Yes, you're completely right, of course. I forgot about the inductance of the coil greatly decreasing the current flow. Thanks for catching that mistake!
I have an APC SmartUPS with two 12 Volt 92Ah Hawker Cells. It's really quite hilarious because the batteries are about 4 times the size of the actual UPS! I worked out the thing should run for about 4 hours before the batteries are depeleted but I still need to hack the UPS's bios to remove the hard-coded runtimes
Seriously though, I kind of LIKE it when the power goes out. It gives me an excuse to shut down the computer and go play in the snow (In Canada where I live we kind of just get used to the cold and dress for it). The coolant in the CPU chiller has so much glycol in it its good to something like minus 40 C, so no worries there.
I tried this mod with my APC SmartUPS 1000 using two 92 Ah 12 Volt Hawker Cells. It does a great job of running the UPS, but it does little to extend my runtime.
It looks like APC "hard-coded" the designed runtime into the UPS's firmware, so the thing shuts off after X minutes at a given load, regardless of the charge left on the battery. The system does this even after putting it through the runtime calibration routine.
I haven't tried this on my SmartUPS 1400 yet (maybe APC has gotten around the issue in this model), but if you have a SmartUPS 1000 you may want to think twice before heading out to pick up a stack of deep-cycle batteries.
I agree! I have a dual Athlon MP 2800+ system and the thing put off so mugh heat I had to have HUGE cooling fans on the CPU's and a total of 5 fans on the case.
The damn thing was so loud, that in order to use the computer without slowly going deaf I had to switch to water cooling. It took two Innovatek Dual 80mm radiators to keep it cool. Even with STEALTH fans, those were so loud I ended up drilling a hole in the wall and mounting the radiator on the OUTSIDE of my house!
I suppose all's well that ends well though. With mods to unlock the CPU's and deal with condensation, when it's -30C outside I can significantly overclock my system for extra processing power!
Actually, you don't even need to change your gas valve. Find out the control voltage for your gas valve (its printed on the valve - likely 24 volts), and then build yourself a small battery back to make roughly the same voltage. A few 9-volt batteries should do.
When the power's off and you want heat, open up your furnace, find the small transformer that powers your gas valve/ thermostat, disconnect the wires on the LOW VOLTAGE side and connect them to the battery pack.
When the thermostat switches on, the gas valve will open (powered by the battery pack) and the furnace will start. Since gas valves in most furnaces generally draw very little current, even a few 9-volt batteries should be sufficient to keep it operating for a long time.
Note however, that this ASSUMES your system is a hot water boiler setup. If you've got a forced-air system, you're going to need a UPS to power the blower!
It wouldn't fill a garage, but it would still be big, heavy, and expensive.
To run the UPS at 240V @ 4A for 8 hours, you would need around 12KWh of battery capacity taking into account system losses. Using lead-acid batteries (currently the best storage-to-dollar ratio), say 12-volt 92Ah "Hawker cells" you would need eleven or twelve batteries.
Stacked up, it would be the size of a fridge and weigh 1,200 lbs. It would also cost you about $3,600. And they would only last about 7 years before needing replacement. And of course, you would need all the plumbing to vent the hydrogen produced during charging.
Read some of the other posts. Extra batteries are probably the LAST way you would want to tackle this problem.
This is actually not a half-bad idea. A typical car alternator can put out over 600 watts and a large alternator like the kind you would find on a truck can often do up to 1,200 watts.
Keep in mind that you will need to carefully choose your inverter if you want to do this approach. First, it will have to be BIG. While your furnace likely draws under 500 watts when its running, it may very well draw over 1,500 watts when its spinning-up the blower. Your inverter will have to be rated for this. If it isn't you'll just blow its internal fuse and >pop!
Second, you ABSOLUTELY MUST use an inverter that puts out a TRUE SINE WAVE. If you use a cheap "Square Wave" inverter, it could burn-out the induction motor in your furnace. Destroy the compressor in your fridge, and possibly "pop" the rectifier diodes and/or overheat the filter caps in your computer's power supply. Be careful!
Note also that you will have to idle your car continuously while the inverter is running. Otherwise the system could drain your car's battery in a matter of minutes.
No, it's not run through a transformer before the first rectification stage. At that point in the circuit, the transformer would have to be HUGE because of the low frequency, defeating the purpose of using a switching power supply in the first place!
Nope, at 240V the power goes directly into a rectifier and then into the bulk caps that feed the switcher. At 120V input the rectifier is rearranged into a single-stage voltage doubler (which also rectifies the input power), then, once again, into the bulk caps.
If you don't want to shell out the money for a commercially built generator, you can likely put together your own system for about $50.00 CDN using some scrap car parts and an old lawnmower.
