DeWalt 20V Max trimmer battery won't charge - any ideas?

Hey all. My DeWalt 20V trimmer battery stopped charging after about 2 years. It's the 5Ah one. Lights on the charger flash red/green. Anyone else have this issue? Thought these batteries were supposed to last longer.

Hate to say it, but sounds like a dead cell. DeWalt's 20V Max batteries are solid, but no battery lasts forever with heavy use. Try a deep discharge/recharge cycle—run the trimmer till it stops, then charge overnight. If that doesn't work, it's probably toast. Check warranty; might still be covered.

I've had good luck with Milwaukee batteries, never had a charging issue. But for your DeWalt, make sure the contacts are clean. Sometimes corrosion or dirt can mess with charging. Also try a different charger if you have one. Could be the charger, not the battery.

Before you buy a new battery, check if you can rebuild it. There's kits online for around $20. I did that with my Ryobi 40V and saved a ton. Not as easy as popping in a new one, but if you're handy with a soldering iron, it's doable.

2 years is about right for those 5Ah packs. They use 18650 cells, and they degrade. If you're comfortable, open the case and measure voltage across each cell. You'll likely find one cell at 0V. You can replace just that cell if you spot weld, but easier to buy a new battery. DeWalt's 6Ah or 9Ah last longer.