DIY emergency computer power.

[Kenny_ms]

So, after finally getting my little 300W inverter in so I can have laptop/charging and whatever power should we have a hurricane or whatever, I find myself with another dilemma.

Right now I'm getting a black/brown out whatever it's called every 2 to 3 minutes (power off and right back on. Maybe a repair man doesn't know what he's doing?) for the last several hours, never seen anything like it, so I'm thinking for things like that and future problems, since I have the stuff just sitting here anyway, I could plug the inverter to my desktop computer and if the power goes out, the inverter will take over, the PC doesn't restart but stays running and when the outside power comes back on it will take over.

Then I realized I'd first need to plug both regular power plus the inverter/battery power in to the Desktop and then If that is possible, would regular power take back over automatically leaving the battery power untouched and charging once the regular power cam back on?

In short, it appears I have the makings for a PC power backup rig already here so, what would I need to make that happen? An auto switch to switch from power source to power source, and can I just rig something to plug both the regular power and the battery power into the desktop or would that blow things up? I would think not but better ask first, lol. It should only draw what it needs unless I end up mistakenly making it 220 with the two power connections.

PS, I think the 300W will run it and let's for the moment just assume it will and I can deal with that later if not. Sorta wish I'd a gotten a bigger inverter now but I can always keep this one in a car I guess if I do need a bigger one.

 

[Edward]

I'll chew on this for a few and see if I can come up with something for you. I'm no expert, but have a working knowledge of circuits and your idea is both interesting and possible.

 

[Kenny_ms]

Thanks Ed, I'm probably a little behind you in knowledge here, just enough to think it possible but not quit sure how to go about it.

 

[Edward]

Thanks Ed, I'm probably a little behind you in knowledge here, just enough to think it possible but not quit sure how to go about it.

Well, like I said, I'm no expert. My knowledge is pretty limited to maintenance and repair situations and such situation are different than your situation. But I'll try, lol.

Right off the bat I can tell you that what you wish to do...sounds expensive. If I read your post correctly, you desire a switch-over that is fast enough that your computer will not go down, the power just switches to the back up system when the grid fails, right?

Such automation could reach deep into your pockets! If you wanted a manual change-over from grid to back-up, it would save you a lot. If I remember right the fastest auto-changeover system is one second. I think that your computer system would go down with one full second of no power...??

I know they do the change overs by the unit sensing the frequency of the power and it's related changes as it goes down, or back on. I *think* that this sort of short timing/delay may give "false alarms" if the grid has an electrical hiccup and then it would go to backup without the need to...could be a PITB to try to construct it cheaply.
So that's why I say, sounds expensive.

Still chewing on it...

 

[Kenny_ms]

I've designed boat electrical systems where this kind of thing is common. You NEVER want to hook an inverter and AC line power to a device at the same time unless the inverter is designed to switch automatically. The alternations of the current will be out of phase and will cause much damage. Chances are if the one you bought has that capability you would know about it because it would be very rare in one that small.

I assume you have a 12 volt battery bank that will be powering your inverter, and this battery bank has a charger of the "smart" type that can be left on constantly. If so, one thing you could do with the equipment you already have is to run your computer off of the inverter full time, leaving the battery charger running to supply the current the inverter will be drawing. That way your batteries will stay charged while your computer is running on the inverter, and if the 120V AC line power fails or "browns out" the inverter will just take power from your battery bank to keep your computer running until the line power comes back on. Of course, this is assuming your battery charger has enough capacity to supply all the current the inverter will be using plus enough reserve to recharge the batteries in a reasonable amount of time after a line power failure.

If you try to rig up some kind of an automatic switch, chances are it may fail and cause damage, or it will have a slight interruption of power as it switches, causing your computer to shut down.

Yes, that's what I have. It's just a good, unused car battery for now, not even a deep cycle that I would likely add later and maybe even a solar panel eventually. And no, the inverter was cheap and as you say, probably doesn't have the switch off. Thanks, good to know about running both the power supplies to it, I would never have thought of a phase problem.

I thought about doing what you mention but I've just got a single amp and maybe just a half amp recharging it. If it came to that, I could get a better charger.

Wonder what they use for the store bought PC constant power supplies I've seen? How would they be switched? Guess I assumed those were somewhere in the neighborhood of what we are talking here but I guess not.

 

[Kenny_ms]

Well, like I said, I'm no expert. My knowledge is pretty limited to maintenance and repair situations and such situation are different than your situation. But I'll try, lol.

Right off the bat I can tell you that what you wish to do...sounds expensive. If I read your post correctly, you desire a switch-over that is fast enough that your computer will not go down, the power just switches to the back up system when the grid fails, right?

Such automation could reach deep into your pockets! If you wanted a manual change-over from grid to back-up, it would save you a lot. If I remember right the fastest auto-changeover system is one second. I think that your computer system would go down with one full second of no power...??

