Energizer stock might be a good idea. My Minimed pump recommends the Energizer brand as the best. I don't know about the Animas Ping but Medtronics recommends that Lithium batteries not be used. I understand that when they die they die quickly.
The Ping is the opposite; they recommend that you only use the Lithium batteries!
I remember a few years ago I calculated my battery cost at about 4 cents a day, that's not bad considering the value my pump brings to the table. My last purchase of Energizer batteries cost me about 50 cents each.
I have a Minimed pump, and I to use just a regular Energizer AAA battery and I probably get about a month or so out of 1 battery. Your settings might have something to do with how long your battery lasts. All my alarms are on vibrate, and my CDE said keeping them on vibrate ran the battery down faster, but it's not like my pump is alarming all the time anyway, and I hate the CGM so I don't use the annoying thing. I got little use out of it.
I get about a month also and because I don't hear so well I keep mine on vibrate also. I would probally never hear a beep.
I have an Animas Ping and usually get three weeks to a month out of an Energizer lithium battery. I date them when I put them in the pump to keep track of its usage life. I don't know of another manufacturer of lithium batteries, and I usually buy them in an eight pack and keep them in the refrigerator until they are used.
You might check your pump settings to be sure that your pump is set for lithium batteries. You can get by with an alkaline battery for awhile in the Ping, but its life is much shorter. To check, take out the battery and replace it again. There should be a prompt on the screen that asks if you are using a lithium or an alkaline battery. Select the lithium option, and click ok. Unless your pump is sending excess alarms, pumping excessive boluses or you are using the light a lot, I would think that you should get more than two weeks from a battery.
I think I would keep in touch with Animas on this subject.