jrcresawn avatar image
jrcresawn asked

Longer absorption with firmware v1.42 for SmartSolar MPPT 75/15

This morning I updated the Victron Energy app on my Android phone. After I updated the app I opened it and selected my SmartSolar MPPT 75/15 from the list. I was encouraged to change the Bluetooth PIN, which I did. Next I noticed that the charger was charging my battery in the absorption stage. Since the battery was fully charged I was surprised that it did not quickly transition to float. I left the charger connected for about an hour and the entire time it remained in absorption. I disconnected the charger before leaving for work since I was concerned that the charging algorithm was behaving so differently than it did with the previous firmware version. Given that the battery was fully charged the previous firmware would have stayed in absorption for less than 5 minutes and then would have entered float. Should I be alarmed or delighted by the newly extended time of the absorption stage? Could it be that the old algorithm never fully charged the battery and firmware v1.42 has corrected a long-standing bug that prevented the complete charging of batteries?

MPPT Controllersfirmware update
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5 Answers
mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Many thanks @jrcresawn for raising this.

There was indeed an issue, exactly as you described in your comment twelve hours ago: re-selecting a preset created with an older version of VictronConnect could cause the new settings to initialise at a wrong default.

Also I’m happy to report that its fixed already: we released VictronConnect v5.10 a few hours ago:

Note that just updating, I mean without thereafter manually reselecting a preset, worked and works fine.

Thanks again, also @Mark and others for the quick turn around. We would not have been able to fix this so quickly without all of you.

I will add a note about this to the v5.9 blogpost soon.

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Mark avatar image
Mark answered ·

Did you happen to configure any of the new settings?

Could you provide a screen image of your full settings?

If you simply just upgraded the firmware then there should be no change with the absorption to float switch logic or settings.

The default absorption time is set to 'adaptive' and with 6h max absorption time. But if your batteries are full and above a certain voltage when the charge cycle starts then the actual max absorption time will be adjusted to 1/6th of this, so 1h.

The absorption phase can also end earlier based on the charger 'tail current'. The default was and is 1A for your MPPT, but now this is also user configurable in the 'expert' settings.

So unless the calculated adaptive time limit has been satisfied or the charge current has dropped to a level below the tail current threshold, then the MPPT should remain in absorption phase.

If you have possibly changed some of the charge settings after upgrading to the new FW then that could be a reason for different behavior.

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jrcresawn avatar image jrcresawn commented ·

After I upgraded the Android app and then the firmware I changed the Bluetooth PIN for both my SmartSolar MPPT 75/15 and Smart Battery Sense. I removed the SmartSolar MPPT 75/15 from the VE.Smart Network and then added it again. After making these changes both devices reported that they were communicating over the VE.Smart Network. I did not change any other settings. I will be happy to provide a screenshot of my settings later today.

I noticed the new "expert" settings button but I did not explore it.

I have made battery profiles for the two batteries I charge with my SmartSolar MPPT 75/15. One is a gel SLA battery and the other is flooded. I am open to suggestions to improve my battery profiles and any other settings.

Later today I will connect the charger, leave it connected for a few hours, and report my observations.

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Mark avatar image Mark ♦♦ jrcresawn commented ·

No worries.

A key point is that the absorption time is only calculated ONCE per 'day', and if the absorption time has already been utilised fully or partly earlier in the same day then that will effect the absorption phase during any new charge cycles later in the same 'day'.

The MPPT does not have an internal clock, so for a new day to be triggered it requires the PV voltage to be under the battery voltage continuesly for at least 1hr.

So to 'properly' conduct a test, I suggest to wait for a new 'real' day or manually force a new day by disconnecting the PV for >1hr - as the first step.

Then record the exact battery resting voltage with the MPPT off, just before it starts up and goes into bulk charge phase.

Then monitor the following;

-The actual absorption time

-If the absorption voltage is maintained throughout the entire absorption phase, or if there is insufficient solar at times and it drops below the absorption voltage target. If so then the absorption timer will stop counting and the total 'reported' absorption time will be longer (but the 'real' absorption time will be honored)

- The MPPT charge current just before switching from absorption to float

In combination with all the charge settings, this information will enable the MPPT behavior to be understood.

