Battery talk- types and applications

[Mark Hammer]

For some reason or other, when putting our 8 year-old to sleep last night, talk got around to batteries, current vs voltage, and different types of battery packages and their current supply capabilities.  (Tip to parents:  Got a kid that can't fall asleep? Give 'em a physics lecture.)  And it got me to thinking.

If you've ever pulled a 9v battery apart, or rather if you've ever pulled apart different brands/types of 9v batteries, you may have noticed that they vary in terms of internal packaging.  The cheap carbon-zinc types tend to have 6 "slugs" stacked on top of each other.  The higher priced alkalines tend to have a half dozen miniature enclosed cells (like smaller AAA's), each electrically coupled to the other by a spot welded connecting strip.  The carbon-zinc batteries have a big surface area between cells, but that surface can develop a high internal resistance in short order.  So, the battery can deliver lots of current, but the available voltage declines more quickly than alkaline.  In contrast, the alkaline has a consistently low resistance contact between cells, but very little surface area so that not as much current can be passed.  The alkaline maintains its voltage longer but seems to be constrained in current delivery.

If you've ever seen one of the Pola-pulse batteries that come in Polaroid camera cartridges, these are multi-cell batteries, but they are wafer thin.  Where a carbon zinc 9v battery is multiple slugs stacked on top of each other, think of the Pola-pulse as several credit cards laid down flat on top of each other.  Although it doesn't hang onto its voltage forever, the Pola-pulses were developed to supply tons of current to the flash and other electronics of a Polaroid camera.

Okay, put that info on the side burner.

Back when Eric Johnson was big news, one of the things you'd hear about was how he could tell the difference between batteries.  And of course, shortly after he became big news, people got interested in "dying batteries", with some sorts of fuzz pedals becoming renowned for sounding great with a dying battery, and eventually sparking the omnipresence of "dying battery" simulators.

As the quick trot through battery technology suggests, though, not all batteries age the same way because of their internal construction.  What seems to be the case (though folks can feel quite free to correct me) is that it is primarily a dying carbon-zinc battery that is most desirable to emulate.  Why?  I suspect the issue is one of how much current it can continue to supply in its mid-life and senior citizen era.  It would not surprise me if what folks want from these batteries and what GE-based distortion pedals respond so nicely to, are the DYNAMIC properties of its current supply capabilities.  In other words, the aged carbon-zinc battery can supply a lot of current for a brief instant when it gets older, but runs out of breath about 10 feet from the starting blocks.  It is the sag people like.

Alkaline batteries will likely not provide a similar sort of sag.  Neither will wallwarts with some sort of downregulation to turn 9v into 8 or 8.5 and such.  The reason being that current supply capabilities are more constant than the humble carbon-zinc.  Even if you make it sag, does momentarily forcing a wallwart to drop from a 100ma supply capability to a 60ma capability do anything differen to the behaviour of a Fuzzface?

The point of launching this thread is not to diss the carbon-zinc battery or those who make a big deal out of battery types or their age.  Rather, I'd like to:

a) find out more about battery type properties and idiosyncracies from those who know more

b) have a better sense of matching battery to specific task

c) have a more finely tuned sense of what one needs to do to an AC-powered supply to make it behave like a battery in a given idiosyncratic state

[petemoore]

What about Ni Cd's and Ni Mh
 Nicel cadnuim /Metal Hydride [spellling?]
 I use these all the time [exclusively], and next trip out will get some nice cheep carbons to do some playing with, so I should be able to tell if there's any difference using Carbon batteries.
 I have my speculations, but should reserve those until [taking for granted there is some] I get some Technology of Rechargables type info and do some testing.
 Maybe using a different battery type than rechargable will render a noticable difference in TS, Jfet Amp Sims, Mini Booster, Micro Amp, FF, Axis etc. and combinations of these.

[Mark Hammer]

The rechargeables are not the sorts of things I tend to take apart, given their price, but you are correct in bringing them up as worthy of mention and thought.

I guess the gist of this thread is that if you want to use power supplies and batteries themselves AS IF they were an effect, then it is important to understand what they are capable of doing under different circumstances.  Give that they are often intended to trade off different factors in their design, there's a lot there to learn about.

