Balance LiFePO4

[sharkut]

Hello,

My solar installation is working with battery for almost 6 months

The configuration is :

 - 16s prismatic LFP of 200Ah connected in serial,

 - Daly BMS 250A

and for now, 2 active balancer

- Daly smart active balancer (1A - 20mV drift)

-Neey 4th generation active balancer (4A - 1mV drift)

 

Currently, active balancers are always active, with integrated solar inverter charger (Float 53,6V and Bulk 55,2V), it's working but the main issue is when battery is unused, they slowly drain the battery and BMS SOC become quickly innacurate because active balancer discharge is not followed by BMS

So I want to properly configure that.

I was trying to top balance only with Neey and set it to 3.335V to start balancing and to sleep at 3.325V

I choose to top balance quite low because I have a least one cell that never go up over 3.4V before the first cell reach 3.650V , even after long wait and balance it's the same, and I don't have single 3,2V charger to charge it individually

So 2 conclusion, I understand nothing at balancing or I have at least one bad cell degrading the whole thing

Maybe in my case it's better to bottom balance with different settings.

 

 I hope my explainations are understandable lol.

 

 

 

 

 

[Chris_S]

8 hours ago, sharkut said:

Hello,

My solar installation is working with battery for almost 6 months

The configuration is :

 - 16s prismatic LFP of 200Ah connected in serial,

 - Daly BMS 250A

and for now, 2 active balancer

- Daly smart active balancer (1A - 20mV drift)

-Neey 4th generation active balancer (4A - 1mV drift)

 

Currently, active balancers are always active, with integrated solar inverter charger (Float 53,6V and Bulk 55,2V), it's working but the main issue is when battery is unused, they slowly drain the battery and BMS SOC become quickly innacurate because active balancer discharge is not followed by BMS

So I want to properly configure that.

I was trying to top balance only with Neey and set it to 3.335V to start balancing and to sleep at 3.325V

I choose to top balance quite low because I have a least one cell that never go up over 3.4V before the first cell reach 3.650V , even after long wait and balance it's the same, and I don't have single 3,2V charger to charge it individually

So 2 conclusion, I understand nothing at balancing or I have at least one bad cell degrading the whole thing

Maybe in my case it's better to bottom balance with different settings.

 

 I hope my explainations are understandable lol.

 

 

 

 

 

Active balancing only works above 3.4V. You can try by starting balancing at 3.45 and charge to 3.5 and try hold it there for 24hrs.

Ideally you want to top balance your pack to 3.65v. Active balancers are not ideal

[Chris_S]

https://diysolarforum.com/threads/top-balancing-how-to.15839/

This is a good read

[sharkut]

Thanks a lot for your advice and document. So I understand that almost one third of my bank is unbalanced since the start for almost 20%. I was fooled by similar voltage with active balancer

I try to set charge at 58,4v and to balance when first cell reach 3.65v and restart charge again and again. It seems to work but I think It's going to Take one entire week imo 

I understand well now why It's absolutly necessary to buy a power supply

 

Edited March 12, 2023 by sharkut

[sharkut]

Finally it works and sooner than expected 

[Raj35]

@sharkut it's should not be draining your battery as it's and active balancer it should be transferring power. Your first setting seems to be good at 55v. I have a 272 amp with 5amp active balancer. Normal charge rate at 100Amp solar it not good today. 

Edited March 13, 2023 by Raj35

[Chris_S]

20 hours ago, sharkut said:

Finally it works and sooner than expected 

So what did you do to balance it? 

[sharkut]

I temporary set bulk and float voltage @ 58.4V and in multiple step wait balance ,restart charge, wait balance, restart again and finally cells that never go up above 3,4V, finally reach 3,6v

[Chris_S]

14 hours ago, sharkut said:

I temporary set bulk and float voltage @ 58.4V and in multiple step wait balance ,restart charge, wait balance, restart again and finally cells that never go up above 3,4V, finally reach 3,6v

Good. If I were you I would only use the Neey balancer going forward and set it to only start balancing after 3.45V. Balancers that run all the time can actually unbalance a pack. 

