OT - 9 volt Batteries and Musical Devices

[John Ludlow]

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?

[cgrafx]

Battery chemistry determines the voltage produced. (See https://batteryuniversity.com/articl...-with-voltages)

Lead Acid cells which is what all AA, AAA, C, D, 9V batteries are based on are 1.5V cells so you can get any multiple of 1.5V

NiMH cells are 1.2V not 1.5V, so you get multiples of 1.2V

Li-Ion cells are 3.6V (sometimes labeled a 3.7 or 3.8)

Lead Acid Batteries like the Duracell ones you were using all drop voltage as they lose charge. So the sparkle that disappeared was the result of the batteries dropping their nominal voltage as they lost charge.

NiMH and Li-Ion batteries have a discharger profile that pretty much maintains voltage until the battery loses charge and they the crash fast (meaning they will be working and the they simply stop).

9V NiMH or Li-Ion batteries either don't actually produce 9V or they must have a voltage regulator built-in to the battery as you can't get 9V from either battery chemistry. Meaning if they actually produced 9V at the output then they are stacked cells that produced more than 9V and are regulated down.

Be careful with the voltage specs as the batteries will be listed as 9V size but the actual voltage could be significantly less.

As an example Tenergy has a 9V Li-Ion, but its actual output is only 7.4V (3.7v x 2 stacked cells)

How sensitive the preamp circuit is to under voltage will depend entirely on the design of the preamp. It might work perfectly fine at 7.4 volts.

If the battery puts out 8.4V then it should work fine as the Duracell only puts out 9V under load when fully charged.

Also, 5400 mWh is approximately 600 mAh

One other thing to consider is the NiMh and Li-Ion batteries tend to be physically larger than their Lead Acid counterparts. So they do not always fit in the battery compartment if its normally a tight fit.

[mr_es335]

Philip,

As always, your responses are always incredibly succinct...and yet, incredibly concise! Thank you!

[jmh]

I was researching this last year and got sidetracked. I have a beautiful Carvin electric with a 9V cavity and the holder has lousy contacts that don't spring nicely and I've had to pop the battery and reinsert it many times to get it back in action. As cgrafx said the lithiums may dc -> dc convert to 9V which may mean it maintains consistent voltage. I found most of them have a usb recharge slot on the wide side - but there was one with the port on the narrow side which is ideal for my guitar. I decided to hold off as I may just pull the active circuit out - as it has humbuckers (or modify the active for only the piezo saddles - which are kind of a gimmick on an electric).

Also contributing to my trepidation was once buying a bulk pack of 9v at home depot - which ruined a couple of ohmmeters... before I realized home depot really was not looking out for me with their crappy supply chain. So you may want to search for leak and corrosion on whatever battery you consider.

My take on active electronics is that they are always ready to stab you in the back. But it is way easier to get a usb charger than a 9V battery!

Anyway, I'll be wery interested to hear what you do in the end, and what the result is...

[John Ludlow]

Thanks Philip and JMH.

>Battery chemistry determines the voltage produced.
I vaguely knew that, although it's confusing because the 'cheap', one-use, kind does clock in at 9 - although they're alkaline batteries, not lead-acid. Hard to believe they go to the expense of putting in a voltage regulator. But... maybe. All the ones on this page advertise 8.4 volts (definitely no regulator).

>Also, 5400 mWh is approximately 600 mAh

ARGH!!! I can't believe I fell for that. What a sneaky way to snare a fool. In the immortal words of Dr. Strange, "Curse me for a novice!". There is one there that is rated in mWh that's higher than that - but it specifically says it's for smoke detectors. So - a trickle for a long time to avoid generating too much heat and starting a fire, I'll bet. The best of the rest are all 600 mAh. Interestingly, the Energizer is 175 mAh - the least of all...

>So you may want to search for leak and corrosion on whatever battery you consider.

