Posted: 11/13/2013 12:49:14 AM EDT
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I'm currently in the research and design stage of my backup power system. I'm planning on 3-4 12V AGM batteries, a Champion inverter generator, charge controller (don't know much about these yet), and a (stackable?) inverter.
This system will be used to power critical devices in my home durning an extended power outage. My number 1 main concern is keeping the sump pump running. After that, lights, fans, and maybe AC/Furnace if possible. I need to get a kill-a-watt and measure my electrical usage for these components. It occurs to me that buying a stackable generator and inverter makes sense for future expansion of off grid power. I'd like to be able to just add components to the existing system instead of replacing components. Also, "2 is 1" applies to this strategy as well. Eventually I'd like to be in a rural location and completely off grid. So the ability to "stack" components at a later date IF I implement a total solar/wind/etc solution would be nice. Thoughts? UPDATE: Thanks a ton for the advice guys. I threw my latest ideas into a Visio drawing. This drawing assumes I can find just the "intelligence" portion of a UPC that will allow me to use my own batteries. I'm also assuming that the UPC has a good charge controller and conditioner built in, If anyone knows of a rack mountable unit please let me know. Also, its not noted in the drawing, but a transfer switch or interlock plate will be installed. Ive decided that my home network will be a critical system when I install cameras. And finally, I'm not an electrical engineer, so go easy on me. 
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Parallel. Let's say I determine that I need 800 watts to achieve my current goal. In the future I need 1600. Instead of buying a bigger inverter, I could just buy another 800 watt version. I know not all models support this feature, but I have seen some with the capability.
I guess I'm wondering if you guys recommend this strategy or not. |
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Quoted:
Parallel. Let's say I determine that I need 800 watts to achieve my current goal. In the future I need 1600. Instead of buying a bigger inverter, I could just buy another 800 watt version. I know not all models support this feature, but I have seen some with the capability. I guess I'm wondering if you guys recommend this strategy or not. I don't know what 'stackable' inverters [other than possibly small grid tie inverter/controllers] have such a low output rating... However [and I think Fullpower thinks poorly of Xantrex 
We have been using Outback FM60 and 80 charge controllers [abt $500 up, ebay] and they are great for series arrays up to ~150 vdc max... They can be paralleled from separate arrays, to connect additively to the battery bank... As far as the inverter, we've been buying the yellow case Xantrex Sine 1800 watt inverters on ebay when we find good deals. For about $500 if you pay attention, I don't think there is much of a better deal out there for a sine wave unit, w/ that wattage, used. We have 4 or 5 good ones now, one or two with goofy outputs and frequency, for parts. We bought 2 brand new during the winter IIRC, for ~$500 each!, way back, and the same one of them has been in continuous service 24/7 since 2009, that's almost 5 friggin years
We add to the Xantrex stock when we find them cheap, if for no other reason, as parts donors, should that ever become necessary. Just this week I changed the fan in it [the original one installed] to a Radio Shack $10 fan because the orig was getting noisy. As far as battery choices for a small system, Costco or preferably Sam's' has the golf cart batteries we've used in a solar ap in the trailer and originally at the container and they are the biggest bang for the $$ for a small system. We replaced the golf cart batteries after a few months at the continer because for our power needs, they just didn't handle the lights and network, and general needs. 4 more of them would have but we just went to Surettes, 2 big 230 pound each 6 volt ones. At the barn there are 8 L16's [I'd suggest if you need more than 2 or 4 golf carts to go with these for cost effectiveness] and 3 Outback's with 3 solar arrays of 2-2-3 and they can easily dump 8000 watts plus into the batteries on a good day. Each array has its own Outback. Rationale... Outback's have great support, are efficient and friendly, lots of features and are cost effective. The yellow Xantrex Sine 1800 have poor support, have an excellently low idling parasitic loss overhead, are highly reliable, cost effective if careful shopping is done. They just work well. They can be supplying 500 watts of loads and still start the biggest Dewalt 12 inch chop saw without breaking a sweat. They are maintainable. Sealed batteries, [altho we have a few lead-calcium sealed batteries we got for free], for a backup system that runs lots of power for years, they are a poor choice. They are great for an alarm backup supply float charged and that sort of application, that we have used them in. Unlike flooded batteries, shorter life, more $, sealed can't be maintained, SG can't be monitored, they can't be 'equalized' and aren't as forgiving to abuse. [Flooded batteries get a bad rap from folks using one or two in their house or something that they evolve gas, and that is true, though the effects are trivial, and make great Whining and Pissing Fodder for Politically Correct EPA Fanboy Sheeple afraid of their shadow.] 
