Portable Power Bank Assistance

[idleprocess]

Those all-in-one battery inverter units can be very handy and it seems like one can be found that has AC pass-through? Or perhaps the rare times grid fails it is not that big a deal if the computer goes belly up when power stops?

Some offer AC pass-through. Some even offer AC pass-through with UPS functionality.

But my reading of available units suggests that they make for mediocre at best UPSs:

• Switchover times tend to be well beyond the ~17ms of a single 60Hz AC cycle; bespoke UPSs tend to switch in the 5-12ms range
• Not all units that claim UPS functionality operate in AC pass-through mode - with those units you'll be running your load off of the AC-DC brick : inverter path all the time
• A number of units with UPS modes have unpredictable behaviors

In general it's not catastrophic for most modern workstation OSs to suddenly lose power; for me the important thing productivity. The laptop will handle a power interruption seamlessly, but nothing else will. My communications devices (ONT, router, switch) will all reboot, knocking me offline for 1-5 minutes. My VPN session will instantly expire. I will be disconnected from application sessions. And I'll lose at least 15 minutes rebuilding focus on what I was working on.

It is thus for reasons of productivity that I'm leaning on a UPS recommendation; almost everything I do for work is via the computer's connectivity to the outside world. That and shorter outages are generally more common than long outages, thus eliminating corner cases makes for a more affordable solution. Some data points:

• Medium UPS (2*7.2Ah /173Wh DC) - 60 minutes : router, switches, PoE cams, access point
• Small UPS (1*7.2Ah / 86Wh DC) - Unknown multiple hours : ONT
• Medium UPS (2*5Ah / 120Wh DC) - 30 minutes : laptop + workstation + docking station + huge monitor

Yep, I doubt he'd want to go through all this time, money, or both just for possibly a few hours a year, if that. Like I said though, I'll show him this and he can decide.
We live outside of town and have a different electric company, which I feel is slightly more reliable. We're all city people, though I have more rural experience than the rest. My wife and I thought about a generator setup when we first moved in almost 18-years ago.

Backup power is expensive - like dollars per kWh expensive. The upfront cost is significant, most solutions require some degree of maintenance, and you generally only need it for a few hours a year.

The generator setup I opted for was pretty minimal : 2x portable inverter generators, parallel kit, inlet, interlock breaker. I spent about $1500 all told and it's run all the important 120V circuits without issue when called upon. Arguably doesn't improve the value of my house by much but also wasn't an automatic whole-house generator costing 10x as much with serious annual operating expenses. I had previously considered the sort of homebrew solution (batteries + inverter), but the cost to power just the home office would have been similar with greatly reduced capabilities and less flexibility. The necessity has faded since my employer has again opened an office locally but I'm still glad to have the ability to run 120V throughout my house.

 

[kilogulf59]

"Backup power is expensive - like dollars per kWh expensive." You said a mouthful.

 

[idleprocess]

"Backup power is expensive - like dollars per kWh expensive." You said a mouthful.

I pay something like 15 cents per kWh (kilowatt-hour) from the grid.

But let's say I need to run my generator. I consume one gallon of fuel. My little generator will produce 5.95 kWh from that gallon of gasoline at 50% load (850W). Simple math on the operating cost : $3 for the gallon of gas / 5.95 kWH = ~$0.50 / kWh. So I'm only ~3.3x as expensive on simple operating costs.

But the generator is a limited-lifespan good. I expect to use it about 10 hours per year for 10 years before it's end-of-life or need major maintenance. Say the generator cost $400; my hourly depreciation cost is $4 divided by 0.85kWh = ~$4.71 depreciation per kWh.

So my total cost per kWh for maintaining emergency backup power is ~$5.21 - or more than 34 times what grid power costs.

Similar depreciation math with UPS / lithium power stations; operating cost will be whatever grid power costs.

 

[orbital]

+

Maybe it was mentioned, but if your sons computer is a notebook, a smaller battery unit will keep him afloat since there is no need to reboot.
..he'll be on his notebook battery power till he plugs in the auxiliary 'battery'

If he has a desktop, you'll need alot more power to go through the reboot process & will need something like the LFP/inverter setup I suggested.

 

[TD-Horne]

However, I doubt he'd want a car battery inside his apartment, what with acid, fumes, and all. GEL and AGM batteries seem safer, albeit expensive.

AGM batteries are appropriate if it will not get really cold inside the building. If it will get really cold then Gel Cell batteries become the way to go.

If you want to maximize run times and minimize complexity and cost of ownership then Lithium Iron Phosphate (LiFePH4) batteries are the best choice. They do need a battery heater to run below freezing and that will cut into the length of time the battery will last when operating in sub zero temperatures. LiFePH4 batteries can be recharged 5 to 8 times as many times as the best Gel Cell can. That is what makes up for the higher cost.

