Posted: 8/20/2009 7:46:10 AM EDT
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I've seen threads here in the past on building battery backup systems for power outages. Can someone give me a idiots guide on the best deep cycle battery to use and how to wire everything up? I understand very little about power/electricity.
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I recently converted a houseboat to all electric in addition to helping with a solar system installation, and have learned a ton. In short, the most important thing to know is what your power requirements are (in watts, amps, whatever). Everything else comes from that.
A good inverter/charger is easily found. Options include grid-tied or free-standing. The more batteries you have, the more juice you have. I'm currently using 6V, 8V and 12V batteries, and ultimately it doesn't matter - it's the capacity at the total voltage that counts, and (long story short) it really comes down to # and weight of batteries. I found the biggest issue with voltage per battery is the price and weight of your particular requirements. On my electric boat, for example, it made sense to use 8V batteries for my main drive motor, 12V batteries for my refrigerators and house bank and 6V batteries for the other appliances (based on weight and size of where they needed to go). Basically, a thousand pounds of 6V batteries produce the same power (amp hours at a given voltage) as a thousand pounds of 12V batteries. Here are some of my favorite intro links on the subject: The mother-of-all battery summaries - http://www.windsun.com/Batteries/Battery_FAQ.htm A good overview of how to plan, wire and use your battery bank, charger/inverter, etc: http://www.ccis.com/home/mnemeth/12volt/12volt.htm (be sure to check out the link for "part 2" at the bottom) I've had good luck with Xantrex (formerly Trace) inverters, with mixed results from Sunnyboy and others. A combination charger/inverter is ideal, as it keeps your batteries charged and then automatically switches to them when needed. The system I'm putting together right now uses a pile of 6V batteries run in three 12V banks (combo of parallel and serial). Output is up to 9kW AC. The batteries stay float charged on the house 110 in normal circumstances. I leave a 30A outlet hooked up to feed power into the house in the event of an outage (see an electrician for code requirements, etc. I'm not going to tell you how mine works  ). I have some honda ultra-quiet generators that can charge the battery bank during the day as needed. The generators will be stored indoors overnight and the electric system produces no noise overnight when you want to stay discrete. So far it's proven to be a nice combination, and is fairly portable if needed.
I'm interested to hear about experiences from those that really know what they're talking about. I'm just a weekend amatuer.... |
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I'm kind of in the same boat. (learning a lot as I go.)
However, with the help of Paul (Site Staff) and my friend Mike (GE Electrician) I am building a battery backup system. Paul provided the Batteries(AR15.Com thread link) The plan provided by my friend is thus: (4) UPS 135 amp 12 volt batteries into two(2) banks of 2. DC Charge controller from my house current with built in desulferizer with an input switch. The input switch will allow me to switch from DC charging to Solar charging. I can run my Ham radio set up, Lap top, and police scanner from the first bank, all as 12 volt. If there is a temporary power outage, I can switch to all (4) batts with an output switch to an inverter and run my fridge and freezer for a while. Couple that with a couple of solar panels and I should be okay. All off the grid. ETA: Like Paul, I will post a thread with pics when the project is done. |
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Tag for information, would it be better to use 6 volt batteries or 12 volt batteries The voltage of the batteries doesn't matter. What matters is the type of battery. If you are going to cycle your bank like I do daily then you want true deep cycle batteries. Not the deep cycle marine type batteries which are a hybrid between a car battery and a true deep cycle battery. Once you decide on the voltage of the bank, mine is 48v because my house inverter is 48v, then you decide on the capacity in amp hours the bank is to have. I prefer to only have one series string. Others have no problem with paralleling multiple strings of smaller batteries to get to their desired capacity. The batteries I used for my bank are Surrette 6cs17ps batteries. A 6v or 12v battery is nothing more than a series string of 2v cells together in a case. My bank consists of 8 of the 6v batteries tied in series. It is 546 amp/hrs at the 20 hour rate. I have 24 cells to maintain with the bank. If i were to used smaller batteries like golf cart batteries to get similar capacity I would at least need 16 which would still be less capacity wise but now I would also have 48 cells to maintain. The difference between true deep cycle and the others will be a much longer battery life. Mine are rated for 5000 20% depth of discharge cycles. Since I usually stay around 15% I could get about 20 years of life out of them. But then again, they are not cheap. |
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The best batteries are free batteries!
Seriously you can spend $400 on one good battery or more. Glass Absorbed Mat batteries are very expensive and avoid lots of problems of the wet cell or lead/acid battery. You're paying for amp hours and the more, the better. Higher voltages are very important if you're going to run the DC some distance beyond 5-10 feet. If you're putting a solar array up on your roof go for 300 volt circuits. I mount my inverter to a panel on front of my battery array so 12 VDC was fine for me. I gave away the last 12 batteries just today. 
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The voltage of the batteries doesn't matter. What matters is the type of battery. If you are going to cycle your bank like I do daily then you want true deep cycle batteries. Not the deep cycle marine type batteries which are a hybrid between a car battery and a true deep cycle battery. True dat! 6 volt golf cart batteries usually deliver the highest number of discharge/recharge cycles for the cost. They're built to withstand heavy, daily discharges in a golf cart, and will outlast any trolling motor or "marine/RV" battery, by a huge margin. Most golf cart shops sell 'em - The GC2 size is very popular, and typically sells for little or no more than your average trolling motor battery. Look for the Trojan brand - American-made and top-notch quality. 
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<Snip> I gave away the last 12 batteries just today. http://i6.photobucket.com/albums/y215/paul1960/Amateur%20Radio/UPS/Batteries01.jpg Damn my procrastination! I was going to IM you today to see if you had any you would be willing to part with. I thought a road trip down South would be a nice diversion. 
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