Milwaukee 1/2 lithium ion 18v drill not working

The batteries were discharged too low. A lithium battery should be recharged as soon as you see a loss of power.

Brushes to the motor could be the cause or heat sensor in the battery pack it switches off or even bad connections on motor check the spades connections could be loose

Your batteries are tired and don't put out enough amps to power your drill. They may show 18V in them on a tester and show fully charged on the charger but one or more of the cells inside are just worn out. If you got three years out of them you did extremely well. The only fix is to replace the batteries.

As far as I know , new lithium batteries need several charge cycles to reach full capacity, maybe 3 to 5 times.

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.

no, I would not try this. You can charge a nicd battery on a lithium-ion charger but not the other way around.

The same thing happened to me. There is normally a 2 year warranty on the batteries from Milwaukee. You can't return them to the Home Depot, you have to send them back via a local repair center.
You won't be able to exchange the batteries at the repair center. The repair center sends them back to Milwaukee and Milwaukee will send replacement batteries. You will probably be able to find the closest repair center on line.

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!

Is this an old battery? Batteries can fail and not charge after a lot of use. If it's new, run it all the way dead, then try to recharge .

If you need further help, I’m available over the phone at https://www.6ya.com/expert/craig_3fa289bf857b1a3c

No, it's showing that the battery is either not taking a full charge or the charger is not charging the battery properly. Find a Milwaukee service center, they will check them and most likely replace one or the other.