question

ulfertg avatar image
ulfertg asked

MPPT 100/20 - FW 1.53 - fixed absorption time defined in the settings is no longer adhered to

Hi,

since FW 1.53 the fixed absorption time defined in the settings is no longer adhered to.

A couple of seconds after reaching absorption voltage the MPPT jumps directly from Bulk to Float.

Tested with two different MPPT's.

Could you please fix this?

firmware updatebug report
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2 Answers
Mark avatar image
Mark answered ·

This will only happen if:

a) The output/charge current falls below the tail current threshold - check your settings (default tail current setting is 1A for the small MPPTs and 2A for the larger ones)

Note that if you have a VE.Smart Network with a battery monitor (BMV or SmartShunt) it will use the current going into the battery as the tail current reference. Same goes if you have a Venus device + battery monitor with DVCC and SCS (Shared Current Sense) active.

or

b) The absorption time set has already elapsed in the same 'solar day' and new charge cycles are being triggered (note that the PV voltage must fall below the battery voltage for a few hours in order to trigger a new 'day' and reset the absorption duration timer.

Please look into these possibilities.

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ulfertg avatar image
ulfertg answered ·

Thank you for your comment and explanations.

a): Tail current was deselected on both MPPT's while the issue showed up.

b): This could have been the case for one of the MPPT's (can't tell for sure anymore), the second one has been sitting on my workbench for a couple of days, connected to a battery but without power source on the PV-side. So elapsed absorption time shouldn't be the cause.


However: I switched tail current on, set it to 0.1V, switched it off again and couldn't reproduce the issue anymore since then.

Also not with V1.54, to which the MPPT's have updated in the meantime.

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