Originally Posted By: Traction
Very good information, and true wrcsixeight, but how do you check specific gravity on AGM and sealed flooded batteries? Also, what type of charger do you recommend,and the best way to maximize battery life?
Can't check SG with an AGM or any sealed battery, so remaining capacity and battery health is only known with a load test and a baseline to compare it to. Amp hour counters to see how much is taken from an AGM/VRLA battery, then comparing it to a rested Ocv voltage chart provided by the manufacturer is another way, but accuracy fades with battery age.
Generally AGM's will stop accepting current at their max allowed voltage, indicating a full charge, where as a flooded battery will always accept a little current even when fully charged. And upping the voltage can always force amps into the battery, whether it is fully charged or not. With sealed batteries this can pop the vents and cause positive plate erosion, with flooded batteries it causes more water usage in addition to positive plate erosion.
Best way to extend battery longevity is to keep it fully charged, and cool. On older vehicles without parasitic loads, a monthly recharge might be as good as keeping the battery on a maintainer. Newer vehicles the parasitic draws are higher so a maintenance charger left plugged in 24/7 is better to counteract self discharge and parasitic draws of engine computer and door locks and alarms ect.
I am personally interested in the Ctek line of chargers, specifically the 25 amp CTEK Multi US 25000, but they are not cheap. This one does have Temp compensation.
I currently have a Schumacher sc2500a Automatic charger that I do not trust to leave unattended as it will go up into the low 16v range, so I am searching for something new.
I also cycle my AGM and deep cycle batteries daily, so my chargers must meet different criteria than those just looking to top up a starting battery when needed.
Those interested in using a Battery charger as a 12vDC nominal power supply need to look into RV converters like Iota, Progressive Dynamics, and Powermax. These come in different amperage ratings. One must provide their own converter to battery cables, but these are like HD battery chargers capable of acting as 12v nominal power supplies while 3 stage charging battery banks.
Unfortunately, very few RV converters come with temperature compensation.
Each choose a different algorithm for charging as far as absorption voltages, durations, and float voltages, and on RV forums the opinions fly as to what is best.
RV converters generally are not put into any fancy cases nor come with fat DC cables and alligator clamps but they are highly capable and can replace most of the Giant wheeled manual chargers that many believe to be the Mecca of battery chargers.