FYI v1.42 has already been extensively tested on many different system configurations (including my own), so it's highly unlikely that anything unexpected is happening with your setup.

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jrcresawn avatar image jrcresawn Mark ♦♦ commented ·

Thanks for explaining how a "day" is defined. I have a van with a gel house battery and a standard flooded engine battery. I made the unusual decision to buy one nice battery charger---the SmartSolar MPPT 75/15---and supply DC power to it from one of three sources. They are a 100-watt solar panel, an Orion-Tr DC-DC Converter Isolated 12/24-10 which is fed by the alternator when I am driving, and a 147-watt ASUS laptop power supply when I am parked and plugged in. I have MC4 pigtails connected to the PV terminals on the SmartSolar MPPT 75/15 and each power source connects to those pigtails with a mating pair of MC4 connectors.

The laptop power supply is often plugged in for days at a time. Would it be wise for me to put the laptop power supply on a timer that will power it off at night and on during the day?

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Mark avatar image Mark ♦♦ jrcresawn commented ·

Yes in order for it to 'reset' and properly determine the correct amount of absorption time required you will need to have a period of time where the PV (or alternative power source connected to the MPPT PV terminals) is disconnected or below battery voltage for more than 1h.

The 1h delay IS an improvement/change that has been made in FW v1.42 in response to some users having the charger turn off and on mid way through a charge cycle (due to bad weather or driving under a bridge / car park) and then the charger resetting / starting a new charge cycle but providing an incorrect absorption time based on the 'new' higher voltage at the time of restart, rather than the original/correct battery voltage in the morning.

Ideally you should only be completing one proper charge cycle (with absorption period) per day. At other times the battery can still be kept 'full' with the charger in float phase.

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klim8skeptic avatar image klim8skeptic ♦ jrcresawn commented ·
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jrcresawn avatar image jrcresawn klim8skeptic ♦ commented ·

Thanks for sharing this blog post.

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jrcresawn avatar image
jrcresawn answered ·

I believe I now understand the longer absorption time which followed the installation of firmware v1.42. It appears that the new firmware brought with it a new switch set to OFF in my battery profile labeled "Adaptive absorption time". The subtitle of this switch is "Automatically calculates the absorption time". With that switch OFF my battery was charged in the absorption stage for about 3.5 hours and then for another 10 hours before switching to float. I changed the switch to ON. It may be the case that this issue is found only in custom battery presets. The two screenshots below tell the tale.

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Mark avatar image Mark ♦♦ commented ·

Adaptive vs fixed absorption was first introduced with Victron Connect Beta 5.9 and FW 1.42.

I checked the inbuilt regular presets and all have 'adaptive' as the default, except for the Lithium preset (as it should).

If you have old presets saved and these have carried over, maybe its getting a little confused since the option never existed before.

But I will highlight your experience to the developers and thanks for reporting your findings.

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jrcresawn avatar image jrcresawn Mark ♦♦ commented ·

I created that battery preset over a year ago since none of the default presets matched my battery's specifications. Unfortunately, I expect others who created custom battery presets will have an experience similar to mine.

Thanks for your valuable feedback with this issue and the education on the definition of a "day".

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Mark avatar image Mark ♦♦ jrcresawn commented ·

Hi @jrcresawn, no problem.

FYI the development team were able to reproduce the behavior when using an old preset.

Thanks again for the report and feedback.

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thomassolar avatar image
thomassolar answered ·

Fw 1.42 is a GREAT improvement, especially for us having a lithiumion battery bank. Before the MPPT changed from bulk to absorption 200mV BEFORE reaching the set absorption voltage. This issue has been fixed.

The possibility to set a fixed absorption time is also Perfect. And the possibility to adjust current and time for equalize is also Perfect for balancing.

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jrcresawn avatar image
jrcresawn answered ·

This morning the battery charged mostly in absorption in about 2 hours, which is a lot better than yesterday.

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