Hi Guys,

I got an outdoor gig coming up and I was informed that there are no outlets at the location. I have a few questions:

Q: What are your thoughts about a battery pack, such as Duracel's emergency battery pack for a keyboard(Nord NP88) with a Roland Cube (30W)?

http://stormprepare.com/Portable-Power.htm

Q: Do you think I can get 3 to 4 hours from this battery pack?

Q: What is the power consumption (watts) for a Nord keyboard or any other similar keyboards?

Thanks.

While that amp might state 30 watts output I rather doubt the amp is 100 percent efficient and it draws perhaps double that or more from the wall. (Take a look at the fuse to have an idea.)

[edit - I just looked at my keyboard] Your keyboard probably uses 100 watts or less. My CP5 draws 50 watts at 230 volts. That's 100 watts at 115 volts.

So, see if your 12 volt battery would provide say a continuous 200 watts at 115 volts for three hours to be on the safe side. (At 12 volts you'd need a battery to handle say a 15 amperes discharge per hour for 3 hours.) A deep discharge trolling battery, one used for boats would do the trick, and so would a regular car battery I'd think. (The deep discharge battery is made specifically to be used without being charged for long periods unlike your car battery. The deep discharge battery only gets charged when you plug it in to the charger. I own a deep discharge battery for my caravan\mobile home and it only gets charged once or twice a year. It powers the motors to the wheels when we arrive at a camp site and don't feel like pushing the caravan into place. It also supplies 12 volt power when there's no line current available.)

You'll need a power converter from 12 volts DC to 115 volts AC. Gasoline powered generators are also possible to rent or buy.

I've never done this for musical jobs so my thoughts are just my thoughts with no practical application. Whatever you decide test it first before you get to the job to be sure the sound is to do your desire.

(If my math was wrong, someone will correct me. )

I think a device like that to power the keyboard looks like a good idea. If you could possibly get a hold of a Roland BA-330, it's probably better sounding, more capable of satisfying outdoor volumes without sounding pushed, and its battery operation would remove the variable of it being a drain on the battery you're running the piano from (the amp is likely to take much more power than the keyboard). I haven't heard the BA-330 myself, but I've seen some nice reviews of it, for what it is. I don't think any Roland amp is likely to do justice to your Nord Piano, though!

Is this a solo gig?

I looked at that link for the DURACELL® POWERPACK 600 and it only supplies 300 watts (115 VAC) for 90 minutes.

If you buy that Duracell Powerpack be sure to run it through its paces to be sure it won't die before the end of the job.

We don't know the exact draw from the amp or keyboard but 300 watts for 90 minutes ... and that might be a slightly inflated number, doesn't inspire confidence for me. I'd look into something else, but that's just me.

There's a reasonably good chance that it will be fine, but I agree that you should test it first. You could also consider measuring the power consumption of the keyboard and amp, using something like this Energy Cost Meter I've actually got one of these and it only cost about $30.00 from a supermarket.

You may find that the average power consumption of the keyboard and amp is far less than the rated power. For example, my Casio PX-330 keyboard is rated at 18W, but it's only measuring 3W, even when I play a few notes quietly through it's loudspeakers.
For the amp, the rated power input will probably be appreciably more than the power output, but depending on how it's designed, it too may measure quite low - even lower than the 30W output rating, on average.

If that power pack does not generate a pure sine wave output, there's a possibility that it will cause interference.

Greg.

Keyboards don't draw much. The Yamaha MOX8 draws 10 watts according to its specs. Even if the Nord draws double that, it should have no problem getting through a gig that can supply 300 watts for 90 minutes.

The Roland CM-30 (not sure that's the model he's talking about) draws 32 watts according to its specs. But as I understand it, a keyboard (with no amp) should draw pretty much the same no matter what, while an amplifier can draw more or less depending on the demands you're making of it, and I don't know how Roland measured that, i.e. that 32 figure might be "typical" or "average" rather than maximum, and it might draw more if it is being pushed hard.

