I bought one a year ago and now both Drill batteries that came with it won't take a charge anymore. The second one failed a month after the first? I normally leave a battery on the charger so I always have a spare, wonder if that is the problem? At first I could leave a battery in the drill for weeks and it would still have power. Later a fresh charged battery would drain in two days even with no use. I love the drill, but this battery problem is disappointing.
Now I need some new batteries, any option other than the stock ones? Any better ways to care for them?
I don't think the battery mfg's recommend leaving batteries in the charger all the time. The Ni-Cad style needed to be cycled to essentially fully discharged before charging, or they would get a memory and short cycle. Later types like Lithium ion are not supposed to do that, but I think you are better off fully charging them and storing in the drill case. When one goes down you should have time to re-charge it while using the other one.
Ni-Cads will normally discharge over about 90 days time just sitting in the case. the Lithium types do not do that to any extent.
Most drill mfg's also do not recc leaving the charger plugged in all the time, from what I have read. Same goes for cell phone chargers.
One other point. Use a pencil eraser to make sure the battery contact and the charger contacts are bright and clean. They will tend to dull and get oxidation on them and that affects the charging ability and battery life in some cases.
Don't know what kind of batteries they are, but the chargers normally operate on heat buildup to tell it when to shut off. This is why they usually tell you not to sit the charger in hot sun, or a hot environment if at all possible.
You might try to fully discharge the batteries and possibly they will be salvageable. It would take several charging/discharging cycles to get some life back, but depending on type of battery, they may be toast.
It is also possible that your charger has gone bad and I would try another one to see if that helps the situation.
I went back and re-read your question. It sounds like there could even be a short in the drill switch, or it is for some reason draining the tool batteries by not being completely off, but you should be able to hear it "growling". Absent that problem the batteries just could be bad at this point, i.e. internal drain.
The battery supply houses may stock batteries for this drill. I doubt that Milwaukee makes their own batteries.
If I may intercede I currently have an 18v Milwaukee that was given to me by the company I work for. And I have to say its the worst cordless drill I've ever had. The 18v provides no more power, torque, or battery life than my 3 Dewalt 14.4v that I keep in my shop at home. In fact the Dewalt batterys actually hold a charge longer. And the best part is that if I do actually burn up a battery, the Dewalt batterys are half the cost of the Milwaukee's. Though I have not yet lost a battery in the 4 years I've been using the Dewalts. On the other hand I replace my Milwaukee 18v batterys about every 9 months to a year. And I too always leave a battery in the charger at home.