[sharkut]

I agree with you, I've set 3,44V to start balance because I revert my bulk charge voltage at 55,2V so 3,45v may be a little too much I think.

 

[wingnut]

13 minutes ago, sharkut said:

I agree with you, I've set 3,44V to start balance because I revert my bulk charge voltage at 55,2V so 3,45v may be a little too much I think.

 

Why even bother balancing if only going to 3.45V?

[Chris_S]

19 hours ago, wingnut said:

Why even bother balancing if only going to 3.45V?

In case one cell runs ahead and triggers bms cutoff

[gimme_power]

I have this problem but with a rackmount battery... Not a DIY battery. I am wondering if it would be worth it to do a DIY mod.

Can anyone point me in the direction where I can buy a Neey balancer or three?

Thanks

[Chris_S]

On 2023/06/18 at 10:46 PM, gimme_power said:

I have this problem but with a rackmount battery... Not a DIY battery. I am wondering if it would be worth it to do a DIY mod.

Can anyone point me in the direction where I can buy a Neey balancer or three?

Thanks

Alibaba or aliexpress 

[Leondavibe]

On 2023/06/18 at 10:46 PM, gimme_power said:

I have this problem but with a rackmount battery... Not a DIY battery. I am wondering if it would be worth it to do a DIY mod.

Can anyone point me in the direction where I can buy a Neey balancer or three?

Thanks

Some of these active balancers have place for a switch and it is just shorted on the board

 

Putting a switch on it and leave the active balancer inside the battery and just have a switch to enable active  balancer from time to time when in the steep section of the soc graph not all the time

I have a shoto server rack battery  with one bad cell that always drifts 

I soldered two wires to this cell routed through a hole to the outside of my case to a quick connector

 

When this cell has drifted i manipulate this cell by connecting a charger to this quick connector or add resistance if i overshoot the charge

[Leondavibe]

You also get one that has a bluetooth app and can enable and disable balance function and if i recall correctly can also set the voltage where balance should start and the balance current

 

Uses same app as jk bms

 

https://www.aliexpress.com/item/1005004322793283.html?pdp_npi=2%40dis!ZAR!ZAR1%2C705.72!ZAR1%2C193.99!!!!!%402103010b16919576739048116eb60b!12000031119255677!btf&_t=pvid:da821a89-9a3b-4f54-a86b-d5795aeeaeae&spm=a2g0n.ppclist.product.0

[Leondavibe]

On 2023/03/14 at 4:11 PM, wingnut said:

Why even bother balancing if only going to 3.45V?

Because you always have cells that differ so you will always have runners

So even if lucky that you don:t have runners at the top ,ie that you have enough cells that peak at the same time to hit pack voltage before single voltage overvoltage

 

You balance because you want to prevent runners at the bottom  that will lead to faster degradation of certain cells which limits packs capacity

[Leondavibe]

On 2023/03/12 at 9:36 AM, sharkut said:

Thanks a lot for your advice and document. So I understand that almost one third of my bank is unbalanced since the start for almost 20%. I was fooled by similar voltage with active balancer

I try to set charge at 58,4v and to balance when first cell reach 3.65v and restart charge again and again. It seems to work but I think It's going to Take one entire week imo 

I understand well now why It's absolutly necessary to buy a power supply

 

Since you have active balancers , you don't need to buy a power supply

 

Whenever you are home while battery is fully charged just lift the float voltage to sustain the voltage at 3.65v per cell and switch on the active balancer

 

When load shedding switch it off

 

Then when fully charged switch on the active balancers again

 

Just don't leave them on all the time

 

As they may move power around in the flat portion incorrectly ie do work it has to reverse again when full

 

All you want is to be balanced at 3.65v ie all cells has to be 3.65v at the same time