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Purchasing a Battery and Power Inverter to Run My PA
Louis Miller:
Hello Forum!
I've not posted before but am in need of some guidance and hoping I might find it here . . .
I am preparing to purchase a deep-cycle battery, along with a pure-sine power inverter, to run a pair of Yamaha MSR100 speakers during outdoor performances. I've done a good deal of research but I'm concerned that I may not full understand the power consumption of the speakers. Both are 100w speakers, and the specs say that they each have a power consumotion of 70w. At a total of 140 watts, I caculated that the speakers consume ~ 12 amps, and that a 50 amp-hour battery could therefore power these speaks for ~ 4 hours (without factoring in % efficiency of the power inverter).
Is 70w correct, or is it only the "idle" power consumotion? Do they draw more than 140 watts when in use? I'll need to know this in order to purchase the right battery and the right power inverter. Thanks so much if any one you can offer some input!
-Lou
Frank DeWitt:
I suspect that you will find that the speakers draw 70watts at full power (At there max volume) and considerably less at idle. You can confirm this by purchasing a device called Kill-a-watt (about $25) Do give some thought to how you are going to ground the AC power.
Art Welter:
--- Quote from: Louis Miller on July 16, 2018, 11:29:42 AM ---Hello Forum!
I've not posted before but am in need of some guidance and hoping I might find it here . . .
I am preparing to purchase a deep-cycle battery, along with a pure-sine power inverter, to run a pair of Yamaha MSR100 speakers during outdoor performances. At a total of 140 watts, I caculated that the speakers consume ~ 12 amps, and that a 50 amp-hour battery could therefore power these speaks for ~ 4 hours (without factoring in % efficiency of the power inverter).
Is 70w correct, or is it only the "idle" power consumotion? Do they draw more than 140 watts when in use?
--- End quote ---
Lou,
The speakers each have a 100 watt amp, at best they are about 90% efficient, so peak power will be over 200 watts for the pair. Average power, "full tilt boogie" will not exceed 70 watts per unit, but likely would be less than 30 watts per unit with typical music run to clipping.
"Pure sine wave" inverters are nice for audio, but many inexpensive stepped square wave inverters are plenty clean enough for any decent audio products.
There are two important factors in your purchase of the battery, number one is the cycle life of lead -acid batteries will be severely reduced if depleted past 50%, about 12.06V when rested.
The other important factor is Peukert's Law.
Peukert’s law states that as the rate of discharge increases, the available capacity of that battery decreases.
SLA batteries amp hour rating is often given over a 20 hour period, if the amperage is discharged in a much shorter time, the battery voltage will drop rapidly, and the amp hour rate will be diminished.
LiFePO4 batteries have virtually no Peukert's effect, can be cycled to 80%, and can deliver as much as 10 times their rated amperage for short duration peaks. They are far lighter than lead-acid batteries. Although they are far more expensive initially, as they can deliver around 2000 cycles to 80-90%, they are actually more cost effective in the long run.
Protection-circuit-modules (PCM) that internally balance cells and provide protection from overcharge should be used with iFePO4 batteries, and are typically built in for "12volt" deep-cycle replacements.
Art
Scott Holtzman:
--- Quote from: Art Welter on July 16, 2018, 05:26:37 PM ---Lou,
The speakers each have a 100 watt amp, at best they are about 90% efficient, so peak power will be over 200 watts for the pair. Average power, "full tilt boogie" will not exceed 70 watts per unit, but likely would be less than 30 watts per unit with typical music run to clipping.
"Pure sine wave" inverters are nice for audio, but many inexpensive stepped square wave inverters are plenty clean enough for any decent audio products.
There are two important factors in your purchase of the battery, number one is the cycle life of lead -acid batteries will be severely reduced if depleted past 50%, about 12.06V when rested.
The other important factor is Peukert's Law.
Peukert’s law states that as the rate of discharge increases, the available capacity of that battery decreases.
SLA batteries amp hour rating is often given over a 20 hour period, if the amperage is discharged in a much shorter time, the battery voltage will drop rapidly, and the amp hour rate will be diminished.
LiFePO4 batteries have virtually no Peukert's effect, can be cycled to 80%, and can deliver as much as 10 times their rated amperage for short duration peaks. They are far lighter than lead-acid batteries. Although they are far more expensive initially, as they can deliver around 2000 cycles to 80-90%, they are actually more cost effective in the long run.
Protection-circuit-modules (PCM) that internally balance cells and provide protection from overcharge should be used with iFePO4 batteries, and are typically built in for "12volt" deep-cycle replacements.
Art
--- End quote ---
LiFeP04 batteries are awesome. If you love a senior using a mobility device, upgrade them to these! About $2500 for a 25ah deep cycle replacement.
Mark Cadwallader:
--- Quote from: Scott Holtzman on July 16, 2018, 06:55:07 PM ---LiFeP04 batteries are awesome. If you love a senior using a mobility device, upgrade them to these! About $2500 for a 25ah deep cycle replacement.
--- End quote ---
For less money (perhaps a lot less) the OP could buy a Honda inverter generator. Not knowing the circumstance of intended use, I don't know if that is a feasible option. If it might be feasible, the little inverter generators are very quiet, lightweight, and pretty darn fuel efficient.
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