Is a current load of 12ma a lot for a 9 volt battery?

[zachomega]

I built a pedal using MosFets and at idle, each mosfet (there are 2) draws about 6ma of current.  That seems like a lot to me for a battery considering most of the time, the whole pedal only draws around 3 - 5 ma. 

The pedal sounds and works great, but I am worried that battery life will be really short (yes I use batteries all of the time).  I didn't put an LED in just to save that little extra juice. 

Any thoughts on this?

Thanks,
-Zach Omega

[Mark Hammer]

Preferred current drain is below 10ma for something to be considered battery-operable.  When current drain starts to exceed 10ma and move towards 15ma, you'll usually see some advisory like "Use fresh alkaline batteries!".  The thing certainly won't drain before your eyes, but once you start to get ito the 15ma zone, you need to start wondering if it is prudent to do gigs without a wallwart supply as your default power.

The Tone Core pedals suck about 60ma and they have a battery slot, surprisingly.  My sense, however, is that such a battery operation is really for music stores, so the sales staff can say "Here, try this" without having to fish around for an adapter and free AC socket.  So, it's not "true" battery operation.

So, long and short, 12ma is not the best case scenario, but neither is it the worst.   Just make sure you build in a wallwart socket.

[Processaurus]

The Tone Core pedals suck about 60ma and they have a battery slot, surprisingly.  My sense, however, is that such a battery operation is really for music stores, so the sales staff can say "Here, try this" without having to fish around for an adapter and free AC socket.  So, it's not "true" battery operation.

Verbzilla sucked a Danelectro "vintage power source" battery dry in the 10 minutes I was messing with it for at guitar center.  Its ironic, because they designed what I'd consider to be the cleverest battery compartment I've seen on a pedal.

12ma doesn't seem totally unreasonable for battery power.  Especially if you're packing the pedal up and moving it around a lot, or playing shows where you need to set up fast.  I've heard (though its a hard number to officially find) that an alkaline 9v has about 400mA hours.  So that would mean you pedal would last ~35 hours give or take.  The lithium ones (like Duracell ultra-life) for smoke alarms have about 1600mAh and cost twice as much.  I had one in my rat that the previous owner had left in it and it lasted years, I'd leave it on overnight a couple times and it would still work, it was disconcerting

[zachomega]

Well lithium batteries it is then!! 

Thanks guys!  You've been awesome as usual!

-Zach Omega

The Tone Core pedals suck about 60ma and they have a battery slot, surprisingly.  My sense, however, is that such a battery operation is really for music stores, so the sales staff can say "Here, try this" without having to fish around for an adapter and free AC socket.  So, it's not "true" battery operation.

Verbzilla sucked a Danelectro "vintage power source" battery dry in the 10 minutes I was messing with it for at guitar center.  Its ironic, because they designed what I'd consider to be the cleverest battery compartment I've seen on a pedal.

12ma doesn't seem totally unreasonable for battery power.  Especially if you're packing the pedal up and moving it around a lot, or playing shows where you need to set up fast.  I've heard (though its a hard number to officially find) that an alkaline 9v has about 400mA hours.  So that would mean you pedal would last ~35 hours give or take.  The lithium ones (like Duracell ultra-life) for smoke alarms have about 1600mAh and cost twice as much.  I had one in my rat that the previous owner had left in it and it lasted years, I'd leave it on overnight a couple times and it would still work, it was disconcerting

[mac]

Recently I made a LM386 mono amp for my mp3 player using a can of "original denmark butter cookies", which is powered by 4 AA batteries. AA holder has a connector similar to a 9V bat. The thing drwas a lot of current so a 9V is out of the question.
When I bought the AA holder I realize that I could use 6 AA to power my pedals. Space is not a problem for me because I build everything with poly caps instead of electros, so I always need a big box.
The 1000000 incarnation of my FF sucks 0.7mA so I expect the 6 AA to last a long time, maybe years of daily use. Purists may complain about the "9V carbon bat resistance" but I don't care.
A 6 AA holder is about 2.2 x 3.7 x 4.2 cm, not sure if it fits on a 1590.


mac

[Ronsonic]

Verbzilla sucked a Danelectro "vintage power source" battery dry in the 10 minutes I was messing with it for at guitar center.  Its ironic, because they designed what I'd consider to be the cleverest battery compartment I've seen on a pedal.

Seems they need it.

Ron

[Izzy]

I was desiging a pedal and when I view the voltage and current in Pspice it shows 8.xx mA current on the battery. So it that how much current its gonna pull?

