This is the float right? What soc does the battery say it is at at this point?
Do you have the internal soc monitor set?
What is your sustain set as?
This is intersting as the switch from bulk to absorption should be triggered after the battery hits the target bulk/absorption voltage set in the charger tab. And triggered by amperage drop.
At what voltage does the battery drop to where the bms request the full absorption voltage again?
Yes 54V is float, BMS reports about 99% SoC at this point.
Battery monitor is not enabled, this is for use with Victron or other smart batteries where the Quattro controls charging (system master) using the SoC reported by the BMS inside the batteries. I suspect that solar/wind priority would work in this mode, except maybe not returning to sustain mode after a āCharge to 100%ā event.
The REC-BMS works the other way round, it is the system master and controls the Quattro (and the MPPT controllers) ā which is why VRM shows āExternal controlā on the system diagram. āBulkā and āAbsorptionā donāt really have any meaning any more, the Quattro should just be a slave to the BMS.
The problem seems to be that the Quattro still thinks itās in charge as far as solar/wind priority is concerned, and it draws the wrong conclusion when 100% SoC isnāt reached after a week ā it thinks that means there isnāt enough solar so gives up on sustain mode and switches to absorption mode.
But the actual reason 100% SoC wasnāt reached is because thatās what the BMS wanted to happen, not charging above the 54V float voltage.
What i am thinking is set your sustain down lower to whatever voltage triggers the 57v CVL raise up from the 54CVL request from the BMS.
That way the issue of the cap while it is trying to charge has a workaround.
Or find the setting where the switch is triggered earlier. Never used REC so canāt help there
I donāt see how that would help. Without using solar/wind priority everything works just fine, with the Quattro under the control of the external BMS ā except that when plugged into shoreline (most of the year!) solar does nothing (waste of potential power) because the shoreline holds the batteries at 54V all the time (except for a trip up to 57.3V and back for 2 hours once a week). None of the Quattro parameters do anything, the BMS completely controls charging by setting CVL and CCL.
With solar/wind enables the Quattro now decides what to prioritise for charging, but still within the voltage/current limits set by the BMS. So if thereās enough solar to recharge every day thatās fine, battery voltage typically hits 54V (99% SoC) by about midday and then sits there until the sun goes down, drops overnight and then comes back up to 54V the next day.
Thatās all fine for about a week, but then the Quattro solar/wind firmware realises that a week has passed without ever hitting 100% SoC and ā as the documentation describes ā tries to charge up to 100% from shoreline, sets the red āCharging to 100% SoCā flag in VRM, and switches from sustain to absorption mode.
Which would be fine if it was the boss but it isnāt, the BMS is, and itās determined to hold the voltage down to 54V (the āfloat/sustainā voltage, 99% SoC) ā and wins, so SoC never reaches 100%. So the Quattro carries on trying to charge to 100% in absorption mode, and the BMS refuses to let it by holding CVL at 54V. And since the Quattro never gets to 100% SoC, it stays like this.
Next time this happens Iām going to leave it for longer and see what happens, instead of manually cancelling the āCharge to 100%ā run. Maybe that will work now the Quattro absorption interval is set to 14 days not 7ā¦
Then why use it?
My suggestion come from understanding the problem as the bms is capping the CV when the system is trying to charge. And sustain is being triggered by wind solar under the cap.
Solution trigger when the bms changes its cap back to full absorption. So the voltage has to fall lower. (The widget would be interesting to compare - dc bus voltage, mppt voltage, bms voltage and cvl)
Why use it? Because otherwise when the boat is plugged into shoreline (most of the time, itās a holiday boat not liveaboard) it makes no use of free solar power even when thereās plenty to run the boat, all the power comes from shoreline at 25p/kWh which needs the bollard to be regularly topped up ā which is a pain when itās 150 miles away, because topup is via a smartcard inserted into the bollardā¦ 
Thereās not really any such thing as absorption with LFP batteries, the only reason to ever go above the āfloatā voltage (54V) is occasionally for call balancing. So the Quattro should use this to decide when to stop charging in solar/wind mode (reaching the CVL), not looking for the mythical 100% SoC ā if it did this, everything would be fine.
I wonder what happens if I change the voltages on the āChargerā panel on the Quattro configuration page? Currently these are set to 54V float and 56.8V absorption (with 52V Sustain voltage on the āAdvancedā tab where solar/wind priority is set).