From the use you are describing I would think that what I'm about to outline would be overdoing it but it is a bomb proof solution. There is a type of Uninterruptible Power Supply called continuous duty double conversion. All of the parts which make it up are always in the circuit. A charger for the battery runs off of the utility's AC power. A pure sine wave inverter runs off of the battery. The computer's ATX power supply Runs off of the inverter. The power is always being converted from 120 volt AC to 12 volt DC, from 12 volt DC to 120 volt AC. When the utility power decides to take some time off the computer is completely unaware that has occurred because it has been running off of the 120 volt AC power out of the inverter and the inverter has been running off of the 12 volt DC from the charging converter via the terminals of the battery. When the charger no longer has 120 volt AC from the utility supply it stops charging the battery but at that point the battery will be fully charged and the inverter that has been running off of the battery's 12 volts will continue to do so. LiFePh4 batteries have very flat discharge rates. They maintain their design voltage through ~90% of their rated capacity in Ah and then the voltage falls off a cliff. The various lead acid batteries all drop in voltage more gradually but that means that they are under the minimum voltage for radio equipment to function long before they are exhausted. The figure most often used is that they can only provide 50% of the nominal capacity.

There is a further step that can be taken to make this type of continuous duty power supply more efficient and this extend its operational duration. That would be to modify the desktop computer itself by changing the power supply to one that runs directly off of 12 volts DC. Such ATX Form Factor 12 volt computer power supplies are available for ~$25. This saves the cost of the inverter which is probably the second most expensive component. Converting the power twice is inherently inefficient. By using DC power supplies in the computers we can avoid the losses which occur in the conversion back to AC to power the computer's ATX power supply.

Tom Horne

 

[Poppy]

So my total cost per kWh for maintaining emergency backup power is ~$5.21 - or more than 34 times what grid power costs.

True, but when grid power isn't available, you are without AC or heat. With a generator set up you can still have heat in the winter, and air conditioning in the summer. Also some first world comforts such as TV, and lights. Also computers, monitors, and routers will still be available so that you can sit and slave at the keyboard.

I see that Harborfreight.com has a Black Friday sale until 4/16/23 with their 3500 watt super quiet inverter generator on sale @ $779 that's $120 off.

3500 Watt SUPER QUIET Inverter Generator with CO SECURE Technology

Amazing deals on this 3500W Super Quiet Inverter Generator at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

I have one and it purrs like a kitten.

 

[idleprocess]

True, but when grid power isn't available, you are without AC or heat.

Or are forced to burn a vacation day. Or tether your laptop to your cell data and try to work at dialup speeds as the 4G/5G bands turn to trash because everyone has to stream Netflix during a blackout (assuming cell sites stay up since their emergency power isn't always all that robust). Or get onto the roads in a blackout, risking signals being down, when the weather is oftentimes bad.

My point in performing that math isn't to make an argument against having emergency power but simply to raise awareness of how much it truly costs vs grid power - often for reduced capabilities.

 

[orbital]

+

The solar charging I do is mainly a hobby, a very expensive one I'll admit.
Can think of dozens of hobbies, dozens of lifestyle choices that are unproductive and simply cost money.
Hobbies don't need to make me money or even break even. Solar is rewarding to me in it's own way.

kilogulf had a good question, by now he has an idea what it'll take.
Does he/his son need an LFP to do the job, no, but it's a good investment for a long life product that'll easily do the task.
...and can be used for other things if needed.

> I'v been running an LFP and inverter setup w/ a laptop & 4K monitor for every one of my posts here,
been doing so for weeks.

 

[KITROBASKIN]

Mr. Horne spoke of Lifepo batteries and I just wanted to clarify that the cells can be used below freezing to a certain point but should not be charged if the cells are below freezing. Some are fitted with heaters that activate before charging of the cells begins.

There is a term called calendar life when it comes to batteries. Different chemistries and conditions affect longevity but even if everything is optimized, batteries will only perform well for so long.

Also, for those who decide to go the solar route and exercise their batteries while having very reliable 24/7 power, know that the costs I mentioned earlier are not the entire picture. Balance of system costs need to be factored in; that very well might include racking, wire, connectors, fuses, breakers, surge protection device, etc.

 

[sledhead]

For simplicity why not go with a power station from Goal Zero , Inergy or any similar products. Their are a slew of them now. Well worth the money in my opinion.

 

[kilogulf59]

@idleprocess I did fairly extensive research into generators a while back. You can read about it here if you're so interested: Generator Talk.... I know what you mean. I even contacted my electric company to see how big of a generator I'd need for the entire house.

I came to the conclusion that generators are something you get based upon actual need, if such a need even exists. Just the fuel type is a big consideration.

@orbital no, it's a regular computer, a desktop.

@TD-Horne Holy Cow. Is there such a critter like that or is this something that one has to make up on his own?

@sledhead That would be something to look into.

