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TOPIC: BK-7m - on batteries?

BK-7m - on batteries? 06 Nov 2015 19:24 #3168

  • n9yty
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Hi everyone!

I found a post by Diki here:

roland-arranger.com/index.php/forum/musi...nitors-for-bk-9#2575

It is stated that the BK-9 (and by extension, the BK-7m?) CANNOT run on batteries. But, is that true, or is that just "factory configuration/supported"?

Ther power supply for the BK-7m is rated exactly the same as the supply for my FR-1xb, and I can run that on batteries. I also can run my Roland Cube Street EX on batteries. It would be AWESOME if the BK-7m could run on batteries as well.

While it seems possible to just buy an 8-AA battery pack with the right connector to plug into the BK-7m, caution is telling me to go slowly. So, anyone here know anything about this? It might not be "supported" or provided this way from Roland, but could it be made to work? I have no idea how long a set of batteries would last, but using 2800mah rechargables would be great even if I got a few hours.

Thanks for your thoughts.
Steve
Last Edit: 06 Nov 2015 19:33 by n9yty.
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BK-7m - on batteries? 06 Nov 2015 19:51 #3170

  • Diki
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Proceed with extreme caution.

BK's are not designed to be battery operated, probably don't have the same kind of shutdown protection that a battery operated instrument comes with (nasty things can happen if the battery voltage or current drops below a certain level) and you are DEFINITELY violating your warranty trying some cobbled together battery solution..!
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BK-7m - on batteries? 06 Nov 2015 20:02 #3171

  • n9yty
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Thanks, Diki. No warranty left. :) But even using the included power supply you aren't isolated from incoming voltage fluctuations and black/brownouts, or just pulling the cord out without warning. I think having an under/over-current and under/over-voltage protection circuit on the battery pack would do more to provide protection than the Roland supply offers when using AC.

I understand there is no official solution, and I know anyone is probably leary of giving advice to "hack" on things with concern about damaging equipment/etc. So I guess this thread probably won't go anywhere helpful, but it was worth asking.

Have a great day!
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BK-7m - on batteries? 06 Nov 2015 23:23 #3177

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More interesting... Yes, both the BK-7m and the FR-1xb use the same power supply, a PSB-1U.

Looking at the manuals, though, the FR-1xb draws 1800mA of current, and the BK-7m only 900mA, so it would stand to reason that it could last twice as long on a set of batteries as the FR-1x would, depending on typical draw. So simply protecting it from under/over voltage/current should be enough, which is a simple circuit. The Cube Street EX, for reference, draws 730mA.

If I ever get this working I'll report back. :)
Last Edit: 06 Nov 2015 23:38 by n9yty.
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BK-7m - on batteries? 09 Nov 2015 18:03 #3189

  • Kurzweil
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I believe that you can use a battery pack power supply for this unit successfully. Modules are typically just keyboards without keys and Roland makes several battery powered units, such as the VK-09, a gigging keyboard. Over-voltage is certainly a concern but due to the fairly dependable characteristic of batteries to drop, rather than rise, in voltage, probably not a serious issue today. One thing you DO need to concern yourself about is that this being improvisational, you will have no power meter or battery warning device. Hence I would refrain from doing any critical saving operations while on battery power, at least to any device which you value, such as the internal memory. Any file being so-saved has the potential of being permanently corrupted if power fails at an inopportune moment. You could save to a USB stick, provided you have a backup in case of sudden power loss. A corrupted file is the worse that should happen, since kicking the plug out is always a possibility and brown-outs not unheard of either. In fact, I routinely pull the plug to turn my stuff off. Why put wear and tear on a locking power switch, since I generally move it each time I play it?
ARRANGERS: Roland E-80, G-70, BK-5
ORGANS: Roland Atelier AT-90s, AT-80s, AT-80, AT-70, AT-60r, AT-30, and AT-15. Roland VR-760 combo
WEIGHTED 88s: Yamaha S-90, Kurzweil PC-3x, Casio Privia PX-330
Atlanta, Georgia
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BK-7m - on batteries? 09 Nov 2015 22:08 #3191

  • Diki
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The thing I'd be most concerned about is under-voltage or current, as your batteries drain. All kinds of weird things can happen as the voltage or current drops below what the keyboard is designed for, up to and including corrupting the OS or altering the default settings (that are only stored in on board flash RAM) you have created.

Mind you, the BK-7m is pretty robust... I did a weekly gig this summer on a Mardi Gras float powered by a somewhat unreliable generator, and often had brownouts or compete power cuts that made the BK-7m switch off (boy was I happy it reboots so quickly!). So far, AFAIK, I have had no memory corruption, but I never had it happen during writing something to memory (either stuff like MIDI settings or writing edits to the stick... I did all that at home on a UPS backed up power system), which may happen to you if you rely exclusively on a battery system.

Just curious though... Do you have a battery operated PA too? There seems to be little point in a battery operated arranger module, if your PA needs to be hooked to mains power, is there? :evil:
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BK-7m - on batteries? 09 Nov 2015 23:44 #3193

  • n9yty
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Great points, as always, Diki.

