question about battery drain in digi pedal

[daz]

So my bass player and I got these digitech "drop" pedals that are basically a dedicated pitch changer do that you can play a song dropped to a lower tuning instead of retuning your guitar. We mainly only use then for a max of 1 step, much more often a 1/2 step. The come with a wall wart but my rig is a one plug rig, a modeling combo with all effects and everything built in. So finding another wall outlet close enough at various gigs and just the hassle of it all for a device i use maybe 2-5 times a night is a PITA. So while it has no battery compartment i was gonna make a 9v clip to barrel adapter to plug a battery in it. It's 300 mA which is no worse than a lot of digital guitar pedals. And its true bypass. But the question is, how does a device like this drain the power source? Will it pull 300 mA even when bypassed or only when the device is in use? Lets not go into the "why not just bring a long a/c cable and just use the PSU" questions. I have more reasons that are too long winded to bother but i WILL be doing that if i have to. But i''d like to now if the battery solution is feasible.

[Greg Robinson]

At 300mA a 9V PP3 alkaline will last under two hours - that is presuming the pedal can actually operate all the way down to 6V, which is not a given. You'd only get about 30 minutes if it can still run at 7V!
But yes, the pedal will still draw current when it is bypassed. It's unusual for bypass to turn-off power on any typical circuit, as you normally get pops and thumps when circuits power up which would be unacceptable.
There are power banks for pedals with inbuilt USB rechargeable lithium batteries, but I'm not sure what options are available that can support 300mA - most are limited to about 100mA per output. Many though can use so-called "current doubler" cables, that plug into two outputs and sum the currents. Using 3 outputs and 2 "current doubler" cables or a custom wired "current tripler cable" would get you 300mA.

Hope that helps.

EDIT: On doing some research there are several rechargeable powerbanks that support 300mA or greater, first results on Google for me were ARTIST PBB01, Warwick Rockboard Power LT XL, JOYO JP-05. I'm sure there's others.

[daz]

I figured as much but i hadda ask. I thought maybe it would pull 300 only under load with signal. Oh well, wall wart it is. Thanks

[Helmholtz]

Why not use a power/socket strip with only one wall outlet?

[JP-Stereo]

The power rating given by the manufacturer on the user manual represent the worst case or maximum power draw.
If you want the real thing you must measure the current and voltage in real time while using it.
You may find that it's a lot less than expected.
Look at the current draw at rest than in average use and look for the peaks.
Current x Voltage = Wattage,
Then set the time for each of the different draw level.
Wattage x Time = Required Power (Watt-hour)
So the total of 3 to 4 "sample" will give you a very realistic target.

Depending on the current a 9v battery will give between 4 and 5.5 Wh.
Batteries can be wired in parallele for more Wh.

[Helmholtz]

Watt-hour (Wh) is an energy.

I would not parallel batteries as the one with the somewhat higher voltage will be loaded by the other ones, thus always discharge to the lower voltage.
Means a waste of unused energy (Whs)..

[g1]

measure the current and voltage in real time while using it.
You may find that it's a lot less than expected.

Good idea and easy to place current meter between one terminal of battery clip and battery. Current in bypass mode might be quite low, although I expect with a digital pedal it will not change much.