As far a solar panels, if you plan to expand the system, panels in the range of 200 or more watts make sense to me. We have stocked Sharp 224 watt, then they went to 240 watts, in the same 30" by 60" roughly, package. That's a hell of a lot of juice in a small format. Cost now is about a $1.10 per watt. http://www.ecobusinesslinks.com/surveys/free-solar-panel-price-survey/ Add an Outback or Morningstar or similar, used, and one of the lower cost Sine wave Xantrex Prosine 600 watt inverters [$120 on ebay], or similar, 2 L16 batteries [~$250 each mfg'd by US Battery and avail from Interstate Battery] and you're good to go. Easy! 
Oh, the 8 L16 batteries are wired for 12 vdc because we have reasons to want 12 vdc, but could be rewired for 24 or 48 vdc. I did get a Xantrex for 24 vdc but haven't seen the need to change to 24 v but could do it in an hour. But then how do we power our 12 volt stuff? We have some 24 vdc to 12 vdc 20 amp or so inverters but that adds one more failure point in a remote and many times unattended system. |
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MAGNUM Energy can stack, uses a proprietary cable.
Outback FX series will stack, up to TEN units in parallel. Outback can also be arranged to make 3 phase power, but you have a limit of only 3 inverters in that config. . I am using a parallel stack of 2 Outback FX series inverters. one mostly sleeps, until loads get high enough and then it kicks on. completely automatic, and seemless, you cant tell unless you are in the battery room, looking at the machines status indicators. |
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Thanks. I'll definitely save your suggestions for later when I eventually get some numbers on paper.
And just to be sure I'm reading you right, the hydrogen gas that's vented from lead acid batteries isn't an issue I should worry about in a small system? I'm a little weary about that for one reason: My dad worked in communications for the state government. Probably twenty years ago they had a contractor do some work on their battery vent system. I don't have all the specific details here, but something was left plugged or routed wrong and they had a big fire a few months later. I understand this is a very unique situation and a cumulation of "mistakes" led to this disaster. Installing a hood and vent wouldn't add too much cost to the system, especially if I'm getting better value from the 105 style batteries. How many guys run lead acid without a vent? Is this generally considered okay without any consideration for gas buildup? We all know hydrogen is lighter than "air", so do we count on it making its way out of the house? |
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Quoted:
Thanks. I'll definitely save your suggestions for later when I eventually get some numbers on paper. And just to be sure I'm reading you right, the hydrogen gas that's vented from lead acid batteries isn't an issue I should worry about in a small system? I'm a little weary about that for one reason: My dad worked in communications for the state government. Probably twenty years ago they had a contractor do some work on their battery vent system. I don't have all the specific details here, but something was left plugged or routed wrong and they had a big fire a few months later. I understand this is a very unique situation and a cumulation of "mistakes" led to this disaster. Installing a hood and vent wouldn't add too much cost to the system, especially if I'm getting better value from the 105 style batteries. How many guys run lead acid without a vent? Is this generally considered okay without any consideration for gas buildup? We all know hydrogen is lighter than "air", so do we count on it making its way out of the house? The gas from a couple batteries is quickly dispersed. In the case of your Father, who knows what the failure mode was? My Father had a bunch of microwave towers he was responsible for long ago and each had a battery bank room and of course they were vented. Probably 24 large glass jar 2 volt cells on racks. Very formal. They ran a vibrator 'inverter' until the diesel genny, in another room, could get started up, then transferred over. 2 golf cart or L16's is not an issue. I've run lead acid w/out a vent, even in the furnace room of a pretty fancy house from the 80's to the 2000's. Also other places. No issues. In the stealth trailer, the 2 batteries are 'recessed' into the floor with battery box covers set on top and I vent the covers into the wheel wells on each side. That's because we have fold down bunks right over them and the trailer is highly insulated and tight. I'd get some experience with them and add a simple vent if later you find it necessary. Very little gas is evolved unless a very heavy discharge or charge is experienced. |
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My thoughts: Grid ties are allways stackable
I don't think you will find what you want under 2kw. To double that, you don't really stack, you feed both legs of a 120/240. After that you can stack, but can you really afford the solar power to do so. With a battery system, you accept enough power in 5 hrs to run the system for 24, so when you need more then 4800 watts of power, you probally need way more watts of solar. Unless your just loaded, it makes more sense to use the grid as your storage battery. The you stack grid tie, so you can invert the entire output of the pannels. We have a solar system at work where we have 2 pairs of 3kW inverters (for 240), basically a house load and a technical load. We have over 40 kW of pannels feeding DC into 12 kW on inverters, and 2 banks of 1500 Ah cells (at 48V). Now this is pre MPPT. In a total off grid, solar only system, you need to have enough solar energy for winter demands, with usually less than prefect tilt, and long lighting days, It would be a pretty impressive system to run out of inverter capacity unless you are starting machinery. |
