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I want to buy an E-Piano for busking and home-playing. When I busk I won´t have a power outlet so I´ll have to battery-power the piano. Unfortunately I don´t have much knowledge regarding electronics so I hope someone here can help me out.

I have the following 2 Pianos in consideration:

Roland FP-30X Specs

Yamaha P-125 Specs

Now, I understand that both need a 12V input. Does that mean that I basically could use any 12V Lithium Ion Battery Pack. Would the following work for my purpose?

Portable Power Station

TalentCell 12/24V Lithium ion Battery Pack

If they are applicable for my intended use: Could you also tell me how long they would be able to power my piano for?

On the Specs-Page it says the Roland has a consumption of 16W and the Yamaha has a 9W consumption. How long would 35000mAh / 52500mAh be able to power that? How do you calculate that?

JYelton
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Helle
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  • Does this answer your question? [How to calculate battery life](https://electronics.stackexchange.com/questions/1478/how-to-calculate-battery-life) – JYelton Dec 07 '22 at 00:37
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    There are _a lot_ of questions on the site asking about calculating battery life for a given load. I voted to close as a duplicate of one I thought applicable. That said, I've also added an answer because I'm biased... I love music keyboards and couldn't resist. – JYelton Dec 07 '22 at 00:54

1 Answers1

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The power ratings for the keyboards will be the maximum which gives you the worst-case scenario.

The power law \$P=IE\$ shows that power \$P\$ is equal to the product of current \$I\$ and voltage \$E\$.

At 12 V 16 W, the Roland FP-30X would require 1333 mA. The Yamaha P-125 at 12 V 9 W would require 750 mA.

If all of the specs are to be believed (don't get me started on Amazon product advertising and marketing) then you divide the current into the capacity to get the run time:

Battery           Roland Run-time      Yamaha Run-time
PPS (52500 mAh)   / 1333 = 39 hours    / 750 = 70 hours
TC  (35000 mAh)   / 1333 = 26 hours    / 750 = 47 hours

Battery capacity must be de-rated (reduced) as current draw increases. You'll have to do some more research to determine whether the current being drawn falls into a range where the battery capacity should be de-rated. Because the keyboard specs are given as a maximum, they likely won't pull as much current as calculated above unless everything is continuously maxed out (volume, options, etc.). In other words, you probably do not have to worry about de-rating at all. I'd worry more about the validity of the specifications!

JYelton
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  • Brilliant answer, thank you!!! One more thing I noticed though: the PPS has a DC12V10A output. The piano ships with an AC-Outlet power cord which goes into an AC-Adapter which connects into the piano via DC-In 12V. I assume I won´t need the Adapter if I use the PPS due to it already being on the right voltage, right? So I would still need to get a new cable if I understand correctly? Just a DC 12V to DC 12V? or should i just get a DC cable which can connect into the Roland factory AC-Adapter which I then simply plug into the piano? – Helle Dec 07 '22 at 11:22
  • Yes, you do not need an AC-to-DC adapter if your power supply (PSU) is already supplying wha the load wants (12 V DC). Make sure you have the polarity correct. Some musical equipment (guitar pedals, I'm looking at you) have center-negative on their DC barrel jacks. Also, in case you need a refresher on voltage and current ratings, be sure to check [this Q](https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings). – JYelton Dec 07 '22 at 17:31