Yes, the Roland Cube Street EX is a battery powered amp, and the Roland FR-1xb accordion is battery powered, so this is the last piece. On the Yahoo Bk-7m group I ran into another person who was doing this, but they were using a 12V Gel Cell type battery and only a downconverter. The circuit I am looking at is more sophisticated as it is an up/down converter to regulate the voltage to a constant 9V whether the source voltage is above or below that. The only concern I have with that is to cut off the battery packs at some safe voltage so they are not over-drained. But that other fellow who had done it has said he suffered no ill effects. Then again, nobody does until they do. :) Thanks again for the great thoughts, I will post back when all is assembled, although caution is good and even if it "works for me" I wouldn't probably be advocating it for others if they aren't aware of the risks for potential damage/etc as you point out.
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BK-7m - on batteries? 12 Nov 2015 18:36 #3204

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Kurzweil wrote:
One thing you DO need to concern yourself about is that this being improvisational, you will have no power meter or battery warning device. Hence I would refrain from doing any critical saving operations while on battery power, at least to any device which you value, such as the internal memory.
Thanks for the thoughts! I would be using just preset lists, I wouldn't plan on doing much (if any) modifications while on battery. I had to laugh, though, about the battery level monitor not being there because it was "improvisational"... The Roland FR-1xb V-Accordion is not improvised by me, but yet the battery monitor it has is all but worthless. It will read a full charge on the batteries right up until it is within seconds of shutting down. No use at all. This seems to be a known problem, with no intention to be fixed. So be it, but you could check the battery before starting each song, and it wiould show full, and it would then die in the middle of the song on you. For what it is with, I am putting a voltage readout in the circuit I am building, but how useful it is remains to be seen. I am also putting a voltage cut-off to protect the batteries from draining below a certain level as well as a up/down converter to provide a consistent 9V output when the 8-AA pack is above 9V and is it goes slightly below 9V until the cutoff circuit kicks in. It should be an interesting project, most of the parts are on their way already.
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BK-7m - on batteries? 12 Nov 2015 21:46 #3205

  • Kurzweil
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Different battery types have different discharge curves. Alkaline are the most smooth and you probably get some warning. Lithium is probably the way you'll want to go, however, for the recharging capability. I have an friend that is a better engineer than I and he recommends a solid state voltage regulator assembly. He suggests a 12 volt lithium battery pack regulated down to nine volts (what the BK-7m requires, yes?). You monitor the 12 volts on the display (which is switchable between battery and output). When the battery voltage begins nearing the output voltage, namely 9 volts, THE END IS NEAR. I think this thing is nominal in cost, something like $20 US. I'll get more details from him when I return on Monday. About to drive to Florida to pick up a desperately needed organ.
ARRANGERS: Roland E-80, G-70, BK-5
ORGANS: Roland Atelier AT-90s, AT-80s, AT-80, AT-70, AT-60r, AT-30, and AT-15. Roland VR-760 combo
WEIGHTED 88s: Yamaha S-90, Kurzweil PC-3x, Casio Privia PX-330
Atlanta, Georgia
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BK-7m - on batteries? 12 Nov 2015 22:13 #3206

  • n9yty
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The FR-1xb manual actually recommends using rechargeable batteries, not alkaline, so one would think the calibration on their display would match that discharge curve. But it doesn't. :) Oh well, no matter, that is a side point. :)

This is the item I ordered, I hope it should work well. It just needs an on/off switch, the under-voltage shut-off and the battery monitor/display...

www.pololu.com/product/2576

It is a step up/step down regulator, so it equalizes the voltage both ways. And yes, I plan to monitor the voltage on the input side of this device to see the battery level, not the level of voltage out of it which would always be 9V. :)

I would be most interested in hearing what your friend might recommend, though. Safe travels to get that organ, and may it arrive safely along with you back home. :)
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BK-7m - on batteries? 29 Apr 2017 19:22 #5866

Hi guys,

I can confirm the Roland BK9 can run on batteries! I use two battery containers for 8 penlites (1,2Volt) in total. I put the batteries in seiral order to provide me with 9,6 Volt.
First I tested with normal batteries (1,5V) of which I put 6 in serial order, but the batteries got pretty hot and could only provide enough power for 3/4 hour.

Now I use rechargable batteries of 2750mAh and this afternoon they lasted about two hours!

There's is no problem if the batteries run flat, the BK9 just powers off and tries to power up again.

I'm sure everything should work the same with the BK7m

I hope to test it out on the street this summer, together with a Mackie Freeplay that can also run on batteries.
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BK-7m - on batteries? 01 Jun 2017 22:17 #5965

  • Diki
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Would you care to follow up with more real world experience using the rechargeables on a regular basis?

And perhaps some pictures of the rig and the power pack?

My only concern is, most of my gigs go past the 2 hour limit.How much does the battery pack cost, is it affordable to carry 2-3 of them fully charged?

I have a little Ion rechargeable PA, seems interesting to see what my power limits are. I'm also taking a very close look at these, nice rechargeable LED lighting. The ultimate 'set up anywhere' rig! www.chauvetdj.com/products/ezpar-64-rgba/

About from 8-20 hours runtime depending on whether flat out 100% all on, or normal use.

Thanks....
Last Edit: 01 Jun 2017 22:18 by Diki.
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