I should also note that the complement to examining any dynamic aspects of current supply capability, is the current demand characteristics of the pedals they are powering.  We bat around current need specs like somehow pedal X would need a constant current supply of 6ma, no matter what we play, how we have it adjusted, whether it's a single note diddle or a slammed power chord.  A little naive, if you ask me.  Knowing what it uses on average is not the same thing as knowing what it demands on peaks and how it might be affected by constraints on what it can get on those peaks or shortly thereafter.

Will use of a different battery necessarily make a pedal sound better/different?  My short answer is no.  The longer answer is that it would depend on where in the battery's life cycle you decide to start comparing.  If current-delivery limitations is part of the "magic" and the slope and knee of the current-supply function will vary by battery type, then the age and voltage at which battery type X sounds great with pedal Y may be different than the age and voltage at which a different battery type sounds good with pedal Z.

[petemoore]

The rechargeables are not the sorts of things I tend to take apart, given their price, but you are correct in bringing them up as worthy of mention and thought.
 >>>I'm gonna check it out.

I guess the gist of this thread is that if you want to use power supplies and batteries themselves AS IF they were an effect, then it is important to understand what they are capable of doing under different circumstances.  Give that they are often intended to trade off different factors in their design, there's a lot there to learn about.
 >>>I'll let you know too/

I should also note that the complement to examining any dynamic aspects of current supply capability, is the current demand characteristics of the pedals they are powering.  We bat around current need specs like somehow pedal X would need a constant current supply of 6ma, no matter what we play, how we have it adjusted, whether it's a single note diddle or a slammed power chord.  A little naive, if you ask me.  Knowing what it uses on average is not the same thing as knowing what it demands on peaks and how it might be affected by constraints on what it can get on those peaks or shortly thereafter.
 >>>Sounds like a simple [lo tekk] test with no measurements or equations is in order, I'm PDCertain if there IS any 'discernable' difference that could be detected by ear, I can hear it...I've become quite accostomed to how these pedals sound using Rechargables...and now they Are older...
Will use of a different battery necessarily make a pedal sound better/different?  My short answer is no.  The longer answer is that it would depend on where in the battery's life cycle you decide to start comparing.  If current-delivery limitations is part of the "magic" and the slope and knee of the current-supply function will vary by battery type, then the age and voltage at which battery type X sounds great with pedal Y may be different than the age and voltage at which a different battery type sounds good with pedal Z.

>>>I'll try to be objective when I report on whatever differences there arent' or are.
 >>>Thanks for bringing this one up Mark! Good thing to think about how much you should think about it...

[fatoldsun]

interesting thread. i personally use the cabon batteries with my vintage ge arbiter ff. i don't know why or how i came about doing this but i hear a difference in the tone. all my other pedals i use your every day alkaline 9v.

[Paul Marossy]

Nickel Metal Hydride batteries can catch on fire if you expose the internals to the atmosphere... at least if you overcharge them to where they bulge and then you try to poke a hole in the casing to "relieve the pressure"...
This happened to my father-in-law with one of his remote controlled electric airplane batteries...

All that to say, be careful taking apart any kinds of batteries other than carbon-zinc / alkaline types!

On a different note, I wonder if carbon zinc batteries do better with battery hogs such as digital delay pedals?

[Peter Snowberg]

Good topic!

Please folks, don't take apart batteries unless it's just removing the outer case or disassembling carbon zinc cells. The chemicals inside are surprisingly toxic in some cases. :shock:

I'm quite sure the instantaneously available current a battery can supply and how that tapers off can make a huge difference. You can really hear the effects with 386 circuits because of the exaggerated current requirements.

To emulate this effect.... try a JFET+resistor current source that charges a small cap which is connected to the effect power input.... just like an RC stage in a tube amp.

[Mark Hammer]

I wonder if carbon zinc batteries do better with battery hogs such as digital delay pedals?

It's ponderings like that which led me to start this thread.

[Fret Wire]

Has anyone built one of the DIY super-batteries yet?
http://www.elektor-electronics.co.uk/miniproj/details/030109.htm

[Paul Marossy]

Mark-

Yes, I also am wondering about these sorts of things...  


