LifePo4-Request for advice about cell balancing?

[Loz]

As far as I know, the difference between the 6 and the 6.1 is It has a max charge function that can be selected that stops the alternator going to idle so you can max charge the leisure batteries that all have battery sensors, but still had the simple relay setup with the engine run control.
I don’t think it would energise the relay if the vehicle was off.

The only odd behaviour I have noticed is when I use a link to back feed the starter battery(to keep it topped up) from the solar maintained leisure batteries. Something keeps waking up and drawing the starter battery back down, which in turn draws more from the leisure batteries. With the link disconnected the systems on the starter side stay asleep and the battery drains slower. (but none of this is relevant to your issue.)

 

[Raul a/3]

Thanks fir this @Dellmassive.


Yep!


I have full control of the charge current of the MPPT and Multiplus from my Cerbo GX.
View attachment 183329This works brilliantly as the combined current is accounted for. (It is a shame that Victron didn't have the foresight to include a VE port on the DC-DC, as this would be useful, but there we are!)



I have never been able to suss out how to do this on the Cerbo. The setting is there but it doesn't work!
Turning on limit "Charge Voltage" doesn't work for me:
View attachment 183330

Any ideas @Raul a/3?

What I currently do is configure the absorption voltage using by downloading the Remote VEconfigure file from the Multi. I then use VEConfigure3 to change the voltage before uploading it to the multi again! It would be a significant improvement if I could make the Voltage Limiter work on the GX device!

I reckon that there is a setting on VEConfigure3 that would allow the GX to take control of voltage limits, but I can't find it. Any help would be much appreciated.

The cerbo, or any other GX can control and override the max amp charging as you set in dvcc. Regardless of the source, the current is red from bmv, so your charging sources will be overruled. But they will supply loads if there is overhead over dvcc.
The voltage it’s not controlled in dvcc like the current it’s a voltage and temp sense. If this info is networked between devices the GX will take account and adjust/ compensate, but not regulate the voltage.
I use temp sense using the probe connected on ve bus. The Bluetooth always reads 1-2C higher than the ve bus one. I do not use v sense in dvcc, just current and temp.

On another note, the new feature from git hub, called gui mods, comes in a package manager with lots of features, to control various things.
Anyone using it? Looks like this, you can click on each tile for extra info or controls,

 

[Samro]

The cerbo, or any other GX can control and override the max amp charging as you set in dvcc. Regardless of the source, the current is red from bmv, so your charging sources will be overruled. But they will supply loads if there is overhead over dvcc.
The voltage it’s not controlled in dvcc like the current it’s a voltage and temp sense. If this info is networked between devices the GX will take account and adjust/ compensate, but not regulate the voltage.
I use temp sense using the probe connected on ve bus. The Bluetooth always reads 1-2C higher than the ve bus one. I do not use v sense in dvcc, just current and temp.

On another note, the new feature from git hub, called gui mods, comes in a package manager with lots of features, to control various things.
Anyone using it? Looks like this, you can click on each tile for extra info or controls,

View attachment 183448View attachment 183449View attachment 183450

Thank you for this. It has confirmed that all is good with my install. I shall Google GitHub gui mods and see if I can gain some understanding!

 

[Raul a/3]

I'm aware that this post is a bit wordy, so I have highlighted my queries in bold to save those that are easily bored!

Back in 2020 I ordered my new T6.1 and I impatiently purchased all sorts of components and planned what I considered to be the ultimate set-up for my off-grid machine.

Whilst the "Order Delays" thread grew and grew, I ended up with shed loads of kit including a 200Ah (Gen1) Roamer Battery, which sat for 15 months before it eventually got installed in my new van in March 2022.

The battery had sat for 15 months and like an idiot I didn't charge it at any time during this period. I consequently found that the cell overvoltage warning was triggering once I got around to installing this in the vehicle. Here is a screenshot from the summer showing the overvoltage issue :

I spoke to the helpful guys at Roamer and they got me to tweak seem BMS settings and told me to reduce the absorption voltage to 13.9V and then "creep it back to 14.2 volts over the coming months, once the BMS stopped triggering overvoltage warnings. They were helpful as they could be and advised me that a cell delta of up to 0.3V is fine.

Whilst mucking about with this battery, I noted that the capacity of the battery was set at 180Ah on the BMS. (This was as it was configured when it was delivered, so I assumed that this would be correct.) I always had my Victron Smart shunt set as 200Ah capacity and the "% charge" info from the Victron was always more reliable than the figure viewed on the BMS. I therefore changed the setting within the BMS to the 200Ah figure.

