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I'm interested in building a portable PA system (on a small wheely-cart) that's very loud (particularly strong in bass, which uses a lot more power than treble) to be used in short increments of time and then recharged at the wall.

What kind of battery do I want? Li-ion, Li-poly, Lead acid, etc?

The battery should be able to deliver say 200W constantly for 10 minutes.

I realize I will need to learn about capacitive circuitry to "buffer" the load between the battery and the constantly-fluctuating amplifier draw, but that's a different question for a different OP.

....bonus question: if I can afford it, would it be suitable to simply use a large number of identical Li-ion cells in parallel?

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Selected versions of -

  1. Lithium Polymer. "LiPo"

  2. LiFePo4 / Lithium Ferro Phosphate

  3. LiIon only if 4 strings used at 24V (or 2 strings at 48V).

  4. A 40 Ah lead acid battery (large car, small truck size) would be up to this with an inverter if you didn't want too too many life cycles. A 12V 100 Ah deep cycle battery would be happy.

Specific specifications need to be checked but it is common to find LiPo cells with 10C charge rates.

You don't say what voltage you want.
I'll assume 24V, although that's probably low.
200W for 10 minutes = 200 x 10/60 Watt.hour ~= 33 Watt hour.
Say 50 Wh of storage to be safe.
At 24V you'd need about 2Ah of capacity which is what you'd get from an 18650 LiIon cell (but the discharge rate is too high) , or a LiPo of equivalent capacity.
So, using a ~= 3V endpoint your need could be met by say 24/3 = 8 x LiPo 2Ah+ cells.

Discharge rate = I = P/V = 200 Watt/24V ~= 8A = 4C for a 2AH cell.

You don't want to be deep discharging your cells in 10 minutes as lifetime will be impacted (and audiences may suddenly be un-sounded so 2 or 3 strings in parallel would be wise, or larger capacity cells.

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You want a "high-C LiPo" battery, as used in the radio control hobby. Actually, you probably want several in series. And then a number of high-capacity chargers to be able to charge all of them in parallel, too.

You can build your own battery pack out of cells, such as the ones found on all-battery: All-battery high-C cells.

No relation, other than a happy customer. Also, if you build your own pack, or use an "unprotected" pack, you will have to build voltage management circuitry to avoid over-charge and over-discharge, or the cells will be ruined. All-battery sells "PCBs" that are protection/charge controllers that you can use for this to make a self-contained battery system.

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