The real reason why your battery won't balance

[houseofancients]

Problem is that many people do top balancing wrong and destroy their cells in the process. An active balancer as part of the BMS eliminates this.

But, that AB doesn't have to be part of the BMS.
In my case I add a 4a active balancer to all my packs, both as a precaution ( I place my batteries in a rack, and goddamn these boxes are heavy), should my cells get older, or if I want to a yearly retop balance, or place a new box in production...
If I look at my boxes and the run time of those AB'S , then that is less than 2,5 hours in 4 years for my oldest boxes, where the AB after initial top balance only starts when the drift is more than 25 Mv

 

[upnorthandpersonal]

Just got this comment four minutes ago.

I just replied to him, let's see what happens

 

[upnorthandpersonal]

But, that AB doesn't have to be part of the BMS.

Correct. But with separate balancer you then have to make sure that they're not active all the time (or starting at 3.2V or something like that). Otherwise they'll increase the imbalance in the pack.

 

[houseofancients]

Correct. But with separate balancer you then have to make sure that they're not active all the time (or starting at 3.2V or something like that). Otherwise they'll increase the imbalance in the pack.

Yeah, I used the neey 4a , which is fully configurable..

All comes down to understanding one's requirements, understanding the chemistry ( to a degree anyway, don't pretent to be a chemical engineer ) and understanding your use case...
Btw the ( possible) lack of sun during november and december here was het reason to stay grid connected for me, both a the cheapest way to have a backup, and for the occasional charge to full.
Now a days I can also "play" the imbalance market automated, but that is not my primary reason to stay grid connected

 

[Skypower]

I know Will had some really bad experiences with active balancers (resistive and Heltec) so I understand what I perceive is his distain for them. He let the magic smoke out in one episode oops and I appreciate Will’s sacrifice and I learned a don’t do that.( And learned a multitude of things from him)

A Heltec is an active balancer but it isn’t smart so it needs a voltage controller or a dry contact from a bms to activate it at a start balance voltage.

The forth generation Neey or the new EnerKey are on a different level with power and control. What would take days if ever, now takes minutes to hours.

If you’re not in a sunny spot or don’t have enough room for more panels, don’t want to start a generator or go to grid without the concern for leaving room for solar fill without hitting bulk to soon. If this is you, you just might not be getting to bulk voltage frequently enough and eventually the passive balancer won’t cut it. So a smart active balancer might be the answer but they even have their limits.

Do active balancers add another point of failure? Absolutely, but so does closed loop which is one of the reasons I don’t run it.

Bottom line, a well designed system, regularly getting to a full state of charge, in a sunny climate probably won’t ever need active balancing, but we all can be that lucky.
Most people don’t need smart active balancers.

 

[marionw]

That was never going to work, you can't fit 22 oz of beer in a 16 oz cup.

I can if I drink while pouring

 

[Tulex]

I can if I drink while pouring

It's been done.....

 

[42OhmsPA]

What is your absorption voltage? When I have a lot of mismatched batteries connected I usually charge them up to 58 volts. And hold them there.

I have it down at 55.2V but I hold for 2 hrs when they get there.
I don't really need every ounce of capacity this time of year, late summer I bump it back up ~56V.

 

[DougL]

It seems like you do initial reviews of build quality and maybe peak current capability. I’d love to see a 300 cycle review. Simulate a basic system with generic charging profiles let it charge and discharge say 2-3 times a day. See which units are able to keep balance, which units can’t.

Disagreeing slightly here. The system would need to be FULLY charged(til the inverter stops because of comms disconnect msg), let sit for a couple of hours then drained and repeat this for about 14 cycles(~ 2 weeks of actual use ). Then evaluate which BMSs have the batteries balanced and how in/out of balance they are.

Once the pack is at less then 20mV difference at full charge after an hour or 2 settling, THEN put it on a daily cycle where it only ever charges to 90% then discharges to 10%. Repeat that for a 2-3 week period cycling 2-3 times per day and keep track of the VDiff at 90% charge.
Try repeating this test at 80% top charge and watch VDiff

Also would want to show what each of the BMSs have for Balance Start V, Balance Diff V Start, Balance Stop, Cell OV Alarm, Cell OV Alarm Stop, etc, Alarm and Protect settings because Alarm will stop the inverter from charging and alarms do the same but can trigger output disconnections. Not for the faint of heart and someone can really screw up and destroy a battery pack or worst if they don't know what's going on and don't have ways back to defaults.

