Can you recharge 9v battery in a guitar's active electronics without removing guard?

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3,977
I am considering adding some active electronics to a guitar that require a 9v battery. Is there any way to use a rechargable battery and charge it without removing the pickguard each time? Either way, is there a way that I can TEST the 9v battery without removing the pickguard?

Thanks!
 

blueguitar

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224
Most active guitar related products specify good quality "alkaline" batteries only. They typically don't suggest the rechargeables. Why? Dunno.
 

Rhomco

Making UPS, FEDEX and USPS richer every day!
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dry cells are 1.5 volts per cell X 6 cells = 9.0 Volt battery. Rechargeable ni-cad cells are 1.2 volts per cell X 7 cells = 8.4 Volt battery.
 

ClinchFX

Platinum Supporting Member
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878
I've been thinking about this question since I read it yesterday. You could add a small switch somewhere. The switch would change the function of the output jack from output to charging input. The alternative would be to fit a DC jack to the guitar. If the guitar has a cavity cover on the back, it would be easy to mount a DC jack there.

BTW, there are some manufacturers who make a 9.6V rechargeable battery.

Peter.
ClinchFX
 

John Phillips

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13,038
I think it should be possible to recharge the battery via the standard jack, if it uses the ring connection to turn on the battery normally, without needing a switch.

You will need to bypass the preamp with a diode, to allow current to go the 'wrong' way around the circuit while charging, and you may also need to add another diode in series with the preamp, to make sure that even the remaining approx. 0.7V is not applied to the it (which may not be good for it). After that, all you would need to do would be to fit your normal battery charger with a cable with a TRS plug, with the positive to ground and the negative to ring (and nothing to the tip).

Again if it uses the ring contact for switching, you can test the battery in situ - not very accurately, but it will show if it's really dead. Simply put a normal cord into the jack just far enough to contact the ring, and measure the voltage at the other end. It should read 9V, or close to it (depending on the resistances of the preamp and the meter). First, do this with a known brand new battery and write down the voltage. Then, if you measure much less than this later, you'll know to change it.
 

ClinchFX

Platinum Supporting Member
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878
Good idea John.:AOK

If you use a Schottky diode (VF <0.4V) you probably wouldn't need the second diode.

Peter.
ClinchFX

 

walterw

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everyone sez that rechargables don't last as long as alkalines and die in an inconveniently abrupt way. i've never compared, so i don't know, but as many 9volts get used in musical gear, from wireless mics to active basses to in-ear monitors to pedals, you'd think that rechargables would be all the rage. pros won't get near them, and every owner's manual says stay away, so i guess there must be a reason.
by the way, early alembic basses had outboard power supplies, probably because their preamps sucked too much current for batteries.
 
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3,977
Wow, responses! I might be over my head with some of this at the moment... Basically, I have a 1988 G&L SC-3 coming into town sometime this week. I was thinking about keeping the original pickguard safe somewhere and getting a replacement one to trick out a little. The MFD pickups on this guitar only have volume and tone control (two knobs, as opposed to vol, tone, tone or vol, treble, bass). So, I wanted to put a GFS MODboard analog delay circuit in the pickguard. It's a strat style guitar, I haven't owned one of those in years. If I could change the battery by taking just the trem back cover off, that would be great, too, or I could order a 20 foot cable for my Pedal Power 2 and just play it like that (did I say I was lazy?)... Or maybe if there were a small outboard rechargable power pack that I could wear on my belt or on the back of the guitar strap or something that could supply enough power and I could just recharge THAT. I would rather have one thing to keep charged/recharge than have to keep removing the pickguard every time it goes out (plus I don't buy batteries for any of my gear, except the ebow and strobostomp (which makes its way around the house). I wouldn't even put it past myself to get a 20 foot pedal power II cable for the ebow (just kidding).

I have been reading a bit about the MFD pickups, usually in the S-500 guitars, they have volume, treble and bass. If they sound great as is, I'll leave them. If I replace them with more traditional sounding ones, that's fine. Will I suffer for not having a separate tone control for the bridge pickup? A blend circuit would be cool, or a switch that lets you use Neck + bridge. Maybe I should just come up with a full replacement pickguard with the delay circuit, new pickups and whatever the best wiring configuration is for a strat style guitar- I'll have to do some research and probably play with the guitar as is for a little while before I can make any big decisions.

