According to Betta Batteries Soi2 Advisory - Note “Correct Size Charger” requirement (includes Solar):
“WHAT CAN HAPPEN IF UNDERCHARGED”
If Betta Batteries Lead Crystal? Batteries are not charged with the correct amount of charge current the Batteries can reduce in capacity and performance. There is a small amount of moisture (Electrolyte) contained within the battery that moves between the positive and negative plates during charge and discharge. If insufficient charge current is used this moisture can eventually be held within the plate. Effectively reducing the electrolyte and therefore the capacity of the battery.
“DETERMINING THE LEVEL OF UNDERCHARGE”
How soon this moisture gets held within the plate will vary greatly depending on factors such as the size of the charger, the numbers of cycles, the depth of discharge and the temperature. Often, simply cycling the batteries a few times with the CORRECT SIZE CHARGER will see the battery recover in capacity. The first warning sign that things are more serious is that the voltages will climb rapidly during charging. This tends to exacerbate the undercharging as the charger will move quickly through Bulk and Absorption resulting in very little amperage going into the battery.”
Many Thanks to FWC for providing the aforementioned helpful Betta link :)
3 tons