Victron SmartSolar Charge Controller MPPT 100/50 absorption time question

[RandyP]

Victron Connect app screen shots (settings):
Battery Preset User Defined



Note from above absorption settings:
absorption duration - fixed
absorption time - 5m
Tail Current - Disabled

Trends graph for Voltage and Current



The battery was fully charged (100AH 12v cylindrical cell LiFePO4 battery, three 100AH batteries in parallell, 300AH total).
I ran the microwave thru the inverter for a few minutes and discharged the battery a few Amp Hours.
Then I watched the Victron SCC charge the battery up. Initially the SCC was on float 13.6v at 0 amps. After battery discharge the SCC changed to CC Bulk charge. When the battery attained the 14.0v absorb voltage, the SCC immediatly changed back to a float charge voltage 13.6v.
No Absorption time allowed by the SCC as shown in the two graphs.

Why was there no absorption time at CV 14.0v, even though the SCC was set at 5m (5 minutes) absorb ?

 

[Jims94vmx]

I was told by Battle Born that 30 minutes per 100ah battery for absorption.

 

[brb58]

You need to get them up between 14.2V and 14.4V occasionally to let them top balance.

 

[RandyP]

OK, so much for BB battery passive balancing statements. Back to the original question.

Why did the Victron Smart SCC not hold the battery at absorb for the absorption time I set in the device using the victron app and my phone?

I read their manual for the device again, more carefully and critically. It seems that the charging cycle starts anew each morning when the sun appears and there is enough solar energy captured by the solar cells to start the charge cycle a new at the CC bulk charge rate.

Also there is an absorbtion time timer that starts when the CV absorb phase charging starts. The timer can be stopped and started by the scc charge power, if there is not sufficient power available to continue the Absorb CV charge voltage (shade, clouds, battery load ect) the timer stops and then continues when the solar power is availabe to hold the battery to the absorb CV voltage, as long as the wait time is less than 1 hour. Otherwise it just starts the charge cycle again in bulk, ect.

So armed with that revelation, I went out mid morning on a sunny day and turned off the solar, then the SCC to battery circuit. Waited at least 10 seconds and turned on the battery to SCC circuit and then the solar disconnect switch ON. The SCC restarted with a bulk CC charge and upon attaining the absorb charge voltage, the charger maintained the CV charge for 5 minutes, then the charger changed from absorb to float and the voltage slowly dropped to the float voltage setting (accelerated by adding 5 amp lighting load to bring the voltage down a little faster). Once the voltage dropped to about 0.01 volts bellow the float voltage setting, the scc brought the voltage back up to float voltage setting and even with the 5 amp lighting load, the charger settled at float voltage and 0.0 amps into the battery (solar was holding the load, but no charge to the battery).

This is what I think happened. Seems to work wonderfully. I can set the absorb charge at 14.1 v for 15 minutes per battery string (3 parallel strings (batteries)), 45 minutes, and let the batteries (3 in parallel) passive top balance. Here's todays trends graph for voltage and current with several different voltage and current readings along the way from float thru bulk, absorb and back to float:

QED.

 

[brb58]

Why do you not have the voltage over 14.1V for your absorption setting?

Your picture in your first post shows absorption time for 5 mins. Set it to 30 minutes and see what the graph shows.

 

[brb58]

I would be setting the absorb voltage at 14.4V.

 

[RandyP]

I am going to look at the victron manual again carefully, and consider using the auto equalize feature to top balance my battery about once a week. My dc discharge current for the battery is less than 1/2C (microwave, 2-3 minutes max mostly), I do not believe that this is a stressful discharge that will drive the battery out of balance daily.

 

[brb58]

You are very confused. Setting a higher absorb voltage does not charge your battery faster. By the time you get to the absorb voltage, your batteries are basically charged. Basically, you are in bulk until you hit the absorb voltage and then you are in constant voltage mode. The absorb voltage just sets the voltage where the controller switches from bulk)constant current) to absorb(constant voltage).

14.1V is not high enough for top balancing to occur. All the videos you and I just posted said this!

 

[RandyP]

I inquired about BB BMS passive balancing routine with BattleBorn this summer. Here's the response. I will use this info to set my battery charging parameters.

Jesse Asay (Battle Born Batteries) Jul 5, 2021, 21:15 MST Hi Randy, A passive balancing process is activated by the BMS at the top of each charge cycle when the battery voltage exceeds around 14V. This ensures that all the cells remain at the same state of charge, which helps for pack longevity and performance. Basically this means that when the batteries reach nearly a full charge, the bms will allow small amounts of energy to pass into the cells that may not be as full as the others. This essentially tops off any individual cell, so that none are out of balance with the others. Manu of the Prismatic cell brands recommend that you dont fully discharge their batteries because it shortens the lifespan and potentially voids the warranty . Prismatic cells also do not cycle as long or dissipate heat as well as the cylindrical. Hope this helps, thank you! Battle Born Team

That's where I got the 14 v + top balance charge cycle info.

 

[Pim57]

Your original question about the absorption time not being executed, is still not answered.

I agree that the SCC should hold the voltage for 5 minutes after bulk ends.

Better ask that question to Victron support. If omitting this 5m timer is a failure or feature?

 

[RandyP]

Your original question about the absorption time not being executed, is still not answered.

I agree that the SCC should hold the voltage for 5 minutes after bulk ends.

Better ask that question to Victron support. If omitting this 5m timer is a failure or feature?

