11 ms·

I've noticed that ALL the devices I plug into my UPSes have external power bricks. Most of them are either 5V, 12V, or 19V So, I replaced all my UPSes with Li

I've noticed that ALL the devices I plug into my UPSes have external power bricks. Most of them are either 5V, 12V, or 19V So, I replaced all my UPSes with LiFePO4 batteries supplied by Victron AC->12V chargers. Routed the battery contacts directly to all devices that consume 12V (WiFi AP, network hubs, SLA 3d printers). Used 12V -> 5V adapters to supply 5V / USB2 devices (R-Pi servers). For 19V, Drok DC-DC boost converters work great. Result: threw away 3 UPSes (different APC models). Overall power consumption with AC present dropped by about 40%. Time on batteries (same Wh battery capacity) increased by a factor of about 20 (yes, 20 times: that's not a typo). Evidently, AC waveform generation is extremely power-hungry

scottlamb 4mo ago
I toyed with this too, but I guess I have a slightly more diverse set of devices than you do. A few more weird voltages, and some things that expect mains. I looked into finding a DC version of their power supplies (e.g. the pico-box X9-ATX-500 to replace a conventional ATX PSU, tracking down DC versions of network switch hot-swappable PSUs from eBay) but decided it wasn't worth it. I just bought a stock LifePO4 power station. I found that I got most of the benefit [edit: measured in terms of runtime after power outage, not power draw while input power was available] just from switching to LifePO4 rather than from avoiding DC->AC->DC, and it was cheap and easy.
- nomel 4mo ago
  If you get your battery pack up to 48VDC, it opens up a whole world of low voltage power converters, since this is standard in telecom/PoE.
dylan604 4mo ago
> Evidently, AC waveform generation is extremely power-hungry Evidence is the heat from that conversion
tredre3 4mo ago
> Evidently, AC waveform generation is extremely power-hungry I've tested a dozen models from APC. The inverter used in those devices uses roughly 15-20W with no load. Then for any load they have about 85% efficiency. Then you have further losses into any PSU connected there because they tolerate square waves but aren't optimized for it. So yes, in the end, less than 40% of the battery capacity in cheaper UPSes is actually usable. The reason you're seeing 20x is because obviously you've also greatly increased your battery capacity (typical under-the-desk APC units have 70-150Wh capacity, less than half of which is usable as explained above). > Overall power consumption with AC present dropped by about 40%. I'm finding that part harder to understand. The UPS consumes almost nothing when AC is on, so that can't be that. You've replaced multiple PSUs by more efficient, bigger ones, sure that can explain part of your improvement. But 40% drop is wild!
- michaelt 4mo ago
  > The UPS consumes almost nothing when AC is on, so that can't be that. Back in the 1990s, one could buy a "double conversion" UPS that converted AC to DC then back to AC, at all times. This was, supposedly, the best type of UPS (in my experience they were also the least reliable)
  - Aurornis 4mo ago
    This is called an online UPS and it's still a thing. It's not a good option for home use because it's always sending power through an inefficient path. The devices we use have power supplies that can handle transients and fluctuations.
    - scottlamb 4mo ago
      Where is it a good option? I'd expect datacenters to be more focused on efficiency, not less.
      - felixgallo 4mo ago
        Music, medical, engineering. Wherever the waveform consistency and noise floor are the optimization point.
aspbee555 4mo ago
I did something similar but made the batteries and solar priority, solar charges battery and wall power only used to top off as needed, otherwise always running on batteries The Drok DC-DC did not work for my minipc that needed 19V/130W supply (would cut off with heavy draw), but the JacobsParts LTC3780 130W has been running my minipc's for almost a year now, gaming minipc, server minipc and networking before that the solar panels barely charged the solix unit, but now my batteries fully charge and I still sometimes have left over solar I feed into the solix
cyberax 4mo ago
I have thrown out my Tripplite UPS because its battery has degraded to the unusable levels. I replaced it with a 5kWh LiFePo4 rack-mounted battery and an AIMS rack-mounted inverter. I'm really surprised that there are no off-the-shelf solutions for this. The traditional UPS makers are just neglecting the recent 10 years of battery advances. I even made an Arduino-based module that provides an SNMP UPS interface for my Synology NAS. It works surprisingly well and has almost 12 hours of autonomy compared to barely 2 hours for the much heavier lead-acid battery. One trick that I'm kinda proud of: I powered my server directly from the 96V DC. And I periodically switch the current direction using a DPDT relay to avoid wearing out one side of the rectifier inside the PSU.
- exmadscientist 4mo ago
  > to avoid wearing out one side of the rectifier inside the PSU If you are seriously worried about this then the whole thing is trash. Either the design is marginal or it is not. You cannot possibly switch a relay fast enough to make a difference here (and have the relay survive).
  - Dylan16807 4mo ago
    I don't understand what you're saying. If you're specifically worried about wear, then you could switch once a month and it would be enough.
    - exmadscientist 4mo ago
      Silicon rectifiers don't wear out. (At least not on timescales relevant to individual humans.) So hearing that makes me get suspicious that something else is going on.
      - Dylan16807 4mo ago
        I'm also suspicious of the idea of that part wearing out, but if it doesn't matter at all then there's no reason to call things trash. Your other comment says: If you are truly close to the design failure point of the rectifier, it's not safe to run at all. (You are almost certainly not.) Well there's no reason to assume it's close to the failure point. Think of it this way: Draw the line in the sand for where you'll approve the design, but just barely. If someone is running a diode close to that line, then it's not trash but trying to improve longevity isn't crazy either.
dreamcompiler 4mo ago
This is the way to go IMHO: Keep the outputs DC. Put a bunch of USB-C PD ports on the thing and you're good with a lot of modern equipment.
exmadscientist 4mo ago
> Evidently, AC waveform generation is extremely power-hungry Yes, it's quite ugly. Open up one of these things and you'll find a big block of four transistors (if not more due to doubling up) on a big heatsink. That's the inverter drive bridge, and it's probably the single largest source of heat in the whole thing. It's not hard to find.
bb88 4mo ago
I've been in the process of cutting the DC side of power bricks and crimping anderson power pole (APP) connectors onto both sides of the wire. For camping and ham radio, it's really nice to hook up to a battery without the AC inverter taking DC -> AC and the power brick sending that to DC again. The only thing to be careful with is connecting different voltages to different connectors, but it's at least possible with the APP connectors to "Build your own" with different color housings and different ways of combining the housings. So maybe 13.8v is red/black and something that's 5V is black/white, etc.
- butvacuum 4mo ago
  theres also anderson's SB series- APC seems fond of knockoff versions.
ErroneousBosh 4mo ago
I've been looking at Victron gear for an off-grid power system up north (initially for a caravan, will get migrated across to a house once the upgrading and repairing is done). A huge decision on that was that they publish a fat PDF with the full spec of the serial data they emit and can be programmed with, and a service sheet to allow a suitably skilled engineer to fully bench test them if there are any perceived problems. They're not cheap, but my late father always used to say he didn't have enough money to buy cheap tools. Edit: handy hint too - many cheap crappy power bricks will work down to 90V and will work just as well off DC as well as AC because the very first thing they do is rectify and smooth the incoming supply. I do not recommend having 90V DC kicking around unless everyone involved knows what they're getting into.
- cwillu 4mo ago
  Yeah, 90vdc is an immediate nope from me: way too easy to suffer a painful death.

