I'll stick with my old lever grease gun. We had one in the shop once, battery always died, spare never charged, hard to get primed, but here's the kicker.
Late last summer I was servicing an excavator in the shop. I noticed the track was a little saggy so I opened it up and used the cordless gun to pump it up. I pump and pump and the track doesn't move. I figure maybe the gun doesn't have enough pressure so I just use my trusty old manual gun and pump it right up. Now last winter we have a laborer servicing the trucks. I tell him to make sure to crawl underneath and grease the drivetrain, brake assemblys and everything that has a zerk. I'm not really paying attention because I'm working on the equipment. I'm using my old gun and notice that every time I go to the bin and grab a tube of grease, the stock isn't dwindling much, but I don't think much about it. Anyhoo, sometime in March I pull a bucket off an excavator to replace some bushings and after I put it back together decided to use the cordless because I didn't feel like pumping about two tubes in there manually. I pull the lever to see how much grease is in it and to my suprise it's almost full. So I pump and pump till the battery dies,(of course) grab the charged one(amazing), and pump some more. After a while I pull the lever back to see if I'm about empty and huh? Still full. Pull the gun off the zerk and push the button, no grease coming out the hose. It sounded like it was pumping, but it wasn't. I asked the guys how long it had been since they put a new tube of grease in it. No one could remember. I figure that gun hadn't worked for at least six months. If it didn't cost so much I would have chucked that damn thing in the dumpster. Last I knew they took it back to where it was bought but I'm sure the warranty was off by then.