Well folks, I think many of these solutions are akin to getting a generator. Based upon our outrage history and in his application, it's probably best in his case to just accept the little bit of down time.

Now, we have folks in the area who have to run sump pumps, especially in the rainy season. Those people usually have a simple gasoline generator that they can hook up is need be. For them, a few hours sans power is a big deal. I guess what I'm trying to say is, for some, backup power of some kind is a necessity. For most of us it isn't.

I'd also like to say thanks, again and you folks know a helluva lot more about these things than I do.

 

[bykfixer]

Nearly all traffic signals use a UPS system that involves a device to communicate as it were and either 1 or 2 car batteries. Well, more like deep cycle marine batteries. But it's a pretty basic setup that can keep a 440 volt system running for up to 8 hours.
It powers not only a fancy computer but also a bunch of LED lamps as well.

Best UPS (Uninterruptible Power Supply) of 2023

Keep the power flowing with the best UPS

www.techradar.com

For home use.

 

[kilogulf59]

@bykfixer I clicked on that link and I'm seeing run times of a few minutes not hours. Am I missing something?

 

[idleprocess]

@idleprocess I did fairly extensive research into generators a while back. You can read about it here if you're so interested: Generator Talk.... I know what you mean. I even contacted my electric company to see how big of a generator I'd need for the entire house.

I came to the conclusion that generators are something you get based upon actual need, if such a need even exists. Just the fuel type is a big consideration.

I did quite a bit of research before committing to my setup in late 2021, although I knew in advance that the math on a whole-house unit wasn't going to pencil out (a solar setup with a battery bank would cost moderately more while being a producing asset). 65% of the utility for 10% of the cost seemed like a favorable tradeoff. I still ponder a big 120V/240V portable generator that could run most of the house, but those fuel logistics would prove challenging... and the need just isn't there.

But the lack of need didn't stop a number of locals - the February 2021 storm fresh in mind - from blowing 5 figures on said units and stretching installation waitlists through most of 2022. Twice now there have been brief outages and a neighbor's ~2022 unit spins up, audible for blocks. Upside they can keep on keeping on like nothing's happened; downside the immense cost for something that spends some 99.9% of the time doing nothing.

 

[turbodog]

I pay something like 15 cents per kWh (kilowatt-hour) from the grid.

But let's say I need to run my generator. I consume one gallon of fuel. My little generator will produce 5.95 kWh from that gallon of gasoline at 50% load (850W). Simple math on the operating cost : $3 for the gallon of gas / 5.95 kWH = ~$0.50 / kWh. So I'm only ~3.3x as expensive on simple operating costs.

But the generator is a limited-lifespan good. I expect to use it about 10 hours per year for 10 years before it's end-of-life or need major maintenance. Say the generator cost $400; my hourly depreciation cost is $4 divided by 0.85kWh = ~$4.71 depreciation per kWh.

So my total cost per kWh for maintaining emergency backup power is ~$5.21 - or more than 34 times what grid power costs.

Similar depreciation math with UPS / lithium power stations; operating cost will be whatever grid power costs.

Overall point stands, and this is really for the generator thread, but my eu2000 units are 19 years old, with 1000+ hours on each. Have replaced the carbs once and air filter once (rotted and was 'consumed' by the engine).

 

[kilogulf59]

@idleprocess "Upside they can keep on keeping on like nothing's happened; downside the immense cost for something that spends some 99.9% of the time doing nothing." Backup power's a balancing act and it takes some serious thought, unless you're rich and/or operate like Chicken Little.
@turbodog so you have about 52½ hours per year of use. Just wondering, how much of that is maintenance running? Of course, maintenance running would only be a couple of hours per year. You're also right, anything I have to say, from here on out, would be generator related and, therefore off topic.

 

[turbodog]

... how much of that is maintenance running? Of course, maintenance running would only be a couple of hours per year. ...

Maybe an hour, give or take.

They get used for races, running air compressor airing up tires for farm equipment/trailers/etc in place (much easier than hooking up, bringing stuff to equipment shed), maintenance buggy (small 120v portable welder/grinder/etc), portable battery charger using 12v leads, and house power before I went w/ standby unit.

They ran through katrina for probably ~200 hours alone... no oil changes, just top up.

 

[Poppy]

Perhaps we can continue our discussion at

https://www.candlepowerforums.com/threads/master-thread-for-disasters-and-generators.241581/

 

[kilogulf59]

I can see where portable power would come in very handy on a farm. We have a lot of dairy farms here and backup power is a necessity on those.
@Poppy I just saw your post and it's OK by me.

 

[orbital]

+

kilogulf,,
scaling back just a bit more for your son, at 30Ah that should be nearing 400Wh runtime.
It will still have the power to boot a desktop & keep him running.

Amazon.com

Amazon.com

https://www.amazon.com/dp/B09ZLD6RJ5/?tag=cpf0b6-20

$275'ish

simply can't scale back more than that and be functional/worth spending money on.