According to their literature, the one I've been looking at is: "Safety & Leak-proof Supports over-charged, over-discharged, over-voltage, and short circuit protection, Durable DBCK steel shell of the batteries ensures complete safety." So, you won't look into the battery compartment one day and find that it's been fused to the guitar - I want that. And, they advertise that it's "Standard Size 48.1mm X 26.1mm X 16.8mm" (you could measure your enclosure ahead of time to know for sure if they would fit). So, like... not that other fat kind. They USB plug on the bottom to charge though - not ideal for you.

I guess there's nothing to do but try it and see. If they don't work out, I can always use them in my smoke alarms. I'll write back what I find out.

[Ed Snape]

May or may not be pertinent to 9V, but over the past 4 or 5 years I have been plagued by leaky, contact corroding, made in China, Duracell AA and AAA alkaline cells. Recently a batch of Duracell AAs dated March 2028 exhibited leakage in storage even before being installed. This has led me to totally abandon the brand. I have invested in Panasonic Eneloop rechargeables. These have served satisfactorily in our church's wireless mics for approaching 10 years. Unfortunately, rechargeable 9 V is not so easy.

[jmh]

A quick search showed most frequently that the usb charging ports are on the bottom, however I saw batteries with both narrow and wide side ports. This site:

https://www.amazon.com/Rechargeable-...860389&sr=8-42

...had an interesting buyer comment that doesn't necessarily mean anything regarding a guitar preamp - other than you might want non-audio uses on deck for your batteries. How elaborate a circuit can you expect in an $8 device - although on the flip side, it is remarkable that it exists at all. In any case, the possibility of interference in the proximity of guitar pickups is yet another possible gotcha to be aware of, and maybe an argument in favor of a simple stack of cells that deliver the approximate voltage you need:


'This device appears to have internal DC to DC conversion circuitry that generates noise in the AM radio band which interferes with reception. The battery seems to work well otherwise. I have not had the battery long enough to confirm longevity or overall recharge cycles, yet.'

[John Ludlow]

May or may not be pertinent to 9V, but over the past 4 or 5 years I have been plagued by leaky, contact corroding, made in China, Duracell AA and AAA alkaline cells. Recently a batch of Duracell AAs dated March 2028 exhibited leakage in storage even before being installed. This has led me to totally abandon the brand. I have invested in Panasonic Eneloop rechargeables. These have served satisfactorily in our church's wireless mics for approaching 10 years. Unfortunately, rechargeable 9 V is not so easy.

Good intel. on Duracells and leakage. Thanks, Ed. I haven't had that problem in storage - but that may be because they don't end up sitting around very long.

[John Ludlow]

'This device appears to have internal DC to DC conversion circuitry that generates noise in the AM radio band which interferes with reception. The battery seems to work well otherwise. I have not had the battery long enough to confirm longevity or overall recharge cycles, yet.'

Yeah. This one doesn't say '8.4v' anywhere. It even says '9.6 v max' in the Product Description section. I don't think it could do that unless it was doing that conversion. It has that one other attribute too though: '1,000 mAh' - and also ':Temperature protection, over-discharge protection, over-charge protection, over-current protection, over-voltage protection, short-circuit protection' - also attractive features. But it doesn't say that it's leak proof. In as much at least one other manufacturer adverts no leaks - that seems like a worthwhile claim. Like you I ruined a VOM with a leaky 9v battery once. It would be an entirely different level of frustration to do that to a beloved instrument. And... it's at least possible that it broadcasts in the AM band. I worry about that less though because, to my knowledge, my new bass does not receive in AM.

I think I'll try the other one first in case 8.4v is sufficient. Only if it is not will I take a chance on this one.

[jmh]

I was reading up on dc dc conversion last year, and read there are several different methods employed. I suspect that the logic clocking for controlling some these circuits may slow to a crawl depending on the load - and could be in the audio range. It woke a bunch of questions and few answers. I'm sure most of the circuit designers are fully aware that the destination for these devices may be various audio devices. On the flip side is lower cost devices are that way for a reason. This might be a good question for the telecaster forum www.tdpri.com which has a huge number of users one of which may have made it his mission to investigate these things. Also, they have some very cool forums aimed at threads dedicated to things like particular self built guitars.