Seplos BMS goes bananas when NEEY is working!

[MrSwede]

Hi,
So i have just completed my first DIY build of two EEL 48V (16s) cases and are using them in parallel with my Victron Quattros (VenusGX).
But when i enable the NEEY (4A Active) balancer the Seplos BMS goes bananas and reports completly wrong voltages per cell.
I have disabled balancing in the BMS.
I have also verified the true/correct voltage on the cells with my multimeter (Fluke 179), and that is the same as the NEEY is showing.



Is this normal or has anyone else experienced the same issue?

Kind Regards
MrSwede

 

[sunshine_eggo]

Are you sharing the same leads between BMS and balancer?

If so, the small gauge wire may show a notable voltage drop/rise when the active balancer is engaged causing the seplos readings to be off.

The NEEY uses wiring resistance values to compensate for its balance current.

If you're using the same leads, you should separate them. If you're using some sort of terminal block that connects the Seplos and the NEEY to a common set of wires, that's the same as using the same leads.

 

[MrSwede]

Hi, and thanks for fast reply
I'm using the same small wire for both BMS and NEEY to measure voltage at the terminal. This is connected to a PCB that both NEEY and BMS are using.

So that means i really can't alter the setup. Perhaps i can tune some settings in order to avoid the warning/alarms in the BMS, would that be a recommended fix?

 

[toms]

If your batteries don’t need a lot of balancing, turn down the balance current in the NEEY (start with 0.5A). The higher the balance current the greater the issue with interfering with the BMS.

In settings, set MaxBalCur(A) to 0.5 and see if that helps.

 

[sunshine_eggo]

Hi, and thanks for fast reply
I'm using the same small wire for both BMS and NEEY to measure voltage at the terminal. This is connected to a PCB that both NEEY and BMS are using.

There's your problem.

So that means i really can't alter the setup.

What? How do you figure? I see bus bars and nuts and a separate attach point for the BMS sense wire. I understand "don't want to" but "can't" is just not arguable.

Run a completely separate harness attaching at the same BMS harness points or at the cell terminals. Attaching a second lead at the same spot won't suffer from the same issue. It's the BMS sense wire itself that's causing the voltage drop and creating the bad reading.

Perhaps i can tune some settings in order to avoid the warning/alarms in the BMS, would that be a recommended fix?

@toms has you covered on that. Unfortunately, given the relatively "high power" nature of the balancer, it seems a shame to cripple it because of a bad installation.

EDIT: three places to attach a separate NEEY harness per bus bar:

 

[Lt.Dan]

Or wire the NEEY direct to cell terminals.

 

[Alkaline]

Hi,
So i have just completed my first DIY build of two EEL 48V (16s) cases and are using them in parallel with my Victron Quattros (VenusGX).
But when i enable the NEEY (4A Active) balancer the Seplos BMS goes bananas and reports completly wrong voltages per cell.
I have disabled balancing in the BMS.
I have also verified the true/correct voltage on the cells with my multimeter (Fluke 179), and that is the same as the NEEY is showing.

View attachment 183409 View attachment 183410 View attachment 183411

Is this normal or has anyone else experienced the same issue?

Kind Regards
MrSwede

OHH NOOO Please don't tell me this is the case, I just got my V3 EEL battery in and if the NEEY ALWAYS 2 amp balancer is going to go beserk in it I'm a be pissed. God damn it. I better not have to buy a flying capacitor 16s AB!

 

[MrSwede]

OHH NOOO Please don't tell me this is the case, I just got my V3 EEL battery in and if the NEEY ALWAYS 2 amp balancer is going to go beserk in it I'm a be pissed. God damn it. I better not have to buy a flying capacitor 16s AB!

I think you will be fine with the 2A version. I'm currently runing my 4A at 1A and seems to be fine atm.
I will consider running separate leads from the NEEY to be able to utilize all 4A.

 

[MrSwede]

There's your problem.



What? How do you figure? I see bus bars and nuts and a separate attach point for the BMS sense wire. I understand "don't want to" but "can't" is just not arguable.

Run a completely separate harness attaching at the same BMS harness points or at the cell terminals. Attaching a second lead at the same spot won't suffer from the same issue. It's the BMS sense wire itself that's causing the voltage drop and creating the bad reading.



@toms has you covered on that. Unfortunately, given the relatively "high power" nature of the balancer, it seems a shame to cripple it because of a bad installation.