My BasenGreen DIY 2A BMS:
Operational settings:
Balance:
Balance_Start_Vol,3.45
Balance_Start_Diff,30 (mV)
Protect:
CELL_OV_Start,3.65
CELL_OV_Stop,3.40
CELL_UV_Start,2.70
CELL_UV_Stop,2.95
PACK_OV_Start,58.40
PACK_OV_Stop,54.00
PACK_UV_Start,43.20
PACK_UV_Stop,47.20
Alarm:
CELL_OV_Start,3.50
CELL_OV_Stop,3.40
CELL_UV_Start,2.90
CELL_UV_Stop,2.95
PACK_OV_Start,56.80
PACK_OV_Stop,55.00
PACK_UV_Start,46.40
PACK_UV_Stop,47.20


Stock data from file within the software directory as CSV:
Balance:
Balance_Start_Vol,3.34
Balance_Start_Diff,30 (mV)
Protect:
CELL_OV_Start,3.65
CELL_OV_Stop,3.35
CELL_UV_Start,2.7
CELL_UV_Stop,3.0
PACK_OV_Start,58.4
PACK_OV_Stop,54
PACK_UV_Start,43.2
PACK_UV_Stop,47.2
Alarm:
CELL_OV_Start,3.6
CELL_OV_Stop,3.5
CELL_UV_Start,2.8
CELL_UV_Stop,3.1
PACK_OV_Start,56.8
PACK_OV_Stop,55
PACK_UV_Start,46.4
PACK_UV_Stop,47.2

 

[DougL]

I think a big issue that a lot of people are not doing is their solar system is not charging the 100%. I mentioned that in my video and people lost their minds. They said that they never want to charge to 100% because it will ruin their batteries. But I think it's really good to charge these things to 100% so they can actually balance. I mean it's lithium iron phosphate. The iron phosphate lattice can handle it just fine. And so can the electrolyte at these

I don't think Joe Sixpack is mentally differentiating Lithium blah-blah-blah from Lithium scooby-dooby-doo. ;-) It seems to all mean the same or something and they hear "Don't charge Lithium batteries to 100%" and they see their EVs warning them "We REALLY recommend you stop charging at 80%". Not understanding Lithium NMC is different from Lithium LFP.
I was just mentioning to another utuber how his 3 year old video on EV batteries is still current 3 years later but people won't look at it that way and won't watch it thinking it won't apply. There were no comments since 3 years ago. Maybe utube would frown on it but it might be handy to re-edit an old video with a new intro stating the data is valid and doing an overview then go into the old video while ending it with any extra thoughts.
You did lots of work, have good data but why they're not looking at it seems a mystery.

 

[740GLE]

Disagreeing slightly here. The system would need to be FULLY charged(til the inverter stops because of comms disconnect msg), let sit for a couple of hours then drained and repeat this for about 14 cycles(~ 2 weeks of actual use ). Then evaluate which BMSs have the batteries balanced and how in/out of balance they are.

Once the pack is at less then 20mV difference at full charge after an hour or 2 settling, THEN put it on a daily cycle where it only ever charges to 90% then discharges to 10%. Repeat that for a 2-3 week period cycling 2-3 times per day and keep track of the VDiff at 90% charge.
Try repeating this test at 80% top charge and watch VDiff

Also would want to show what each of the BMSs have for Balance Start V, Balance Diff V Start, Balance Stop, Cell OV Alarm, Cell OV Alarm Stop, etc, Alarm and Protect settings because Alarm will stop the inverter from charging and alarms do the same but can trigger output disconnections. Not for the faint of heart and someone can really screw up and destroy a battery pack or worst if they don't know what's going on and don't have ways back to defaults.

