Battery balance and BMS with balanicing function


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Eihab Bannaga

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If I use a BMS with balancing function, does it neglect the preliminary need to balance the batteries for a long time??
 
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OffGridInTheCity

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If I use a BMS with balancing function, does it neglects the preliminary need to balance the batteries for a long time??
Could you clarify a bit more what you're asking?

Some general comments that may help you:
When you create a battery, you typically pre-balance the cells before assembling them into a battery. This means the battery starts off balanced and if the cells are healthy then very little ongoing balance is needed. A balance capable BMS may provide ongoing touch-ups.

Eventually, one or more cells will fail. In the graceful scenario of gradual degradation, the failure will manifest one or more cell's voltage being more often and more quickly out of balance with the other cells. A point will be reached where the BMS will not be strong enough to counteract thru balancing. If all goes as it should, the BMS will shut-off the load to protect the situation from getting worse and the battery will need attention.
 

Eihab Bannaga

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Could you clarify a bit more what you're asking?

Some general comments that may help you:
When you create a battery, you typically pre-balance the cells before assembling them into a battery. This means the battery starts off balanced and if the cells are healthy then very little ongoing balance is needed. A balance capable BMS may provide ongoing touch-ups.

Eventually, one or more cells will fail. In the graceful scenario of gradual degradation, the failure will manifest one or more cell's voltage being more often and more quickly out of balance with the other cells. A point will be reached where the BMS will not be strong enough to counteract thru balancing. If all goes as it should, the BMS will shut-off the load to protect the situation from getting worse and the battery will need attention.
that means i should balance the batteries even if the BMS has balancing function??
what is the case if I have separate balancer??
 

Eihab Bannaga

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My question in other words is to escape from balancing batteries for a long time if I have a balancer function in the battery BMS, is that right practice?
what if I do not have an ability of continuous power to balance the batteries? How can I balance them??
 

Roland W

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My question in other words is to escape from balancing batteries for a long time if I have a balancer function in the battery BMS, is that right practice?
what if I do not have an ability of continuous power to balance the batteries? How can I balance them??
If you have new cells, and the pack is big enough to keep currents inside the standard C-rating for charge, stay away from absolute limits, you might need to balance once in hundreds cycles.
None of my two packs has an active balancer, while the LiFePo pack doestn't even balance passively. In one year running on currents of 0.2C, there was no need for balancing at all, and those cells are well degraded already.
So it is mostly the individual used case, which will make active balancing a requirement or not. That you will see, once you build and operate your system.
 

OffGridInTheCity

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My question in other words is to escape from balancing batteries for a long time if I have a balancer function in the battery BMS, is that right practice?
Could you explain what kind of battery you're thinking of? Is this one you would build yourself? Is it lithium? Is it 12v or 24v or 48v?

If you're building a lithium battery (lithium-ion or lifepo4) yourself, then you need to select the BMS that you will use. It would be helpful (for you) to learn a bit about the levels of BMS / costs - and the features they have. There are many but I tend to think of them as being in 3 broad categories:
* Cheaper - these BMS(s) work on internal settings and shut-off the load if cell voltage, current, temps exceed internal min/max settings. They may (or may not) include balancing.
* Middle price - BMS(s) where you can set several parameters and see what's happening thru bluetooth apps and screens.
* Top end BMS(s) where you can set / control every aspect.

I'm familiar with
* Middle price - Chargery BMSs let you set several parameters and see the individual cell / settings thru their own screen.
1628643236085.png
For example - the "Diff Of Cell Voltage" = 13mV - tells the Chargery how close to 'balance' the voltage of the cells to each other.

* Top end - Batrium BMS system let's you control every aspect.
1628643320689.png
Just 1 of many screens - notice you can set the min/max voltage and temps.


I read that
A popular / cheaper BMS example would be DALY.... (and there are many others). These can be fixed and/or offer phone based apps to see/control some basic settings.

what if I do not have an ability of continuous power to balance the batteries? How can I balance them??
This question will be answered by the type of BMS you buy/apply to your battery.
 
