do rechargeable 9v work well with pedals?

[bonkdav]

I was curious if using rechargeable 9v batteries in my positive ground fuzz pedals.  I have a neg ground supply for all my other pedals.  I just feell kinda bad for all the 9 volts i go through.  I am thinking of ordering a solar charger i found on the net.  otherwise would it just be easier to build some sort of circuit to tag on to my fuzz power  so i can use the negative ground but power my positive ground pedal in the chain?

Gratuitousness

[goulashnakov]

It depends on which type of rechargeable you get.  There are three main types of materials commonly seen in rechargeable batteries:  Nickel-Cadmium (NiCad), Nickel-Metal Hydride (NiMH), and Lithium-Polymer (LiPo). 

In the case of "Nine-Volt" batteries, the oldest technology, NiCad, has a nominal voltage of 7.2 V (which I think means what their voltage is when fully charged or at a stable charge point) and a capacitance of about 120 mAH. (aka milliampere-hours.  I believe that means it can supply a current of 120 milliamps for one hour before it starts to die down.  If the current is less than that, it will hold that current for longer.)  For some pedals, this may be simply too low.  NiCads are also known for their "memory," where if you don't discharge them all the way before recharging, they'll eventually lose their ability to hold a charge as well.

Somewhat newer technology like NiMH typically higher capacitance than NiCads, but their nominal voltage may vary.  Some may only be 7.2 volts.  8.4 V is more typical for a NiMH, but there are some that are 9.6 V.  Capacitance ranges from 175-300 mAH.  NiMHs supposedly don't have the "memory" problem of NiCads.  But, NiMH's need a charger designed for them (i.e. a NiCad battery charger won't work for NiMHs unless it says so in the specs).

LiPo's, the newest technology, are 9.6V and around 520 or so mAH.  LiPo's are also known for having a much lower internal resistance.  But LiPo's require a special charger for them, and both the batts and the chargers are expensive.  Also, many people observe that the lithiums have a smaller number of times they can be recharged before they are dead for good, when compared to the other rechargeable types.  But, like NiMHs, they supposedly don't have "memory" problems.  Honestly, I have never seen a LiPo rechargeable 9V in my life, but I guess they're out there somewhere.

If you find any rechargeables in the store, there should be something on the package that tells the nominal voltage and capacitance.  If not, you may have to do some research on the net for different battery manufacturers to see who makes the "strongest" (highest nominal voltage) and "longest" (highest capacitance) batteries.

What you might want to do first is see what your pedal demands, what the voltage of that battery is when it is considered "dead" in that pedal.  You might also benefit from checking the current draw of that pedal, as that might be affected by the internal resistance of the battery.  That should help you decide if any type of rechargeable will work.

My gut instinct is, LiPo would definitely work, if you can find them and the charger for them.  NiMH might also work if you can find ones that are 9.6V, and again a charger for them.  Does it say anywhere what kind of batteries that solar charger will work with?

In comparison, your typical non-rechargeable 9V's are usually:

Carbon-Zinc ("non-alkaline," "heavy duty" etc):   9V nominal, 400 mAH
Alkaline (more often recommended for electronics):  9V nominal, 565 mAH

Interesting to note that sometimes the non-alkaline batteries are used by pedal users for the voltage sag they give sooner.  Danelectro sells their own battery that is supposed to yield that "vintage" sound.  It's nothing more than a regular carbon-zinc with a fancy label.


Sorry if this is too wordy, but I hope it helps.

[MetalUpYerEye]

I can't remember where it was, but I recall reading an article on the net at some point that discussed the idea of recharging regular (not rechargeable) alkaline and carbon zinc 9v batteries.

The guy had a circuit all built up and had recharged several different kinds with very positive results. Could be useful for your typical DIY'er if you're a battery user like myself.

[petemoore]

  I had fine results with rechargable Nimh and Ni-Cad [cad's have more memory and I found the NiMh to be more suitable for pedals].
  That is until I left it to discharge overnight and then it was done. Another one started burning a hole in my leg when an undetected nickel shorted it out.
  Hafta say I just bought a 3bundle of batteries, I could have had 'higher-tech' 2 pack for the same price.
  Considering my pile of batteries, some of which were lost long enough to discharge beyond reclamation, others left on the pedal for hours or overnight...doesn't matter how good the battery 'was' at this point, just how much I wasted on it...ie 3 cheep-o's' were my choice to invest in.
  Under 7v, 9v batteries are basically done, though they can hold 8-some-volts for a little while.
 If you catch them before 7v they can be recharged to 9v or so, and hold charge pretty good.
 Overcharge includes risk of 'explosion' which looks more like seepage IMCases, nonetheless ugly and caustic mess in the recharge unit.
 I put on a timer, then put the battery on a charger.
 Since I don't know the battery or the charger you'll probably misuse, all I can say is:
 Monitoring charge rate and voltage starts with voltage redaing to determinte how discharged it is, if under 7 it's hardly worth messing with.
 Start with <40minutes charge time.
 I didn't get much more voltage/time when charging over 4 hours, probably less.
 When the charge rate tapers off, the voltage nears peak, hardly any increase over 3 minutes means there's not much room left in the battery for further charge holding.
 Overcharging seems to damage them, undercharging gets a touch less than full possible charge this time, and possibility of later recharge.
 After about three charge cycles their voltage is limited and they have less charge-hold-power. I