Since changing the BMS's Battery Capacity to 200Ah I have had consistently reliable results from both the BMS and the Smartshunt in terms of "% charge", but, I set the "Total Cycle Capacity" to be the same as the "Total Battery Capacity" - Not sure of this is right, so if anyone can confirm that would be useful?

So....... back to the cell balancing topic; It has taken me ages to get to a point where I have got the battery to reach the end of its absorption without triggering the overvoltage warning. This can be seen below:
View attachment 183227

Roamer have confirmed that my Delta figure of 0.269V is within spec, as it is less that 0.3V (Shown in the above picture as 0.269). I consequently don't want to bother them with my queries, as the battery is operating within the parameters that they have defined.

This is an expensive battery and I'd like it to last as long as possible. The battery has currently cycled 38 times and I was hoping that the maximum Delta figure would come down to the 0.15V as per the "Delta to balance" shown below.

View attachment 183248

It seems that the cells will never, ever truly get balanced and that cell 3 will be weaker than cells 1, 2 & 4.

1. Is that normal to have weak cells?
2. Are the cells likely to get balanced eventually?
3. How long would you expect them to fall in line with the other 3 cells? (as in number of charge cycles.....It has currently been 38!)
4. Should I creep the absorption voltage a little higher than 14.2V (Say 14.4V, over the next ten charges or so) and then reduce this figure back to 14.2V in the future, in an attempt to get the cells more closely balanced at 14.2 Volts?
5. Should I try something else to reduce teh Delta figure?

What I would do, is, find out at what voltage per cell is the balance activated, multiply by 4 and set that as absorb. You need to spend absorb time with low current to give a chance to the passive balancer, to reduce the delta. If balance kicks in at 3.45vpc, set absorb at 13.8v and let the current tapper to 1-2 amps. This is what it can handle. Repeat until delta is close to 5-7mv, and then increase CV absorb. Until then any increase is pointless as the balancer is minute.

If you what something less painful, fit a external 2-5A balance board, or change the bms to a JK smart with 2A active balance built in. JK, it’s fully configurable, every parameter is adjustable.
While delta of 300mv it’s safe, it screws the total pack capacity.

 

[Samro]

What I would do, is, find out at what voltage per cell is the balance activated, multiply by 4 and set that as absorb. You need to spend absorb time with low current to give a chance to the passive balancer, to reduce the delta. If balance kicks in at 3.45vpc, set absorb at 13.8v and let the current tapper to 1-2 amps. This is what it can handle. Repeat until delta is close to 5-7mv, and then increase CV absorb. Until then any increase is pointless as the balancer is minute.

If you what something less painful, fit a external 2-5A balance board, or change the bms to a JK smart with 2A active balance built in. JK, it’s fully configurable, every parameter is adjustable.
While delta of 300mv it’s safe, it screws the total pack capacity.

So my balance kicks in at 3.4v.
So if I set the absorption at 13.6, should I extend the absorption time from 1 hour. How long should I extend this for I am thinking continuously with a tiny charge of 2-3 amps?

 

[Raul a/3]

This guy is very helpful, I managed to copy what he done. The gui mods are Kevin Windrem’s work posted on git hub.

 

[Samro]

What I would do, is, find out at what voltage per cell is the balance activated, multiply by 4 and set that as absorb. You need to spend absorb time with low current to give a chance to the passive balancer, to reduce the delta. If balance kicks in at 3.45vpc, set absorb at 13.8v and let the current tapper to 1-2 amps. This is what it can handle. Repeat until delta is close to 5-7mv, and then increase CV absorb. Until then any increase is pointless as the balancer is minute.

If you what something less painful, fit a external 2-5A balance board, or change the bms to a JK smart with 2A active balance built in. JK, it’s fully configurable, every parameter is adjustable.
While delta of 300mv it’s safe, it screws the total pack capacity.

In fact thinking about it why don't I just set absorb and float at 13.6v for a week with a very low charge current?

 

[Raul a/3]

So my balance kicks in at 3.4v.
So if I set the absorption at 13.6, should I extend the absorption time from 1 hour. How long should I extend this for I am thinking continuously with a tiny charge of 2-3 amps?

I would start with 2hrs, at 13.65v absorb, and see where it gets.

 

[Raul a/3]

In fact thinking about it why don't I just set absorb and float at 13.6v for a week with a very low charge current?

You will force the high cells to peak for to long.

 

[Samro]

I would start with 2hrs, at 13.65v absorb, and see where it gets.

Done! I've turned off solar and dc-dc and will see how I get on.

 

[Dellmassive]

This guy is very helpful, I managed to copy what he done. The gui mods are Kevin Windrem’s work posted on git hub.

love that guys YT channel.