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daromer

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Yes you can skip initial balancing if you have a decent bms that can balance. BUT if the battery is out of balance to a large extent it will
1. TAKE a long time to balance if the battery is big and balancer is small
2. You may not even be able to use it meanwhile since you need to top charge slowly while balancing

So its often alot faster to paralell all cells in the beginning and just top charge them all at once. This is the fastest way. Though i have have often relied on the BMS to balance but as said it can take 1-2 weeks easily. I recommend to prebalance for people that ask this question.
 

Eihab Bannaga

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Could you explain what kind of battery you're thinking of? Is this one you would build yourself? Is it lithium? Is it 12v or 24v or 48v?

If you're building a lithium battery (lithium-ion or lifepo4) yourself, then you need to select the BMS that you will use. It would be helpful (for you) to learn a bit about the levels of BMS / costs - and the features they have. There are many but I tend to think of them as being in 3 broad categories:
* Cheaper - these BMS(s) work on internal settings and shut-off the load if cell voltage, current, temps exceed internal min/max settings. They may (or may not) include balancing.
* Middle price - BMS(s) where you can set several parameters and see what's happening thru bluetooth apps and screens.
* Top end BMS(s) where you can set / control every aspect.

I'm familiar with
* Middle price - Chargery BMSs let you set several parameters and see the individual cell / settings thru their own screen.
View attachment 25821
For example - the "Diff Of Cell Voltage" = 13mV - tells the Chargery how close to 'balance' the voltage of the cells to each other.

* Top end - Batrium BMS system let's you control every aspect.
View attachment 25822
Just 1 of many screens - notice you can set the min/max voltage and temps.


I read that
A popular / cheaper BMS example would be DALY.... (and there are many others). These can be fixed and/or offer phone based apps to see/control some basic settings.


This question will be answered by the type of BMS you buy/apply to your battery.
let us say the battery pack is 48V 100Ah or 200Ah
 

Eihab Bannaga

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Yes you can skip initial balancing if you have a decent bms that can balance. BUT if the battery is out of balance to a large extent it will
1. TAKE a long time to balance if the battery is big and balancer is small
2. You may not even be able to use it meanwhile since you need to top charge slowly while balancing

So its often alot faster to paralell all cells in the beginning and just top charge them all at once. This is the fastest way. Though i have have often relied on the BMS to balance but as said it can take 1-2 weeks easily. I recommend to prebalance for people that ask this question.
The main issue is that I cannot rely on power supply for 2 weeks continuously.
 
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daromer

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Exactly. Thats why you should prebalance. You can prebalance within a Day or so. Of course dependant on the Soc and your charger
 

Eihab Bannaga

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Exactly. Thats why you should prebalance. You can prebalance within a Day or so. Of course dependant on the Soc and your charger
So how can I balance these batteries without power supply??
do you mean I should discharge them all until reach certain voltage??
this is the only way of balancing that I have
 

daromer

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No you should top balance them. Get something that can output the top voltage. Best and easiest way
 

Eihab Bannaga

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what is the sour
No you should top balance them. Get something that can output the top voltage. Best and easiest way
what is the source of that power? I hope not to say the national power grid? we cannot rely on the grid for 24 hours continuously?
can you suggest other sources for balancing for 2 weeks continuously??
 

daromer

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Who says you need 2 weeks? You need a total input so that all cells get to equal state of charge. You can have a generator powered by a bike, solar, grid or a generator or even your car.
It doesnt have to run continously. You can start and stop it every 5 minutes if you like. It just takes longer time. The amount of current the device can give out and the SOC will determine how long/much it need to run.
 

Eihab Bannaga

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I understand that I should reach a certain voltage, when I reach it, the balancing of batteries end??
Who says you need 2 weeks? You need a total input so that all cells get to equal state of charge. You can have a generator powered by a bike, solar, grid or a generator or even your car.
It doesnt have to run continously. You can start and stop it every 5 minutes if you like. It just takes longer time. The amount of current the device can give out and the SOC will determine how long/much it need to run.
 

daromer

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reach a certain voltage and the current is basically 0 and there is no current between the cells. Thats when you have it fully top balanced.
 
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