Victron MPPT absorption tail current settings

[Rotary]

I'm using adaptive absorption on my Victron 150/85 mppt. The default setting for tail current is 2A to exit absorption and move onto float. Im running 2 x 260Ah AGM @ 24V. Is there a general rule on what tail current figure to use relative to battery size? I'm also VE. networking a victron smart shunt (i believe the mppt uses the shunt current data to terminate absorption)

Another question I have is; will i have to increase the tail current setting as the batteries age? Absorption termination times seem to be getting longer.

 

[TomC4306]

Check your specific cell datasheet.

 

[Rotary]

I'm unsure how to determine tail current value from the data below

 

[mikefitz]

Try 1 amp per 100 Ah of capacity, some suggest lower at 0.5 amp per 100Ah.
Issues with this method of terminating charge will occur if current into the battery is not reported correctly. With the VE network this should not be a problem.
Battery ageing will have an effect but the batteries may have reached end of service life before the tail current increases significantly.
My experience with AGM suggests a total minimum charge period ( bulk plus absorbtion) of 5 hours with an available 0.2C charge rate, from a 50% discharged state.

 

[Rotary]

Thanks yet again @mikefitz

 

[pollenface]

I observed the current required to keep the batteries in float without a load and set that as the "tail current"

 

[STW]

I adjusted my tail current in my RV to 5a. That is because my RV pulls 3a with base loads.