Fret Wire-

That's cool, I have never seen that before. Have you actually built one of these devices? Reading the article, it's kind of hard to tell just how long that type of battery would last with a typical guitar FX circuit...

[alex frias]

The link seems dead...

[Nasse]

http://www.elektor-electronics.co.uk/magazines/2003/october/supercap-battery.55383.lynkx

If that was the dead link you talked about... If I remember right it uses supercap and step up voltage generator so I think it might be noisy in some applications. What´s best it recharges in seconds. So who cares if it does not last so long you can charge it between songs, if it works I think, never build that thing

[demonstar]

It's funny I should come across this thread as I was talking about something very similar to this to someone the other day.

We were talking about why the battery indicator seems to go down quicker near the end of the batteries charge. I proposed that the battery indicator reading was directly proportional to the voltage of the battery. So this made me think that the phone battery is probably running into a regulator to obtain a constant voltage for the circuit. This regulator will probably put out a constant current (the current required by the phone circuit) and by nature it's putting out a constant voltage. Lets assume once the battery voltage drops below the regulators output voltage the phone dies.  As the voltage falls closer to that point in order to maintain the power input required to allow the voltage and current output to stay stationary a larger current must flow in to the regulator. So to summarize that bit... the battery voltage is falling so to keep the power input into the regulator the same (as the power output is still fixed by the phones requirements) the current flowing from the battery into the regulator increases.

So this is where my thoughts (question) lies. If the battery starts drawing a larger current as it's voltage is falling does the voltage on the battery then fall quicker? If so this would mean that, that would explain why a phone battery indicator would fall quicker as the battery gets closer to needing to be charged.

Wow... there are lots of assumptions in there but anyway that's what I was thinking. Any thoughts on this? Especially as to if the battery drawing a larger current as it's voltage is falling does the voltage on the battery then fall quicker? I hope it makes some sense!

[sfx1999]

On a different note, I wonder if carbon zinc batteries do better with battery hogs such as digital delay pedals?

Actually, alkaline batteries completely destroy carbon zinc batteries. I have experienced this first hand with my Gameboy.

Here is something to note. Many generic battery brands that you see are actually manufactured by big name battery companies and relabled.

[petemoore]

  disposable batteries really don't work that well.
  10x performance can be had if you work with them.
  Greater than that by many times also if you recharge them, can't recommend you try exploding them, a real possiblity if left to overcharge.
  Stimulation by heat or impact releases many many times the initial potential of some batteries, 1rst hand exp. with remote control [ >10x performance gleaned before recharge], and camera [fresh heat stimulation allows pictures to be taken and downloaded, new super-alka's dont'].
  Rub vigorously between hands [ great for AA's, AAA's], or insert into thick water tight bag, and run a cup from a hot water tap 190 degree or so water, insert bagged batteries for about 30 seconds...plenty of output to do what I need now, for the 10th time, they wouldn't even do it at all when new [trying to take quick-o pics on the sly, after about 15 seconds the lense would be stuck in the out/open position again.
  Hafta say, often enough, there is very little potential in disposable batteries until they've been 'properly stimulated'.
  That's before the 1rst recharge [do it outside, observe that timer, can't recommend more than 40 min. on rundown batteries on small charger, YMMV...check the voltage, compare to the time...dont' exceed the rating.

 

[afrogoose]

Well, I can't speak too much to the technical side, but a carbon zinc battery sounds darker than a modern/alkaline battery in my fuzz face.  I have no idea why.  I think part of the reason why people always say to use a carbon zinc in a fuzz is because most fuzzes are Ge and most people don't like them to be to farty and dark, so the alkaline "brightens" it up.  Mark, I wonder how you could account for this difference?

I've also noticed the dying battery thing, but didn't realize it was a "phenomenon" until I was online.  I just assumed I was being crazy.  Specifically, I've used a FullDrive 2 for an overdrive pedal for about 8 years.  I use it all the time, so I guess I felt like I was really familiar with the way it sounded.  I noticed that right before the battery would fade (just as the led was starting to lose a touch of brightness) the pedal would sound really cool.  As I'm typing this, I'm still not convinced it's not BS. 