That's probably less than it would cost you to add a SINGLE additional battery to your system.
Here's how: Find yourself an old "horizontal" style lawnmower engine (anything over 2HP will do) and a car alternator - the bigger the better. Put a pully on each, string a V-belt between them and bolt them down to a thick piece of plywood or better, some sort of metal frame. Using the wire from a set of old booster-cables, hook the output from the alternator (which should be outside, of course) through the nearest convenient window (or drill a hole in the wall) and across your UPS battery (making sure it is the CORRECT POLARITY). When the power goes out for more than 20 minutes, go outside and start up the engine for practically unlimited runtime.
Even with a small car alternator, this rig will easily give you 12 volts at fifty amps. If you use a larger alternator, like the kind you would find on a truck, you can get 12 volts at up to a HUNDRED amps (= 1,200 watts).
I once put a system like this together for fun for under $50.00 CDN, ($30.00 for a beat-up old engine in the local bargain-finder and $20.00 for an alternator from the local scrapyard.) This is significantly less expensive than buying even a single extra battery, which would cost about $80.00. The thing would run for HOURS before needing refueling, and if I wanted longer runtime I could have just added a bigger gas tank.
Now, before you pack up your wrenches and head down to the local scrapyard, there is something you need to check: Does your UPS use a single large 12-volt battery, or does it use two smaller 12-volt batteries in SERIES for a total of 24-volts? If your system has two 12-volt batteries in series, you're going to need a 24-volt alternator. Where do you get a 24 volt alternator? Well, most Land Rover vehicles have 24-volt alternators, as would practically any kind of emergency vehicle, most military vehicles, and many large trucks. So, if you need a 24-volt alternator and can't find a Land Rover at your local wreckers, head to an INDUSTRIAL vehicle scrapyard.
For the load you initially described, (250 volts @ 4 amps = 1,000 watts at continuous use) you would need a sustained power INPUT of about 1,200 watts. Note however, that in reality you will probably NOT need 1,000 watts continuous output as your furnace blower will be cycling on and off as will the other loads in your house. The UPS's battery will cover the extra load when everything IS running and recharge from the alternator when it ISN'T. This means you can likely get by with a smaller alternator.
Overall, the solution I have described is ugly, noisy, and isn't likely to last through more than 100 hours of use. But it's also cheap, light (compared to a battery), easy to hook into the UPS, quite reliable, and works great if you only need a few hours of additional electrical power. If you're mechanically inclined, this is the cheapest and most effective solution I can think of.
If you're really keen on the whole batteries/UPS/alternator modding-it-to-run-on-practically-any-source-of-pow er thing or just want even more reasons why trying to run it off solar power would be a terrible idea (at least where you live), I did a really interesting writeup on this for an anti-landmine technology competition a few years back. We made the whole reference design that we came up with effectively "open-source", so feel free to use it as you please. You can have a look at that here: http://www.intellicharge.ca/Downloads/Downloads.ht m The server has pretty serious bandwidth so it should be relatively/. resistant, but please don't rack up our hosting bill by downloading the full 1200dpi 114 MEG "print resolution" version unless you have good
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Yes, you're completely right, of course. I forgot about the inductance of the coil greatly decreasing the current flow. Thanks for catching that mistake!
Seriously though, I kind of LIKE it when the power goes out. It gives me an excuse to shut down the computer and go play in the snow (In Canada where I live we kind of just get used to the cold and dress for it). The coolant in the CPU chiller has so much glycol in it its good to something like minus 40 C, so no worries there.
It looks like APC "hard-coded" the designed runtime into the UPS's firmware, so the thing shuts off after X minutes at a given load, regardless of the charge left on the battery. The system does this even after putting it through the runtime calibration routine.
I haven't tried this on my SmartUPS 1400 yet (maybe APC has gotten around the issue in this model), but if you have a SmartUPS 1000 you may want to think twice before heading out to pick up a stack of deep-cycle batteries.
The damn thing was so loud, that in order to use the computer without slowly going deaf I had to switch to water cooling. It took two Innovatek Dual 80mm radiators to keep it cool. Even with STEALTH fans, those were so loud I ended up drilling a hole in the wall and mounting the radiator on the OUTSIDE of my house!
I suppose all's well that ends well though. With mods to unlock the CPU's and deal with condensation, when it's -30C outside I can significantly overclock my system for extra processing power!
When the power's off and you want heat, open up your furnace, find the small transformer that powers your gas valve/ thermostat, disconnect the wires on the LOW VOLTAGE side and connect them to the battery pack.
When the thermostat switches on, the gas valve will open (powered by the battery pack) and the furnace will start. Since gas valves in most furnaces generally draw very little current, even a few 9-volt batteries should be sufficient to keep it operating for a long time.
