Just saying you could put a big fat variable resistor across the PD40 and crank the voltage down to 10 volts and it would hum along putting out 40 amps all day.
If the battery starts fully dead at 10.5 volts the voltage will only rise from there.
You may not even get 40 amps through 4x GC2 when fully dead because the resistance is so high.
Lots of time I had a dead battery come into the shop for a charge. I think the shop charger was about 60 or 80 amps with several steps from 13.4 to 15.6 volts. I would crank it all the way up and get maybe 5 amps on the gauge. Then after some time the amps would actually increase as the resistance dropped faster than the voltage potential climbed. Once it got close to 50% charged it would start acting like a normal battery. I would tell the customer if they ran it down like this again he would be buying a new battery.