@Samro has vic` Cerbo GX installed, not a R-pie.

im not sure if you can run that Firmware on a GX,

+++++++++++++++


if you want to know about getting a R-Pie,

I've shown it here:

Solar Sheds & Other Non-t6 Solar Projects - How We Done It -

Solar Sheds & Other Non-T6 Solar Projects - How We Done It - @Pete C requested it, so here it is . . . . . Dell, What do the batteries in your shed power ? I too have a solar powered shed - perhaps we should have a separate thread for sheds :) Pete Lets Post here any NON - T6 related ECO...

www.t6forum.com

+++++++++++++++

 

[Samro]

@Samro has vic` Cerbo GX installed, not a R-pie.

I have an R-Pi in my work van and genuine Cerbo GX in my camper. I bought one of these to see if I could cheaply get the Pi to operate with operational relays, but had no joy:

DollaTek LCUS - type 1 USB relay module USB intelligent switch control https://amzn.eu/d/2qkPT6j

If anyone else has made a Pi work with relays that can function using the GX OS then I'd love to hear how?

Also got an old Venus GX in my caravan. Check out my VRM Home Screen :

 

[Raul a/3]

love that guys YT channel.

@Samro has vic` Cerbo GX installed, not a R-pie.

im not sure if you can run that Firmware on a GX,

+++++++++++++++


if you want to know about getting a R-Pie,

I've shown it here:

Solar Sheds & Other Non-t6 Solar Projects - How We Done It -

Solar Sheds & Other Non-T6 Solar Projects - How We Done It - @Pete C requested it, so here it is . . . . . Dell, What do the batteries in your shed power ? I too have a solar powered shed - perhaps we should have a separate thread for sheds :) Pete Lets Post here any NON - T6 related ECO...

www.t6forum.com

+++++++++++++++

GUI mods work on all GX devices, I have it installed on my house Colour Control to. Particularly the gen start is helpful for me, along with the ruvvi that are going next.
Here is the colour control running gui mods.

 

[Oceanis]

@Samro

Fwiw....

@Oceanis also has a T6.1

Which he now has a 3rd party leisure battery charge system.

he may be able to offer some insight.

Glad the van isn't a California Coast/Ocean etc .... if I were to do mine again, I would keep the Engine and Leisure battery systems completely isolated when moving to a Lithium leisure battery setup.

The 2/3-Battery T6.1 Californias. with the relay under the seat connecting leisure and engine batteries, have an emissions related smart-alternator and start/stop system that normally keeps ALL BATTERIES somewhere between 80 and 90% charged - the max-charge function in the camper unit effectively switches off this strategy and allows all batteries to be charged to 100% and should be activated at least an hour or so before parking up on a camp site. Because it switches off an emissions related system, it will not retain the setting after stopping the van so must be re-engaged if the van is stopped to refuel or for a coffee break.

Under normal running, the system keeps the batteries at a state of charge where the alternator can dump large charge currents into the batteries during braking or when the engine is in over-run ... this uses the kinetic energy of the van during braking or slowing down to store charge in the batteries. On accelerating, the alternator switches off, removing the alternator load from the engine and all electrics run from the batteries during acceleration - this strategy saves fuel. The relay under the seat is controlled to enable charging of leisure batteries from the engine, and all 3 batteries are used for the emissions system - but most importantly, during start-stop cycles, the relay is disengaged to ensure the starter current is not drawn from the leisure battery wiring.

On top of this, the charge voltages and profile of the on-board charger are all set up for AGM batteries, not Lithium, as is the software in the camper unit which uses the measurement shunts attached to all batteries for its display, warnings etc. Switching a factory spec Ocean/Coast etc. to Lithium is a real challenge if the original VW camper unit etc. are to remain fully functional.

There is a company in Germany that offers a conversion service but this was done in conjunction with VW and involves changing software in the camper unit and is unbelievably expensive. €4999.

Reservierung Lithiumpaket VW T6.1

Nachrüstung LiFePO4 für T6.1 mit originaler Aufbaubatterie ab Werk, vollumfänglich vom Fahrzeug unterstützt. Durch die vorliegende Unbedenklichkeitsbescheinigung wird der Umbau dem Fahrzeug hinterlegt und bleibt auch bei Servicearbeiten erhalten. Die Werksgarantie bleibt durch den Umbau...

camperelektrik.de

 

[Raul a/3]

If anyone try to install GUI mods, following the advise given by Andy in the vid above, the blind install is the easiest way with a usb stick. Works instantly, then you go in package manager and download/install bits that you need, including GUI.

