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Float, Absorption and Equalization V for Lithium Battery ESM-48100B1

xuhaibkhan

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Joined
Jun 11, 2024
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8
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Lahore, Pakistan
Hello,
I recently got a 8KW Hybrid Solar System installed at my home. The company who installed the system have set the setting, which I am not sure if they are correct.
I am using 580w x 18 Jinko Bifacial Panles, with 8KW Inverex Nitrox Hybrid Inverter and a Lithium Battery ESM-48100B1.
I have 2 ACs running on smart load.
As soon girld is offline, it switches to battery and battery volts right away drop from 54.5V to 50V.
I guess soemthing is wrong with the setting, so I would really appreciate if you guys could guide me.
Are Float V, Absorption V and Equalization Volts are correct for this battery, also they enabled float charge, (I read it should be disbaled for Lithium Battery)
 

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As soon girld is offline, it switches to battery and battery volts right away drop from 54.5V to 50V.
The battery datasheet:


It feels like this is a 15S battery, 15 cells in series which has a nominal voltage of 48 volts. Most "48 volt" LFP batteries people use are 16S, 16 cells in series and have a nominal voltage of 51.2 volts.

The discharge curve in the datasheet shows the battery drops to 50 volts rapidly under load so your battery is acting per the datasheet.

1718110414620.png

Are Float V, Absorption V and Equalization Volts are correct for this battery, also they enabled float charge, (I read it should be disbaled for Lithium Battery)
What worries me a bit is that the charge voltages seem appropriate for a 16S system and will over volt a 15S system. 56.4 volts is 3.76 volts per cell in a 15S system and that's pushing it hard for LFP cells. Normally, 3.6 volts/cell (54.0 volts total) is max, and you might want to back that off to 3.5 volts/cell (52.5 volts total) to extend the battery life.

The datasheet does say 56.4 volts for charging, though, but I am leery of that, and you can see how much higher that is than their charge curve in the datasheet.

Personally, I would use these settings:

Float: 51.0 volts
Absorption: 52.5 volts
Equalization: 52.5 volts
Equalization days: 10
Equalization hours: 0
Shutdown: 44.0 volts
Low batt: 46.0 volts
Restart: 48.0 volts
Tempco: 0
Batt resistance: 8 m (depends on cable length, your are probably less than this)

Another thing to keep in mind is if you expand this system to more batteries, you CANNOT tie a 16S battery in parallel with your 15S battery. That will not work.

Basically, you have an oddball 15S battery and it seems to be working the way it should, and you are likely overcharging it. Dropping to 50 volts under load is normal.

Mike C.
 
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This is a 15S Pack and therefore will suffer the same problems as PylonTech batteries.
These are/were made as a "Direct Replacement" for 48V FLA and thats why their Nominal Voltage is 48.0V and not 51.2V (standard 16S LFP)
Below is a "Moderate" profile for 15S LFP that will not trip Over/Under Volt protection and leave safe margin at the bottom to prevent bricking the Battery Pack BMS.

SETTINGV per cell48Vnotes
Bulk / Absorb: (boost)3.45051.75Absorb < 60min Transitions to Float
Equalize: 0NOT for Lithium Based Batteries (set to FLOAT Voltage for safety)
Float3.43751.55allows cells to balance internally
Min Volts:2.65039.75Never allow to drop too low. Safe Buffer
Max Volts:3.57553.625
Rebulk Voltage:3.20048.0
End Amps / Tail-Current:formula: 100AH X 0.05 = 5A
 
I have made the following changes. Thank you so much for such details and help.
Also there is a setting which the installer said that I need to adjust as per my requirements to use the battery for ACs.
It’s as Micro INV input values.
Which I want to use so when there is no grid or solar I can use the battery till it has 70%remaining.
So currently I just reduced the ON value to 52.5(so battery is full) and OFF at 47.0 I am not sure if 47is like 70% remaining.
Also “Disable float charge” is unchecked so should I check or leave it. Thank you so much for you help and time I really appreciate you guys
 

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Float provides enough input to keep the cells just above the Working Voltage Range, allowing the cells to saturate & balance out at that level. (Also dependant on BMS if it has Active Balancing or not. Passive Balancing of packs with cells larger than 50AH is pretty much useless and quite pointless in reality.