I think both of these things are related to the reality that getting a good guitar tone is a very inconsistent thing, from day to day or gig to gig.  I get this from talking to other pros (and maybe someone like Eric Johnson feels the same way), but when you are playing all the time through the same exact rig, sometimes even in the same room week after week, you would think that your sound or tone would always be the same.  But for a million tiny reasons it's never the same.  Sometimes it's plain crap, but other times your like, "oh man, do I sound good tonight!"  I think when everything is working you start to look for reasons why you sound "sooo good."  I think this is a slippery road because this is where some gear myths are borne, depending on your neurosis.  I started wondering, "maybe I need to use this sequence of cables!" to get reproduce that awesome tone from last nights gig, but it never seems to work that way. Instead,  I think unusually good tone might just be a combination of a million intangibles instead.  Sorry for the meandering... 

[Mark Hammer]

No apologies needed.  Meandering takes us....everywhere!

The fundamental fact one has to grapple with when it comes to powering pedals for guitars is that the guitar signal is inherently unstable.  You pick and there is a sudden and urgent need for current in the pedal (assuming it applies gain), then things sort of die down.  It is this curious relationship between signal and current draw, plus the fact that different battery types (at different points in their lifespan) permit or have different types of dynamic response to current draw, that produces this ongoing debate about what batteries sound good with what devices at what point.

[R.G.]

We were talking about why the battery indicator seems to go down quicker near the end of the batteries charge. I proposed that the battery indicator reading was directly proportional to the voltage of the battery. So this made me think that the phone battery is probably running into a regulator to obtain a constant voltage for the circuit. This regulator will probably put out a constant current (the current required by the phone circuit) and by nature it's putting out a constant voltage. Lets assume once the battery voltage drops below the regulators output voltage the phone dies.  As the voltage falls closer to that point in order to maintain the power input required to allow the voltage and current output to stay stationary a larger current must flow in to the regulator. So to summarize that bit... the battery voltage is falling so to keep the power input into the regulator the same (as the power output is still fixed by the phones requirements) the current flowing from the battery into the regulator increases.

So this is where my thoughts (question) lies. If the battery starts drawing a larger current as it's voltage is falling does the voltage on the battery then fall quicker? If so this would mean that, that would explain why a phone battery indicator would fall quicker as the battery gets closer to needing to be charged.

Wow... there are lots of assumptions in there but anyway that's what I was thinking. Any thoughts on this? Especially as to if the battery drawing a larger current as it's voltage is falling does the voltage on the battery then fall quicker? I hope it makes some sense!

You're correct on all counts. All of the simple/cheap battery indicators are voltage readers. Battery voltage does fall off much more quickly when they near exhaustion. And a constant power load, like a step-up regulator, does pull more current as its input voltage goes down.

A battery is a little container of chemicals. The chemicals react to force the electricity out. As more electricity is used, more of the chemicals get used up. They get used up first nearest the  + and - electrodes, and this gets further away as it's depleted. So the internal resistance from the active chemical region to the terminals gets further away as it's used up. Heating makes them more chemically active, giving a boost. Mechanical agitation shakes them up and moves fresh chemical slightly nearer the terminals.

I noticed that right before the battery would fade (just as the led was starting to lose a touch of brightness) the pedal would sound really cool.  As I'm typing this, I'm still not convinced it's not BS.

Anybody remember how effects sound different when they are mis- or other-biased? Changing the power supply often changes the bias point; in opamp circuits it changes the available power supply voltage before the opamp bangs into it.

The fundamental fact one has to grapple with when it comes to powering pedals for guitars is that the guitar signal is inherently unstable.  You pick and there is a sudden and urgent need for current in the pedal (assuming it applies gain), then things sort of die down.  It is this curious relationship between signal and current draw, plus the fact that different battery types (at different points in their lifespan) permit or have different types of dynamic response to current draw, that produces this ongoing debate about what batteries sound good with what devices at what point.

