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Need HELP! 9.1kW solar system charging batteries with my generator.

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tdry253:
I have a solar array with battery back up. I want to know if I add a Generac generator 15kW to my system in the event the sun doesn't shine for hours on end how long will it take for this generator to recharge my batteries to 90%

My system components:

32 - 285watt Solar world mono panels -9.12kW system
01 - four star outback Radian GS8048a 8000
01 - Four star classic 150 double PV center includes MidNite Solar Classic 150 MPPT Charge Controller
01 - Crown battery bank (8 total batteries) AGM 390ah x 48volts = 18,720ah. Controller is set to never allow batteries less than 50% or  9,360ah.

I want to add into the mix a 15kW Generac generator for emergency situations  if the sun doesn't shine for days,  I want to  power on my generator for a short period of time and recharge my batteries. I do not know how to calculate what the run time of the generator will be to charge my bank. I have figured that my solar array can charge the batteries in 1hr 10mis with full sun.

chrisdfw:
the generator can charge the batteries faster than the solar array if you have a charger that can put out the current necessary, a 15kw generator can put out more than a 9 kw solar array.

You will destroy your batteries very shortly either way,     390 ah of battery at 48 volts is very small relative to the size of your solar array. The generator can probably charge the batteries in 45 minutes or less from 50% discharged. This is not good for the batteries

Even your solar array would be charging at a grossly fast rate. you are putting almost 40% of the capacity in the battery per hour, that is too fast for long life. you need either a larger bank or second string of batteries. Whoever designed the system did you a big disservice in undersizing the battery bank. I hope there is note to the story here and the system is not really set up to charge the batteries that fast. 

I see that your inverters are grid interactive so I hope that the charge controllers and inverter are set up to send power to the grid and not into your batteries at the rate the panels are capable of putting out. You really want to charge the batteries at a little lower rate if you want them to last. Without knowing more about how it is set up I can't say.


But the short answer to your question is that the generator can change the batteries from 50% in under an hour with the right charger. If all you are wanting the generator for is to charge the batteries, then a smaller generator would be more than sufficient, something in the 5kw range would be more than adequate.

Carl:
I use a small solar setup BUT To hammer your batteries at a C1 rate will most certainly do damage to the batteries.
I don't believe that your solar panels charge at anywhere near that rate as it would turn your batteries to worthless lumps as batteries are just not designed to take current in such a manner. You should check with the company who sold you the system to discover what they suggest as no wet cells will take a charge at C1 and not suffer as chemical storage just does not work that way.

Your charge controller is rated for 80 amps maximum for 48 volt system...or about 4,000 watts and that should be at least 30% over expected usage.You need at least a 3 stage charger to do your battery bank properly and I would say(but what do I know) a 48 volt at 50 amp charger would be max for that and would actually take 4 to 6 hours or more to bring your batteries to 90% of an unknown starting level(maybe 50%)Also you just as well run on generator power as your inverters are grid tied and will not power anything when the grid is down...though this does explain some of the odd math on your setup.

I suggest you ask an installer,better yet ,pay one to set you up correctly as the math on your system just appears out of balance.

Good luck with your project.This is NOT the kind of project you ask just anyone's advise on.

tdry253:
I greatly appreciate all the help! A lot of this is new to me and by no means do I know anything about electricity. So far I have purchased all the products, but have not had it installed yet. I've got just over 30k in all the equipment.

I do have a hybrid inverter and two MMPT charge controllers that I've purchased. The charge controllers will manage the battery storage and I'll only ever use the batteries in the event of a full power loss. My goal with the generator was to give me the ability to  run a separate panel I've already had wired in and charge the batteries in the rare even the sun doesn't shine to recharge them. My goal would be to run off the batteries as much as possible and use the generator in rare situations in order to conserve propane.

I have all components of the system purchased including racking for my ground mount. My next step was to hire a good installer, but as you've pointed out I may need to look into the system further to make sure it's well balanced. 

cidyl:

--- Quote from: tdry253 on August 04, 2016, 10:03:52 AM ---I have a solar array with battery back up. I want to know if I add a Generac generator 15kW to my system in the event the sun doesn't shine for hours on end how long will it take for this generator to recharge my batteries to 90%

My system components:

32 - 285watt Solar world mono panels -9.12kW system
01 - four star outback Radian GS8048a 8000
01 - Four star classic 150 double PV center includes MidNite Solar Classic 150 MPPT Charge Controller
01 - Crown battery bank (8 total batteries) AGM 390ah x 48volts = 18,720ah. Controller is set to never allow batteries less than 50% or  9,360ah.

I want to add into the mix a 15kW Generac generator for emergency situations  if the sun doesn't shine for days,  I want to  power on my generator for a short period of time and recharge my batteries. I do not know how to calculate what the run time of the generator will be to charge my bank. I have figured that my solar array can charge the batteries in 1hr 10mis with full sun.

--- End quote ---

Nice equipment, wish I'd have gone with 48v in hindsight.  You got twice as much system for the same price as I paid not that long ago, I think I hate you :)

You'll be attaching the generator to the generator AC 'in' on the inverter/charger right?  If so just adjust the Radian charging amps to be what Crown recommends (http://cdn2.hubspot.net/hubfs/435823/Brochures/SafetyFirst-AGM-sec.pdf?t=1470065130834), 10% of C/20.  For 8 6v batteries in series, that's about 39A.  To  bulk charge them from 1/2 drained at the recommended amperage it'd be about 5 hours.

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