Charging a lead acid battery with a lower bulk voltage
Nearly all cars have a Lead-Acid battery. In a car huge temperature fluctuations occur (engine on / off, car is outdoors). Lead-Acid batteries are quite robust and can handle some overcharging. As far as I know, in a car the charging voltage isn't changed with temperature and still most car batteries last for years.

As far as I know, what is advisable for an increased battery life is to not charge above 13.6 to 13.8 V (see battery's datasheet). If you then also limit the charging current (a series resistor will do that) as the battery voltage increases the current decreases as well and no damage should occur.

Instead of changing the voltage (which would be a challenge to get right as the battery voltage is quite unpredictable) it is better to limit the current to for example C/10 (where C is the battery's capacity in Ahr, so for a 1 Ahr battery C/10 = 0.1 A) then even when the battery voltage is low due to temperature, the charging current is limited and causing no damage.