Victron smart 12.8v smart lithium battery

Great to see some progress!

All the cells being at 3.6V shows that the battery is balanced. This shows the balancing circuitry working, looks like it works at 3.6V and not 3.55. So what has happened is that when the first cells hit 3.6V the balancing circuitry switched on and kept the voltage of the cells at 3.6v from going any higher which allows the other cells to catch up. If the charge current had been too high it would have overwhelmed the balancing circuit and the voltage of the cells at 3.6V would have continued to go higher.

24 hours at 2A is 48Ah which is 48% of your batteries capacity. The batteries should have been shipped at less than 50% SOC so it is possible that 24 hours is not enough time.

I agree that doing all the sixteen batteries like this is going to be a chore. You could do two at a time in parallel at 7A which would speed things up.

Simon

Yerf said:

The funny thing is the cells were balanced after the charger finished its charge cycle (it may have took 26 hours, life is a bit of a blur right now since we have a newborn So I believe the batteries were charged.

weird thing is that the charger ran on bulk setting the whole way through. But I never saw the cells reach a higher voltage than 3.35vdc. When using the chargers lithium setting.

From my reading of the manual When the bulk and lion indicators are on it is supposed to be charging normally. If so it should be charging at 7 amps. Do you have a means of measuring the current output from the charger to confirm this.

Simon

It might be worth getting a multimeter, I have a two, a UNI-T UT61E for high accuracy work and a UNI-T UT210E DC/AC clamp meter which allows me to read AC and DC current without breaking the circuit. They are cheap and cheerful but do the job well. If you only wanted to get one I would get the clamp meter or maybe get a clamp meter with a higher current range, the 210E only goes up to 100A.

Simon

To be precise getting the cells balanced is getting then all at the same % SOC. If we have two cells with the same capacity, one at 50% and one at 51% SOC the voltage difference between them would be in the order of 0.001V. If we add 45% charge to both cells connected in series we get individual SOCs of 95% and 96% and the voltage difference will be around 0.050V. If we add another 3.5%SOC to 98.5% and 99.5% the cell voltages will be ~3.5V and ~3.6V, a difference of 0.100V. If we add another 1% of charge we get one cell outside its safe operating zone and one at ~3.6V.

This is the reason for having to balance the cells. With LFP batteries it is only practicable to balance at an SOC close to 100% or close to 0% SOC because this is the only time the individual cell voltages are far enough apart from each other to accurately measure the difference in SOC.

As far as I can tell your batteries use what is known as passive balancing. Passive balancing is where current is bled off through a resistor when the cell voltage gets to a preprogrammed voltage, in your case 3.6V (which is very close to 100%SOC) so that rather than overcharging the cell the charge current heats the resistor up. All the cells that haven't reached 3.6V continue to be charged until they too reach 3.6V. At the end of the balancing you get all the cells at the same SOC. If you then remove the charge current the voltage will naturally relax back down to ~3.35V.

You should only connect cells is series if they are all at the same SOC.

Balancing is further complicated by the fact that the individual cells might not all have the same capacity. If we have two cells, one with half the capacity of the other and we balance them both at 100% (this is known as top balancing) what happens when we discharge the battery by 60% of the stronger cell? The stronger cell ends up at 40% and the weaker cell at -10% which will damage it beyond repair. This is why you have to have a BMS that will detect that the voltage of the week cell is outside its safe operating region when it gets close to 0% SOC and will take action to stop the cell being damaged and potentially becoming dangerous.

Simon

+1  and explain the high voltage referred to... which is up in the FLA battery range...

I contacted victron they said that the battery should be reaching at least 14.2 Vdc.

@Yerf
That's the thing with lithium batteries. The initial top balance is critical and time consuming, but once done, maintaining balance is easy and lasts a long time.

Rick

Yerf said:

I have to put it on normal charge + recondition mode to get it to go into long and slow absorption. But it's a bit scary because I fell asleep and woke up to a high battery Vdc. For some reason the battery charger was charging at 14.4vdc and then suddenly switched itself to 14.6vdc. Luckily I caught it just in time.