 

[Rids]

As far as I know, the difference between the 6 and the 6.1 is It has a max charge function that can be selected that stops the alternator going to idle so you can max charge the leisure batteries that all have battery sensors, but still had the simple relay setup with the engine run control.
I don’t think it would energise the relay if the vehicle was off.

The only odd behaviour I have noticed is when I use a link to back feed the starter battery(to keep it topped up) from the solar maintained leisure batteries. Something keeps waking up and drawing the starter battery back down, which in turn draws more from the leisure batteries. With the link disconnected the systems on the starter side stay asleep and the battery drains slower. (but none of this is relevant to your issue.)

Actually that sounds quite similar to my problem…

 

[Samro]

@Dellmassive said:

They state the BMS balance current is only 50mA.... And might not be enough.

@Raul a/3 said:

I would start with 2hrs, at 13.65v absorb, and see where it gets.

I have followed @Raul a/3's advice and can instantly see that this is going to be a slow burn! Even with the absorption set at 13.65V, cells 1,2 and 4 run away leaving cell 3 at 3.344V. It seems it would take forever before I'd see an improvement, given that the cells are only loaded with 50ma during 2 hours of balancing (during the absorption stage).

So I took a look at the BMS settings and have had a cautious fiddle. I temporarily changed the "balance only during charging" to be off.
I have also reduced the balance start voltage to be 3.375V. (Float 13.5V /4):


The effect seems to be that the cell balancing now takes place during the float stage when there is no current flow in or out of the battery.

I've not left the battery like this yet, but was just seeing what would happen with these settings.

If this is a bad idea can somebody please tell me why before I reinstate these settings and leave my van on charge for weeks in the hope that I will slowly remedy the small imbalance in my cells?

 

[Dellmassive]

As far as I know, the difference between the 6 and the 6.1 is It has a max charge function that can be selected that stops the alternator going to idle so you can max charge the leisure batteries that all have battery sensors, but still had the simple relay setup with the engine run control.
I don’t think it would energise the relay if the vehicle was off.

The only odd behaviour I have noticed is when I use a link to back feed the starter battery(to keep it topped up) from the solar maintained leisure batteries. Something keeps waking up and drawing the starter battery back down, which in turn draws more from the leisure batteries. With the link disconnected the systems on the starter side stay asleep and the battery drains slower. (but none of this is relevant to your issue.)

Something keeps waking up and drawing the starter battery back down,

if were talking about your T6 cali with the REDARC fitted. . . . .

do you think its the "AUTO VSR" feature on the Redarc kicking in and powering it up when it sees the starter battery voltage rise to the trigger ON point?

 

[Loz]

if were talking about your T6 cali with the REDARC fitted. . . . .

do you think its the "AUTO VSR" feature on the Redarc kicking in and powering it up when it sees the starter battery voltage rise to the trigger ON point?

I’m Using the trigger cable, not sure I have the A-VSR feature?

 

[Dellmassive]

I’m Using the trigger cable, not sure I have the A-VSR feature?

I've noticed that "MOST" DC-DC chargers will switch ON when the starter battery voltage creeps up from say EHU charger, back charging from solar, reverse trickle charger etc etc


regardless of thge IGN switch feed.

BCDC Classic Under Bonnet 40A DC Battery Charger

The REDARC BCDC1240D is a 12V, 40A In-vehicle DC to DC Battery Charger designed to keep your auxiliary battery charged when driving or with portable solar panels when parked.

www.redarc.com.au

example:



(IGN not connected - when engine not running) the BCDC 1240 - will switch ON when it sees the starter battery voltage 12.9V

the back OFF again when the starter drops to 12.7v

(*1Tested every 100 seconds)

(this will apply as the BLUE wire id effectively floating as no High 12v signal applied)






then with IGN feed connected to blue wire (when engine running):


the units ON above, 12.0v and off bellow 11.0v




++++++++++++++++++



its easy enough to test . . .


just reconnect you back trickle charger,

or connect a EHU charger to the starter. . .



then watch the Redarc LEDS

you will find with the engine OFF the Redarc will switch ON when the starter battery feed hits 12.9V





+++++++++++++++++






if you get a chance to test it let us know. . . .




+++++++++

• DC-DC Charger - AUTO VSR - feature testing

[Guide] DC-DC Charger (for leisure battery) -- How I Done It --

@Farnorthsurfer did you set the Dc-dc to lithium mode for the TN100 battery? Also have you got any more BM2 views showing more days? Yes the unit is set to Lithium profile. Easy enough to do when it was powered up. Yesterday was a flat line all day as it just sat on the drive. Back to work...

www.t6forum.com

++++++++++++++