As a result of too high a charge voltage excessive current will flow into the battery, after reaching full charge, causing decomposition of water in the electrolyte and premature aging.
If you connect a charger which limits the maximum voltage to 17.5V and a maximum of 10A to that battery the voltage would be a little over 14.4V (14.5V) and the current would be 10A. Charging at elevated voltages is OK for very short periods but a lot depends on the temperature of the battery.
If the voltage drops below ~12.7 volts, the battery supplies current to keep the voltage in range. If it is above ~12.7 volts, the battery absorbs the extra current instead. Most MPPT charge controllers are "relatively" slow (cannot respond instantly to changing loads).
If the battery charges faster with the higher V. The energy that goes into the battery, let's say 17.5V @ 10A = 175watts where charging at 13.8 @ 10A would give 138watts. If the battery is very low in charge, will it store this excess of 37watts or would that excess be lost as heat?
What happens if no current passes through a charge controller?
First, if no current is passing through the panels (i.e., the charge controller isn't consuming any of the power to charge batteries), the panels only have a Potential. That is what the open circuit voltage Voc is. There is no current, so electrically, there is nothing that is converted to heat.
How do you charge a Li-Poly battery?
The basic algorithm for Li-Poly batteries is to charge at constant current (0.5 C to 1C) until the battery reaches 4.2 Vpc (volts per cell), and hold the voltage at 4.2 volts until the charge current has dropped to 10% of the initial charge rate. In addition, a charge timer should be included for safety.
Can a Li-Poly battery catch fire?
Instead, it would likely heat up and worst case catch fire. The basic algorithm for Li-Poly batteries is to charge at constant current (0.5 C to 1C) until the battery reaches 4.2 Vpc (volts per cell), and hold the voltage at 4.2 volts until the charge current has dropped to 10% of the initial charge rate.