What I did was put the battery on charge at 2 amps on liion setting. Waited over 24 hours to finish and then charged it on normal + recondition setting. Then I started seeing the voltage climb to 3.6vdc per cell, it was scary because one was lagging behind at 3.49vdc. It took around 5 hours to get the other cell to 3.6vdc which then I had to turn off the charger manually.

I've only done that with one of the batteries so far. Should I do the rest in the same way? I've already charged all of them fully on the liion setting.

Do not use the Recondition function. It will charge up to a voltage of 16.2V and could reach this voltage in a short period of time after the battery is full which could easily damage your batteries.

Although not ideal what you could do is charge each battery using Normal mode only. In Normal mode the charger manual says that it will do a minimum absorb time of 1/2 an hour then drop to a float voltage of 13.8V. If the charger has switched to float when you are about to take the individual voltage readings you could start a new Normal charge cycle and check the individual cell voltages around the 25 minute mark while the charger is still in the absorb phase at 14.4V to see if they are all the same, if they aren't run another normal cycle.


Simon

You have to laugh about the situation when I make the statement in bold in my previous post and you come back with but the manufacturer said ...

I did think about using the Recondition mode as it is current limited to 8% of the charger output, in your case 0.56A. If all the cells in the battery being charged are full and balanced and not accepting any more current the balancing resistors will have to bleed all the current supplied by the charger to keep the battery voltage at 14.4V. In this situation they will be dissipating ~8W as heat. It is possible that they are capable of doing this but I didn't think it is worth the risk.

Hopefully the person you have been corresponding with in Victron is aware of these technical details, one of my favourite sayings is "the devil is in the detail".

Now that I am on my soapbox, one thing that I find really frustrating these days is the lack of technical details supplied with products like your batteries. It the good old days (there was no such thing, but it sounds good) there would usually be a page of very detailed technical specifications supplied with something like your battery. Information that would have made life allot easier would have been

• What type of balancing does the battery employ (passive or active)
  
• What voltage does the balancing start at
• What is the maximum current that the balancing circuitry can bypass

along with all the other information on maximum charge and discharge current, working temperature range etc. etc. all in one place so you don't have to wade through the whole manual trying to find the information. Enough of my rant.

Ideally you would have something like a laboratory power supply where you would dial in the output voltage and current and hook it up to the battery and wait for the charge current to reduce to less than C/100. Then you would check the individual cells voltages. When they were all the same you could disconnect the charger.

Simon

Yerf is very lucky for your help Simon as he has said!  I hope when he gets this sorted out he can explain how Victron has let this get so borderline dangerous. At least the cells are some of the safest out there.

The thing I have to laugh about is how "wild west" a major company like Victron is about a battery with their name on it. If I am wrong about this I would like to know.
I have seen their gear over the years and since none of the major solar dealers I use has ever carried Victron in North America I really do not know how they have historically dealt with situations like this.

Thanks for the update, it is always good to know how things are progressing.

I don't think you need to hope for the best. What you are doing will balance the cells correctly.

Regards
Simon

Have you set up the Battery Capacity, Charged Voltage, Tail Current and Charged detection time on the BMV? See page 19 of the manual.

The difference in battery voltages means there is a discrepancy between the SOC of the different batteries. The difference should get smaller over time as the batteries balance themselves.

Simon

The values are dependant on what you have set your charge controller to.

The Charged Voltage needs to be slightly less say 0.1V-0.2V less that your Bulk/CV/Absorb voltage.
The Tail Current needs to be set slightly higher than the charge current when it has tapered down just before the controller switches to float.
I would set the Charged Detection Time to the minimum 1 minute.

The SOC meter will reset to 100% when the battery voltage is still higher than the Charged Voltage and the charge current is less than the Tail current and these conditions must be met for at least the Charged Detection Time.

What are your controller settings at the moment?

Simon