is battery drain linear with resect to Mah?

[Mick Bailey]

You could try a couple of diodes in series with the +ve battery lead to drop to the right voltage.

[daz]

I could, but same as having to compensate with EQ....have to remove them once voltage is normal.

[eschertron]

Let me stick my foot in my mouth (keyboard in my mouth?) once again; most rechargeable batteries will hover near the nominal voltage for the lion's share of their charge, then drop drastically. I would think it very bad engineering if the battery voltage were related closely at all to the residual charge.

[daz]

Well hell, i hate these things. Waste of $50 unless i can find a non music use for 9 volt batteries. It's not just bass and it's not subtle and it is NOT placebo. i went back and tried a alkaline thats down to about 8.3v and theres my sound again. Swapped them back and fourth and noticed 2 things. With the alkaline the tone is balanced and focus and dynamic. The rechargeable seemed stiff and i checked the volume dynamics playing soft then hard. With the rechargeable there is a much less difference in volume between light picking and hard. Thats what was bothering me most, a lack of touch response and this proved it clearly. Going to the alkaline it all comes back.

Now the thing is, i dunno if thats due to the rechargeable vs alkaline of because the rechargeable is over 10 volts still and the alkaline is just over 8v. But even if thats it, 2 potential issues....1-if what you (eschertron) said is true, then 'm screwed, as it will never hit 8 volts or so but die long b4 that. And 2- even if u are wrong this means i will have to charge them then put them in my board and leave it on and check it at regular intervals till it reaches 9v or thereabouts.
I would never in my wildest dreams thought a battery could change my tone so drastically. I guess i'll have to try mick's idea of a couple diodes in series with the +. Mick, which direction should they go and what type of diode?

[daz]

So much for dropping the voltage. Stuck 4 rectifier diodes in series on the + and it dropped to 8.7v, but when i compared it to the alkaline it still failed the test. Better, but still missing that touch and tone too. It's like having a compressor on and the transients are partially squashed when you pick hard. With the alkaline when i hit it hard it not only gets louder but dirtier as it should be.

[Enzo]

Two thoughts:

Eric Johnson used to swear by one brand of battery - I forget which - and would only use them for tonal reasons. We all thought he was nuts. He agrees with you. If I could play even 1% as well as he does, I'd be something.

The differences. Try putting a scope across the batteries while you play to see if they react to the signal or not. Another thing to try would be to bypass the battery with a cap, like say a 0.1uf film cap. Possibly the internal impedance of the batteries might matter.. You demonstrated to yourself it isn't simply voltage already. I mean there must be an actual reason they sound different. If we can determine what that is, a simple change might be all it takes to make your new batteries useful.

[daz]

Two thoughts:

Eric Johnson used to swear by one brand of battery - I forget which - and would only use them for tonal reasons. We all thought he was nuts. He agrees with you. If I could play even 1% as well as he does, I'd be something.

The differences. Try putting a scope across the batteries while you play to see if they react to the signal or not. Another thing to try would be to bypass the battery with a cap, like say a 0.1uf film cap. Possibly the internal impedance of the batteries might matter.. You demonstrated to yourself it isn't simply voltage already. I mean there must be an actual reason they sound different. If we can determine what that is, a simple change might be all it takes to make your new batteries useful.

Well, this is not eric J stuff, this is not near that subtle. I can't hear the difference between brands. But this is quite obvious in touch response. That being maybe the #1 most important tonal detail to me. When u say bypass the battery do you mean strap a cap across the + and - terminals?

[Enzo]

Yes, exactly. The value of it isn't special, just trying to make sure there is a low impedance path. Not right on the batter, but say where the battery clip wires solder to the board. And if that makes it worse, then we at least know the area of the problem. Just a quick experiment. It may do nothing, of course.

[daz]

I'll give it a go tomorrow. Getting late here but i'll post the results then. Thanks Enzo.

[Mick Bailey]

One question that comes to mind is the difference in internal resistance between the batteries. The pedals' own supply bypass capacitors should eliminate AC resistance and with several pedals the cumulative value increases as they appear in parallel. It may be that you'd need to add resistance to the new rechargeable as well as dropping the voltage. Jack Orman proposed a series diode + resistor to emulate a dying battery with its increasing internal resistance. The same idea in the Stompbox Cookbook.

[J M Fahey]

Yes, exactly. The value of it isn't special, just trying to make sure there is a low impedance path. Not right on the batter, but say where the battery clip wires solder to the board. And if that makes it worse, then we at least know the area of the problem. Just a quick experiment. It may do nothing, of course.

Your point is valid, and I *suspect* (may be wrong of course) that itīs more of an internal resistance problem than a raw voltage one.

I suggest DAZ 2 experiments:

1) "voltage matters" : get/make/kludge a regulated or variable power supply, just as simple as a TIP 29 transistor or similar, collector to +12V (old PC supply), base to a 1k pot which goes from +12 to ground, and emitter feeding pedal/bass.
Vary to taste, anything from 11V to 0V and listen.

2) "battery impedance matters": use your 10.5/11V battery, but insert a series resistor so actual voltage *reaching* Bass is "magical" 8.4V
Guess resistor will be between 500 ohm and 1k or so, but experiment.

EVEN IF both feed 8.4V to Bass, results will be very different.

Experiment 2 simulates a dying battery, as I mentioned above, actual internal/chemical voltage does not vary, itīs an atoms/electrons thing, but path resistance varies, a lot.

My personal test for AA alkaline batteries which I use a lot, is not to measure voltage but current
I set meter to 10A scale and place probes across battery, which it sees as a SHORT.

Fresh out of the pack ones give me up to 2A , normally a good 1.5A (which means internal resistance is 1 ohm).
When they give me less than 500/600mA I know remote controls start to weaken.

Never measured 9V alkalines or rechargeables but in any case I warn you NOT to try the experiment with Lithium ones, they will explode/catch fire/burn your meter. Not kidding.
One suspect reason for disappearing Malaysian Airlines plane was it was carrying a pallet of Cellphone Batteries; a couple weeks earlier a small box of them caught fire in another flight and extinguishers could not put it down ... by chance that plane survived, although full of smoke and steam.

And there is where difference with Alkalines lies (I suspect)

But anyway try both experiments.

[daz]

Thanks guys, i will have t take my time and read your posts a few times to soak it all in and see if i can try your ideas (including Enzo's) and i will likely have questions. Juan....I was wrong earlier....these are not lithium but regular NiMH. I thought i had read only lithium were capable of voltage as high as alkalines but i read the package to find they aren't

[daz]

Tried Enzo's idea and couldn't hear/feel any difference. Then i tried Juan's dying battery idea but i don't understand what yoiu mean by "reaching bass". In any case i tried 1k in series with the + then gradually more resistance with no change. So i jumped all the way to 100k and only .3v less ! 9.7 vs the 10.05v where the battery is after a bit of use. So not sure what i am doing wrong.

[daz]

Oh, and i don't know if it's my ears or what, but at about 1/2 volt less today the difference seems not as noticeable. Maybe artificially lowering it with diodes isn't the same as the battery voltage naturally being less? The also say it takes 3 recharge cycles for the battery to work optimally (paraphrasing) so maybe that could make a difference?

[Helmholtz]

Did you compare loaded battery voltages (i.e. in circuit with effects engaged) or with batteries disconnected?