nhbassguitar
Well-known member
- Joined
- Dec 31, 2015
- Messages
- 127
I figured I'd experiment to see just how long a 9V alkaline would last if I left my '15 SR plugged in 24x7. I used an Amazon generic, which I've had extremely good luck with in terms of life span and reliability. I wanted to see if the degradation curves I found for Energizers here would line up with what I experienced.
It's important to note that I run my volume no higher than maybe 1/3, so I'm not swinging that much voltage (and therefore current) into whatever I'm running the instrument into. It works out to be slightly less than a Precision with a '62 CS pickup or '63 Pure Vintage pickup, both of which run hot, and that's at full volume. (I own both, and yes, I did the comparison.) I make up the gain in the preamp, and I still have plenty left.
During the test, the battery seemed not be draining at all, and I was checking its voltage every other day, so I popped the back cover to see what was on the preamp. The components and the board look totally different than anything I've seen on the 'net. Everything's super tiny now, mostly all surface-mount. Even the ICs are tiny SMDs -- only half the size of my pinky fingernail. I'm guessing the idle current of the entire preamp is way down in the microamp range.
Anyway, everything was fine until the battery got down to just below 6 volts. That was after about 5 weeks of leaving the SR plugged in constantly, except of course in transit to and from Sunday gigs. What's interesting, though, is the way the battery became useless when it hit that level: It was sudden. Yesterday I was rehearsing for maybe 2-3 hours with the battery at 5.8 volts, more or less, and things were fine. Then this morning I fired everything up, and... nothing. Dead silence. Took the battery out and it measured 1.5 volts. There was no warning at all. This sort of lines up with the PDF at the link above, where battery voltage decrease rate accelerates as battery voltage drops. The graphs' Y axes probably stopped short of the really low voltages because of how quickly the voltage can tank at those levels. I'm guessing it would've been an almost vertical line down.
It's also possible something weird (biasing-wise) happens inside those ICs when their supply voltage drops below spec. Could be those things start drawing a lot more idle current than they do at spec voltage.
Looking at the graphs again, they exactly mirror my experience of everything being fine with the battery sitting between 7 and 8 volts. The SR ran fine day after day for weeks with the battery in that range. It ran for many more days with the battery at 6+ volts.
What's interesting about the graphs is that 9 volt batteries, relative to their useful life, really aren't. They're really 7-8 volt batteries. Again, the SR is perfectly happy with this.
So, the rule I'm going to adopt is to test the battery once a month, and replace once it hits 7.5 volts.
(Oh yeah, and start unplugging the cord now when I'm done.
)
YMMV, etc. I hope this was helpful.
It's important to note that I run my volume no higher than maybe 1/3, so I'm not swinging that much voltage (and therefore current) into whatever I'm running the instrument into. It works out to be slightly less than a Precision with a '62 CS pickup or '63 Pure Vintage pickup, both of which run hot, and that's at full volume. (I own both, and yes, I did the comparison.) I make up the gain in the preamp, and I still have plenty left.
During the test, the battery seemed not be draining at all, and I was checking its voltage every other day, so I popped the back cover to see what was on the preamp. The components and the board look totally different than anything I've seen on the 'net. Everything's super tiny now, mostly all surface-mount. Even the ICs are tiny SMDs -- only half the size of my pinky fingernail. I'm guessing the idle current of the entire preamp is way down in the microamp range.
Anyway, everything was fine until the battery got down to just below 6 volts. That was after about 5 weeks of leaving the SR plugged in constantly, except of course in transit to and from Sunday gigs. What's interesting, though, is the way the battery became useless when it hit that level: It was sudden. Yesterday I was rehearsing for maybe 2-3 hours with the battery at 5.8 volts, more or less, and things were fine. Then this morning I fired everything up, and... nothing. Dead silence. Took the battery out and it measured 1.5 volts. There was no warning at all. This sort of lines up with the PDF at the link above, where battery voltage decrease rate accelerates as battery voltage drops. The graphs' Y axes probably stopped short of the really low voltages because of how quickly the voltage can tank at those levels. I'm guessing it would've been an almost vertical line down.
It's also possible something weird (biasing-wise) happens inside those ICs when their supply voltage drops below spec. Could be those things start drawing a lot more idle current than they do at spec voltage.
Looking at the graphs again, they exactly mirror my experience of everything being fine with the battery sitting between 7 and 8 volts. The SR ran fine day after day for weeks with the battery in that range. It ran for many more days with the battery at 6+ volts.
What's interesting about the graphs is that 9 volt batteries, relative to their useful life, really aren't. They're really 7-8 volt batteries. Again, the SR is perfectly happy with this.
So, the rule I'm going to adopt is to test the battery once a month, and replace once it hits 7.5 volts.
(Oh yeah, and start unplugging the cord now when I'm done.
)YMMV, etc. I hope this was helpful.
