I have the SmartSolar MPPT 100/50 set to Absorption duration Adaptive, Maximum absorption time 6 hours, tail current 2A (the defaults). It went to float after just under 1 hour when current was 18.4A. I have another identical setup that works properly. Both are on the same software version, both have the same solar panels, battery and monitoring, both are brand new.
Am I missing something here? I’m trying fixed mode today but shouldn’t it have stayed in absorption until either the current hit 2A or the time hit 6 hours?
The absorption time of a Charger will adapt itself as follows:
after each period of bulk charge (= the charger has reached its maximum current) an absorption period of 20 times the the bulk charge period will follow, with a maximum set at, for example, 4 hours.
So if one battery was fairly full then it would take a short bulk charge and the Absorption charge would be short. If the other was at a lower SOC then it would be correspondingly longer charge.
Were the two batteries at the same SOC when they started?
The bulk charge period that day was 2 hours 40 minutes. The absorption period was 55 minutes and ended at 18.4A.
The two systems were not at the same state of charge, but only different by a tiny amount (about 3%). The one that stopped absorption early was the one at the lower state of charge.
If you want to reliably use tail current to end absorption I found using fixed absorption the best option to force it to continue until the tail current was satisfied. Just make sure the tail current is suitable for your battery type and capacity.
Well, the sun came out this afternoon, unexpectedly, and that seemed to work. It dropped out of absorption into float at the same moment the current dropped below 2A. Thanks!