Strange solar puzzle

[catlotion]

I've been away from my boat for 3 months and came up yesterday to find batteries all nicely charged to 100%.

However, when I checked the history, there's a weird blip of bulk charge activity about 10 days ago. Every day before and since has a tiny bit of bulk charge before returning to float. But there are three days showing with significant bulk charge (almost like someone has been aboard consuming power).

I thought it might have been temperature related but all this week the stats seem normal.

The boat has been vacant for the whole time - and no otter visits either (thought they might have had a party or used the fridge to keep their fish cold)

Any ideas?

 

[jac]

DO you have anything like an automatic bilgepump that is discharging via an unmonitored circuit?

 

[catlotion]

no - nothing at all. Electric bilge pump is manual.

 

[William_H]

Solar power regulation is not like a staged battery charger. Generally the limiting factor in charge rate is the power from the solar panels them selves.
So a huge solar array and small battery in bright sun will give enough input to then controller to give the classic bulk charge then maintenance charge.
But often with limited sunshine and limited solar power into a large battery your controller attempting to provide bulk charge will just hobble along giving max current available. It might eventually get to reducing charge to maintenance but likely not. I might suggest OP question of different amount of bulk charge might more relate to sunshine that day and possibly boat/panel orientation to sun. ol'will