Help designing Back solar system

emoralesemorales Posts: 2Registered Users
Hey New to the forum,
I live in Puerto Rico and going on 90+ days without power after Cat 5 Hurracaine so decided to invest in a solar system to use as a back up and when power returns use to power certain things in the house.

So here's my soon to be system:
(8) Duracell Ultra High Capacity 6V Golf Cart Battery (230 A/H) wired for @48V (purchased)
(3) 260W Allmax Plus Solar Panels (purchased)
(1) 60A MPPT for 48V and 150V max OPV (pending)
(1) Reliable 1500W @48VDC to @120VAC true sine wave inverter (pending)

Well the goal is to later on keep expanding to hopefully cut the ties to energy company. Any suggestions are more than welcomed.

My questions are:
What can I use to recharge battery bank on 48v (can't seem to find one without it being an inverter/charger and the cheappest one I found takes me out of budget.
Is js it better to downgrade to 24vbor 12v in order to have a charger accessible? But was told batteries in series/parallel shortens life span of batts
Can I leave batterie bank without recharging for 2 days of cloudy days without putting load on them while discharged?
Has anyone use/recommend chinnese components?
Any input/advice is more than welcomed

Comments

  • EstragonEstragon Posts: 2,049Registered Users ✭✭✭✭
    We need to know what you intend to run with the system. 24v could work with 2 strings in parallel, but will be costly to expand and be limited in the size of loads it can support.

    As for leaving batteries discharged, it depends on 3 factors; how deeply discharged, how long they're left, and temperature. Warm/hot batteries at a low state of charge will sulfate much more quickly that cool ones at a higher state of charge, for example.

    I have nothing against Chinese products in general, but solar gear seems to be a bit of a crap shoot. Just because it says true sine wave, for example, doesn't mean it is. It may also lack (genuine) ETL safety certification. Personally, I'd stick to the brands sold by our hosts, but some folks seem to do okay rolling the dice. The Iota 48v charger at $285 is a bit small (13a), but you could add a second one when funds available. As a stop-gap, they could be charged in pairs with a 12v automotive charger.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • emoralesemorales Posts: 2Registered Users
    > @Estragon said:
    > We need to know what you intend to run with the system. 24v could work with 2 strings in parallel, but will be costly to expand and be limited in the size of loads it can support.
    >
    > As for leaving batteries discharged, it depends on 3 factors; how deeply discharged, how long they're left, and temperature. Warm/hot batteries at a low state of charge will sulfate much more quickly that cool ones at a higher state of charge, for example.
    >
    > I have nothing against Chinese products in general, but solar gear seems to be a bit of a crap shoot. Just because it says true sine wave, for example, doesn't mean it is. It may also lack (genuine) ETL safety certification. Personally, I'd stick to the brands sold by our hosts, but some folks seem to do okay rolling the dice. The Iota 48v charger at $285 is a bit small (13a), but you could add a second one when funds available. As a stop-gap, they could be charged in pairs with a 12v automotive charger.

    My plan is to run a couple of 90w/h fans some led lights and a fridge. Discharge @50%
  • EstragonEstragon Posts: 2,049Registered Users ✭✭✭✭
    The fridge would likely run okay on a 24v system with short heavy cables to the inverter, but 48v would handle the start surge better and would be more expandable.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • dennis461dennis461 Posts: 99Registered Users ✭✭
    Is the grid in your location 120VAC or 220VAC?  48VDC battery chargers are available for under $200 US if you have 120VAC grid.
    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
  • MichaelKMichaelK Posts: 74Registered Users ✭✭
    If you have 8 230ah batteries wired for 48V, then what you've got 230Ah X 48V =11040 AV total, or 11040 watthours of total power.  Assuming you never want to drop lower than 50% charge, you get to use 5500 watthours of power.  How you use that 5.5kwh depends on the automony your require.  Let's say you can tolerate 3 days of cloudy, no sun weather before charging your batteries.  You could use about 1.8kwh total per day, for three days, before you reach the 50% limit.  You'll need to do the math on your end to figure out what you can run on 1.8kwh.  With a little frig, an hour of  TV, and lights, you might stay in a 1.8kwh budget.  A big frig, and you're limited to maybe it and 1 lightbulb.  You'll have to tell us what all your loads are likely to be.

    Your three 260W panels are not enough to keep that kind of system charged.  Assuming you've got 230Ah batteries at 48V the math is
    (230/8) x 59.3Vcharging X 1.25 panel derating = 2130watts.  That works out to be eight of your 260watt panels.

    At a minimum acceptable charge level the math works out to be...
    (230/12) X 59.3V charging X 1.25 panel derating = 1420watts.  That's 6 of your panels. (math would 5, but it's prime number)

    This Schneider inverter would do you well.  It's a big, high capacity inverter.  It's pricy, but it has a built-in-charger, so that's one other thing you don't have to pay extra for to charge the batteries with the generator.  The big plus with it is that it's both 120/240VAC, and if it's capacity eventually limits you, you can parallel it to a second unit.
    https://ressupply.com/inverters/schneider-electric-conext-sw4048-120240-invertercharger

    15 Renogy 300w panels,  Midnight 200 CC, 8 Trojan L16 batteries, Schneider XW6848 NA inverter, AC-Delco 6000w gen.
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