On powering pedals
Since I stopped playing in bands (only recently making an exception for the LCW project) I have been striving to reduce the amount of gear I use to make music. I'll probably never go as far as switching to an acoustic guitar; I'm very comfortable playing the Koll guitars that I have had custom-built to my specs.
When I play in front of an audience, most of the time I do so as a solo performer. There are advantages to playing solo: there are no schedules to coordinate and I can (and usually do) compose as I'm playing. I've had a good response to my particular style of performance, which is ideally suited for low-key conversation-friendly venues like galleries, wineries and restaurants. Between paying gigs I'll go to local open-mics and ply my trade for ten or fifteen minutes at a time. This sometimes leads to new fans and contacts.
Part of the challenge of playing an open-mic is to minimize set-up time. Most open mics are structured for singer-songwriter types who need only sit in front of existing mics before performing. My setup involves at least a DI; sometimes a pedal or two; occasionally an amplifier. All of these things take time to place and wire, interrupting the flow of the open-mic and cutting into my playing time. With this in mind, I thought it would be illuminating to write about my experiences with powering pedals.
A few pedals can only be powered by an AC adapter. In the best case I can use any Boss-style adapter. I use either the adapter supplied with the pedal or a universal adapter like the One Spot. The benefit of the One Spot is that I can easily supply enough current to power multiple pedals through a daisy-chain cable. When I'm powering only one effect I'll still use the One Spot because I don't have to worry about whether it can suppy enough current for the pedal.
Some pedals can only be powered by the manufacturer's adapter. Pedals that are like this include some from Electro-Harmonix and Line6 as well as Peterson tuners and quite a few multi-FX units. You're stuck running these from the included adapter (or in rare cases, from batteries). This is somewhat of a liability when performing live as you can't substitute a generic adapter upon failure. You have to be prepared to carry a spare adapter (which means additional expense and more to carry) or do without that effect if necessary.
Most pedals will run on either an AC adapter or on batteries. If you keep fresh batteries in your pedals you'll always have a backup power source in case your AC adapter fails. This approach is most useful if you carry a few loose pedals rather than using a pedalboard. Access to battery compartments becomes less convenient once you mount pedals on a board.
The length of time that a pedal can operate on battery power is dependent upon two factors: how much current the pedal draws and how much power the battery can provide. Expected run times can range from hundreds of hours for a simple analog pedal down to just a few hours for some pedals which contain digital processors. Even a few hours of run time should get you through a show, but you may not wish to incur the expense of replacing batteries every few hours.
There are some benefits to running your pedals entirely from batteries, including noise reduction, freedom to mix and match modern pedals with certain vintage-derived pedals, and convenience of set-up. You won't have to locate an extra outlet and run a power cable across the stage if your pedals all run on batteries. Some vintage-derived pedals run on a reversed-polarity adapter; you can't share a power supply when mixing pedals that expect opposite polarities. Finally, some pedals are known for inducing noise in other pedals that share the same supply. The only way to deal with the polarity and noise issues is to use multiple AC adapters or an adapter that has multiple isolated outputs.
You might want to run your pedals on rechargeable batteries in order to reduce long-term costs. Rechargeable batteries are slightly more expensive than disposables. Add in the cost of a charger and you're set to reuse your rechargeable batteries hundreds of times. Sounds like a good deal, right? Well, it can be. However, there's no free ride.
For any given size of battery, a rechargeable will have less capacity than the equivalent disposable alkaline battery. This means that your pedal won't run for as many hours on the rechargeable battery. If that was the end of the story, it'd still be a no-brainer to adopt rechargeable batteries for all of your effects. But the rechargeables suffer from three other differences: lower voltage, sudden loss of voltage when the charge is exhausted, and poor charge retention.
A disposable alkaline battery has a resting voltage of about 1.5V. A NiCd or NiMH rechargeable has a resting voltage of about 1.2V. This in itself is not necesarily bad; pedals are designed for alkaline batteries and expect the voltage to gradually decline over the life of the battery. The rechargeables lose less of their voltage as their charge is exhausted.
The end-of-life behavior of alkaline batteries, however, is radically different from the end-of-charge behavior of NiCd or NiMH rechargeables. The rechargeables deliver very near their full rated voltage right up until their charge is completely exhausted. At that point the voltage drops to zero almost immediately. In practical terms, this means that any low-battery indicator designed into your pedal is completely useless. One minute it'll tell you that the rechargeable battery is fine, the next minute your pedal will be not function because the battery has gone dead. I've seen this happen; it takes place literally over a few seconds or tens of seconds. There's no warning. Accurate low-charge detection is possible for NiCd and NiMH batteries, but this would add cost and complexity.
Finally, rechargeable batteries don't hold their full charge over extended periods. Rechargeables must have their charge refreshed on a regular basis. Newer NiMH rechargeables include some titanium in their formulation (sometimes referred to as TiNiMH) to reduce the self-discharge. NiCd rechargeables have a lower self-discharge rate (and lower total capacity) than NiMH or TiNiMH rechargeables. None of the rechargeables can come close to the charge retention of disposable alkaline batteries which can retain 85% of their charge after seven years on the shelf.
In practical terms, this means that you must maintain your rechargeable batteries. If you use your pedals frequently you can probably get away with throwing a charged-up set of spare batteries in your gig bag for replacement after some certain number of hours of use that you'll have to determine experimentally. (Remember the sudden loss of voltage at the end of charge: you'll want to swap in a fresh set of batteries long before that's likely to happen.) If you use your pedals less often you'll still need to swap and charge your batteries periodically because of the self-discharge behavior.
Personally, it seems to me like there'd be a lot of maintenance and record-keeping involved in using rechargable batteries effectively. Not so bad, perhaps, if you're playing several shows a week. But if you play occasionally, keeping freshly-charged batteries in your pedals seems like it's almost more trouble than benefit.
If you must run your pedals on batteries and don't have a tech to manage the logistics, it seems to me that the best approach is to use alkaline batteries. Alkaline batteries are what your pedals were designed to use and have the lowest logistical overhead. When the pedal displays its low-battery indication you can still finish the show. Then recycle the dead batteries and put in a fresh set at your convenience. That's a lot simpler than tracking use-hours and preemptively swapping in freshly-charged batteries.
The downside of using alkaline batteries is their higher long-term cost. One thing you shouldn't do is to pay supermarket prices for batteries. Buy them in bulk to save 50% or more.