doesn't that defeat the purpose of having a high output alternator and at 14.2 you're a fair way off full charge?
As for the 14.2v, anything over 13.8v (3.45v/cell) with a short amount of absorption time will get an LFP to full charge. My battery, on shore power is charged 60A charging current. To recharge from 0% SOC to 100% SOC whould take the following.
- A fully discharged at 0% SOC at 10v [2.5v/cell] (the bottom limit where the BMS shuts the battery off) it would take about 10-minutes to raise it to 12v [3.0v/cell],
- about 9 hours to raise it to 13.8v [3.45v/cell]
- Another 15-minutes to raise it to 14.6v (3.65v/cell)
On shore power, I charge only the LFP and it is set for 13.8V with a 12A tail current which gets it to 100% without worrying about tripping the high cell voltage limit in the BMS.
The purpose of a high output alternator is to recharge a battery bank as fast as the alternator is capable of. None of the "high output alternators" that I know of are capable of charging a large LFP bank at
full output without overheating. My alternator is an old Ample Power 108A externally regulated alternator. It has heavy duty windings and should be able to run continuously at a case temperature of 100ºC [210ºF].
When I installed my battery, I found that the alternator temperature would be going past 95ºC about 10-minutes after it started charging. I have a fully sound insulated engine compartment and it was staying at over 80ºC just from the engine. I throttled the alternator to 60A AND run my bilge blower anytime the engine is running and that lowered the case temp to 90ºC max. I have now rerouted the bilge blower so that it is pulling the hot air directly from the alternator's cooling fan and that lowered the case temp to about 80ºC. I further plan to add a cool air duct with blower fan that blows cool outside air directly into the alternator inlet ports which will allow me to increase the output current. My aim is to set it as high as I can while staying below 90ºC.
I am currently limited to 60A mostly due to the 3/8" v-belt and cannot go higher than that until I install a serpentine belt.