I havent Breadboarded the pdesign yet so Kinda curious

[stm]

I've heard (though its a hard number to officially find) that an alkaline 9v has about 400mA hours.  So that would mean you pedal would last ~35 hours give or take.

A better formula can be found in the following posts:
http://www.diystompboxes.com/smfforum/index.php?topic=41922.msg362255#msg362255
http://www.diystompboxes.com/smfforum/index.php?topic=41922.msg362294#msg362294

In summary, a 9V Duracell battery can be expected to last about 26 hrs when discharged at a 12 mA rate until its residual voltage is 7.2V.

(Note: 0.55 * 580 mAh / 12mA = 26.58h -- refer to the second link for the derivation of the formula)

[zachomega]

Awesome!  That just got saved in a text file! 

-Zach Omega

I've heard (though its a hard number to officially find) that an alkaline 9v has about 400mA hours.  So that would mean you pedal would last ~35 hours give or take.

A better formula can be found in the following posts:
http://www.diystompboxes.com/smfforum/index.php?topic=41922.msg362255#msg362255
http://www.diystompboxes.com/smfforum/index.php?topic=41922.msg362294#msg362294

In summary, a 9V Duracell battery can be expected to last about 26 hrs when discharged at a 12 mA rate until its residual voltage is 7.2V.

(Note: 0.55 * 580 mAh / 12mA = 26.58h -- refer to the second link for the derivation of the formula)

[petemoore]

  It's a shame, I must have a dozen batteries around here that worked at one time in a molded battery compartment like cordless phones.
  I can't hook 'em up, seems silly to use batteries with super limited application options, perfectly good batteries which are destined to never be used.
  I have a couple rechargable multi-cill packs, [like for RC cars] these are pretty nice and have the two wires to connect them with...mucho coolo IMO...sometimes 6-7v is just right. Minibooster sounds great @ 3v...

[Mark Hammer]

That's pretty much why I resported to "recharging" nonrechargeable batteries, whether they be 9v for my pedals, AA and AAA for the old Game Boy, the various and sundry remotes and CD players, or the C cells for my battery-powered amp.  The pile of weak batteries can get so big so fast that you feel criminal simply disposing of them.

[mac]

That's pretty much why I resported to "recharging" nonrechargeable batteries, whether they be 9v for my pedals, AA and AAA for the old Game Boy, the various and sundry remotes and CD players, or the C cells for my battery-powered amp.  The pile of weak batteries can get so big so fast that you feel criminal simply disposing of them.

I've built it some days ago and it works fine. BTW I use a voltage regulator to set the mac voltage.

[Processaurus]

A better formula can be found in the following posts:
http://www.diystompboxes.com/smfforum/index.php?topic=41922.msg362255#msg362255
http://www.diystompboxes.com/smfforum/index.php?topic=41922.msg362294#msg362294

In summary, a 9V Duracell battery can be expected to last about 26 hrs when discharged at a 12 mA rate until its residual voltage is 7.2V.

(Note: 0.55 * 580 mAh / 12mA = 26.58h -- refer to the second link for the derivation of the formula)

Thanks for that!  So 319mAh of pedal usable current in a Duracell alkaline is a reasonable rule of thumb?

[Ronsonic]

A better formula can be found in the following posts:
http://www.diystompboxes.com/smfforum/index.php?topic=41922.msg362255#msg362255
http://www.diystompboxes.com/smfforum/index.php?topic=41922.msg362294#msg362294

In summary, a 9V Duracell battery can be expected to last about 26 hrs when discharged at a 12 mA rate until its residual voltage is 7.2V.

(Note: 0.55 * 580 mAh / 12mA = 26.58h -- refer to the second link for the derivation of the formula)

Thanks for that!  So 319mAh of pedal usable current in a Duracell alkaline is a reasonable rule of thumb?

Not that simple since you'll get more than that out of it with a lower discharge rate. Even less at a higher rate. It just isn't linear.

Ron

[Paul Marossy]

This is another way to make a 9V battery that lasts a very long time:
http://www.diystompboxes.com/smfforum/index.php?topic=48519.0 

[mac]

Another options are the 9.6v batteries on electric screwdrivers, a 12v camera battery with a LM317 to convert to 9v or better a motorcycle bat. The last one can feed several pedals at the same time for a long time

But the best solution is a solar cell. You can feed your pedals with the stage light! 

[Ronsonic]

This is another way to make a 9V battery that lasts a very long time:
http://www.diystompboxes.com/smfforum/index.php?topic=48519.0 

I'm going to bolt one of these and a cheap charger under my pedalboard:




http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=21

Ron