My BasenGreen DIY 2A BMS:
Operational settings:
Balance:
Balance_Start_Vol,3.45
Balance_Start_Diff,30 (mV)
Protect:
CELL_OV_Start,3.65
CELL_OV_Stop,3.40
CELL_UV_Start,2.70
CELL_UV_Stop,2.95
PACK_OV_Start,58.40
PACK_OV_Stop,54.00
PACK_UV_Start,43.20
PACK_UV_Stop,47.20
Alarm:
CELL_OV_Start,3.50
CELL_OV_Stop,3.40
CELL_UV_Start,2.90
CELL_UV_Stop,2.95
PACK_OV_Start,56.80
PACK_OV_Stop,55.00
PACK_UV_Start,46.40
PACK_UV_Stop,47.20


Stock data from file within the software directory as CSV:
Balance:
Balance_Start_Vol,3.34
Balance_Start_Diff,30 (mV)
Protect:
CELL_OV_Start,3.65
CELL_OV_Stop,3.35
CELL_UV_Start,2.7
CELL_UV_Stop,3.0
PACK_OV_Start,58.4
PACK_OV_Stop,54
PACK_UV_Start,43.2
PACK_UV_Stop,47.2
Alarm:
CELL_OV_Start,3.6
CELL_OV_Stop,3.5
CELL_UV_Start,2.8
CELL_UV_Stop,3.1
PACK_OV_Start,56.8
PACK_OV_Stop,55
PACK_UV_Start,46.4
PACK_UV_Stop,47.2

Why start your balance at such a high cell delta? Why not get ahead of the issue and start at 0.005v delta?

 

[fuzzmunky415]

It's been done.....

HEY! Look at that over there!....


I'm just pleased we're talking about helpful relevant information, not a virgin capacity test.

 

[740GLE]

Not charging to 100% often, running high c rates, and using pack in extreme cold can create imbalance pretty easily.

That's why all my new recommendation videos say you should charge these things to 100%.

For some reason people charge to lower voltages and they think it will allow their batteries to last longer. With these solar systems, they are rarely held at 100%. Usually they are at 50-70% for most of the time if days of autonomy is designed properly.

So that’s the thing, what’s 100%?

What’s your opinion, do you feel cells need to see 3.65v to be 100%, or can a cell be 100% if held at say 3.5v for long enough?

Set the absorbtion for 3.5v/cell and hold it for +2 hours, is that 100%

I do agree that high C rate charging doesn’t help, shove 30a at a 100ah battery (heck even a 300ah), it has such little time to balance. It only takes a few minutes to go from 3.4v to 3.6v at that rate.

 

[740GLE]

Charging them manually to 100% and letting BMS do its job is best.

Wouldn’t a 10ah unbalance be simulating a 100ah battery only pulling 90% capacity?

Doesn’t seem that unreasonable for people complaining of lack of capacity.

 

[740GLE]

The active balancers also created a new failure point. I've destroyed a few of them in the past.

Your experience with active balancers is quite curious, I’ve had a haltec 4s that did wonders in my 2p4s 230ah DIY pack. I wired a switch to the on/off port and would only turn it on when cells were >3.5v, delta was 0.100v it only took 20, 30 min and delta was under 0.015v.

Yes I had to wire it into the BMS cell connections and another electronic device that could fail, no idea why yours failed. Improper wiring maybe?

Also when a BMS has a 2a active balancer (jk) is that really another failure point?

Charging them manually to 100% and letting BMS do its job is best.

But how do you know the BMS balance settings? That’d be the thing to find out. Does the BMS start balance at 3.5v? Start at 3.2v? Start at cell delta .030v? Start at 0.005v? Knowing those settings would then allow you to make sure your charge settings allow that balance system work the best it can.

No amount of balancing will fix mismatched cells. It will just continue to pull less capacity and one or two cells will be stressed more than the others and will have a different rate of degradation.

What voltage nominal was the 170Ah pack? I don't know about that one. It was completely disabled?

12v unit, fair amount of posts in the DIY battery folder a while ago.

M

Thread 'Problems with renogy 170ah batteries'

Dec 10, 2023

Hi, new to this forum but have built a number of solar systems for motorhomes over the years.

I installed 2 x renogy 170ah lifepo4 batteries in my van 18months ago, parallel 12v setup.

They are acting very strange and I wonder if anyone has any idea how to fix them. I've asked renogy for warranty replacement but they are being difficult about it, so not sure it will happen.

Basically, individually the batteries charge up to a certain point, then the battery cuts charging and won't let it get any further. When turning off charger the battery is at about 12.9v. If I apply a load to...