These would normally be set based on how your battery is set up. Since you have a custom set up with your rec, it needs to be worked out based on the rec settings and commands.
What isnāt clear to me ā or possibly anyone outside Victron! ā is what the various Quattro voltage settings and modes (Bulk, Float, Absorption, Sustain) mean or do when an external BMS is controlling chargingā¦
With the Quattro in charge itās clear ā bulk charging is constant-current until it reaches the absorption voltage (56.8V in my case) where is stays for the programmed time (e.g. 2 hours), then it stops charging until the voltage drops down to the Float voltage (54V) where it is then held. The mode changes depending on where the Quattro is in this charge cycle.
When solar/wind it prioritised, it uses solar power instead of shoreline if available (Sustain mode), unless a week passes without hitting 100% SoC (which I assume is defined as the absorption voltage being reached?) when it triggers a ācharge to 100%ā cycle, and then doesnāt return to sustain mode, it stays in Absorption mode.
(the documentation says this period is a week, but in VEConfig it kind of implies that this can be changed with the absorption repeat delay setting ā does anyone know for sure which is the case?)
Is this all correct?
So what happens when itās under external control from a BMS, in my case with 100% SoC defined as 57.3V and Float voltage as 54V? The BMS normally stops charging at 54V by setting the CVL, but once a week raises this to 57.3V for 2 hours to balance the cells and reset the SoC counter ā assuming thereās enough solar. If there isnāt and voltage drops below float, once SoC reaches 95% the CVL is also raised from 54V to 57.3V.
So how does the Quattro decide what mode itās in (and what do they mean with external control?), and when does it switch between them?
Should I set the Quattro Float voltage to the same value as the BMS one like it is now (54V) or lower?
Should I set the Quattro absorption voltage to the same value as the BMS one (57.3V) or lower? (itās currently lower at 56.8V)
If the BMS raises the CVL to 57.3V after 7 days but the Quattro delay is set to 14 days what should happen ā nothing until 14 days (SoC continues to fall due to lack of sun) then a charge to 100% SoC? (which should work)
Once this has happened, is there any automatic way to get the Quattro to go back to sustain mode, and wait another 14 days before the next āCharge to 100%ā is triggered?
This would be preferred behaviour so that whatever solar power is available is used (even if it canāt keep the batteries full) rather than shore power.
Iāve attached a plot showing what has been happening ā in each case I manually stopped the āCharge to 100% SoCā since there was no sign of this happening automatically, next time Iāll leave it alone for longer and see what happens.
Set your absorption to 54v since that is the max the system is supposed to charge to and that way the CC CV charge wonāt be mistriggered.
The higher CCL than set is not an unusual request from a battery it happens with other manufacturers. The system will follow the bms set charge even if that voltage is higher than that the programmed one.
I still think the issue being experienced is because the balance in programming is not optimal for your custom set up.
Thanks ā I assume you mean set absorption voltage on the Quattro to 54V? (56.8V now)
Do I also set both absorption times to 2hrs, which is what the REC-BMS aims for?
What do I do about the Quattro float voltage, which is currently also set to 54V (same as the BMS targets)? Do I leave it the same as the absorption voltage (is this possible?), or reduce it to something like 53V?
P.S. CCL is set to 0.3C above 95% SoC and 0.6C below this (recommended for Winston 700Ah cells ā maximum is 2100A!!!) ā even 210A is bigger than maximum possible from shoreline/generator + solar so this limit should never be reached.
(on the Advanced tab where solar/wind priority is set, sustain voltage is set to 52V)
You can set float and absorption to the same voltage.
Thanks, Iāll try that ā also set both absorption times to 2hrs.
P.S. Thanks for all the helpful replies, Iāve been trying to resolve this for ages 
I am sure we can work it out. Might end up being a ling thread 
OK, made those changes ā letās see what happensā¦ 
Checked voltage readings in BMS and Quattro and they can be slightly different (ten mV or so), so when BMS stops charging at nominally 54.0V the Quattro can read 53.9x V.
So have changed Quattro settings to 53.9V absorption and 53.8V float, so it always thinks it has reached full charge at 54V. Having them all set to different voltages means I can tell what is controlling the voltage if it sticks at a particular value.
