Rechargeable battery pack for FX?

[Steve A.]

I've been looking into this for a few years now and prices have come down a lot. I am planning to get a Tenergy 12v battery pack for an Android tablet that is really great but the battery drains down way too fast. Tenergy has a smart charger for about $20 that will work for 6.0 to 12vdc battery packs. There is a switch on the front to select between 1.0A and 2.0A but I was wondering how it figures out what voltage the battery pack is rated at.

My second question is what would be a good way to drop the 12vdc to 9vdc to power FX pedals?

Amazon.com: Tenergy Universal Smart Charger for NiMH/NiCd Battery Packs (6V - 12V) Perfect for RC or Airsoft Battery Packs --- NEW!: Sports & Outdoors

Amazon.com: 12V Tenergy 2000mAh NiMH Battery Pack with Bare Leads for RC Airplanes: Toys & Games

Thanks!

Steve Ahola

[Mick Bailey]

For dropping the voltage I use the LD1085P LDO regulator to go from 12v down to 9v. I usually set my FX supplies slightly higher to allow for daisy chain and connector losses - around the 9.3v mark. A simple zener regulator would also work. I'm thinking about what the voltage on your battery will drop to when its under load and partially discharged - a Zener may hold its regulation better, long after the linear regulator would have dropped out - even the LDO type.

A while back I took a peek inside my own intelligent charger and is an SMPS stuffed with SMDs on the output side, so I guess there's a fair bit of 'intelligence' at work.

[Mark Hammer]

Common power sources for pedals have a higher bar to clear these days, thanks to the general migration from analog to digital. Some of those digital pedals have the sort of power-line controls/filters that keep clock-generated spikes off the power lines shared with other pedals, and some not so much. All of which makes isolation of power fed to individual pedals as important as quality of regulation.

I mention this because regulation is much less of an issue for a DC battery supply, but the isolation challenge still remains. As far as the best-and-cheapest way to provide that isolation...well, I'll leave that to the brighter minds here.

[Steve A.]

Mark: What I have in mind are a few analog pedals which work fine sharing a OneSpot 9V adaptor. Digital pedals? Heck, you might as well get one of those digital modeling amps if you have no taste whatsoever.
The idea is to free my pedals from an AC adaptor. At jams you often have an amp to plug in to but no AC outlet for a 9V adaptor.

Steve Ahola

P.S. So to use a 9v zener you would connect it to both leads of the 12vdc supply in a reverse bias arrangement? Would that drain the battery pack excessively? Like a constant 3v leak from negative to positive? Or could you use a 3v zener in series with the power supply? Or perhaps even running 5 diodes in series (each with a 0.6v drop)?

[Mark Hammer]

Now now, Steve. While I would concur that there are presently few acceptable substitutes for the sweet sweet sounds of a germanium or even silicon-based distortion that responds differently (rather than algorithmicly) to every nuance of picking and string energy, the world is much wider and deeper than distortion alone, and most other categories of effects can do a marvelous job when the effect is produced in spite of the signal properties, rather than because of them.

It would be nice if everything stayed blissfully analog forever, but pedal companies are migrating to digital because it allows them to do some things that are largely impossible in the analog domain (e.g., the POG's polyphonic octave-dividing), or allow them to pack in more features per dollar, or simply produce things with much greater unit-to-unit consistency. I'm not expecting folks like yourself to have an army of such pedals, but even two can spell heaps of trouble if they aren't sufficiently protected against heterodyning.

Whatever, keep in mind that regulator chips want 2V more coming in than going out, so a 12V battery supply needs to feed a 9V regulator at least 11V to get 9V out. Choice of zener or any other diode type needs to factor in current draw.

Also, keep in mind that a great many pedals will do just fine, thank you, on 12V. They might sound a teensy bit different, but at least it'll save you the nuisance of having to down-regulate. Once you get up to 15V+, you can run into problems with CMOS chips frying. But something like an analog delay, or chorus, or Phase 90 will have on-board regulation to drop the supply voltage down to what it requires. So, come 12V, 9V, or whatever, that BBD is going to see 5Vdc, and those phaser FETs are going to see 3-point-whatever volts. I.E., don't sweat it.

[Steve A.]

