Help with existing sytem to battery backup

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Help with existing sytem to battery backup

Postby Thorsdad on Fri Feb 10, 2012 11:44 pm

We have a 10kw grid tied solar sytem , what is the best way to add battery back up and what perameters do I need to establish for my electrician . I will not be insulted if you dummy this down as far as possible Thank You in advance Jay .
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Re: Help with existing sytem to battery backup

Postby vtmaps on Sat Feb 11, 2012 2:51 am

Cannot answer your question until we know why you want the battery backup. What loads do you expect to power on battery and for how long? How often is your grid down? If you just want to keep a few lights on without running your generator, that is one thing. If you expect to keep the air conditioning running during a 3 day power outage, that is another thing. Perhaps your grid power is flaky and you just want a reliable circuit for your computer. In many cases running a generator will be the most cost effective and reliable option. Batteries and their associated electronics are expensive and they are not something that you can just set and forget.
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Re: Help with existing sytem to battery backup

Postby Thorsdad on Sat Feb 11, 2012 6:44 pm

We would like to have power to a refridgerater , TV , a few plug in's ,and some exterior lights . Our generater panel has a 50 amp breaker . We are thinking at least 5 day's without power , and if longer it would be conserving battery useage highly important . We also understand this will be an extra cost some people might not justify but hopefully we can . If you knew how many times my wife has had my sqeege off the solar panels than you'll understand battiery maintinance can be easily added to the list . Thank you for any help . Jay and Cheryl
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Re: Help with existing sytem to battery backup

Postby vtmaps on Sun Feb 12, 2012 4:04 am

The first step in designing a battery backup system is to exactly define your loads. Get a kill-a-watt meter (about $25) and find out how many kwHours per day you will need. The next step is to specify how many days autonomy you want... in your case 5 days. Then you can decide what size and type of battery bank you will need. I think that 5 days is too much autonomy. That makes sense for unattended remote systems. You should probably aim for a day or two. If the power has not been restored, run your generator for a couple of hours. Since you are on the grid, your battery will be spending most of its life fully charged, with just an occasional deep discharge. Perhaps you should look into an AGM type battery. They require no maintenance and they can handle high charge and discharge rates. The high charge rate is important if you want to charge it with the least amount of generator run time.
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Re: Help with existing sytem to battery backup

Postby blackswan555 on Sun Feb 12, 2012 4:32 am

You could use one of these http://outbackpower.com/products/flexpo ... xpowerone/ and a set of batteries, The mains would keep it at float until you had power outage`s then it would take over, mains returning or your gen would charge after, But reading between the lines I presume you would like to use your panels in the equation ? Then it becomes difficult due to the way the panels are wired, In you system they will be wired in series to get a VMP voltage of around 400 volts, If you want to charge a set of 24v batteries ( using an OB FM60/80 charge controller) they would be wired with a VMP of around 50 volts,

Tim
My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.
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Re: Help with existing sytem to battery backup

Postby Thorsdad on Mon Feb 13, 2012 9:34 am

Yes Tim the goal would be to have the solar panels be able to feed the battery's . Looking at the website Ithought this was easy to do but now not so sure maybe a bad idea . Jay
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My RE system: 44-Solar World sw245 Mono 245watt Modules , 2- SMA Model#SB5000US Grid Tie 240volt Inverters , and 2-Crouse-Hinds #CCBS04-F15-DS30 Combo Disconnect/combiner Boxes , plus a manual generater switch

Re: Help with existing sytem to battery backup

Postby jhillock on Sun Apr 22, 2012 8:29 pm

I have developed a dc transfer switch that will switch the solar panels to the grid tied inverter to the off grid inverter and used high voltage charge controllers (wont mention brand) not Outback to accomplish what you trying to do. I had a very difficult install that had a feed in tarrif (34cents kwh) gen , outback inverters, and batteries. I wanted to use the the highest eff grid tied inverter around and charge the batteries off the grid 10 kwh and sell the the 34cent solar power, i plan to install a gen transfer switch between the gen , inverter,and load( house) when there is a power failure the batteries come on line first until the mate call for gen then the transfer switch sends the gen to the house and charges the batteries at the same time I can send you a one line if you want send me your email .
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