Generator options

requiredwhen

Hello,

We're currently living in an off-grid cabin but are planning to build an off-grid house with a larger solar power system. We won't have the house for a year or two and our current battery bank is getting long in the tooth. 

Our current system is 48V with a 300 aHR battery bank. The new house will have a 550 aHR battery bank and also be 48V (Original post had wrong aHR amounts).

I'm anticipating needing a backup generator this winter to top up the batteries and it seems like we have a few options:

Option A - Use a construction 7500watt gas generator that we already own and add 2 IOTA 24V 25A or 40A chargers in series. The 2 chargers will cost about $800-1000 (Canadian Dollars). My rough estimate that they will take 2-3hrs to top up the batteries from 50% and the generator will use a lot of fuel. We'll use the system 60 times this winter I guess.

Once we have the new house, maybe I could re-use these chargers and run them off a small efficient diesel generator. Or sell the charges used.

Option B - Buy a new generator designed of off grid now. The supplier who gave us a quote for the new house system recommended a Winco 8KW system. They cost about $8,000 Canadian dollars. We'll need this anyway, so maybe just get it now.

Any advice or other options would be appreciated. Thanks!

wellbuilt

600 hrs a season seams like a lot .
   My place uses a 430 ah battery and I use 10/15% over 24hours in winter with the solar turned off .
  I just run a 2800watt generator a hour or so a day and charge to full every 3/4 days 
  I run one frig/freezer and one freezer , tv  radio , cell booster  , lites , well pump 800/1000 watt 
  And really any thing I need . 

  4000ah plus battery seams like a lot .
 My place is 2800sf living space   3 car garage and 26x32 shop . Propane water heater,  stove , radiant heat floor 
  But I heat with wood .

wellbuilt

There is a lot to be said for using Chargers and genarator to charge battery’s .
but I would use the chargers off the generator you have and  buy a unit that works with 80% load 
 I think you could run off of 5500 watt generator  your inverter and battery’s will power your loads any way . 

  I think a absorb charge will take a long time you may want to use a small unit to absorb /eq 

mike95490

Whoa !  That's a huge battery bank and you will need 440A DC to properly charge FLA batteries.   Are you really sure a 4400ah bank is needed ?

Generator & charger.   Most larger 48V inverters are able to use a 240VAC generator to charge the batteries.  Generally they are high quality, good PF of .9 and in the 100A range .  Have you considered that option ?    100A @ 56V = 5,600watts and you want to allow for 50-75% surplus capacity in the generator since battery charging at high power for hours, is VERY demanding on a genset and alternator cooling.

  Unless Iota has told you specifically you can series a pair of 24V supplies, I would not try it, unless I was able to fully verify the outputs are totally isolated to a couple hundred volts.

Ralph Day

Really think about battery size.  While the "autonomy for x number of days" is great in theory, you have to be able to recharge the beast.  I've found it's better to have smaller battery size, more pv and a reliable generator (see mike95490 above).  

requiredwhen

Sorry, I just added up the aHR of each battery, forgetting that they are in series  

I'll fix the original post for new readers. But the current system is 300 aHR and the new system will be 550.