[Strategy]

I've been considering moving to NiMH pedals because the consumer grade rechargeables have a droop that can affect headroom in some circuits. The curves of discharging between non-rechargeable and rechargeable differ: rechargeables start to lose voltage right away in a continuously graduate way over time, whereas single-use batteries hold a charge for a while and then drop off relatively abruptly by comparison. I can't remember what kind of batteries the 'consumer' grade ones are but the NiMH are supposed to have much better performance. I am getting about 3 years' life out of the consumer grade ones but they are not great for distortion and fuzz because of the lower headroom.

My science is probably not 100% on this, I am still in the process of doing my homework and there's a LOT of information to sift through on this topic online

Strategy

[PRR]

> , NiCad, has a nominal voltage of 7.2 V (which I think means what their voltage is when fully charged or at a stable charge point)

NiCad is 1.20V to 1.25V per cell.

However this is very consistent until it is about to quit.

Since _most_ "9V" gear (radios, toys, etc) is expected to run a 9V zinc battery down to 7V and still work acceptably, most types are built as 6-cell.

> and a capacitance of about 120 mAH. (aka milliampere-hours.  I believe that means it can supply a current of 120 milliamps for one hour before it starts to die down.

"Capacity", not capacitance.

120mAH probably means 12mA for 10 hours, some long slow rate. 120mA life will be much less than an hour.

> NiMH typically ... 7.2 volts.  8.4 V .... 9.6 V.

Full-up NiMH is over 1.4V and droops past 1.25V to 1.1V. From your values, it appears they come in five-cell and six-cell and braggarts (or seven-cell construction which will not charge a lot past 9V on standard changers).

> rechargeables start to lose voltage right away in a continuously graduate way over time, whereas single-use batteries hold a charge for a while and then drop off relatively abruptly by comparison.

It isn't primary versus secondary.

Carbon-zinc (primary) and lead-acid (car battery) voltage drops with charge in a very predictable way. If you plot a scale from 1.54V to 1.1V and measure your D-cell (9.2V-6.6V for a "9V") you know just how much life is left.

Mercury (primary, now illegal) and NiCad (rechargeable) have very flat discharge curves. NiCad will go 1.23V 1.22V 1.21V 1.20V hardly-dropping then very quickly fall below 1V to zero.

When replacing a drooping type with a steady-voltage type, the trend is to aim for the center of the droop. Hence "9V size" NiCads are generally six-cell 7.2V, the mid-point of a carbon-zinc's useful droop.

Carbon-zinc (including alkaline) "can" be recharged. The chemicals do not go back 100%, you lose some capacity on each cycle. They are not protected against over-charge and careless charging will cause heat, possibly damaging, possibly explosive (most likely a quiet mess). 9.6V through 100 ohms should be slow-but-safe for "9V" alkalines.

> feell kinda bad for all the 9 volts i go through

You know that six C-cells will last a LOT longer with much lower cost per hour? Slightly less sorta-toxic waste over a year. Yes, a six-C-pack is bigger than some pedals.

[bonkdav]

what started as a simple question opened up a thousand doors......as usual.  I cant thank all of you enough for the valuable information you posted.  I am definately going to rig up a C cell pack and put a 9v clip on it and give that a try for now.  I will have to check on rechargable c cells as well.  I just need to figure out the draw and specs on all my circuits and compare them to the batteries available to me while using these great posts  I have an extra vexilar battery.......its 12v rechargeable but its just a brick of power. im thinking about making a rechargeable power supply and voltage regulating circuit behind it but that seems like more than my current knowledge can handle.  a power wheels battery maybe? im liking the idea of turning this question into a project and if anyone has any encouragement on this I may jump on it.

[goulashnakov]

I vaguely remember doing something similar with C's or D's.  I don't know if it was because I was looking for a way to make longer-lasting battery supply for a ruby amp, or I was too lazy to buy a wall wart?  Either way, it lasted a hell of a lot longer.

[Processaurus]

What would be great is a rechargable 9v battery that got charged in the pedal.

[Ice-9]

What would be great is a rechargable 9v battery that got charged in the pedal.

You could do that easily, but the problem there is you need a power source to charge the battery. Might as well just run the pedal off a PSU.

[Skruffyhound]

I think that's what Ben is saying. Charges up while you practice at home pull out the jacks and take it to the gig on the now charged up battery inside the pedal. No problems with the dubious wiring at lots of venues.
Because of the size of "intelligent" chargers with a fan etc., the way to go might be to see how many leads you can take out from the charger to your battery pedals rather than incorporating some kind of charger in the pedal.
I can recommend UNiROSS - NiHM, 9.6V, 200 mAh, French I seem to remember, but I may just have made that up.