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New and looking to upgrade existing 48V Off Grid system.

kah68

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Jul 4, 2022
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So I bought an off grid lake property, cottage is wired for 120V AC and is run by a small solar array ( not sure of the config but 2x 150w and 2x 90w ). The battery bank is 8 6v FLA's that are over 10 years old and won't hold charge. There is Pro Star PS 30 Charge controller, Iota DLS 55/IQ4 charger, and a pro watt 1500 inverter, Iota ITS 30R transfer switch and a distribution box. For back up there's a Honda Eu 3000is.

I would like to keep with the 48 volt system, and my daily requirements add up to roughly 4.4kw. I have purchased 4 sok 12V 206 Ah batteries for my bank. I'm thinking I'll need a new MPPT and I'd like a larger inverter as well. I was checking out the Victron Multi Plus 2 48/3000/35 as an all in one approach to the upgrade.

I'm pretty sure I'd need to upgrade my array as well but would like to get the system up and running first before I do that.

This system would be in service approximately 8 months of the year with winter use largely by generator only so batts would come home to store.

I am totally new and looking for input. Am I missing info? is this practical? Should I seek professional advice?
 
Make sure you disconnect the PV before you pull the batteries to take home. SCC'S don't like voltage with no dump source.
 
Basically, I'd say just throw everything away and start over. Recycle the batteries though. Sticking with 48V is a good choice, though I'd say you'd be just fine with a 24V system if you don't have to power a well-pump. At my own cabin, my daily needs run in the 3.5-4.0kWh range, so your estimated numbers are looking a lot like my numbers.

Those 206Ah batteries will like charging ~ 1/4th C so that would be [(206Ah/4) X 50Vcharging]/85% = 3030W of panels. Those would be handled by a 60A charge controller. 3000W for a 48V inverter is rather small. I think you'd do better with a unit in at least the 4000-5000W range. Take a look at the Conext 4048. It's output is 4000W and can make both 120VAC and split-phase 240VAC. It also has a built-in generator charging circuit. You just hard-wire your generator into the ACin terminals, and you can charge your battery bank directly from generator power.

Shop for grid-tie panels on Craigslist. Don't buy smaller 12V panels for automotive use. You'll get far more W/$ with grid-ties. With a 150-200V MPPT controller, you could wire three or four grid-ties in series to reduce resistance loses.
 
Basically, I'd say just throw everything away and start over. Recycle the batteries though. Sticking with 48V is a good choice, though I'd say you'd be just fine with a 24V system if you don't have to power a well-pump. At my own cabin, my daily needs run in the 3.5-4.0kWh range, so your estimated numbers are looking a lot like my numbers.

Those 206Ah batteries will like charging ~ 1/4th C so that would be [(206Ah/4) X 50Vcharging]/85% = 3030W of panels. Those would be handled by a 60A charge controller. 3000W for a 48V inverter is rather small. I think you'd do better with a unit in at least the 4000-5000W range. Take a look at the Conext 4048. It's output is 4000W and can make both 120VAC and split-phase 240VAC. It also has a built-in generator charging circuit. You just hard-wire your generator into the ACin terminals, and you can charge your battery bank directly from generator power.

Shop for grid-tie panels on Craigslist. Don't buy smaller 12V panels for automotive use. You'll get far more W/$ with grid-ties. With a 150-200V MPPT controller, you could wire three or four grid-ties in series to reduce resistance loses.
Sorry for the late reply but thanks for the info, Victron also makes a 5000VA (4000ish W) 48V multi plus 2 as well, but I'll look at the specs on Conext as well.
 
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