This may help for understanding LFP better.
quick-voltage-chart-lfp-jpg.150247
 
Float provides enough input to keep the cells just above the Working Voltage Range, allowing the cells to saturate & balance out at that level. (Also dependant on BMS if it has Active Balancing or not. Passive Balancing of packs with cells larger than 50AH is pretty much useless and quite pointless in reality.

This may help for understanding LFP better.
quick-voltage-chart-lfp-jpg.150247
So I am going to check “Disable Float Charge”
The battery is not connected to a BMS port on inverter and installer said it has one built in. Here is the picture of full setup and battery.
 

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None of my Inverter-Enabled packs are connected to my inverter system because they do not support Samlex.
I float the batteries as a matter of course. Typically, by the time they reach end of Absorb, the cells are within 0.015 of each other across the different packs let alone within their own packs. Within a 1/2 hour of float, they are all less than 0.005 differential in all packs.
I am presently running 3x 280AH Packs and by end of week the final 3 will be online (these were already in bank, just getting new cases & JBMS -Inverter editions to match the rest.
 
None of my Inverter-Enabled packs are connected to my inverter system because they do not support Samlex.
I float the batteries as a matter of course. Typically, by the time they reach end of Absorb, the cells are within 0.015 of each other across the different packs let alone within their own packs. Within a 1/2 hour of float, they are all less than 0.005 differential in all packs.
I am presently running 3x 280AH Packs and by end of week the final 3 will be online (these were already in bank, just getting new cases & JBMS -Inverter editions to match the rest.
Would you suggest that I enable the float charge ?
 
YES !
If you set ABSORB to 51.7 You can safely set FLOAT to 51.6 or 51.5 which will top off the cells in the pack and if there is internal balancing that will ensure they are all balanced out (pending on balancer type).
NEVER EVER run Equalisation on Lithum Based Batteries ! NEVER EVER !!! That is for Lead Acid & Variants. If it cannot be disabled then set it to the FLOAT Voltage for safety reasons.
 
There is no option to disable equalisation.
So should I set the following
Float v 51.5
Absorption V 51.7
Equalisation 51.5

Please advise
 

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There is no option to disable equalisation.
Can you set equalization days and hours to zero?

Wouldn't that be "off"? As in, when the charge stops, it will go directly to float and not hold voltage at equalization levels for any meaningful time.

One thing to check is if "zero" means "forever". Sometimes that is what it means. We don't have your inverter manual, and sometimes they are vague, so it is hard for us to know what it will do.

If you can't set it to zero (or zero is forever), then set it to the shortest time you can. 1 hour at 52.0 volts would be harmless.

Mike C.
 
Here are the current setting as per your recommendation. Thank you.

The installer set the equalization days to 90. I have now changed it to 0.

I need help with setting the correct ‘ Micro Inv input’ values

What it does is to allow battery to be used by ACs from ON volts till OFF volts and what I need is to set it the ON value to 100% (so when battery is full) it would drain for ACs till it has 70% left then switch off.

Can you suggest what volts I should set so battery can be drained 30% at 3.5kw.

I also have attached SOLARMAN smart app device battery info.

As the battery soc is 100% at 51.4v would 48v will be 70%!

ACs consume around 3.5kw will it put or decrease battery life if I use it from 100% to 70% at 3.5kw
 

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I'd suggest absorption be 52.5 volts, which is 3.5 volts/cell.

Equalization volts can be the same, probably doesn't matter with 0 times.

Float at 51.0 volts is 3.4 volts/cell which is okay. It doesn't seem to actual provide a float voltage since your voltage has drooped below the setting naturally (you reported 50.79 volts above).

Your GEN Port seems to be set to Smartload Output, and I think it means the GEN port will act as an AC output and turn on at 50 volts and off at 48 volts. Whether that is any particular SoC is dependent on the load and temperature so you can't be quite sure what SoC you will hit with those numbers. Suggest you experiment with them and see what works best. Your setup (wire length and size for example) can have an effect as well.

A possible problem is that unloaded you are above 50 volts and then when loaded (like starting an AC compressor), it drops below 48 volts and the port switches off. Then the cycle repeats. So you need the two voltages to be far enough apart that once it starts, it doesn't drop out immediately.

Battery voltage will droop down once charging stops. That is normal.

Mike C.
 

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