# question

## Cell balancing importance

Hi , Dear all,

I have a question regarding the lithium batteries cell balancing, if i have frequent charge discharge cycles as shown how cells are balanced? I have a 48 volt 100Ah batteries with 15 cells.

as shown there is very rapid charge and discharge cycles , will it provide the advertised cycle life.

graph is shown for a single day, does BMS balance the cells or there are some other circuitry.

further to add as the battery ages there is definitely variation in individual cell resistance /capacity , connections etc. what would the impacts ?

1721804650862.png (71.1 KiB)

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@Inam Your post has no details, and your graphs have no reference. A pointless, empty, nonsense post.

If you want to learn about Li batteries and cell balancing, you could spend a couple of hours looking at Victron's Lithium Smart Battery Manual.

Starting Here would be a good starting point. But read the appropriate sections.

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thanks, I have read the relevant material as you mentioned, the document describes that cell balancing needs to be done at absorption stage for 2 hours, but i have given a real life example of battery current curve it charges and then discharges frequently , so I needed your expert opinion...

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inam ·

@Inam but i have given a real life example of battery current curve it charges and then discharges frequently

No. Your chart shows a charge / discharge of 15a, without any absorption time, or yhe charge current dropping down to an acceptable tail current.

To be considered fully charged, the battery charge current has to fall to 2-4% of the battery C rating.

And to be considered properly balanced, at the end of absorp, the cell voltages have to be similar.

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klim8skeptic ♦ ·

Voltage and current graph is given below as you required , I had mentioned in the earlier post that there is unstable grid so overtime there would be difference in the cell voltages , i tried to ask the specific question

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1721823552909.png (88.3 KiB)

hi, no one can answer your question due to lack of information. what we can see that you charge one hour, followed by discharging for one hour and so on.

this says nothing about balancing. if done right you use an active balancer above 3.45V cell voltage for a sufficient long period before discharging again.

so two things:

- above 3.45V. we cannot identify if this happens from your screenshot

- for a sufficient amount of time. this depends on your battery:

-- type and performance of the internal balancer

-- contact and wiring resistences between the cells

-- resistences within the cells

-- how far have the cells drifted off from eachother

-- …

none of these things we can identify from your informations

what you can do:

charge your battery to 3.45V per cell

have a look to the BMS data

if cell diff voltage is 100mV or bigger your balance strategy is very poor

if lower than 30mV it is excellent

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