Also, keep in mind that a great many pedals will do just fine, thank you, on 12V. They might sound a teensy bit different, but at least it'll save you the nuisance of having to down-regulate.

I wish the pedal makers were more clear about using a 12vdc supply. I have sent them emails that were never answered. Fulltone is cool- you can run the OCD at anything between 9vdc and 18vdc, and at the higher voltages I think that you get more clean headroom and a much solider sound all around. One thing I have noticed about the Joyo copies of SansAmp Character series pedals is that they sound much better plugged into a 9vdc supply rather than running off a fully charged 9vdc battery.

I got a Boss digital delay pedal back in the mid-80's. I was happy because it was a lot cleaner than my Deluxe Memory Man and the tape cartridge in my Echoplex was wore out. I am not as impressed with the swiss army knife approach to digital processing these days, throwing in everything but the kitchen sink.

I love the analog amp emulators (modelers) that I have tried- I think that they make the digital modelers sound very flat and lifeless.

I have to say that I've been very impressed with what Ken Kantor has done with his Lunchbox amps- he has the digital chip in them programmed to sound and respond like a real amp, and a nice sounding amp at that. Not necessarily a tube amp but an amp that you enjoy playing because it gets a nice sound. I volunteered to be a beta tester and he burned me a custom ROM chip that had a fuller frequency response (the early lunchboxes had quite a mid-range hump which was good for cutting leads but not so good for clean rhythm parts.) I also had him cut out the clipping diodes which were not in his original design. A common complaint of the early beta testers was that the amp didn't get very dirty when you cranked up the gain- it just got louder. So due to popular demand he added in the clipping diodes...

Funny thing was back at AMPAGE 15 years ago the joke was that when amps eventually went digital the modders would rewrite code rather than rewire circuits...

Steve Ahola

P.S. The Belton Brick is pretty cool for a digital reverb chip.

[Mick Bailey]

You'd need to switch the supply otherwise your battery will always see a load, so your regulator would be after the switch. The Zener needs to be current-limited with a series resistor before the diode, and shunted with a decoupling cap.

With either regulation circuit (Zener or Linear) the excess voltage is 'wasted' as heat, so when you're calculating power consumption you have to add in this wasted power. With no load connected the Zener still conducts via its series resistor.

Here's something interesting;
Pedal Juice

[Steve Conner]

Also bear in mind that all lithium ion batteries require an undervoltage cut-out circuit as they can be destroyed by even one deep discharge. Unlike the battery packs for laptops and other consumer electronics, the RC model packs don't have the cut-out built in, it is supposed to be provided by the motor controller in the toy.

It is also good practice to have a redundant overvoltage cut-out in case the one in the charger fails, as again the battery can be destroyed by a single overcharge, often with quite an impressive toxic fireball, as the electrolyte in lithium ion batteries is basically gasoline doped with fluoride salts. Again, the batteries for RC models don't have this built-in and they have been known to catch fire.

I see lots of hobbyists using these RC model packs as power supplies for their projects, but you have to be disciplined. They are really not safe enough for general household use IMO.

Otherwise, you are better getting something like this Buy 12V 1800mAh Rechargeable Portable Emergency Power Li-ion Battery that has the protection circuitry built in. 4 or 5 1N4007 diodes in series with the output will drop it to 9V.

PS: Lithium ion cells are 3.6V each so you can't make a 9V battery, the nearest you can get is 10.8 nominal. It will go from 9.0V when almost discharged, to 12.6V when freshly charged. I expect the DealExtreme thing has a switching regulator built in.

[Mick Bailey]

I saw an electric bike Lithium Ion pack and there was a sticker on top "Caution, may vent with flame"

Remember the Dell laptops?

DealExtreme? "Warning, Will Robinson" I have a rifle scope that has to be re-sighted after every shot. I reckon its made by the same people who make those googly eyes for toys. So bad it's funny. Maybe it was intended for fairground use.

[potatofarmer]

Also bear in mind that all lithium ion batteries require an undervoltage cut-out circuit as they can be destroyed by even one deep discharge. Unlike the battery packs for laptops and other consumer electronics, the RC model packs don't have the cut-out built in, it is supposed to be provided by the motor controller in the toy.

