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I found out now it...
 
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I found out now it takes a lot of battery to go off-grid at night .

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(@dickson)
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Sean  live chat say  he only  run off-grid  for one hour at night  with  battery .    I  have over  40 kwh   lithium ion  battery  and  still  need to  recharge at night  .   Battery  cost more than    any   inverter  or solar panel   and the  copper wires  needed  makes  complete  off-grid  too expensive  for me .   


   
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(@thebutcher)
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I'm guessing you have a fair amount resistive heating, both room and water, and several people in the residence?


   
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(@dickson)
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I  can not run a heat pump on battery  but  run  a  large  1 hp  240vac swamp cooler  on  continously  in the summer  and refrigerator and freezer .   I  have to rechage  one third  of the  battery at the same time   I am using  the  other  two third of the baatery  to run the inverter off-grid at night .     The problem  is I  only have  6000 kw of  solar panel  to charge   two third  of the battery  during the  day   .       The battery  is only  usable  from 62 volt  to  46 volt  .       I  will need another  20000kwh  of battery  or    60000 kw of solar  panel  which is  impossible to hide in the backyard  with 7  palm trees  blocking the sun .       One  man a few  miles from  me  hide  60000 kw of solar  panel  in his backyard  and use  a  12kw inverter  with built-in  MPPT solar controller  to run his heat pump  12 hours a day  using only  solar panel  and  4 AGM  battery  .       


   
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(@robertm)
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I have 1/10 of the battery storage that you have. It is 2.4 kwh of LiFePO4 batteries and about 2.4 kwh of flooded batteries which cannot discharge as deeply. There is a new experimental battery technology in development that uses a molecule of carbon, hydrogen and nitrogen that can change shape and become energy-rich when exposed to sunlight. It can be stored, as a liquid, for years, and can release stored energy on demand, in the form of heat.

https://lithium-news.com/a-breakthrough-in-solar-energy-storage/

 


   
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(@notmario)
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I run off grid 24/7 with 10KWH. No AC needed here and heat is powered by diesel.
Most consumption is idle draw from misc devices and freezers.
The only difficult component to deal with is the electric drier.

Thankfully the GS is very reliable. 3000 hours already and nothing to complain about.

FYI, you can buy ~2.5KWH of LiFePO4 for ~350$. (everything already done for you - just hook up) It's not really that expensive when appropriately sized...


   
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(@dickson)
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20000kwh  of battery  or    60000 kw of solar  panel 

Suppose   to be  20000 watt hour of battery    or  60000 watt of solar panel  .      Thank you .   


   
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(@dickson)
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FYI, you can buy ~2.5KWH of LiFePO4 for ~350$. (everything already done for you - just hook up) It's not really that expensive when appropriately sized.

My  5  MSB 60A  solar charge controller is set at  66volt  so LiFePO4  will not match  .    Used  lithium ion  BMW  car battery is 300 dollars each  include shipping tor 2.0KWH  which is what I am using .   If I  get  10 more then I  can be off-grid  at  night   but the  Delta fan sound   like a jet  engine in my back yard  so maybe  still  not be completly   off-grid  because  of the noise .   


   
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(@dickson)
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I have 1/10 of the battery storage that you have. It is 2.4 kwh of LiFePO4 batteries and about 2.4 kwh of flooded batteries 

I  started 3 years  ago with 4 kwh  AGM  battery  that is till being use every day .     I  use a special  AGM  charger  to keep it like new   .     I also  had  LiFePO4 batteries  but in the begining  I  let it discharge  too low  and  is  damage .     At the  time I know  nothing  about  charging  battery  .    


   
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(@inphase)
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It can be done but it can't be done with an on-grid lifestyle. You have to change how you live in most aspects. So do laundry during the day. Run the air conditioner hard when the sun is shining and get the house chilled and coast through the night. Put a timer on the ghost loads so they turn off while you're asleep. The electric water heater shouldn't be allowed to cycle after dark either. Etc.


   
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(@dickson)
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It can be done but it can't be done with an on-grid lifestyle. You have to change how you live in most aspects.   

I  can  live off-grid  on solar and battery  .    My  wife get mad  when the  house is  hot  and  do not care how much  the  heat pump  cost  in electric usage .      It is  over  100   degree  every  day now   and next month  it will be over  100  degree  all night  .    I  uae to  grow  over 100 pounds of  squash  in my backyard  but  now nothing   grow but bermuda  grass  and  russian  giant sunflowers  .   
 


   
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dochubert
(@dochubert)
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On 5/29/2022 at 6:47 AM, InPhase said:

It can be done but it can't be done with an on-grid lifestyle.

Words to live by, ...literally!