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I'd just buy enough inverter the first time around and be done with it. If you need 240, then get a 240v inverter. I agree w/ CB, you're going to run out of battery WAY before you run out of inverter capacity in most household applications. If you need two working pieces of equipment to perform the function of one, you're not increasing your redundancy (2=1 rule), you're actually decreasing it, as you need both pieces of equipment in operation to be functional. If you need major power (for a house) take a look at the Xantrex XW series (designed/made/sold by Schneider/square-D btw). You can get 18kw continuous of 240v from 3 inverters tied together, and surge up to 36kw. You'll need $100K or more in batteries to ever make that useful for an extended period of time, however, but you can do it... ETA: Link |
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Quoted:
Thanks. I'll definitely save your suggestions for later when I eventually get some numbers on paper. And just to be sure I'm reading you right, the hydrogen gas that's vented from lead acid batteries isn't an issue I should worry about in a small system? I'm a little weary about that for one reason: My dad worked in communications for the state government. Probably twenty years ago they had a contractor do some work on their battery vent system. I don't have all the specific details here, but something was left plugged or routed wrong and they had a big fire a few months later. I understand this is a very unique situation and a cumulation of "mistakes" led to this disaster. Installing a hood and vent wouldn't add too much cost to the system, especially if I'm getting better value from the 105 style batteries. How many guys run lead acid without a vent? Is this generally considered okay without any consideration for gas buildup? We all know hydrogen is lighter than "air", so do we count on it making its way out of the house? I use the outback stackable inverters. Most any stacking inverter is going to be much bigger and more expensive than the little 800W type inverters, and will probably have a communications channel between the inverters to get them sychronized. Also, even the smallest system here has to have a hydrogen vent, unless all the batteries are AGM's. |
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Quoted: Also, even the smallest system here has to have a hydrogen vent, unless all the batteries are AGM's. I'm not so sure about this. While my big battery bank is in a sealed box and vented outdoors w/ a FumeOut, I also have a pair of L-16's sitting on the basement floor that powers my ham gear. These aren't outside vented, and they're about 20' from our woodburner. I think if there was a huge problem with hydrogen from smaller batteries, we'd see golf pro shops blowing up all the time from charging their golf carts. Just my $.02 tho, I might not be the best guy to take safety advice from  |
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I'm not so sure about this. While my big battery bank is in a sealed box and vented outdoors w/ a FumeOut, I also have a pair of L-16's sitting on the basement floor that powers my ham gear. These aren't outside vented, and they're about 20' from our woodburner. I think if there was a huge problem with hydrogen from smaller batteries, we'd see golf pro shops blowing up all the time from charging their golf carts. Just my $.02 tho, I might not be the best guy to take safety advice from
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Also, even the smallest system here has to have a hydrogen vent, unless all the batteries are AGM's. I'm not so sure about this. While my big battery bank is in a sealed box and vented outdoors w/ a FumeOut, I also have a pair of L-16's sitting on the basement floor that powers my ham gear. These aren't outside vented, and they're about 20' from our woodburner. I think if there was a huge problem with hydrogen from smaller batteries, we'd see golf pro shops blowing up all the time from charging their golf carts. Just my $.02 tho, I might not be the best guy to take safety advice from
I hope the batteries aren't sitting on a... gasp... concrete floor...
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Actually, they're sitting on a board. Not because it matters at all (it doesn't), but it wasn't worth arguing about w/ someone who claims that concrete is a battery killer...
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I hope the batteries aren't sitting on a... gasp... concrete floor...
Actually, they're sitting on a board. Not because it matters at all (it doesn't), but it wasn't worth arguing about w/ someone who claims that concrete is a battery killer...
Uh, yes it is...
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Thanks guys!
One more quick question- Does anyone make just the "intelligence" portion of a UPS that I can add my own batteries to? It seems that I could grow the battery bank as my funding improves over time. I've been looking on Tripp Lite's site and I cannot find anything so far. |
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Quoted:
Thanks guys! One more quick question- Does anyone make just the "intelligence" portion of a UPS that I can add my own batteries to? It seems that I could grow the battery bank as my funding improves over time. I've been looking on Tripp Lite's site and I cannot find anything so far. Not the best of ideas but you can do it. |
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Not the best of ideas but you can do it. Quoted:
Quoted:
Thanks guys! One more quick question- Does anyone make just the "intelligence" portion of a UPS that I can add my own batteries to? It seems that I could grow the battery bank as my funding improves over time. I've been looking on Tripp Lite's site and I cannot find anything so far. Not the best of ideas but you can do it. Is this because It's not recommended to mix used batteries with new ones? I understand. I'll plan on updating when replacement is due. |