Can I charch my new ryobi batery lithium whith the old charch

How about brushes..they wear ritedown. Armature ok..also fuses may lookgud but not

If the old charger has a deep-uncharge-protection contact and was also made for Li-ION ther is in any case a marketing technical design by a notch to protect the battery to place on the charger if this cells are not correct.
(this answer applies to all brands with a quality mark)

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.

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

the batter cells are weak and wont hold a full charge, replace with a new battery, also check that there is nothing in the way of the contacts such as foreign debris inside the battery cavity of the impact.

NO! Never charge lithium batteries in a charger designed for nickle based batteries like the NiHi your old charger was meant for. Ryobi did design the new Lithium charger to be backwards compatible so you can charge your older 18V NiHi batteries in the Lithium 18V charger.
Also note, NEVER miss-match the voltage, for example, make sure you are not trying to charge 12V batteries in an 18V charger unless the manufacturer has specifically stated that the charger is capable of multiple voltages.

the batteries are getting weak,I bet if you buy a new battery and fully charge it your drills will run like your used to.

No, just return it, for the money they should give you one that works. It is common to get a defective Ryobi 18v lithium battery. I've had 2 out of 7 purchased that wouldn't hold a charge. But when you get a good one they work awesome!

something is wrong. take it back if possible.

If you're speaking of the new green lithium battery charger working with the older yellow and black batteries, yes you can. You can't use the OLD charger to charger the New lithium batteries.