the list of what the DC system looks like:
Here's the list of what the DC system looks like:
- $85 - HDPLEX HiFi 250W DC-ATX (nanoATX Series)
- if you buy directly from them (they have a CA warehouse), request the appropriate PCIe power connector (by default it comes w/ an 8 & 6+2, but you probably want a 6 & 6)
- $61 - HP Firebird 350W Power Supply
- When you don't feel like plugging in a battery
- ~$10 - 7.4x5.0mm DC Male Barrel Connector to Male XT90 Connector
- I feel a bit conflicted on recommendations. For expediency, I Amazon Primed a cheapy $8 power brick, chopped it off, and soldered it to an XT90 connector ($10/5), but this is certainly not rated for more than 5A. Nothing you can readily buy (save for chopping up another 350W power supply) seems to be, however... I have some 10AWG XT90 cables, but those wouldn't solder well
- Your best best might be to buy a plug (here or here) and and solder w/ a 12 or 14AWG wire (guide, guide). If this is too daunting, you may want to talk to an Electrician friend, I couldn't find anything off the shelf
- $4 - XT90 to Banana Plug charging cable
- Of course this may be quicker/easier to just make your own if you already have your soldering iron out.
- $8 - Battery Voltage Checker/Alarm (alternative)
- Put these on your JST-XH plug to alert you to when your power is too low
- $103 - MultiStar High Capacity 6S 12000mAh LiPo
- You can of course buy any capacity you want, keeping in mind that the max continuous discharge for these guys is 10C. You won't find anything remotely close in price to this, btw (the Tattu 12000mAh 6S's for instance are $200)
- $115 - Ultra Power UP300AC Touch AC/DC Charger
- $105 if you're not in a rush for shipping.
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Again an awesome writeup !
http://www.ebay.com/itm/DC-CORD-TIP...Connector-Cable-DELL-HP-65W-90W-/251055736304
This might work just as well but with more shipping time:
http://www.ebay.com/itm/DC-CORD-TIP...Connector-Cable-DELL-HP-65W-90W-/251055736304
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When I was getting started on doing initial research on the project a few months ago, was surprised how little info was out there gathering all the components you need for a portable battery-powered, high amperage rig (the few writeups around were using decidedly non-portable lead acid batteries), like I mentioned, I plan on cleaning this up and publishing, so basically these posts are like a first draft, just to get stuff out there. I know something like this would have made my life a lot easier, even with my maker background/experience.
I actually saw those while I was searching last night just to make sure I hadn't missed anything - the wires look about the same as the power brick I chopped off - tiny 16 AWGs that probably shouldn't be running the type of current that can be drawn. \_(ツ)_/¯
One more power note: I did get a chance to do a rough power rundown test w/ the SteamVR apps I had handy. I ran through about a dozen of them - CPU usually averaged 20-50% in these apps, and GPU ran at 6-80% TDP @ 1300MHz. Battery started at 25.1V and at 1h10m in, is still at 22.3V (alarm is set for 19.8V). You can watch YouTube in SteamVR's browser (GPU TDP is around 40%, CPU around 20%). I'm pretty confident I can get close to 2 hours, but it's 9PM in the office and I'm heading to Unity Vision Summit tmw, so I'll probably just leave this at that.
Quick question - since the endgame for this project is to make the rig "portable", have you thought about how this will be strapped to the individual, or otherwise carried around? Dealing with convenience, the facility of some of the parts, thermals, etc., seems like a really interesting problem to solve in its own right.
The only real bummer is that either the GPU or the CPU fan is going to be blowing into the back. I've been looking at these mini-DTX boards which honestly, from a pure backpacking perspective would be better. I personally don't expect to need a backpack unit for more than a year though - there's good wireless 5/60GHz 1080p60 stuff out there and I think it won't be long before someone comes up w/ a HDMI Mode 87 wireless device (there's also COTS wireless USB 2.0, but I haven't seen any good USB 3.0 yet).
But yes, have given some thoughts on the backpack stuff, in fact have a frame that's been sitting in the office for a month. The one I'm using is titanium and the frame weighs in at 755g.
One of those boards with an angled PCIe connector could work, it would allign the ventilation of the CPU and GPU on the same side.
https://smallformfactor.net/forum/threads/asus-b85m-view-paker.82/page-3#post-7169
https://smallformfactor.net/forum/threads/asus-b85m-view-paker.82/page-3#post-7169
This is what I was imagining, though it makes you wonder how everything in the backpack will be oriented... There isn't really a pretty elegant or clean-looking way to do it, but at least heat exhaust on the back can be avoided (which I'd consider to be a pretty big deal)