scottlamb 4mo ago

I toyed with this too, but I guess I have a slightly more diverse set of devices than you do. A few more weird voltages, and some things that expect mains. I looked into finding a DC version of their power supplies (e.g. the pico-box X9-ATX-500 to replace a conventional ATX PSU, tracking down DC versions of network switch hot-swappable PSUs from eBay) but decided it wasn't worth it. I just bought a stock LifePO4 power station. I found that I got most of the benefit [edit: measured in terms of runtime after power outage, not power draw while input power was available] just from switching to LifePO4 rather than from avoiding DC->AC->DC, and it was cheap and easy.

nomel 4mo ago
If you get your battery pack up to 48VDC, it opens up a whole world of low voltage power converters, since this is standard in telecom/PoE.

dylan604 4mo ago

> Evidently, AC waveform generation is extremely power-hungry Evidence is the heat from that conversion

tredre3 4mo ago

> Evidently, AC waveform generation is extremely power-hungry I've tested a dozen models from APC. The inverter used in those devices uses roughly 15-20W with no load. Then for any load they have about 85% efficiency. Then you have further losses into any PSU connected there because they tolerate square waves but aren't optimized for it. So yes, in the end, less than 40% of the battery capacity in cheaper UPSes is actually usable. The reason you're seeing 20x is because obviously you've also greatly increased your battery capacity (typical under-the-desk APC units have 70-150Wh capacity, less than half of which is usable as explained above). > Overall power consumption with AC present dropped by about 40%. I'm finding that part harder to understand. The UPS consumes almost nothing when AC is on, so that can't be that. You've replaced multiple PSUs by more efficient, bigger ones, sure that can explain part of your improvement. But 40% drop is wild!