• meerkatmag
• Replies: 81
• Forum: DIY LiFePO4 Battery Banks

Actually that's false, many of the batteries are batched and matched. That's why many of the cheaper ones now have lower cell voltage differential than many of the more expensive ones. again, litime and wattcycle are good examples. test any of them and look at the voltages.

Is that initial cell delta? or cell delta after a year or two?

Can you post links to the OVP kicking on after a year or two?

A

Thread 'Eco-Worthy is telling its customers that 10% degradation in first year is normal?'

Apr 26, 2025

Ever since "liberation day" I've been searching the web for something cheap to get my lifepo4 fix. I have looked at every single discount, solar, golf cart, marine battery out there. And once you dig into them the actual long term reviews are absolutely horrible for most of the cheap ones. There is so much bad stuff out there that makes me want to overpay for something half decent. Lately thanks to the testing of some of the members on this forum I have been looking at Eco-Worthy, a brand that only 2 years ago I would never have considered.

So I did some digging into it and I couldn't...

• aussiesam
• Replies: 21
• Forum: DIY Solar General Discussion

• 

I’m pretty sure that video example is an unbalance issue

Thread '#2 Battery Voltage too high, Victron, Wattcycle 300ah'

Apr 8, 2025

Currently I have a Victron 150/35 Solar Smart solar charge controller, charging a Wattcycle 300ah Mini (280ah). Absorption at 14.5v, float 13.6v. Haven't really charged it that many times, maybe 3 or 4, but it seems like I keep getting #2 Battery Voltage too High error in Victron. Whats causing this? Today it was being charged by two 410 watt solar panels. They are used panels, but typically put out around 330-350 watts. Somewhere around 90v. I've included a picture. It's showing 20v in the Victron app. I also have a Bluetti power supply from a AC200 that I was told I can use to charge...

• Matsuhkr
• Replies: 36
• Forum: DIY Solar General Discussion

 

[DPC]

No I love them I don't think there's an issue. for the price, just use the stupid batteries.

Does everyone forget how long I ran grade b cells for without issue?

And the litime and wattcycle cell voltage deviation is lower than most of the higher quality packs. It's hilarious. It's so good

What recommendation do I have that you disagree with and you're trying to "call me out" on. Pisses me off when people ask questions like this when I literally open the packs up and show all the testing. What is the issue here? I use these cheap packs all the time and love them.

I feel a lot better about many of my choices .
You repeat these sort of things often but its nice to keep hear them until I get more experience.

 

[DougL]

Why start your balance at such a high cell delta? Why not get ahead of the issue and start at 0.005v delta?

those are my current settings and IIRC also the default from BasenGreen, I did lower the balance start charge and opened up the DiffV value. Then I adjusted tighter once they were balanced down to 0.020V diff.

I run my batteries to 100% about 3 times a week so not worried about balance any more. I think I need to run it low every couple of months to get the BMS SoC more accurate though since I can get below 50% every now and then or maybe 40% but need to take it down closer to 10%.

 

[fnnwizard]

When there are a # of mismatched cells, its better to start with a lower pack target V likely in the 55V range for 16s. Going to 58V just about guarantees a cell OVP. Many BMS's have cell OVP in the 3.8V range and if your cell gets there, the anode is in negative territory = bad.

Especially true for packs that don't provide cell level data. For packs that do, aim for initial pack V that brings cell any to 3.55V first and see what the rest of pack looks like.

I don't like telling someone to charge to 100% because that depends on bms soc being accurate. it's always better to stipulate V @ current.

Can anyone guess about how much imbalance (% wise to stay applicable to all capacities) there is when the low cell is at 3.480V vs high cell at 3.650V = 170mV delta @ charge current .02C? I'm curious to see the answers.

If you have passive balancing, best overall V to set start balance at is 3.41V with a delta 10-15mV. Whether it is during initial bulk or float. For anyone that thinks otherwise, show us why or show some data. Hint: time delta is less than 30 min = 75mAh at typical balancing rates.

The typical passive bleed resistors are providing around 150mA of discharge current, while most of use are charging >15A range during this time.
So the net effect is the high cell, if being balanced is still charging at 14.85A.

