Building pedal power supply with laptop battery

[Sequimite]

Searching the internet I see many instances where using a PC power supply has been raised and shot down. I haven't found this idea discussed however.

If you take a functioning battery and power adapter from an old laptop wouldn't the battery be an ideal clean power source to build a pedal power supply from?

I'm a retired CPA and lifelong drummer who is currently trying to learn both guitar and a little bit of electronics. Decades ago I was pretty good with a soldering iron and building a pedal power supply seems like a good first project. Maybe I'll have more than two pedals by the time I'm done.

[GibsonGM]

Welcome, Seq...yes, the battery should work fine as long as you 'deal with' the voltage (regulate it to where you want it, 9V, or whatever....just something to be aware of).    I can't say how long it would last - enough for a gig, I'd think!!   Then you could recharge it when not using it.
Nothing wrong with your thinking on that idea that I can see!    As the battery is intended to supply current to the screen and all that, it probably has a lot of capacity if used for our little energy-efficient pedals.

The reason the SUPPLY isn't recommended - the actual 'plug in the wall' thing - is because it will likely be a switching supply, which is very noisy; creates pulses as it switches on and off.  You would get buzzing from your effects constantly, and it's not easy to filter that out.

[Sequimite]

Thanks, GibsonGM. I envisioned using the battery WHILE plugged into the charger so that the function of the battery would only be to eliminate the noise coming from the Ac Dc adapter. I'm thinking that you might be indicating that the battery will not eliminate that noise if used while plugged in.

Frankly I'm relying on the many times I've been told over the years that a laptop doesn't need a power conditioner because the battery effectively filters the current. So, is this claim true or false? If true, then doe smy idea work or does it get hung up on some fiddly technicality?

[Sequimite]

Now that I wrote that last post, it sounds kind of silly. I can't think of any reason why the laptop battery wouldn't pass through any noise if used while charging.

[GibsonGM]

You know, I'm not sure!  My gut tells me there is no filtering action done by the battery, though...I would be willing to bet that you'd still get the noise passing thru...i mean, the actual source of the energy would be the charger...

But I still contend that you can use the battery alone, if you want      

Old wall warts are great power supplies if you don't want to buy one pre-made...you'd just need to find 1 or more and use a voltage regulator to get them down to 9V, keep them there, and filter out ripple.   So you'd need 12V minimum at the wall wart, or find one that is regulated.   For the (low) cost, I preferred to just buy one with many 'power outs' to plug mine in.  A company can build one better than I can make...

Or, build a dedicated power supply using a transformer, rectifier, filter caps/regulator - that's a really cool project!    Altho that would be bulky for pedals.  Great for the test bench, tho

[Sequimite]

What the battery does do while connected to the charger is eliminate power surges. That might be what everyone was telling me way back when.

I went through my wall wart collection and will be using them for pedals until I decide I can build one, or give up and buy one. My old Panasonic wireless land line phones have very nice 9V adapters.

[PRR]

> a functioning battery and power adapter from an old laptop

*Usually* the laptop external supply goes to a *charge regulator* INSIDE the laptop, _then_ to the battery.

Hot-wiring the external supply direct to the battery will probably over-charge real quick, and throw flaming Lithium Ions all over the room.

If you mean: you have a stand-alone battery charger for a laptop battery (they are rare but exist for heavy users, for some models), then yes it seems safe.

> an ideal clean power source to build a pedal power supply from?

The battery is like a huge poor capacitor. Switching to a car battery (which I know better): it is hard work to pull a full car battery much away from 12.6V. A BIG alternator will slowly drag it up to 14V. Leaving all the lights on slowly drags it down to 10V. Connected to a basic line-power charger which outputs zero to 15V 120 times a second, you get a 12.6V-12.9V 120Hz ripple (not 12.70V steady because it is electro-chemical, not electro-static, and it takes time for chemistry to happen). In the car environment, spikes to 40V are possible (field dump), though probably nothing in a pedal application could cause such kicks.

A general demerit is that you are "wedded" to a specific battery and charger. The battery sure will go downhill over the years. The charger can fail at any time. While they may be $20 on eBay today, the day they fail suddenly nobody is listing one for speedy delivery. (I maintain some aging laptops, and I know how parts go in and out of common supply.)

Nevertheless, "cleaning" power is not a big deal. For 9V out, pick a nasty 13+V supply and use a 3-pin regulator and a couple caps. Total cost of "cleaning" is $2, all common parts used by the millions in many fields.

When you figure connectors and labor, the pedal-market "Spot" and similar power supplies can be found for stupidly great prices. Clever engineering and MASS production trumps some DIY tasks.

[Sequimite]

Well, the thought came to me because I'm constantly running into working laptops headed for landfill, so the components would be free. Be that as it may, if there isn't an advantage, ie getting close to clean battery power by using a laptop battery connected to a charger, then there is no point. If I can't do it cheaper or better, then I'll buy it.

[GibsonGM]

I'd take a look at the external 'stuff'.  The power cord and its associated "little black box".