So, to be clear, the battery would be for the delay circuit in the guitar, not for an "active preamp" (though the optional buffer might qualify as such, I think I'll go with the true bypass wiring, doesn't use the battery when the circuit's off, so)...

http://www.guitarfetish.com MODboard-> Analog Delay. That's what I'm looking at... Anybody tried their pickups? (GFS is one letter short of a searchable term here)... I'm reading some reviews on H-C...
 
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3,977
Hmm... check out this: http://www.guitarelectronics.com/product/PMTXBAT9

Basically, it's a power pack that is connected to a stereo cable that you plug into your guitar. So, it works as a cable and powers a circuit in the guitar. I surmise that one line from the stereo cable goes to your effects and the other goes to the power pack. Basically a rechargable external power supply, so I can avoid batteries.

$70 to avoid exactly what I want to. I wonder about using that cord or if it will mess with my sound with fuzz pedals or anything, but I'm open to checking it out.... cool idea.

If I switch guitars, do I have to use a standard cable (will this one blow up my pickups with no battery in that guitar?)????

EDIT: Actually, it appears that you just put the batteries in the unit. There is no internal/rechargable battery. I think I'll just use the 9v battery jumper and a really long cable to the pedal power 2!!!
 

CGrisamore

Member
Messages
989
everyone sez that rechargables don't last as long as alkalines and die in an inconveniently abrupt way. i've never compared, so i don't know, but as many 9volts get used in musical gear, from wireless mics to active basses to in-ear monitors to pedals, you'd think that rechargables would be all the rage. pros won't get near them, and every owner's manual says stay away, so i guess there must be a reason.
by the way, early alembic basses had outboard power supplies, probably because their preamps sucked too much current for batteries.
Until recently, 9v rechargeables haven't been even close to the capacity of alkalines. That has changed. I've been using 9v rechargeables without issue for several months in my Strobostomp tuner and my Shure PSM400 ear monitors.

here's the ones I use.

http://www.thomas-distributing.com/ipower-9v-lithium-rechargeable-battery.php
 

walterw

Platinum Supporting Member
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38,738
now that's cool! my psm400 eats a battery per gig, so if they can hang in yours, you might really be on to something!

how long does a charge last for your psm? can you do a whole show without seeing the power level drop in the little window?
 

CGrisamore

Member
Messages
989
now that's cool! my psm400 eats a battery per gig, so if they can hang in yours, you might really be on to something!

how long does a charge last for your psm? can you do a whole show without seeing the power level drop in the little window?
I haven't done a stress test to see how many hours before the battery actually dies. My goal was to get through a gig with a single battery and then put it back on the charger so that I always started a gig with a full charge.

Last Thursday we had a short 1 hr charity Christmas gig and I didn't bother to recharge the batteries from the previous Saturday (4 hr) gig. Plenty of juice and got through the gig without issue. Best part is that the batteries recharge in about 90 minutes..
 

donnyjaguar

Member
Messages
4,194
I was thinking you could use an inductive type arrangement where a pickup coil in the guitar would rectify the induced current and charge the battery. This wouldn't help you determine the charge on the battery itself though. There's also the issue where the induction coil would tend to demagnatize the pickups. I guess this wouldn't be a problem if the pickups weren't a conventional permanent magnet and coil type.

The trend in electronics is definitely away from 9V cells. Quite frankly you don't need that much voltage for an instrument level signal anyway. There is much more energy in a pair of AA cells than any 9V, but the musical instrument industry seems to have its feet firmly planted in the past. I bet the LED indicator on many effects pedals draws more current than the circuit itself. :)
 
Messages
3,977
Well, it's for a delay circuit and I'm not going to use the buffered output (always on, I have fuzz pedals after the guitar, they don't want to see the buffered input)... Can you fit a small 9v battery clip in the back trem spring cavity of a strat without modifying it? I don't want to drill/mod, but if I could double stick tape a 9v clip in there and use rechargables... I wonder what the longest cable for a PP2 would be, as that would be very simple- just plug in like any other pedal...
 

walterw

Platinum Supporting Member
Messages
38,738
I haven't done a stress test to see how many hours before the battery actually dies. My goal was to get through a gig with a single battery and then put it back on the charger so that I always started a gig with a full charge.

Last Thursday we had a short 1 hr charity Christmas gig and I didn't bother to recharge the batteries from the previous Saturday (4 hr) gig. Plenty of juice and got through the gig without issue. Best part is that the batteries recharge in about 90 minutes..
most excellent. now to figure out how to mount the charger on my pedalboard!
 




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