It's a Hitachi cordless drill and neither battery would recharge. No charging indicator on the in-wall charger. They have been sitting unused for a while. I have seen videos of people charging a dead battery with ANOTHER working battery but in my case BOTH are dead and won't recharge... Can I use a NOCO trickle charger to charge/boost them? (+ to+ and - to -) . Any danger in doing that?