Let me tell you a bit of a story about my X2 battery from Batteries Plus. I believe it’s essentially an Odyssey in special clothing, but here’s the story:
Battery was about a year old when my altnerator died. I didn’t know it had died because the car was running so well on just the battery. Got home, car would not restart. Repeated jump starting attempts and I managed to get the battery down to 7V.
Hooked my battery tender and tried more starting attempts and managed to get the battery down to 4V. By any rational measure, this battery is mortally wounded. I it took a couple days in spare time to get the alternator, but I got it done. Battery was (presumed) dead.
I hooked up the GooLoo battery charger and it would kick off saying “battery is toast” after about 20 min. Reset the charger, tried again. I noticed it would go a bit longer before kicking into “your battery is toast” mode.
After a dozen or so cycles of this, I just left the charger on overnight to see what happens. In the morning, the battery was up to 10.8V or so, but the charger had kicked out into “battery is toast” mode. But clearly the battery was growing in charge.
A couple more cycles and the battery was up to 12.7V and is started the car.
I let the car run, battery got up to full charge.
Three years later, that battery was still powering that car when I sold it just after Christmas recently.
Now, show me another car battery that can shrug off being pulled down to 4V!!