I think I discovered a potential cause for the absorb timer behavior. Its in a comment above and repeated here:

OK, so much for BB battery passive balancing statements. Back to the original question.

Why did the Victron Smart SCC not hold the battery at absorb for the absorption time I set in the device using the victron app and my phone?

I read their manual for the device again, more carefully and critically. It seems that the charging cycle starts anew each morning when the sun appears and there is enough solar energy captured by the solar cells to start the charge cycle a new at the CC bulk charge rate.

Also there is an absorbtion time timer that starts when the CV absorb phase charging starts. The timer can be stopped and started by the scc charge power, if there is not sufficient power available to continue the Absorb CV charge voltage (shade, clouds, battery load ect) the timer stops and then continues when the solar power is availabe to hold the battery to the absorb CV voltage, as long as the wait time is less than 1 hour. Otherwise it just starts the charge cycle again in bulk, ect.

So armed with that revelation, I went out mid morning on a sunny day and turned off the solar, then the SCC to battery circuit. Waited at least 10 seconds and turned on the battery to SCC circuit and then the solar disconnect switch ON. The SCC restarted with a bulk CC charge and upon attaining the absorb charge voltage, the charger maintained the CV charge for 5 minutes, then the charger changed from absorb to float and the voltage slowly dropped to the float voltage setting (accelerated by adding 5 amp lighting load to bring the voltage down a little faster). Once the voltage dropped to about 0.01 volts bellow the float voltage setting, the scc brought the voltage back up to float voltage setting and even with the 5 amp lighting load, the charger settled at float voltage and 0.0 amps into the battery (solar was holding the load, but no charge to the battery).

This is what I think happened. Seems to work wonderfully. I can set the absorb charge at 14.1 v for 15 minutes per battery string (3 parallel strings (batteries)), 45 minutes, and let the batteries (3 in parallel) passive top balance. Here's todays trends graph for voltage and current with several different voltage and current readings along the way from float thru bulk, absorb and back to float:

View attachment 67807 View attachment 67809
View attachment 67808

View attachment 67995 View attachment 67814


QED.

Thank You for addressing the original Question.

 

[brb58]

Set your absorb time for 20 minutes minimum.
Voltage between 14.2V and 14.4V


Per the manual page 6:

https://battlebornbatteries.com/wp-content/uploads/2019/01/10012-2021-Manual.pdf

 

[RandyP]

Set your absorb time for 20 minutes minimum.
Voltage between 14.2V and 14.4V


Per the manual page 6:

https://battlebornbatteries.com/wp-content/uploads/2019/01/10012-2021-Manual.pdf

Thank you for the advice on BB LifePO4 100AH 12V battery charger settings.
Have you any info on the original question of this Post, absorb voltage time duration setting and resultant time duration ?

 

[brb58]

Thank you for the advice on BB LifePO4 100AH 12V battery charger settings.
Have you any info on the original question of this Post, absorb voltage time duration setting and resultant time duration ?

I already did many posts ago. Set it for 20 minutes or longer and see how it reacts to a longer setting. You need at least 20 minutes anyway for balancing.

 

[RandyP]

I already did many posts ago. Set it for 20 minutes or longer and see how it reacts to a longer setting. You need at least 20 minutes anyway for balancing.

I guess I missed "Set it for 20 minutes or longer and see how it reacts to a longer setting." I misinterpreted you first comment.
I'm not asking or looking for your advice RE: SCC charger setpoints. Just wondering why the SCC did not preform the absorb duration as set.

 

[brb58]

I guess I missed "Set it for 20 minutes or longer and see how it reacts to a longer setting." I misinterpreted you first comment.
I'm not asking or looking for your advice RE: SCC charger setpoints. Just wondering why the SCC did not preform the absorb duration as set.

Look at my post #7.

Its possible that the resolution of the time for duration is an increment that is close to 5 minutes which is why you wouldn't see it. The duration needs to be 20 minutes or more per BB so why not set it at that larger number anyway and rerun the test.

 

[RandyP]

Look at my post #7.

Its possible that the resolution of the time for duration is an increment that is close to 5 minutes which is why you wouldn't see it. The duration needs to be 20 minutes or more per BB so why not set it at that larger number anyway and rerun the test.

I do not agree. I think you are blowing smoke. But thanks for the suggestion anyway. I think I can set the absorb duration at about any minute duration and it will perform as set during the first charge cycle of a new solar day.

 

[brb58]

I do not agree. I think you are blowing smoke. But thanks for the suggestion anyway. I think I can set the absorb duration at about any minute duration and it will perform as set during the first charge cycle of a new solar day.

It's going to do it multiple times a day if you have discharge enough that it goes back into bulk. My Victron solar controller goes into bulk multiple times a day.

You seem to have all the answers. Not sure why you even post a question. I am just an electrical engineer. What do I know?

 

[RandyP]

The subject line of this thread is :

Victron SmartSolar Charge Controller MPPT 100/50 absorption time question​

My post ask a question about absorb duration setting, asking why the device did not provide the absorb duration as set.​

I never ask for help with BB Battery charging set points.​

Your comments and direction are not within the scope of this thread. Post them somewhere elese please.​

I have great respect for EE's. Unfortunately you may be the exception.

 

[brb58]

Set it for 30 minutes and see what you get! It's what you need to set it for anyway. There...does that answer your question? BTW..it's what I have said in at least 4 posts.