Will a nicd charger work to charge lithium-ion batteries?

No, the P110, 18V NiCad battery charger, will not charge a 18V lithium ion battery. You need one of the dual-chemistry chargers. If you have the Ryobi ONE+ batteries, you can get the P117 charger ($30) or a charger with an extra battery (P126) from a store like Home Depot. A 6 battery charger and a 12V in-car charger are also available.

I wish that I had better news for you.

Cindy Wells
(who has the Ryobi 12V drill and charger, a few of the 4V tools, and a number of the ONE+ 18V devices and chargers. The single chemistry battery charger is not used much any more.)

This can happen if the battery is too dead for too long. Keep trying to make it work like you have maybe 20-30 times. Or you can leave the battery in for a few days and let the logic chip do it's job. It should start working in a day or two.

NO THE OLD CHARGER FOR THE BLUE ONE+ TOOLS WILL ONLY CHARGE NICD BATTERIES. HOWEVER THE INTELLIPORT DUAL CHEMISTRY CHARGER WILL CHARGE BOTH NICD AND LION BATTERIES. ALL BATTERIES ARE COMPATIBLE WITH ALL ONE+ TOOLS

That is true the One+ 18V Li-Ion battery packs will work in any One+ 18V Ryobi tool. However the Lithium ion batteries will not charge in the original P110 NiCd charger. You will need one of the the new series Ryobi One+ 18V "dual chemistry" chargers for that. The will charge both types of battery packs.

As long as the voltage of the battery is the same as the tool, the tool won't mind if the power is coming from a NiCd or lithium battery. You do have to have a charger that works with lithium batteries to charge them up. Chargers that can charge lithium batteries can also charge NiCd and NMH batteies. NiCd chargers are not always programmed to detect when lithium batteries are full and may continue to charge them to the point of melting or starting on fire.

If you have a P100 NiCad battery, the charger for that will not charge the new Lithium Ion P103 or P104 batteries. You need a specialised Ryobi Lithium Ion battery charger like this one

Do not try this since the charging circuit for lithium batteries are different than nicad! Improper charging of lithum batteries can cause a fire.

Use
AC / DC Power Adapter Replaces Ryobi One+ Batteryhttp://lcdpayless.com/ryobi_one_power_adapter.php

I think your tryiong to charge NIMH batteries oon a charger designed for Lithium Ion batteries. With all the new style batteries such as NICAD, NIMH and LI-ION, charging becomes difficult. Most chargers pre NIMH and LI-ion, were designed for NICAD's. The best advise, match your batteries with the correct charger