I have the shorai. Lithium batteries have less amps when cold. You can turn on the headlight for a couple minutes before cranking and warm the battery. Cranking can drain it before it has a chance to warm. At 40F in my garage it cranks more slowly but starts reliably. If that tender does simple trickle charging it's OK, desulfating is bad for LiFePOS. If you charge at all you need to be sure the voltge does not go above the never-exceed coltage, I think it's 14.3? Lithium batteries have a lower max acceptable voltage when cold, it's a lithium thing.