The link in the original post is for a NiMH pack. I was considering suggesting Li-ion, or the IMR chemistry (Li-Mn?) for the higher current capacity and lack of memory effect but they are sort of a hassle. I'm an e-cig hobbyist so I have a little familiarity with them. Li-ion explode when they fail, whereas IMR "only" vent flame. Either way a vented enclosure is recommended. Since we're not looking at the massive current draw of a 2 ohm bit of wire like an e-cig where the IMRs really shine, a known high-quality protected Li-ion would be a better way to go.

Finding one you know is good (and you know has a working protection PCB) can be a little challenging though. All the Li-ion cells are primarily manufactured by only a couple companies (sound familiar?) and the majority of cells you can buy are rejects that didn't pass QC for consumer electronics applications. I managed to snag a few genuine Panasonic CGR18650CH cells before they stopped making them - you can still find these, but counterfeiting is so rampant that unless you're buying from an importer with a good reputation you can't trust them.

If you're looking for Li battery cells, check for vendor reviews through the flashlight modding forums out there - I couldn't believe that was a thing, but these people take it pretty seriously. Those guys test everything, and they're particularly rigorous about battery chargers.

Anyway. Some stuff to think about if you consider the Li route.

Also, regardless of your battery chemistry: it would be much less fun than building your own but I believe TI sells some pretty efficient switching-mode PSU boards and they'll send you a couple as a sample if you ask nicely.

[Steve Conner]

I've heard of flashlight modding, but I couldn't believe e-cig hobbyism was a thing.

I don't know how I never noticed that the pack Steve originally specified was NiMH. NiMH cells are much tamer than Li-Ion, and at 1.2V nominal, you can just get an 8.4 or 9.6V pack to power your pedals directly.

All-Battery.com: 9.6V NiMH / NiCd Battery Pack Series

[km6xz]

There are several ways to approach this. You can modify the stompbox regulators to accept the battery packs you want or you can convert the battery pack's output to 9v using a high efficiency switching buck boost regulator which can be in the range of 93% efficiency and would cost about $3 in parts

[Steve A.]

Here's something interesting;
Pedal Juice

I looked into that before and with a street price of $149.99 I think I need to pass on that. Thanks anyway!

Sanyo Pedal Juice Rechargeable 9v Power for Effects Pedals | Musician's Friend

I see lots of hobbyists using these RC model packs as power supplies for their projects, but you have to be disciplined. They are really not safe enough for general household use IMO.

Otherwise, you are better getting something like this Buy 12V 1800mAh Rechargeable Portable Emergency Power Li-ion Battery that has the protection circuitry built in. 4 or 5 1N4007 diodes in series with the output will drop it to 9V.

Damn- $16.00 delivered, complete with AC adaptor! So the 1800mAh rating means that it can provide roughly 10x the wattage of a 1800mAh NiMH battery? I just ordered one- it looks like the DX.COM site is a gadgeteer's paradise!

Thanks for posting that link!

Steve Ahola

P.S. I guess I could switch in more 1N4007 diodes to get the effect of an old Eric Johnson battery... or I could make up a few adaptor cables with different voltages.

[R.G.]

Just ran into this. I've posted about this a couple of times, but apparently not here.

A good recipe for a pedalboard power supply is to go find a 12-16V cordless drill-driver. Garage sales are OK, but know what the battery packs cost first. Take the drill-driver, disassemble the thing and cut the handle+battery socket off the motor section. What you want is the socket.

Glom this onto your pedalboard somehow. Arrange a regulator to make 9Vdc out of the DC coming out of the batteries. Now you can charge a battery pack, and run with it while the other battery pack charges. When you run out, swap.

An alternative is the skinny little 2.5A-H sealed lead-acid battery. This would fit under the platform of many pedalboards and power them for a long time. For this one, arrange a socket somewhere on the PB so you can float charge the PB when it's not in use.

[R.G.]

Forgot to mention: I was investigating the drill-driver based idea and the SLA idea for commercial products when Sanyo brought out their power system. I was *amazed* at how poorly it was set up for guitarists and how expensive it was for what it did.

Ultimately we decided not to pursue pedalboard battery systems, not least because of the sheer cost of custom plastic parts needed to make it fit and work well with - um, non-technical consumers.