By observing voltage, current, and energy readings I'm able to manually stop the charger before the battery reaches a full charge.
For the ePure and 14-cell 5.7s, 80% charged works out to about 55 VDC. For the 13-cell 5.7, it's about 51 VDC. Note that those voltages are for the battery “at rest” (measured 90 minutes after charging or discharging ceases).
In order for the charger to push current into the battery, the voltage it emits must be greater than the battery's voltage. Generally, I stop the charger when the DC power meter's voltage is 1.5 to 2 volts greater than my desired battery voltage.
It would be nice to automate this process, but so far I have not. My first thought was to use something called a “countdown timer” on the AC side of the charger. This would turn the charger off after a preset time interval. Give the battery, say, 1 hour of charge rather than allowing the charger to shut off automatically at full charge. Unfortunately, none of the countdown timers I've found meet my standards for quality (have ETL or UL certification). Because the battery charger's current draw is not insignificant, I want a safe high-quality device to interrupt it.
Since I probably have to build something anyway, a “voltage comparator relay” would be better. This would shut off the charger at a specific DC voltage. I'd need an analog voltage comparator to compare the battery's voltage to an adjustable reference voltage and open a relay on the AC side. I've just been too lazy to build it.