What does the thing output? Should say right on it.  If it gives you oh, 12V or so DC, you can what PRR just said - use that with a 9V regulator and some caps, and get clean power!    It all depends on what that little circuit is doing - and I don't even own a laptop, so can't help ya there!  

I do use power supplies from phone chargers, printers, things of that nature.  It's very easy, as noted ($2....) to use a regulator to 'make the voltage you want'!  But I do NOT use the stuff I make this way on stage, where I'm being paid...I've just purchased what I need (cheap) to run pedals.   This DIY stuff is, for me, to run things I only use at home, other circuits that do other things, not necessarily audio, and the like.

I do think you have a good idea, and good recycling etc.  Read up on regulators...somewhere down the road, they'll probably play a part in your projects anyway, so it's a good way to start out with them.

Here is an example of one guy using a 9V brick to make a 5V regulated supply.  BIG diff. between what's on the wall wart, and what YOU will get out of it if you try to use it as-is, if it is UNregulated, as most are.  Hence the need to use a few volts to run the regulator, gaining you well-filtered, quiet and stable voltage output.  The process is the same to get a 9V supply, altho you'll need a few volts over for the regulator (12V wall wart).    

http://www.alpharubicon.com/elect/buildavoltageregulator2manytoyz.htm

[J0K3RX]

Don't really understand why you want to keep the battery connected to the charger whilst using it? The battery itself may keep your pedal/s powered for many hours... keep one of the junk laptops on life support just for the simple task of re-charging the batteries..  I believe running it while plugged into the charger will be like a PC that is plugged into a UPS system but some laptops are different than others. The external power adapter is only part of the charging system as Paul said there is a charger board inside the laptop that actually does the charging among other things.. I had a few laptops that I could run from the external power only without any battery at all but if I stuck a battery in there the thing wouldn't power up.. bad charger board. I would use'em if ya got'em.. if you need to regulate them down to 9v then no biggie.. There are many battery power bricks out... I think the Sanyo Eneloop Pedal Juice is really cool for the size and it can power 5 or 6 pedals for 15 or 16 hours I believe..  You could probably get comparable for a good laptop battery or you could even use 2 or 3 of them for those marathon jams

[Sequimite]

The reason why I initially planned to have the charger connected while tapping the battery to run pedals is because I was going to use an old laptop which has a battery with diminished capacity. "Capacity" is also a key word in that I wondered if the battery, as a capacitor, would output clean power even connected to the charger. Unfortunately that doesn't appear to be the case. I also imagined that the internal electronics between the charger and the battery would be discrete and easily removed from the laptop. I can see that this may be incorrect as well. I did have a laptop which had an adapter which charged the extra battery directly, but that was many years, and presumably many technologies, ago.

I've moved on to thinking about using a disconnected battery, but that would require a particular "junk" laptop with one or more high capacity batteries so I'll wait until I come across the right opportunity before moving in that direction.

[tca]

The reason the SUPPLY isn't recommended - the actual 'plug in the wall' thing - is because it will likely be a switching supply, which is very noisy; creates pulses as it switches on and off.  You would get buzzing from your effects constantly, and it's not easy to filter that out.

I've tested some 5.7V .8A  cellphone switching supply  for a small class A amplifier and they work great, no noise from switching.

P.S.
This one: Nokia ACp-12E Charger

[Gus]

I don't know how safe laptop switching regulators are for humans when being used for effect power supplies

[tca]

^ What do you mean exactly?

[GibsonGM]

Some are noisy, some aren't.  I don't care, personally - all you need is 1 or 2 caps, maybe a resistor, and you're generally good to go.  Good use for things that otherwise would get tossed, IMO.

Switching regulators not safe?  How so?  Can some malfunction put line voltage on your equipment??

[J0K3RX]

Good reads...

http://hackaday.com/2013/04/19/replace-your-project-power-supplies-with-recycled-li-ion-cells-and-a-switching-regulator/

http://www.dr-iguana.com/prj_fitzy_and_carraldo/prj_fitzy_and_carraldo_buck_regulator/

[Jamdog]

Reviving this old interesting thread because I am currently working on a rechargeable power bank.
I don't own a commercial pedal,  so I don't have a suitable power supply that does not hum.  Therefore,  I had to use 9V batteries,  and turn them off (remove input)  individually everytime.  It became something of a deterrent.

I build a huge power bank with li-ion cells.  Output just shy of 9V and should last days.  It is powerful enough to Daisy chain many stompers.
Downside is,  it takes about 16h to charge with the smart charger and protection circuit.

That said,  I have a single positive ground pedal that doesn't play well with others,  so within the enclosure I added a second circuit that use a 9V battery and is switched by the same 4PDT switch.  Might convert it to another 9v pack in the future.

Now I am planing LED indicators to show what circuit is powered,  and in use (bicolor led)  but other than that,  it works and I have a single-switch pedal board activation. It may last months without recharge!  Lol

[thermionix]

[Jamdog]

Not as classy as this



And I am preparing a voltage indicator circuit to go on that monster 37.8Ah battery pack.  Not sure your solution lasts as long.