michaelt 4mo ago
> The UPS consumes almost nothing when AC is on, so that can't be that. Back in the 1990s, one could buy a "double conversion" UPS that converted AC to DC then back to AC, at all times. This was, supposedly, the best type of UPS (in my experience they were also the least reliable)
- Aurornis 4mo ago
  This is called an online UPS and it's still a thing. It's not a good option for home use because it's always sending power through an inefficient path. The devices we use have power supplies that can handle transients and fluctuations.
  - scottlamb 4mo ago
    Where is it a good option? I'd expect datacenters to be more focused on efficiency, not less.
    - felixgallo 4mo ago
      Music, medical, engineering. Wherever the waveform consistency and noise floor are the optimization point.

aspbee555 4mo ago

I did something similar but made the batteries and solar priority, solar charges battery and wall power only used to top off as needed, otherwise always running on batteries The Drok DC-DC did not work for my minipc that needed 19V/130W supply (would cut off with heavy draw), but the JacobsParts LTC3780 130W has been running my minipc's for almost a year now, gaming minipc, server minipc and networking before that the solar panels barely charged the solix unit, but now my batteries fully charge and I still sometimes have left over solar I feed into the solix

cyberax 4mo ago

I have thrown out my Tripplite UPS because its battery has degraded to the unusable levels. I replaced it with a 5kWh LiFePo4 rack-mounted battery and an AIMS rack-mounted inverter. I'm really surprised that there are no off-the-shelf solutions for this. The traditional UPS makers are just neglecting the recent 10 years of battery advances. I even made an Arduino-based module that provides an SNMP UPS interface for my Synology NAS. It works surprisingly well and has almost 12 hours of autonomy compared to barely 2 hours for the much heavier lead-acid battery. One trick that I'm kinda proud of: I powered my server directly from the 96V DC. And I periodically switch the current direction using a DPDT relay to avoid wearing out one side of the rectifier inside the PSU.

exmadscientist 4mo ago
> to avoid wearing out one side of the rectifier inside the PSU If you are seriously worried about this then the whole thing is trash. Either the design is marginal or it is not. You cannot possibly switch a relay fast enough to make a difference here (and have the relay survive).
- Dylan16807 4mo ago
  I don't understand what you're saying. If you're specifically worried about wear, then you could switch once a month and it would be enough.
  - exmadscientist 4mo ago
    Silicon rectifiers don't wear out. (At least not on timescales relevant to individual humans.) So hearing that makes me get suspicious that something else is going on.
    - Dylan16807 4mo ago
      I'm also suspicious of the idea of that part wearing out, but if it doesn't matter at all then there's no reason to call things trash. Your other comment says: If you are truly close to the design failure point of the rectifier, it's not safe to run at all. (You are almost certainly not.) Well there's no reason to assume it's close to the failure point. Think of it this way: Draw the line in the sand for where you'll approve the design, but just barely. If someone is running a diode close to that line, then it's not trash but trying to improve longevity isn't crazy either.

dreamcompiler 4mo ago

This is the way to go IMHO: Keep the outputs DC. Put a bunch of USB-C PD ports on the thing and you're good with a lot of modern equipment.

exmadscientist 4mo ago

> Evidently, AC waveform generation is extremely power-hungry Yes, it's quite ugly. Open up one of these things and you'll find a big block of four transistors (if not more due to doubling up) on a big heatsink. That's the inverter drive bridge, and it's probably the single largest source of heat in the whole thing. It's not hard to find.

bb88 4mo ago

I've been in the process of cutting the DC side of power bricks and crimping anderson power pole (APP) connectors onto both sides of the wire. For camping and ham radio, it's really nice to hook up to a battery without the AC inverter taking DC -> AC and the power brick sending that to DC again. The only thing to be careful with is connecting different voltages to different connectors, but it's at least possible with the APP connectors to "Build your own" with different color housings and different ways of combining the housings. So maybe 13.8v is red/black and something that's 5V is black/white, etc.

butvacuum 4mo ago
theres also anderson's SB series- APC seems fond of knockoff versions.

ErroneousBosh 4mo ago

I've been looking at Victron gear for an off-grid power system up north (initially for a caravan, will get migrated across to a house once the upgrading and repairing is done). A huge decision on that was that they publish a fat PDF with the full spec of the serial data they emit and can be programmed with, and a service sheet to allow a suitably skilled engineer to fully bench test them if there are any perceived problems. They're not cheap, but my late father always used to say he didn't have enough money to buy cheap tools. Edit: handy hint too - many cheap crappy power bricks will work down to 90V and will work just as well off DC as well as AC because the very first thing they do is rectify and smooth the incoming supply. I do not recommend having 90V DC kicking around unless everyone involved knows what they're getting into.

cwillu 4mo ago
Yeah, 90vdc is an immediate nope from me: way too easy to suffer a painful death.