Battery powered BK-7m

[davidplaysaccordion]

I just tried running my BK-7m from a Ravpower powerbank and a 5v usb to 9v converter. So far, seems to work great. I still need to test it for duration but the same setup running my pedal board with 3 pedals and some other stuff on it runs fine for several hours so I have no reason to believe this will not be usable for longer than I can play! My bk is on a stand so time to fire up the 3d printer and make a mount and it'll be one less wire/plug to worry about.

This is the converter I used:




https://www.amazon.com/gp/product/B07GD54Q66/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

It also occurs to me that if I hooked up the BK outputs to a 2 into one (mini TRS) adapter I could plug that into the Roland's audio input jack and play the backing stuff through the Roland's speakers.

 

[JerryPH]

What is the power source that you are running it from?

 

[davidplaysaccordion]

Ravpower 26800 mAh powerbank

https://www.amazon.com/gp/product/B01IVONCAG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[JerryPH]

Might be interesting for buskers... get a battery powered amp, the battery powered BK and you are all set!

 

[davidplaysaccordion]

Might be interesting for buskers... get a battery powered amp, the battery powered BK and you are all set!

That’s what I was thinking, busking is my thing.

 

[JerryPH]

All you really need is a wireless MIDI, wireless acoustic transceiver and you are all set to rock and roll without wires attaching you to everything.
If you really wanted to take things to the next level, you could use an iPad, bluetooth pedal and after setting up your performance list, move from song to song without needing more than 1-3 seconds to push to the next song, where it would reprogram a V-accordion and the BK-7m to the needs of the next song and off you go with the press of a button to start things off!

 

[davidplaysaccordion]

Jerry, I have seen your setup. Very interesting. Funny thing is that I switched to accordion to simplify the amount of stuff I had to carry when playing, basically one thing, the accordion but I now see the amount if stuff slowly increasing again to where it was before. The Roland is a lot of fun but I think I need to be careful not to forget the joy and simplicity of a true accordion.

 

[davidplaysaccordion]

Someone on the facebook bk forum suggested an xtpower mp-10000 https://www.amazon.com/XTPower-MP-10000-External-Battery-10000mAh/dp/B00935L44E?ref_=ast_sto_dp it has a nine volt output built in rated at two amps rather than the max 800ma of the cable I am using. Just have to be careful about polarity of the cable at the BK end.

 

[JerryPH]

Both of the units you references are not available or sold out (might be because I am in Canada)... I know that TalentCell also has a good reputation and have portable batteries with 9V outputs.

 

[davidplaysaccordion]

So a little update.
I measured the current draw by the converter (not the BK7m as I previously stated) and it is around 980mA so just under an amp. Given that the converter steps the voltage UP, the output current would go down by a similar amount so I guestimate the BK7m is taking around half an amp (500mA), well below the 800mA rating of the converter.
I also made (3D printed) a battery holder and clamped it to my stand, so one step closer to being mains power free which is handy for a bit of busking!

 

[davidplaysaccordion]

Oh, and I made myself a 'FC-7' foot pedal only mine has 8 switches. 7 for the Fc-7 function and one that goes to a jack that I can plug into the switch/expression port on the BK7m.

 

[JerryPH]

We share very similar tastes in foot pedal design.
This is very much how I envisioned doing it before I did the 4X3 pedal design that I have now... well done!

Have you tried to push the battery and see how long it could power the BK in real world use yet?

Back from my photography days I have a portable battery/120v inverter setup that can power a 1000 watt studio flash at full power for roughly 3000 flashes over the course of a weekend. A while back I used it to power a video camera, my Zoom F4 and that F4 was powering 2 mics via 48 volt phantom power to cover my niece's violin recital in a church. It lasted 4 hours and was nowhere near drained to the point that the red light came on (under 20% left). I bet that could power the BK, 8X and a medium sized amp for at least 2-3 hours... I'll have to play with it over the weekend and see, just for the sake of curiosity, because I never busk.

That experiment would be interesting for me!

 

[davidplaysaccordion]

Several years ago I built a 'portable' mains supply from a couple of 35aH Sealed Lead Acid Batteries and a pure sine wave inverter. I use the term 'portable' loosely because it weighed around 50 lbs, mostly from the batteries although I don't do 'light' construction. The box was 3/4 ply and built like a rock. I would have fared well in the Victorian era. I did have a dolly to move it around though. It powered my mixer, pedal board, keyboard and my PA (QSC K10) and I could typically play for 3 hours no problem with maybe 40 to 50% left on the batteries (based on the charger reading when I got it back home and plugged it in). I played farmer's markets mostly (still do) and often there is no power, being in a car park somewhere but it worked great. There are now several Li-Ion based inverter type setups on the market, mostly for cpaps and the like so I don't know ho long they would last in a musical environment but it is amazing how technology has moved forward, even over the last few years.

This was my keyboard setup one cold December morning many years ago that will give you an idea of the size of my power supply.



The inverter was only 600W max and according to the meter on the front, typically I was only using around 150Watts, maybe 250, even powering my big pa and the keyboard so these instruments seem to draw far less than we think they do.

For my new setup, I put a meter between the battery and the USB to 9v converter and the converter draw is around 1 amp at 5V when driving the BK7m and the output level cranked up on the BK7m. The battery pack I am using is 360000maH or 36Ah so I would more than enough time for a couple of 3 or 4 hours sessions before I even need to think about charging it. I have already played it a few hours and it's not really touched the charge level of the battery pack, at least based on the 4 led indicators on the front of the battery anyway.

It did occur to me as well that while the converter is drawing about 1 amp, that means the BK7m is only drawing just over half an amp (500 mA) at 9v (voltage goes up, current goes down) which puts it well within the capabilities of the little USB converter (rated at 800mA on the output).

 

[Keymn]

All good stuff…so innovative ?