I know they do the change overs by the unit sensing the frequency of the power and it's related changes as it goes down, or back on. I *think* that this sort of short timing/delay may give "false alarms" if the grid has an electrical hiccup and then it would go to backup without the need to...could be a PITB to try to construct it cheaply.
So that's why I say, sounds expensive.

Still chewing on it...

Yeah, now that you mention it and I run what has to actually happen there through my mind again, it does have to be instantaneous and does sound expensive.

They do have ways of running a generator to your home wiring and using outside power but I'm not sure if that has to be switched manually or not. Same basic thing, I think.

What was happening today was unusual and if I ever lose power, I could just do as Obidiah mentioned...that on and off thing probably won't happen again, but keep chewing on it.

I'll check circuits on the commercial always on power supplies and see if they give a clue. I'm thinking they have no battery at all and maybe just use, what is it? One of those doohickies that charge up to jump your car off of but aren't an actual battery or a plug in charger/jumper? A condenser of sorts?


Thanks to both of you for the input.

 

[Edward]

I've designed boat electrical systems where this kind of thing is common. You NEVER want to hook an inverter and AC line power to a device at the same time unless the inverter is designed to switch automatically. The alternations of the current will be out of phase and will cause much damage. Chances are if the one you bought has that capability you would know about it because it would be very rare in one that small.

I assume you have a 12 volt battery bank that will be powering your inverter, and this battery bank has a charger of the "smart" type that can be left on constantly. If so, one thing you could do with the equipment you already have is to run your computer off of the inverter full time, leaving the battery charger running to supply the current the inverter will be drawing. That way your batteries will stay charged while your computer is running on the inverter, and if the 120V AC line power fails or "browns out" the inverter will just take power from your battery bank to keep your computer running until the line power comes back on. Of course, this is assuming your battery charger has enough capacity to supply all the current the inverter will be using plus enough reserve to recharge the batteries in a reasonable amount of time after a line power failure.

If you try to rig up some kind of an automatic switch, chances are it may fail and cause damage, or it will have a slight interruption of power as it switches, causing your computer to shut down.

Yeah, that seems to be the crux of it, a sensor to catch it when the power is beginning to fail and switches it to backup...but before anything is fried, and without letting the computer drop out. He's not asking for much, is he, lol.

You may be onto something. Perhaps he should put his money towards a total generator system, and run off of that normally with one or two days a week being grid days to recharge his backup system, oh and laundry day since it is a very high amp draw appliance.

There's no question that a bank of deep cycle marine batteries would be at the core of it, regardless of the low amp draw of a computer system. More batteries means more "normal time" of running the 'puter on backup. Hmm, maybe just want to wire up one room to run off of backup (computer room) so that most of the house is on grid and there's no effect if the power drops out. Prolly save thousands doing it that way, lol.

 

[Edward]

A condenser of sorts?

A capacitor.

 

[Edward]

Brother Kenny, what size is your inverter? How many watts/amps. What brand & model is it?

 

[King Dan of Great the 1st]

Would you like me to tell you my genius idea on never ending natural artificial power that has not been invented yet?. Its so simple yet unknown.

What you do is.... Ok, i need a patent before i go any further

 

[Edward]

Really, I think your cheapest and easiest way is to add a better battery charger and just run the computer off of the inverter full time.

That's what I was thinking too. It sure would be easier and cleaner to hard wire up one room from the source wire by the panel in the garage (if it's a dedicated circuit) instead of running extension cords from the inverter. You want to put the inverter real close to the batteries anyway to minimize voltage drop.

As for upgrading your battery bank when you are ready to do that... Stay away from marine deep cycle 12 volt batteries. You'll get many times more bang for your buck by using 6volt lead acid flooded golf cart batteries wired in series to get 12 volts. You will get more amperage than a huge 12volt 8D battery in about 2/3 the space and they will last much longer and handle deep discharges much better than any 12 volt marine battery every will. The last set I had lasted me over 15 years of continuous use!

Really. I stand down to 15 years exp with those, lol. My idea was to just stack up some batteries so he doesn't have to recharge so much. Maybe once a week. Depending on what his inverter is rated for he'd prolly have no problem running lights & TV and stuff too in there. I found some inverters with auto transfer switch, but I bet they'd still make his computer to reboot in the delay.

 

[Kenny_ms]

Brother Kenny, what size is your inverter? How many watts/amps. What brand & model is it?

Bestek 300W. Very cheap. And I already have a little Generator. I really just wanted something quiet and simple, and fairly low power to run a few things. You know, power goes out for a few hours/day or more and you have your computer/TV and a fan blowing right on you int he FL heat and don't have to bother with or listen to the generator or pay for the gas, that's a lot.

Another thing to consider for your laptop... It might run on 12VDC right off the batteries. The factories won't tell you that, and most laptop power supplies produce more like 18V, but in boats I've run a lot of them by rigging up a plug to run 12VDC directly into the laptops and they've worked fine.

