I recently purchased a Die Hard manual charger for my e-tank. I noticed that when I fire it up, it runs for about 30 seconds, then shuts off. Roughly a minute later, it turns back on, runs for 30 seconds, and shuts off, and so on. It is not an automatic/manual charger, straight manual. Is this normal operating procedure, or do I have a faulty charger? Or is something else askew? Thanks in advance for replies and help!