I have an OT question for all y'all who are musicians and have used 9v batteries in their preamps. I recently bought a new Sire P10 bass. I really love it except for one thing. The internal preamp requires 2 - 9 volt batteries, and it chews through them in no time flat. So, I was thinking that the obvious work-around is rechargeable batteries. I've used rechargeable batteries for lots of other things - but they were AA or AAA 1.5v batteries. Micro Center doesn't carry rechargeable li-on 9 volters, so I went online to Amazon. There, I found that 1) they exist; 2) there is wide disparity in mWh between the various offerings; 3) they don't charge up to 9 volts - only to 8.4 volts (presumably to avoid accidentally setting say, your bass, on fire).

Back in the early '80s, when I played for a meager living, I went through a lot of Duracells. And I noticed that long before my preamp no longer amplified, a certain sparkle had disappeared from the sound. Like, not the volume, particularly, but some harder to quantify edge to the sound. Or something. I could feel the difference and it affected my performance. As a result, I seemed to constantly be replacing Duracells that would still have powered a smoke detector for many months. And if I was unlucky enough to buy a pack that had been sitting around for awhile - my guitar might never sound its best with them. Oh - and I used Duracell batteries because I was convinced that the sparkle lasted longer with them than other brands (when they hadn't spent too long sitting on the shelf).

On Amazon, I found some 9v, li-on rechargeables that have outrageous 5,400 mWh power density as opposed to some others that only have 200 mWh. I'm thinking maybe I wouldn't have to even recharge them very often.

So, here's my question. My VOM says a new Duracell puts out right on 9v. Before I lay out the cash for rechargeable batteries and a rig to charge them through, am I foolish to think that 8.4 v might be just as good as 9 v when they are all charged up?