You know that's the first thing I did. I ordered a multipurpose converter that would convert the voltage from the battery to what my Dell LT required and several other voltages so I could plug it directly into the battery but decided in the end not to try it due to voltage drop possibly damaging my LT. I'm sure I could have gotten some sort of cut out switch to kill the power once the voltage dropped so much but decided with my limited knowledge, I might best go with the inverter that I could also plug other things into. Now that I think about it, that system would work fine plugged in to the cig lighter of a an always running car. and yeah, it's around 18/19 volts.

Concerning the straight DC power...I get a warning on the LT when the power is low and for some reason I assumed the regular automatic shutdown for the LT was in the box in the AC line (you know, the little box that normally converts the AC to DC) but if that's not the case and the shutdown is in the LT itself, I can use the DC system, or at worse, just pay attention to the warnings the LT gives an turn it off manually when the power indicator get's so low.

Yep the starting of the backup generator would take way too much time.

Setting up even a small system with batts and solar panels is going to run more than I want to invest right now though I would l'd love to be able to do that. But when/if I ever do, that's interesting about the 6V golf cart batts, I'd a never known. Lots of people on youtube or whatever are using the marine Deep Cycles but it does seem like the last system I looked at was using the GC 6V batts, judging by the size anyway.

I'm not too concerned about an all out disaster though it could happen, but if I could eventually just get enough solar power to guarantee running at least a 5000btu AC window unit and just a few more things, I could relax. going without AC in FL at times, could be close to and in rare instances a death sentence, certainly no fun to those of us who aren't use to it and I stay in these days when the heat comes around so, I'm not.

I just did get here before falling asleep last night so haven't had a chance to look into it.

https://en.wikipedia.org/wiki/Uninterruptible_power_supply

 

[Kenny_ms]

Yep, the marine battery advertising would be the culprit there, and why many don't know about the GC batts you mention...no doubt.

Solar panels are costly and take forever to pay for themselves and they likely never would pay for them selves with what I want to do. But what they are is power, where even a tiny bit might be great if, under the worst of scenarios, there is no gasoline or any type fuel. I think it would run me around 3 to 5 grand to even get a little system like I'd like eventually for AC and all, but I'm afraid I'll have the setter for laptop power and a small fan for now lol....or not much more than that.

Not sure if you do any long distant trips on your boat but surely you have a panel or 2 just in case?

Just a 50W Panel/charger and battery I have would put me in better emergency shape than many, even if I couldn't run full time off it.

On these standard car batteries, I know they aren't made for this type thing but how would be best to use them it terms of them lasting as long as they can? discharge a lot before charging or shut things down and let them recharge before they have a chance to discharge too much like I hear one should do with Deep cycles?

 

[Kenny_ms]

Actually, I guess the car batteries should be used just as they are in the car, use a little to start the car and let em charge. so then the question would be, how much do they use for the average engine start?

 

[Kenny_ms]

OK, good.

I have the voltmeter and now the figures for charge/discharge levels and I'll go with what you say to do, use it up and go from there.... Thanks so much.

 

[jasonc]

gel cell or hybrid batteries

 

[jasonc]

Gel cells still have electrolyte (which is part water), only it's in a gelled form. If accidentally overcharge (it WILL happen eventually, probably more than once) the electrolyte will still "gas off" through the vents and loose some of that water. The advantage of conventional flooded cell batteries is that when that happens you can add water back in. Can't do that with gel cells. Once they've gassed of enough water, the battery's history.

I'm not sure what you mean by "hybrid batteries"?

mixed deep cycle with car batteries.

 

[jasonc]

I wouldn't recommend mixing them together (and the manufacturers also warn against doing this). Both the charging and discharging profiles need to be different for each type to utilize their advantages. I have both in my boat, but the starting (car) batteries are dedicated to starting the main engine, the generator, and running the anchor windlass (a short term high amperage draw similar to engine starting, and they are on a separate circuit with it's own charging system separate from the house batteries (deep cycle). The deep cycles run everything else, from refrigeration, electronics and inverter, to the cabin lights and are charged by a 4 stage shore power charger (also can be run off of the generator) or a dedicated 2nd large alternator on the main engine with a special regulator that can be adjusted for the proper deep cycle charging profile.

no they built that way.most oem car batteries are hybrid. they do sit for months. that isn't good for car batteries. besides most car batteries are maint free meaning that you shouldn't add water.

 

[jasonc]

Yeah, those aren't the kind I'm talking about. I would never use those in a house power situation. Keep in mind that most of those batteries are shot after 4 or 5 years too. I'm talking about systems where I expect them to last 15 years or more, and that's what I get out of the systems I build.

I know who to ask but florida you aint getting that life out of any battery, not even golf cart batteries.

 

[jasonc]

My last set of golf cart batteries were replaced after 15 years of continuous service with proper use, care, and maintenance. They were still working, but had lost enough capacity that I replaced them so I could get my full capacity back.

heat is the enemy of batteries here. the fleet has golf cart batteries. not many but they at the most get five years. your power saver uses them. they swell up when they go. I have a former coworker who does what you do for his home. he would know.