XW battery methodology

Hello, my first post, although I've been lurking for a while.
I am close to finalizing a Zantrex XW with battery back up system. Here is a question I'm not clear on about the XW.
I believe that the XW inverter and charge controller will keep the batteries topped off and ready for an outage, but will not use them during hours of darkness unless the grid goes down. Is that correct?
It is important because I don't think I need to buy batteries that are as expensive (good for continuous deep cycles) if the XW only uses them when there is a grid outage.
Thanks for any info you have.
E
I am close to finalizing a Zantrex XW with battery back up system. Here is a question I'm not clear on about the XW.
I believe that the XW inverter and charge controller will keep the batteries topped off and ready for an outage, but will not use them during hours of darkness unless the grid goes down. Is that correct?
It is important because I don't think I need to buy batteries that are as expensive (good for continuous deep cycles) if the XW only uses them when there is a grid outage.
Thanks for any info you have.
E
Comments
Mostly, yes. You could get by with a small string of batteries (go 48V, that's 4 ea, 12V deep cycle batteries. 100AH @ 48V, 50% discharge gives 2.4KWh) You will only use them a couple times a year, when grid is down, but you will NOT have much capacity. Just enough to run a couple lights, radio and fridge for couple hours.
This is just a very rough summary.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
What Mike said, but what you’re talking about will work and 100 amp battery is about the smallest I would go, the inverter can really hit the batteries hard starting a load and if you go with a smaller batteries the inverter might shut down due to low voltage.
The big advantage with this setup is you can sell back to the grid if you’re not using the power and if the power is out and it's sunny you can use all the power your panels can generate. In a situation like that you might want to shut off the fridge overnight and turn it on when the sun is out again.
The other advantage is with a smaller battery bank you will have less standby losses with the battery bank.
From another thread, Solar Guppy recommended a minimum of 400 AH @ 48 volts per inverter minimum: