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Is Boost battery charging voltage the same as absorption???

xristostsilis

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I have a phocos 5kw inverter and I am trying to get my lifepo4 batteries to work with it however I saw here that I have to set absorption voltage to 48v. Is this the same parameter as "Boost battery charging voltage" (page 30 menu 26 on the manual) on my inverter?

so to sum up should me settings be (16s 48v):

  • (menu 26) Boost battery charging voltage: 58V
  • (menu 27) Floating battery charging voltage: 54.4V
  • (menu 29) Low voltage disconnect: 42.8V-48V
:unsure::unsure::unsure:

I hope someone knows the answer to this one as I can't seem to find a solution online


off-topic:
Also does anyone know what is the "RS-485 (MODBUS RTU) battery" under menu 5 page 27 of the manual? I am trying to find a solution to communicate the JK BMS to the inverter. I have already found that I can do it via solar assistant but it would be great if it could work directly with my inverter.

FYI: phocos 5kw inverter is basically a rebranded version of voltronic 5kw
 
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Looks like "Boost Battery Chargin Voltage" is the same as "Absorption".
You will need to select one number for voltage for "Low Voltage Disconnect".
 
58 volts is 3.625 per cell. I prefer to use a lower setting of 3.45 V per cell.
Float at 54.4 is above resting voltage. I prefer a setting of 3.3 V per cell for float to prevent the cells staying at high voltage too long. Many people recommend not even using float unless the charging is from solar and limited to the hours of the sun and when there would be small loads on the system.
As far as the bottom setting 3.0 volts per cell is very close to the knee of the discharge curve and that is whery my BMS is set for low voltage disconnect. My inverter is set for slightly higher to be conservative. I am on grid and try to only use 60 percent of my pack for longevity.
 
thanks guys I did what ampster suggested and hope for the best.

I have a small problem tho, it seems that my battery voltage drops kinda fast when in idle. could it be a bad cell or something. see uploaded picture of my BMS. I had a low voltage disconnect today and I am kinda worried.

However I had my inverter set from off grid mode to grid mode at 44v instead of 48v that I should according to low voltage disconnect setting that ampster told. Should I be worried? May I have a bad cell?
 
This is from my inverter. As you can see the battery voltage is dropping however I am not using battery to power my loads rn.

Could be the BMS balancing the cells?
 

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May I have a bad cell?
Cell 14 is lower than the others but that is the reason I suggested not going below 3.volts per cell. That cell may not be bad, it just may have a slightly lower capacity and when balanced at the top that cell hits the knee of the discharge curve sooner. One more reason to use conservative settings. There is not much capacity below 3.1 volts per cell or above 3.5 volts per cell.
 
Cell 14 is lower than the others but that is the reason I suggested not going below 3.volts per cell. That cell may not be bad, it just may have a slightly lower capacity and when balanced at the top that cell hits the knee of the discharge curve sooner. One more reason to use conservative settings. There is not much capacity below 3.1 volts per cell or above 3.5 volts per cell.
I did use the settings you suggested. However I had 2,6v yesterday at the BMS and 2,75 at the inverter ?

So now I use 3v per cell for voltage cutoff however why is pack voltage dropping? Is it because of the calibration happening from yesterday’s mistake?
 
So now I use 3v per cell for voltage cutoff however why is pack voltage dropping? Is it because of the calibration happening from yesterday’s mistake?
Your batteries must not have gotten charged. Normal resting voltage is 3.2-3.3 volts per cell. A float setting of 3.3 volts per cell should have maintained that voltage. Did you have large loads overnight?
 
Your batteries must not have gotten charged. Normal resting voltage is 3.2-3.3 volts per cell. A float setting of 3.3 volts per cell should have maintained that voltage. Did you have large loads overnight?
I always have the same load running 24/7 at 1kw

However I set my inverter to switch to grid mode (therefore only use grid) when battery voltage is at 48v. So it’s not using battery rn it uses grid. Why is battery voltage dropping then?
 
However I set my inverter to switch to grid mode (therefore only use grid) when battery voltage is at 48v. So it’s not using battery rn it uses grid. Why is battery voltage dropping then?
I do not know why your battery voltage is dropping except to offer the concept that it is not charging. Try setting grid charging at 50 volts and it will give you some margin. Maybe a reset or reboot of your inverter would help those settings take affect.
 
I have a phocos 5kw inverter and I am trying to get my lifepo4 batteries to work with it however I saw here that I have to set absorption voltage to 48v. Is this the same parameter as "Boost battery charging voltage" (page 30 menu 26 on the manual) on my inverter?

so to sum up should me settings be (16s 48v):

  • (menu 26) Boost battery charging voltage: 58V
  • (menu 27) Floating battery charging voltage: 54.4V
  • (menu 29) Low voltage disconnect: 42.8V-48V
:unsure::unsure::unsure:

I hope someone knows the answer to this one as I can't seem to find a solution online


off-topic:
Also does anyone know what is the "RS-485 (MODBUS RTU) battery" under menu 5 page 27 of the manual? I am trying to find a solution to communicate the JK BMS to the inverter. I have already found that I can do it via solar assistant but it would be great if it could work directly with my inverter.

FYI: phocos 5kw inverter is basically a rebranded version of voltronic 5kw
Let me see if I can explain it all. Battery charging consists of various stages.

First stage is constant current also called boost or bulk. During this stage the battery is charged at the max current level (amperage) of the charger or the current limit set point if it is adjustable. It does this until battery and charger output voltage (they are in parallel so that voltage is a combination) reaches set point.

Second stage is constant voltage (what the boost voltage limit is set to) also called absorption or even boost charge time since often the time the charger holds it at the voltage is settable. Absorption time brings the state of charge to 100% if it can.

Third stage is float. This is a lower voltage just above full charge battery voltage at idle. It can some times be called trickle charging. Often not used in lithium battery charge programs. In PV production float is implemented to keep the SCC active and supplying loads after the battery has been fully charged. It at best is a trade off in terms of how it may impact battery life span.

A forth stage for lead acid batteries is Equalization. This is a period of higher than normal voltage ran for a period of time that allows cells to equalize. It runs on a schedule that may be settable on some chargers.
 
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Thanks for all the info guys. I will put an eye into inverter settings to see if it fixes the problem I am having.
 
Thanks for all the info guys. I will put an eye into inverter settings to see if it fixes the problem I am having.
While you are at it compare the voltage readings from a voltmeter and compare that to what your inverter and BMS are saying. It could be that the inverter has a calibration error and has not reached 48 volt setting to turn on grid charging but the voltages your BMS is reporting are lower.
Also it is possible that when your BMS went into battery protection mode it disconnected and needed to be reset before it would allow the battery to be charged.
 
So it did it again. BMS cut off the battery due to the same error. Voltage pack was dropping while I didn’t use the battery. It’s like it’s self discharging.. any thoughts?
 
These are my settings. Maybe need to change calibration voltage?
 

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Fyi I have my batteries near electromagnetic field due to being into an FM radio station transmitter site.

Can my BMS readings be wrong and it shuts off the battery completely?
 
So it did it again. BMS cut off the battery due to the same error. Voltage pack was dropping while I didn’t use the battery. It’s like it’s self discharging.. any thoughts?
You unit probably has idle current to operate even if not powering loads that can drop battery charge level. Your BMS cutting off at low voltage would seem to indicate a problem with a higher load than expected or lower capacity of the batteries due to damage or insufficient charging.

If possible charge your batteries with a dedicated grid powered charger or use a power supply and carefully go through the CC and CV stages to see if things improve.
 
You unit probably has idle current to operate even if not powering loads that can drop battery charge level. Your BMS cutting off at low voltage would seem to indicate a problem with a higher load than expected or lower capacity of the batteries due to damage or insufficient charging.

If possible charge your batteries with a dedicated grid powered charger or use a power supply and carefully go through the CC and CV stages to see if things improve.
My batteries were 70% when I start using them.

Don’t know why is this happening. I will try to charge them..

What do you thing about the electromagnetic field? Could be this one?
 
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