And on top of all that, you have this very apt observation. The load varies. As a battery gets older, its internal resistance goes up and that makes its output voltage even more sensitive to loading.

It's almost like the Devil is in the details. 

[bkanber]

I know a litttttle bit about batteries, but not all that much. One comment that caught my attention was the idea that the difference in batteries is how much current they can supply to the audio circuit. It's true that different batteries have different maximum current supply abilities-- but this is on the order of amps. For AA batteries, I've seen some that can deliver 6 amps, others that can give 9 amps.. The NiMH 9V I just tested easily gives 3A continuously. So I'm not sure the difference in batteries has to do with the amount of current it supplies, as you'd be hard-pressed to find a stompbox circuit that demands even 100 mA.

However, it is also true that different battery chemistries have difference discharge characteristics. Demonstar pointed out that batteries tend to drop in voltage more quickly near the end of their life-- this is true of most chemistries (but not all). Although his observation about the cell phone's voltage regulator makes sense, I don't think it's valid (I could be very wrong here), because the effect is more a virtue of the battery's internal chemistry than it is of it's loading environment. You'll see the same effect if you attach a battery to a light bulb with no regulator--the battery will stay at a high voltage for a while, then drop quickly. Simply put, the effect of a battery discharging quickly near the end of its life has to do with its internal chemistry, and not so much environmental factors (though temperature and the circuit it's connected to can have an effect, generally these are negligible).

Alkaline batteries and NiCd rechargeables (and probably NiMH) both have that same deal of having 50% of their energy in 10% of their voltage (ok, I made those numbers up. you get the point ). i.e., a 9V battery will use half of its total storage capacity towards supplying 8-9V or so. Once you see that the voltage has dropped below maybe 7.5 volts, you've used up most of its stored energy-- the relationship between stored energy and supplied voltage is NOT linear in most batteries.

I know that the big thing with Li-Ion batteries is that this doesn't happen to them... they are able to supply a constant voltage over 90% of their storage capacity.. you'll only see the voltage drop once the battery is basically dead.

So.. to sum this all up:

I think the difference in batteries in these circuits is not a virtue of the amount of current they supply (even a near dead battery can supply enough current for most of these circuits), but rather the voltage they tend to stay at longest while discharging. If your pedal sounds really really awesome at 7.1 volts, you're probably SOL with an alkaline battery, because those are gonna stay at 8-9 for the longest time, and then really quickly drop in voltage from 8V down to say 5 or so.

Maybe you have a rechargeable NiCd (or any other chemistry.. I don't know the specifics about different chemistries' discharge characteristics) that you've noticed sounds really awesome with your pedal once youi've used it for a little while. That's because you charge the battery up to 9V, and you start using it-- It then drops quickly in voltage to say 7.8V, and then uses most of its charge in the 6.8-7.8V range. Once it gets below 6.8, it then drops in voltage quickly again. That battery's gonna sound awesome in your pedal, because it stayed at your pedals sweet spot the longest.

If your pedal sounds best at 9V, you'd want to use a 9V li-ion--that battery will stay at 9V through most of its life, and then immediately die down to 4 or 5 or wherever they die to.

Please note that I made up most of the numbers in this post.. but my ideas should be sound.

And there's always the possibility that I'm completely wrong about everything I've ever said. So take it all with a grain of salt

Burak

Edit: Another thing that occurred to me is that the battery's response time to a current demand might play a role in all this--maybe a battery with a slow response time can't keep up with the quickly fluctuating current demands of high frequency notes. This would cause the battery to deliver less current than the circuit is asking for, and will also introduce a -180 degree phase shift in the current supplied vs current demanded. But, I don't know anything about battery response time. It may be so quick that it falls outside the realm of human hearing and audio applications. I'll do some research.

[StephenGiles]

Funnily enough, I have about 20 used alkaline AA batteries, and rather than just throw them away ( in the correct recycling container - Gez will understand!), I thought of binding groups of 8 together, connecting them in series if they will solder and using for testing purposes for dual 9v purposes, with perhaps an 8v regulator and the diode trick. I think this may work for longer than 2 x pp3.

The rubbing in the hand trick also pokes a little life back into them I have found.