We have a very large battery bank (lifepo4) and more than enough solar to keep it charged and run the house 24/7 from late March to late October (usually!)  The exceptions are the electric dryer and the central AC, both of which run when needed only on grid power.  My 15kw powerjack can't run either one reliably so they are only grid connected. (The powerjack is really just a decent 6kw, ya know) My wife hangs the laundry out in good weather (most all the time march to october) and the central AC unit is typically only needed a couple of weeks per summer.  The oven is used in the daytime and she tries to limit its use to sunny days.  The microwave is not enough to worry about.  Two freezers and a large refrigerator, plus a well pump are the normal larger loads.

When we have consecutive rainy days (like right now!) I have to keep an eye on things but there is usually enough solar to get by on without switching to grid.  If my wife really wants to use the oven on a cloudy day I can always switch it to grid for the time she's using it.

The water heater has its own battery bank (also lifepo4), solar to charge it, and an 8kw (realistically a 3kw) powerjack that only runs the water heater in powersave mode.  The 8kw has a timer to limit it's running to daytime hours, a protection circuit to allow it to run only when the batteries are in proper voltage range, and it has been running winter and summer non-stop for nearly 2 years, providing hot water for my wife and I.

Between October and March if there's enough sun I run the house on the powerjack during the day and switch to grid overnight.  Sadly I have to use grid power a lot in december (shortest days).  I could run on batteries more than I do in winter but I'm trying to preserve my battery life by going easy on them.  Someday soon there might be no grid to switch to, then we're all on our own, like it or not.


   
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(@robertm)
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On 5/30/2022 at 8:34 PM, dochubert said:

Words to live by, ...literally!

We have a very large battery bank (lifepo4) and more than enough solar to keep it charged and run the house 24/7 from late March to late October (usually!)  The exceptions are the electric dryer and the central AC, both of which run when needed only on grid power.  My 15kw powerjack can't run either one reliably so they are only grid connected. (The powerjack is really just a decent 6kw, ya know) My wife hangs the laundry out in good weather (most all the time march to october) and the central AC unit is typically only needed a couple of weeks per summer.  The oven is used in the daytime and she tries to limit its use to sunny days.  The microwave is not enough to worry about.  Two freezers and a large refrigerator, plus a well pump are the normal larger loads.

When we have consecutive rainy days (like right now!) I have to keep an eye on things but there is usually enough solar to get by on without switching to grid.  If my wife really wants to use the oven on a cloudy day I can always switch it to grid for the time she's using it.

The water heater has its own battery bank (also lifepo4), solar to charge it, and an 8kw (realistically a 3kw) powerjack that only runs the water heater in powersave mode.  The 8kw has a timer to limit it's running to daytime hours, a protection circuit to allow it to run only when the batteries are in proper voltage range, and it has been running winter and summer non-stop for nearly 2 years, providing hot water for my wife and I.

Between October and March if there's enough sun I run the house on the powerjack during the day and switch to grid overnight.  Sadly I have to use grid power a lot in december (shortest days).  I could run on batteries more than I do in winter but I'm trying to preserve my battery life by going easy on them.  Someday soon there might be no grid to switch to, then we're all on our own, like it or not.

How deeply do you discharge your LiFePO4 batteries? As low as 20%? 


   
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(@dickson)
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Topic starter  

How deeply do you discharge your LiFePO4 batteries? As low as 20%?
According  this youtube  he say  do not discharge  to 2.5 volts  but  discharge to 3.1 volts .    LiFePO4 batteries  has a  flat  discharge curve  and  2.5 volt  will damage the battery .   

Busting the 20%-80% SOC myth for LiFePO4 batteries.           

Jun 2, 2022       


   
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(@thebutcher)
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I saw that clip from Andy.  The only thing he busts there is the method less experienced (?) people try to do 80/20 cycling with, voltage monitoring.  80/20 cycling absolutely improves lifepo4 cycle count and he does attempt to disprove that either.  There's plenty of research out there about it going back decades (yes, lifepo4 is quite old).


   
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(@notmario)
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Posted by: @robertm
How deeply do you discharge your LiFePO4 batteries? As low as 20%?

With LiFePO4s, they actually tend to dislike being fully charged. For myself, i try to keep SOC between 75% to 25%.
So Depth Of Discharge is somewhat of a different concept compared to Lead Acids. It's not merely a "50%" or "100%" anymore, it's a SOC range; 100-40 will result in [significantly] shorter cycle life than 70-10, even though they both grant 60% capacity.

Posted by: @thebutcher
I saw that clip from Andy. The only thing he busts there is the method less experienced (?) people try to do 80/20 cycling with, voltage monitoring. 80/20 cycling absolutely improves lifepo4 cycle count and he does attempt to disprove that either. There's plenty of research out there about it going back decades (yes, lifepo4 is quite old).

Yeah... SOC shunt is an absolute must.
The science is pretty clear. LiFePO4's are mildly damaged when fully charged, a chemical reality much the same as how 0% will kill them.


   
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