question

Hi @Bossrox

Can you share some screenshots of your custom settings, and of history?

I don't have software to do a screenshot so I'll write out the settings, hope that helps.

Batt v 24

max charge 100 amps

batt preset user

expert mode on

absorb volts 29.0

float volts 27.6

eq volts 29.1

rebulk offset 1.5v

absorb mode adaptive

max absorb time 1 day

tail current 3 amps

auto eq disabled

max eq time 1 hr

eq current 100%

On the graph, this is how it reads for today. It did go into an absorption cycle briefly without my presence as the batteries were near topped off at the start of the day but after that I sat & watched most of the day as the batteries weaved back & forth discharging more than charging but every time when it reached 29v, it switched directly to float with anywhere from a 30 to 50 amp tail current. So it appears it will only go into absorb mode just once in the user mode, whereas in preset mode it will do absorb as many times as it needs to when it get drawn into bulk on it's way back towards float.

Hope that's enough clues to find a solution, thx!

Say Dan... This must be some kinda weird karma but After responding to your post, I went back to monitor the system some more & it started working as I would expect. It's now switching to absorb from bulk & floating at the set tail current. I'll keep an eye on it the next few days to see if it acts up again & report any clues that might be helpful if it does but if you don't hear back from me soon, the issue may have worked itself out

Well it's now reacting as it did before. I saw in another post that it's programmed to only use absorb until it has it's 1st float event, then if it drops into rebulk, it goes strait to float after that, & that's what appears to be happening.

Well today I was able to see 1 event where it switched from bulk to float with a 30 amp tail current.

Victron programming staff, I'm no expert on this but when I saw a 50 amp tail current on float the other day & switched it to equalize @ 29.1, there was a significant jump in solar utilization from 27.6.

From some research, I learned that absorb is the same voltage as bulk but at a lower current. So it wouldn't be as strong as equalize? Is that correct?

Even tho it's still charging on float, I doubt it's doing it near as strong as in absorb before going to float & isn't the idea behind a smart charger of getting the batteries topped off as quick as possible without over stressing the batteries?

It appears to me there could be a better way to program how it charges. I believe it would charge better if it always went to absorb after reaching it's set voltage & waiting for the set tail current to switch to float.

Unless there's evidence that wouldn't be a better method of charging, I'd like to have that choice in settings to work like that & could it be implemented?

Can you tell me otherwise why your method is the preference you choose for your chargers? I'd really like to have a better understanding why what I perceive a better way might be flawed thinking.

In order to to maximize battery life (minimize the amount of recharge cycles and also the amount of time the battery is held at the elevated absorption voltage) it's generally undesirable to purposely/frequently have multiple recharge cycles in the same day.

If this is a common occurrence, it's typically a sign that you are using very large loads for a portion of the day and your system (batteries & solar) just can't keep up.

However, it is currently possible to have multiple charge cycles in a single day which are triggered by the re-bulk voltage - including multiple absorption phases.

When you setup your charger and specify the absorption time, that time relates to the entire day.

If the initial absorption phase is ended 'early' due to the tail current condition being satisfied (before the absorption time is complete), then the remaining time is still available for use later in the same day if multiple charge cycles are triggered due to the re-bulk voltage threshold.

If your MPPT moves direct from bulk to float during re-bulk cycles later in the day, that's simply because the full absorption time specified for that day has already been utilized (in one or multiple absorption cycles), and the timer will not reset until the next day (triggered when PV voltage is below battery voltage for a few hours). This is correct and exactly how the absorption time limit should work.

If you are using 'adaptive absorption' then the absorption time specified is subject to a multiplication factor based on the battery voltage in the morning when the MPPT 'wakes up' in the morning - see: https://www.victronenergy.com/live/victronconnect:mppt-solarchargers

So if you use adaptive absorption and specify say 6h max, if you have a high battery voltage on a given morning, then the actual maximum absorption time for that day will be calculated as only 1h or 2h (which is normally and perfectly appropriate for most systems) - this might be the part confusing you...

Now for your particular use case/expectations, if you want to always use tail current as the logic to end the absorption phase and you want to frequently have multiple absorption phases in the same day - then it may be best to just select fixed absorption and specify a long absorption time like say ~12h (or even 24h if you really want...). When the tail current condition is satisfied it will always end absorption phase and move into float phase, regardless of how much time is left on the timer.

Now frequently having ~12h of absorption in 1 day is not exactly ideal, but if that's what you really want to do, you can do it...