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DIY Stompboxes => Building your own stompbox => Topic started by: Constantin Necrasov on March 26, 2005, 03:16:05 PM

Title: 23A type batteries
Post by: Constantin Necrasov on March 26, 2005, 03:16:05 PM
Hey everybody!
I'm trying to find a compact alternative to a 9V battery to power an onboard preamp for bass guitar.  I found these 12V barrel type batteries, half length of AA and 12 Volts. My question is:
Judging from your experience, how long would those last when the current draw is around 10-15 mA?

Thank you very much.
Title: 23A type batteries
Post by: Paul Perry (Frostwave) on March 26, 2005, 07:26:42 PM
I don't have any experience, but life is roughly proportional to weight, for batteries of the same type. It's an alkaline, so that helps.
You can get rechargables that size.
Title: 23A type batteries
Post by: Hal on March 26, 2005, 08:33:18 PM
that seems very high current draw for an on-board preamp.  My preamp has lasted for the last 2 years wtih the same 9v battery...
Title: 23A type batteries
Post by: Constantin Necrasov on March 26, 2005, 09:12:40 PM
it's a tl062 based pre. one half of it is variable gain, other - tone control. hence the current draw.
Title: 23A type batteries
Post by: zachary vex on March 27, 2005, 03:14:24 PM
you'll be replacing them from time to time at that current draw.

a 9v alkaline has about 565 mAH energy capacity, and a 12V photo battery has about 33 mAH (according to the Mouser catalog.)  that's not a very good ratio!  i'd stick with a nine volt.  looks like you'll get 2 hours use out of a photo battery.
Title: 23A type batteries
Post by: ESPguitar on March 27, 2005, 03:21:21 PM
Quote from: zachary vex
you'll be replacing them from time to time at that current draw.

a 9v alkaline has about 565 mAH energy capacity, and a 12V photo battery has about 33 mAH (according to the Mouser catalog.)  that's not a very good ratio!  i'd stick with a nine volt.  looks like you'll get 2 hours use out of a photo battery.


:lol:

:D
Title: 23A type batteries
Post by: Ardric on March 27, 2005, 06:00:57 PM
I tried to use one of these onboard to power a set of EMG pickups.  The pickups are rated for 9 to 18VDC, so I figured by replacing a 9V with one of these I'd save a ton of cavity space and get more headroom to boot.

But the pickups hated the battery.  There was less output and noticable distortion.  I don't have measurements, but I'm guessing it's because the battery has a very high internal resistance.

There's no room for a full 9V in the cavity of my steinberger spirit, so I came up with a drastic solution:  some 9V's are internally constructed as 6 descrete 1.5V cylindrical cells, all stacked together (2x3) in the metal shell and wired in series.  I dissassembled a battery and moved the cells around until I had a shape that would fit, then carefully soldered them up and wrapped the whole thing in electrical tape.

I'm not looking forward to replacing that one again.  I'd like to use something like this 23A, or perhaps a stack of button cells.
Title: 23A type batteries
Post by: Constantin Necrasov on March 27, 2005, 09:26:52 PM
Well, distortion is because EMG eats up the battery fast. THe battery was probably lythium, so the internal resistance grew as the battery was discharging. Resulkt - distortion at the voltage that is not so low for distortion. (unscientific explanation, but that's all i know).
Ok, back to good ol' 9V. I'll have to do some routing I guess.
Thank you gentlemen for your input, all is greately appreciated.
Title: 23A type batteries
Post by: zachary vex on March 27, 2005, 11:37:34 PM
upon further review, the lithium version seems to have more like 1400 mAh, about 50% more than a 9V alkaline.  it's the alkaline version of the 12V photo battery that's under 40 mAh.  the difference in price is around $5 for the lithium, under a buck for the alkaline, per mouser.com.
Title: 23A type batteries
Post by: Ardric on March 28, 2005, 01:53:38 AM
It was the alkaline version I used.  I had two, but they had at least a year of shelf time.  They read 12V on a meter though.  According to EMG's web site, I should only be seeing about 0.25ma of draw at 9V.

I think I should give a lithium battery a try.
Title: 23A type batteries
Post by: Paul Perry (Frostwave) on March 28, 2005, 02:05:23 AM
See if the distortion goes away when you put a large (say 1,000uF) electrolytic in parallel with the battery.
I must agree that current drain sounds damn high for a preamp!!