I've designed a system that remotely logs some data (position, some weather data, etc.) in remote areas that currently uses a single lithium-ion battery (~850mAh) that is recharged via a solar panel with a BQ24210 solar charging IC that stops charging when the battery reaches 4.2V. The system wakes periodically throughout the day to transmit data and consumes roughly 50uA while sleeping. The BMS I have on the board (TI BQ29707) has an overvoltage lockout at 4.28V and an undervoltage lockout at 2.8V. So far, the system works well and performs as expected.
However, I have realized that the weather at the testing locations is much more volatile than the lithium-ion battery is specified to operate in (can easily reach over 110°F and below -10°F each year). Because of this, I am looking for alternative batteries that won't require a board redesign.
I have found some 2-cell lead-acid batteries that have a much larger capacity than what I need, but have a more relaxed temperature range. According to this article, it appears that lead-acid cells have a range between 1.93V and 2.15V which results in a 2-cell lead-acid battery having a voltage range of 3.86V and 4.3V.
Will I run into any issues making the substitution to a 2-cell lead-acid battery in my system? Size and weight are not a big constraint in this scenario.