Gear / Technical Help > Battery Boxes, Preamps, Mixers, ADCs, and Processors

Tinybox 9 volt Mod

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Walstib62:
I decided to change the internal 7.2 volt internal cell to a 9 volt rechargeable. It just fits inside. I can now power from the internal, or also connect an external 9 volt pack simultaneously, which extends the run time significantly.

jerryfreak:
cool move. those li-ion 9Vs arent 9V but thats good, as they run at the same voltage as the packs.

does it charge ok with the default setup? Out of the box the TBs couldnt charge and operate at the same time, so what you describe is def. different

Walstib62:
The internal battery and external DC input are in parallel, so yes the tinybox is powered by both at the same time.  With the 7.2 volt pack, you could do the same thing, but you would have to limit the external input to 8.4 volts max. With this mod it is much easier because you can use 9 volt cells.
The internal cell has to be rechargeable.

9 volt operation has the added advantage of keeping the amplifier circuits at proper DC supply levels. There have been performance issues noted with the 7.2 volt battery discharging during use and causing distortion due to low DC levels. 

jerryfreak:
yes but again it’s not a ‘9V’

it’s the exact same configuration as the original li-ion (if so equipped)... 2 3.6V (aka 4.2V) cells in series

if the previous battery didn’t operate the unit correctly, it shouldn’t have been because of the battery type, it was likely because the battery was defective (same for the 5*nimh cells batteries, which are slightly lower voltage but still operate the unit to full spec, afaik.) they run about 6v until they start to tail off

more importantly, putting 9v in parallel with that battery sounds dangerous. they can take higher voltages as long as cell voltage isn’t above 8.4, but once they hit 8.4 the voltage needs to be controlled. with an external 9v you can be well past 1C charge rate and hit 8.4 sooner than you think. practically speaking those 9V alkalines wont be above 8.4v for long with any significant load on them. in any case if you didn’t alter the circuit inside there’s a charge controller onboard, as tiny boxes charged from any unregulated wall wart of adequate voltage.

TheMetalist:
Thank you for the pictures and clarification.

I still don't understand how it's possible to fit a 9V battery inside of the unit? I have tried in mine but no... The 9V battery is too long. Looking at your pictures, your TB seems to have a different circuit board than mine. Perhaps yours is smaller so you have more space inside.

What kind of connector do you use for the external power? I have tried various connectors but none really stick nicely in the 9-15V input plug. I'm afraid it would come loose when in stealth mode and stuffed away in my bag.

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