Hybrid battery system story
Freezing outside, furnace is running on the FLA battery.
Battery fails, (5 years old) dropping to 8.6 volts.
Fan slows down, furnace overheats. Sail switch does not open, overtemp switch does not open. Maybe they would have but the high temperature smell required action.
Switching to lithium the fan speed increased markedly, furnace cooled down and all was well. This was a 6AM action initiated by raising the thermostat from 55F to 73F. The battery monitor did not give an audio alert. I'll have to look into how It is programmed.
Not a big thing as a Walmart was 30 minutes up the road, but could have been in an isolated setting without the redundancy.
Just an anecdote. Have a nice day.
Anyhow, I enjoyed the redundancy. Still concerned about the safety systems in the furnace not activating and the low voltage alarm not being audio. (I have probably programmed it off.)