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Hi all -
Trying to fit all the pieces of an off-grid system into my head. Yeah, its hurting...
Current problem is batteries. No issue figuring out required capacity for 5 days run time or anything like that. Recharging them after 5 days of run time is a problem though. Obviously the PV array isn't going to magically come up with 5X extra power to recharge them in a day or would the normal charge controller be able to handle the current to do so.
So in comes a backup generator to help out - probably starting whenever the bank dropped below 75% or so (day 2 or 3 of an outage, or day 20 of on-again, off-again sunlight that has just slowly depleted the batteries). Nice thing about generators, they can run 7x24 if rigged to fuel, like the propane tank I would be heating from. For sake of conversation, lets presume I have 4800W array, charging away at 48V, with concurrent usage (e.g. almost zero) such that the charger can actually charge at 80amps. At C/8 charging rates, that means I could fully charge 640amp hrs of battery from dead, double that capacity if they were 50% charged - using VERY simple, I know inaccurate, math. That would take about 2 days to actually happen via the PV array, since it would only be charging about 4 hours a day.
Question 1: Do the batteries care, long term, that they would get a charge current for 4 hours, then a small drain, then another charge current vs. being fully charged all at once? I know lead-acid doesn't suffer from any form of memory (beyond that associated with damage from deep discharges).
Question 2: Do the batteries care if they are charged at C/16 or C/32 instead of C/8? e.g. Instead of using a 4800W array, could I use a 1200W generator and just run it 7x24, effectively providing a shorter overall charging period but at a lower rate?
Question 3: How do most charge controllers feel about being starved for charging power? I'm guessing they would consider that normal business since 20 hours/day they don't have it anyhow.
Question 4: My current inverter choice has a charge controller powered by either a generator and/or grid. Is that charge effort going to conflict with the normal PV supplied charge controller when I power up the generator?
Thanks in advance.
Trying to fit all the pieces of an off-grid system into my head. Yeah, its hurting...
Current problem is batteries. No issue figuring out required capacity for 5 days run time or anything like that. Recharging them after 5 days of run time is a problem though. Obviously the PV array isn't going to magically come up with 5X extra power to recharge them in a day or would the normal charge controller be able to handle the current to do so.
So in comes a backup generator to help out - probably starting whenever the bank dropped below 75% or so (day 2 or 3 of an outage, or day 20 of on-again, off-again sunlight that has just slowly depleted the batteries). Nice thing about generators, they can run 7x24 if rigged to fuel, like the propane tank I would be heating from. For sake of conversation, lets presume I have 4800W array, charging away at 48V, with concurrent usage (e.g. almost zero) such that the charger can actually charge at 80amps. At C/8 charging rates, that means I could fully charge 640amp hrs of battery from dead, double that capacity if they were 50% charged - using VERY simple, I know inaccurate, math. That would take about 2 days to actually happen via the PV array, since it would only be charging about 4 hours a day.
Question 1: Do the batteries care, long term, that they would get a charge current for 4 hours, then a small drain, then another charge current vs. being fully charged all at once? I know lead-acid doesn't suffer from any form of memory (beyond that associated with damage from deep discharges).
Question 2: Do the batteries care if they are charged at C/16 or C/32 instead of C/8? e.g. Instead of using a 4800W array, could I use a 1200W generator and just run it 7x24, effectively providing a shorter overall charging period but at a lower rate?
Question 3: How do most charge controllers feel about being starved for charging power? I'm guessing they would consider that normal business since 20 hours/day they don't have it anyhow.
Question 4: My current inverter choice has a charge controller powered by either a generator and/or grid. Is that charge effort going to conflict with the normal PV supplied charge controller when I power up the generator?
Thanks in advance.
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