New rechargeable batteries, old charger

Factual Questions
1

What numbers do I need to look at to tell if it’s safe to use my new Eneloops in an old Energizer charger that I have?

TIA

2

You need to look at the battery chemistry. The new batteries are likely NiMH (nickel metal hydride) where older rechargeables were often NiCD (nickel cadmium, aka ni-cads). A NiCD charger usually won’t charge a NiMH battery properly.

3

If the old charger has an NiMh setting, it’s OK for the Eneloops.
If it’s NiCd-only, don’t use it.

If it’s a simple trickle charger, you can charge the Eneloops with it, but don’t keep them on the charger past 14 hours or so.

4

It both has a switch for NiCD-NiMH and is a trickle charger, so this is all good info.

Thanks again!