I fly RC planes and use Lipo type batteries. My fancy charger will charge all types of batteries, but will not charge a Lipo that is too low. The trick is to set my charger on nickel metal hydride and set the charging current very small, maybe half an amp. Once it gets the cells up high enough, my charger recognizes it and I can reset the charger to charge it as a Lipo.
Where I got into trouble was I have a multiple connector that will charge 6 at one time. That would be fine if they were close to the came voltage, but connecting a few in parallel the strong ones try to bring the lower ones up, and if they are too far apart it does it VERY fast. I had a very low battery and was just going to connect it to the other 2 and let them all equalize, which would have brought the lower one up where it needed to be. What actually happened was the damned thing started smoking and I had to disconnect it and throw it out onto the concrete driveway before I needed a fire extinguisher. Be careful connecting 2 together that are not close to the same voltage, it may not work out.