FYI, my MP9000 DP (no internal speakers) gets very close to it's rated power when just sitting idle - rated 15W, measures 13W.

My hi-fi amp (50W + 50W) measures 23W at idle.

Give or take the meter tolerance of course. (+/-4% or +/-10W)

Greg.

My Nord Electro 3 draws only 12W along with a 100W inverter:

http://www.norduserforum.com/accessories-and-amplification-f8/inverter-power-supply-t1099.html

Rune

Even assuming those numbers are close... the DP is probably about the same power at all times, not drawing much (if any) more power when you're playing than when it's sitting idle, whereas I think the amp will probably draw a lot more power when you're cranking it than when it's sitting idle. Though the 30 watt mono Cube probably draws less power than your 50 watt x 2 amp.

That 4% or 10w variance spec would be more useful if they told you whether the variance was whichever was the lesser of those two, or whichever was the greater!

Anotherscott - agreed on all counts.
EDIT: Btw, a 10W light bulb is measuring 12W, so I think my measurements are usable, if not of lab quality.

Greg.

I took a look at my 12 volt deep discharge battery (it's in the hallway for the winter) and saw that it was rated at 90ah \ 20 hours.

The following link might be of some use to someone ...

http://overlandresource.com/what-is-an-amp-hour-and-how-to-calculate-battery-capacity

After reading that article, I learned that my big ass battery (90 ah \ 20 hours) will delivery continuously 4.5 amps (or 54 watts at 12 volts) for 20 hours before the battery is dead, but you don't want the battery to go dead so you take a 60 percent reading. I now have 4.5 amps \ 54 watts for 12 hours (instead of 20) at 12 volts without harming the battery.

Someone correct me if I did not understand this.

Nothing in that link actually says 12W (you may have been confused because it mentions a 12V source). In fact, the .6 amperage difference would imply more, except I don't know what "overhead" is involved in the operation of the inverter itself.

That Duracell inverter looks quite suitable for your purposes.

I get 12W by multiplying 12 volts with 1 Ampere.
Watt´s Law

Ah. But he said that the inverter itself draws .4, and it goes up to 1 amp with the Nord plugged in, so then the Nord is drawing .6 so then 12 volts times .6 amps = 7.2 watts, no? Assuming that the use of the inverter itself isn't doing anything else to introduce some variable into the equation, I don't know much about them.

It appears that the inverter´s efficiency goes up when under load.
With the NE3 plugged into a 225V wall socket, I measured the current to 0,48 mA
225 x 0,048= 10,8VA

Note, the term Watt should not be used for simple AC calculations like this. The correct term is VA (Voltampere= AC apparent power)
Although the Waeco inverter works fine, I will replace it with a true sine wave equvialent soon. I´ve heard from several sources that the high transient output on cheap inverters can harm delicate electronics in the long run.

Rune

Thanks everyone! Wow that was overkill! But great information. This will be used for a solo gig and I will consider looking into a battery powered speaker, such as the Roland BA-330 or the KC-110. Thanks for the suggestion.

I'll be heading over the WalMart or Sears this weekend to purchase the Duracell 600 power pack. I'll let you guys know how it does. Thank you very much

Holy Smokes!! The Roland BA-330 cost a whopping $650 and the KC-110 cost $400 based on my initial search on Amazon.com. I'm really hoping my Roland CM-30 will not drain too much power from the power pack.

I hope that gig pays well

Are you completely sure that a good old extension chord is out of the question?

You're not playing on the beach are you? If so, I'd be worried to bring the beautiful keyboard.

I would suggest an inverter and a car battery
The claimed 2-hour run time for a 100W vacuum cleaner on the Duracell unit indicates a battery capacity of 16 Ah. Even the smallest car battery would double that.