 

[Robbert]

But, that AB doesn't have to be part of the BMS.
In my case I add a 4a active balancer to all my packs, both as a precaution ( I place my batteries in a rack, and goddamn these boxes are heavy), should my cells get older, or if I want to a yearly retop balance, or place a new box in production...
If I look at my boxes and the run time of those AB'S , then that is less than 2,5 hours in 4 years for my oldest boxes, where the AB after initial top balance only starts when the drift is more than 25 Mv

Adding a 100 dollar Neey to a 2000+ dollar battery is a no-brainer.
If configured right (balance start/stop voltage in combination with a good absorption time) I simply don't understand why people don't add such a balancer.

Especially in DIY boxes, where we often don't use the best matched cells, a Neey or JK balancer is the best addition one can add.

 

[marionw]

Adding a 100 dollar Neey to a 2000+ dollar battery is a no-brainer.
If configured right (balance start/stop voltage in combination with a good absorption time) I simply don't understand why people don't add such a balancer.

Especially in DIY boxes, where we often don't use the best matched cells, a Neey or JK balancer is the best addition one can add.

But adding a $100.00 Neely or Enerkey to a $900.00 battery is a different issue. I would expect an active balancer in any battery I am paying $1200.00 or more for when sub $900.00 batteries are available.

I am looking at adding the Daly $38.00 1 amp active balancer to some of my sub $900.00 batteries. The Balancer can be turned off and the parameters can be modified and the balancer can be monitored via Bluetooth or RS232-TTL.

Most folks (like me) can't afford to spend more money on an active balancer after spending good money on an $1100.00 plus battery. My first purchases were the $1100.00 plus range batteries and I have found the sub $900.00 range batteries perform as well (if not better) so why spend $1100.00 or more for a battery that performance wise is no better than the sub $900.00 batteries. Spending some addition money for an active balancer is more of an option (and affordable).

 

[fuzzmunky415]

But how often are we talking needing to actively balance a server rack battery? Few times a year?

 

[740GLE]

But how often are we talking needing to actively balance a server rack battery? Few times a year?

If you go 4 months before you are able to hit balance voltage, it’s not about how often you use it be how fast it works

 

[BarracudaBob]

I found that I didn't need to permanently install an active balancer in my $700 rack battery. I just needed it for top balancing and then a few cycles. I removed it after that and the battery pack operated and balanced properly.

Now on 2 of 6 of my $1200 + shipping of by big brand name "Bata Box" a few years ago I had to install active balancers because they refused to keep their balance.

It is just a tool that helps save time. It preforms better than a low current passive balancer on the BMS. Fully controllable and programable via Bluetooth and in the above "Bata Box" there was no Bluetooth so it had added value for monitoring.

The performance and time saving of having another tool at my disposal it a huge benefit


Top Balancing welded cell batteries

 

[marionw]

I found that I didn't need to permanently install an active balancer in my $700 rack battery. I just needed it for top balancing and then a few cycles. I removed it after that and the battery pack operated and balanced properly.

Now on 2 of 6 of my $1200 + shipping of by big brand name "Bata Box" a few years ago I had to install active balancers because they refused to keep their balance.

It is just a tool that helps save time. It preforms better than a low current passive balancer on the BMS. Fully controllable and programable via Bluetooth and in the above "Bata Box" there was no Bluetooth so it had added value for monitoring.

The performance and time saving of having another tool at my disposal it a huge benefit


Top Balancing welded cell batteries

I am assuming you are speaking of the "Unspecified" V1 batteries or which I have six. The batteries are not bad, that is to say the Cells are OK, the BMS sucks so to compensate I am/will be adding an active balancer.

 

[AshleyL]

I am looking at adding the Daly $38.00 1 amp active balancer to some of my sub $900.00 batteries. The Balancer can be turned off and the parameters can be modified and the balancer can be monitored via Bluetooth or RS232-TTL.

Don't.
That Daly 1A balancer has serious flaw.
It will only start balancing if EVERY CELLS reach the balance start voltage unlike Neey/Enerkey/JKBMS

Example, let say if you specifiy 3.45v balance start in a 4S configuration for that Daly 1A balancer. If there is one cell reaches 3.6v and the other three cells are mere 3.33v, this useless Daly 1A balancer will not start balancing at all.