There’s a few variables worth considering such as, total battery capacity, charge wire size (and length if excessive), battery type and total available charging amps from all sources…
For example, often a lithium battery (LiFePo4) is capable of a maximum charge rate as high as it’s amp/hr capacity (say, 100amp/hr capacity receiving 100amps current – though this uber high rate somewhat at the hidden cost of longevity), which makes Lithium the King of the Hill for rapid charge acceptance, an especially important attribute when considering solar harvesting (e.g. exploiting the ‘peak harvesting hours’ window)…
Though lithium may or may not be in your future (??), either way the best place to start would be to understand what ‘the system’ is really doing and go forward from there – JMHO… So my first step would be to install a good shunt based SOC meter (assuming you don’t already have one?) so that you can ‘actually see’ the activity traveling in and out of your battery, and know the battery’s current SOC (state of charge), etc. This will better help you arrive at a more proper diagnosis, and in the long run serve you well indeed in seasons to come…My personal favorite’s are Victron’s BMV 712, or their ‘Smart shunt’ both of which are smart phone capable and lithium compatible, the latter (as lithium prices continue to drop) in the event you later decide to change battery types…
A good SOC meter (Li compatible, such as Victron) will use both a coulomb counter and an embedded ‘look-up’ table to help arrive at an accurate SOC…
Phil