Ok, I respectfully disagree ;-)
Provided that the DP is wired for both 115 and 230 volts, the power consumption will be the same. At 230 volts and 50W, the current draw will be roughly 0,25A. At 115 volts 0,5A
Watt´s Law
(Thats the reason why the mains fuse need to be replaced when altering the mains voltage switch)

Rune

It appears to have a 28AH battery, according to these detailed specs: http://stormprepare.com/Powerpack-600-Specs.htm

Greg.

If you have the need to guesstimate the AC watts when all you have is audio output power, tripling or quadrupling the audio watts will be pretty close. A small amp that puts out 30 watts of speaker power will pull 90-120 watts from the wall or your inverter/battery set-up.

Kurt

Re-think that. An amp may be ABLE to put out 30 watts, but it will VERY SELDOM do so.

I have a stereo 50+50 watt amplifier/receiver.
With no sound output, it pulls 30 watts AC.
When blasting, it pulls about 50 watts AC.

So ignore the output power. Just look at the input power figure on the label on the back. That will give you a good, representative figure for power consumption.

Also, the amp may be a lot more efficient than that anyway - take a look at the Class D amp for example.

Greg.

If I were in this situation I think I would rent or borrow something for a one time job.

In all the years I've played I only had one job that was relatively remote; the power cord run was over a hundred yards. At the time I had problems with my amp because the amp was voltage sensitive and the long cord run dropped the voltage.

I learned my lesson on that job. The amp in question was one of those very light weight amps that put out a lot of power. (It was something like an 11 pound amp that put out close to 500 watts per channel RMS.) The down side of that technology, the amp wants to see line voltage close to what it should be.

If you were doubtful that it would last long enough, you could hook up an additional car battery to the jump-starter leads. That way you still run it through the inverter, but you have probably tripled or even quadrupled the capacity.

Or you could buy a spare battery of the correct type for the power pack and have it pre-charged, ready to install, on the off chance it is required.

Note that car batteries are not designed to be fully discharged - deep cycle batteries are better for this application.

Greg.

That's true, but I was suggesting the car battery because it seemed like this was a one off gig and everybody can come up with a car battery. Deep cycle batteries are pretty expensive for a one off jaunt. A car battery won't mind being run down once or twice, but you can't do it too often.

Would a computer UPS work for something like this?

Thanks for the head up. I didn’t took the power loss in the inverter into account


According to the manufacturer, the power consumption in the Roland Cube 30 is 34W.
I don´t think the amp will exceed that figure, as long as it´s not driven into distortion.


My 13” MacBook Pro works fine with the original adapter, a 100W Waeco inverter and a sealed 7,2 Ah Lead battery. A true sine wave inverter is recommended for computers though.

Sorry for poor english grammar,
Rune

... bring along an accordion.

You used a DC load (the 12V DC vacuum cleaner) for your calculation, so the only loss in the inverter is the static loss, which is under 0.2A/2.4W, which is tiny compared to the 100W load. ;^) The discrepancy could be due to Peukert's Law. Looking at some of the run times, especially for the high power AC loads, they may also be taking into account the typical duty cycle (ratio of on vs off time for typical usage), and of course power factor as well.

Greg.

Oops, I forgot the vacuum cleaner was a DC device

Then a more appropriate equivalent to the Nord Piano/Cube 30 setup would be the 40W table lamp with a run time of 7 hours

Rune

Yeah but, even the 'better' ones these days are battery powered!

Here's a 350W Class-D amp from Roland - the SA-1000. The power consumption is just 94W, so it appears that this would be the power consumption for typical music. (presumably at maximum volume) If Roland are consistent, that would mean that the 32W power consumption spec for the CM-30 is also the typical spec. (and perhaps we can also deduce that the CM-30 is not Class-D, because the typical consumption is much closer to the maximum output power).

Greg.
p.s [off topic] Look at this - a 350W + 350W Class-D amp that's the size of an Ipod! http://www.eetimes.com/design/audio-desi...em=audio-design