Note however, that this ASSUMES your system is a hot water boiler setup. If you've got a forced-air system, you're going to need a UPS to power the blower!
Stacked up, it would be the size of a fridge and weigh 1,200 lbs. It would also cost you about $3,600. And they would only last about 7 years before needing replacement. And of course, you would need all the plumbing to vent the hydrogen produced during charging.
Read some of the other posts. Extra batteries are probably the LAST way you would want to tackle this problem.
Keep in mind that you will need to carefully choose your inverter if you want to do this approach. First, it will have to be BIG. While your furnace likely draws under 500 watts when its running, it may very well draw over 1,500 watts when its spinning-up the blower. Your inverter will have to be rated for this. If it isn't you'll just blow its internal fuse and >pop! Second, you ABSOLUTELY MUST use an inverter that puts out a TRUE SINE WAVE. If you use a cheap "Square Wave" inverter, it could burn-out the induction motor in your furnace. Destroy the compressor in your fridge, and possibly "pop" the rectifier diodes and/or overheat the filter caps in your computer's power supply. Be careful!
Note also that you will have to idle your car continuously while the inverter is running. Otherwise the system could drain your car's battery in a matter of minutes.
Overall, not a bad idea in a pinch though!
Nope, at 240V the power goes directly into a rectifier and then into the bulk caps that feed the switcher. At 120V input the rectifier is rearranged into a single-stage voltage doubler (which also rectifies the input power), then, once again, into the bulk caps.
So yes, it would run just fine on DC INPUT.
That's probably less than it would cost you to add a SINGLE additional battery to your system.
Here's how: Find yourself an old "horizontal" style lawnmower engine (anything over 2HP will do) and a car alternator - the bigger the better. Put a pully on each, string a V-belt between them and bolt them down to a thick piece of plywood or better, some sort of metal frame. Using the wire from a set of old booster-cables, hook the output from the alternator (which should be outside, of course) through the nearest convenient window (or drill a hole in the wall) and across your UPS battery (making sure it is the CORRECT POLARITY). When the power goes out for more than 20 minutes, go outside and start up the engine for practically unlimited runtime.
Even with a small car alternator, this rig will easily give you 12 volts at fifty amps. If you use a larger alternator, like the kind you would find on a truck, you can get 12 volts at up to a HUNDRED amps (= 1,200 watts).
I once put a system like this together for fun for under $50.00 CDN, ($30.00 for a beat-up old engine in the local bargain-finder and $20.00 for an alternator from the local scrapyard.) This is significantly less expensive than buying even a single extra battery, which would cost about $80.00. The thing would run for HOURS before needing refueling, and if I wanted longer runtime I could have just added a bigger gas tank.
Now, before you pack up your wrenches and head down to the local scrapyard, there is something you need to check: Does your UPS use a single large 12-volt battery, or does it use two smaller 12-volt batteries in SERIES for a total of 24-volts? If your system has two 12-volt batteries in series, you're going to need a 24-volt alternator. Where do you get a 24 volt alternator? Well, most Land Rover vehicles have 24-volt alternators, as would practically any kind of emergency vehicle, most military vehicles, and many large trucks. So, if you need a 24-volt alternator and can't find a Land Rover at your local wreckers, head to an INDUSTRIAL vehicle scrapyard.
For the load you initially described, (250 volts @ 4 amps = 1,000 watts at continuous use) you would need a sustained power INPUT of about 1,200 watts. Note however, that in reality you will probably NOT need 1,000 watts continuous output as your furnace blower will be cycling on and off as will the other loads in your house. The UPS's battery will cover the extra load when everything IS running and recharge from the alternator when it ISN'T. This means you can likely get by with a smaller alternator.
Overall, the solution I have described is ugly, noisy, and isn't likely to last through more than 100 hours of use. But it's also cheap, light (compared to a battery), easy to hook into the UPS, quite reliable, and works great if you only need a few hours of additional electrical power. If you're mechanically inclined, this is the cheapest and most effective solution I can think of.
If you're really keen on the whole batteries/UPS/alternator modding-it-to-run-on-practically-any-source-of-pow er thing or just want even more reasons why trying to run it off solar power would be a terrible idea (at least where you live), I did a really interesting writeup on this for an anti-landmine technology competition a few years back. We made the whole reference design that we came up with effectively "open-source", so feel free to use it as you please. You can have a look at that here: http://www.intellicharge.ca/Downloads/Downloads.ht m The server has pretty serious bandwidth so it should be relatively /. resistant, but please don't rack up our hosting bill by downloading the full 1200dpi 114 MEG "print resolution" version unless you have good