EDIT: three places to attach a separate NEEY harness per bus bar:

View attachment 183414

I hear you, and yes, i meant "not eager to" when i wrote can't
And i understand that there will not be any voltagedrop over the small BMS wires if i run separate leads from the balancer, even if i use the same mounting points. So that is not that big of a deal to do.
Do you perhapos now if its possible to buy just the leads, with a connector in the other end? Not happy about splicing on to the current cables.

 

[Alkaline]

I think you will be fine with the 2A version. I'm currently runing my 4A at 1A and seems to be fine atm.
I will consider running separate leads from the NEEY to be able to utilize all 4A.

Sorry its the 4A its the version that is in a black box it came with the kit it has 2 metal straps to keep it in place. Same as yours.

Man... I already know this is going to not work...

 

[houseofancients]

Hi,
So i have just completed my first DIY build of two EEL 48V (16s) cases and are using them in parallel with my Victron Quattros (VenusGX).
But when i enable the NEEY (4A Active) balancer the Seplos BMS goes bananas and reports completly wrong voltages per cell.
I have disabled balancing in the BMS.
I have also verified the true/correct voltage on the cells with my multimeter (Fluke 179), and that is the same as the NEEY is showing.

View attachment 183409 View attachment 183410 View attachment 183411

Is this normal or has anyone else experienced the same issue?

Kind Regards
MrSwede

Check you balance contact
Did you drill seperate holes for the needy balance leads on your busbars ?

 

[houseofancients]

Sorry its the 4A its the version that is in a black box it came with the kit it has 2 metal straps to keep it in place. Same as yours.

Man... I already know this is going to not work...

This works quite excellent in all installs I have done so far, which is 23+8 .
I see no reason why this isn't a user error

 

[Skypower]

If you share the bms leads with the Neey, both will be less accurate even with the Neey turned down. You’re so close to an ultimate battery, with a little more effort of removing the splice in and using dedicated leads for the Neey to the cell terminals you’ll have it. Not many batteries can be a week without absorption voltage and then when it does, It’ll balance in minutes with the full 4 amps of balancing power.

 

[Skypower]

A lot like this other guy did:

 

[MrSwede]

Lowering the equ-current to 1A did the trick quite nice.
I have however ordered extra cable leads, so i weill be using the full power of the balancer shortly.

 

[houseofancients]

Lowering the equ-current to 1A did the trick quite nice.
I have however ordered extra cable leads, so i weill be using the full power of the balancer shortly.

View attachment 183536

And it also confirms it is a connection issue

 

[MrSwede]

And it also confirms it is a connection issue

How do you figure?

 

[houseofancients]

How do you figure?

If you up the amps, and connections aren't good , they will get hot and cause issues.

How are you current connections done ?
Did you use the crush rings below your busbar ?
Did feel for heat?
Did you torque to 4-5 nm ?

 

[MrSwede]

If you up the amps, and connections aren't good , they will get hot and cause issues.

How are you current connections done ?
Did you use the crush rings below your busbar ?
Did feel for heat?
Did you torque to 4-5 nm ?

My issue is probably not a connection issue, but that the BMS and balancer are sharing thin cables. So when i discharge (or charge) a cell, the BMS sees a voltage drop (or spike). This was causing the BMS to throw warnings and alarms all over and ultimatly shutting it down.

I have torqued the lugnuts to 6Nm, the balance/BMS leads are not torqued, but its a snug fit.
I have used a FLIR camera when charging at 8kW and nothing stood out.

No, no "crushring" under busbar, i have busbar direct on the terminals, and then a lug.

 

[houseofancients]

My issue is probably not a connection issue, but that the BMS and balancer are sharing thin cables. So when i discharge (or charge) a cell, the BMS sees a voltage drop (or spike). This was causing the BMS to throw warnings and alarms all over and ultimatly shutting it down.

I have torqued the lugnuts to 6Nm, the balance/BMS leads are not torqued, but its a snug fit.
I have used a FLIR camera when charging at 8kW and nothing stood out.

No, no "crushring" under busbar, i have busbar direct on the terminals, and then a lug.

So wait.. you spliced the cables ?

Battery terminal > crush ring > busbar > ring connector from PCB > (ring need BMS) > curated nut .. is what I used a few times before I drilled extra holes in busbar and never had any issues with that, although for safety the torque on all nuts is checked every year , and changed to drilled hole.

You do realize this BMS calculates resistance to cells amongst other things on every pcd connection I hope ?
Would surprise me at all the splicing causes issues with that process