I have 16 x 200ah prismatic cell with a Daly BMS and active balancer

For now on my Easun SMW 8K : I use 54V float and 56,4 bulk voltage, but I really don't know if it's ok for a 51V system (16S)

On web I see parameters for 48V (15s) but almost nothing for 16S

On my BMS , I set 2,50V to 3,55V limits for cells

Is this OK ? What are you using ?

 

I plan to already replace Daly Active Balancer by Neey one because it's too slow with only one amp. My cells deviate faster and BMS cut-off

Many questions need to be asked before the parameters will fit your profile.

1) do you have solar PV attached to your plant? 

2) Did you do a Top or bottom balance before you built the battery? 

3) The active balancer at 1A should be sufficient. How far is your delta at 54.8V ? 

4) 56.4v is bit excessive because the cells stress & will drift at that high voltage. 54.8v to 55V is a good Bulk. A Neey won't help that problem. Stay away from the stress at the top & bottom of the flat curve. So meaning absorb at a lower voltage. The cells can & will accept more charge in amps at 54.8v until they are saturated then they will start increase their internal resistance & slowly throttle the charging amps. So the charger will revert to CV & the current drops. 

Great project 👍👍

Yes I have 12x400wc PV,

I don't really balance cells with specific charger. i just mounted them in parallel and wait one week to passive balance and once in place i charge them in series at 30A with inverter and wait active balancer reach 0,02v between cells (sort of top balancing no?) After I discharge battery deviation was much higher  and i need to wait before recharging it.

I don't have try more than 54v, my deviation is 0,070v 3hours After end of charging

With low charge i was able to reach 0,018v but I take very long time.

 

But even if this I will reduce bulk voltage to preserve cells

Thanks

 

 

 

 

 

On 2022/11/08 at 10:37 PM, sharkut said:

On web I see parameters for 48V (15s) but almost nothing for 16S

Basically you can just add 3V to the parameters given for a 48V (15 cells) battery.

9 minutes ago, Beat said:

Basically you can just add 3V to the parameters given for a 48V (15 cells) battery.

3.2... is the nominal value for the LiFePO4's... hence 48/15=3.2V per cell nominal and thus 51.2V for a 16 cell battery... if you see a LiFePO4 advertised as 48V nominal, its a 15 cell battery, even if they do not state that, if the nominal Voltage is stated a 51.2V, then its a 16 cell battery...

Ok so deviation problem seem to be solved since I top balance the entire battery for one entire day. 

But with my settings even with back to grid set at a minimum of 44V i was only able to extract approximately half of the capacity (100ah) 

The pack voltage never go up than 54v even unless I apply high current 

And 54v/16 is 3,375v so far from 3,65v maximum limit. 

I set my BMS to disconnect if cells reach 3,55v so if i understand well i Can set float to a little less of 56,8v (3,55x16) and bulk to 60v instead of 56,4v

 

 

 

Edited November 12, 20223 yr by sharkut

1 hour ago, sharkut said:

I set my BMS to disconnect if cells reach 3,55v so if i understand well i Can set float to a little less of 56,8v (3,55x16) and bulk to 60v instead of 56,4v

Bulk charge at 3.45V per cell = 55.2V for a 16S battery

the maximum Voltage per cell is 3.6V and not worth aiming for, since you will shorten the expected life of your cells... and at 60V bulk which is 3.75V per cell, assumption still is a 16S battery, you are exceeding the individual cells max Voltage by 150mV and this will guaranteed hurt them...

 

See attached screenshot from batteryuniversity.com, note the Li-phosphate charge limit of 3.6V...

 

Ok i start to understand 🙂 i set bulk to 3,45v per cells and i set float to the same value or less ?

51 minutes ago, sharkut said:

Ok i start to understand 🙂 i set bulk to 3,45v per cells and i set float to the same value or less ?

Yes, ideally slightly less for float...

Float set at 53,6v, after one week and neey balancer installation everything is working well balance between cells now reach 0,001mV. Daly balancer equalize too but very slowly

The Neey works well. The Daly Balancer is rubbish 😂