18 volt dewalt lithium ion battery charger stopped working for no reason....

You don't.

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.)

Either bad batteries or a bad charger. You can use a multimeter to test for DC voltage output in the charger.

No they are two different types of battery on the inside but the electric charge they put out is the same.

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

No. The P110 is for NiCad batteries. Any of the Li-Ion chargers like the P113 are backwards compatible and can charge either but do not try to charge Li_ion batteries in a NiCad or NiHi charger.

Probably, the battery has seen better days. After full charge, the battery should read more than 14.4 volts until used for a little while. You should either replace the battery or have it rebuilt with either Ni-cads or much-better lithium ion cells. Check with www.primecell.com for information. I had this done for a Skill drill battery (Li-ion) and the charge holds for long periods of time when stored and lasts far longer when used. The original charger worked ok for this modification. Hope this helps!

No, but the Lithium charger will charge the NiCads.

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