Solar Power Sound System

[Naptown]

Time to explain the difference between a watt and a watt hour
A watt or a KW which is 1000 watts is an instantaneous measurement of power used you would use this to calculate wire and inverter sizes and to a lesser extent batteries.

A watt hour or KWH which is a function of watts x time. This is primarily what is used to calculate battery sizes.

From what I read in the op post about what the kill a watt read is he used 1.5 KWH over a 5 hour period.
This would be an average load of 300 watts

300 watts x 5 hours = 1.5 KWh

Within that there may be peak and valley loads. ( loud vs no sound)

For inverter sizing see if the kill a watt will measure and save the peak load.
This is what you will use to size inverters and to some extent batteries.

[DanKegel]

Should I be looking to use a 48 V system and forget about 12 V for this application?

Is 3kWh the same as 3KWH?

Yes and Yes. Using a higher voltage reduces the current and thus resistive losses everywhere, which lets you use thinner wire without it overheating.

Where do you get the 2 V battery's? What brand? Are they Lithium Ion? (I think I would prefer that), would I have to build this battery pack or would the battery company build it?

Packaged systems are starting to trickle into the market, e.g.

http://www.freecleansolar.com/mobile/product.aspx?ProductCode=Tesla%2DPowerwall%2D7

but that's not meant to be mobile.

BTW if you need 5kWh of energy, you probably want a bigger battery than that, e.g. 10kWh, if the show must go in rain or shine, since batteries wear out quick if discharged too far.

[Naptown]

What I meant is that you used 3 KWH over a 5 hour span
That works out to be an average load of 600 watts per hour.
That said you have 8 times the inverter needed to run that load.
Or did you use 3 kW for 5 hours which would be 15 kWh

[SolarSoundMan]

3 kWh at 12v = 250 amp hours
3kwh @ 24v = 125 amp hours
3kwh @ 48v = 62.5 amp hours.

3 kWh / 5 hours = 600 watt hours.

2. 3000w inverters will kill you from inefficiency losses at low loads.

Hi Naptown,
Thanks for the info on this! If you have been following this thread it is explained in Post #1 what I want to power and why I would use 2 inverters (I could be wrong about this though?). 1 inverter would power the front of house speakers (FOH) and the other would power the monitor speaker system (MSS). Each of these systems would be rated at 3000 watts, hence the "2" 3000 watt inverters. I am not sure of the ineffiencey of using 2 inverters, they are for 2 different systems?

[Naptown]

3 kWh at 12v = 250 amp hours
3kwh @ 24v = 125 amp hours
3kwh @ 48v = 62.5 amp hours.

3 kWh / 5 hours = 600 watt hours.

2. 3000w inverters will kill you from inefficiency losses at low loads.

[SolarSoundMan]

Fairly simple. Assume first a 48V battery bank (it will be harder to build with a 12V battery bank.)
3kWh is 62.5AH at 48 volts. You should try not to run your battery bank down by more than 20% per use before recharging, so your 48v battery bank would need to be 625AH.

It is hard to get 625AH batteries except at 2V each, so one solution would be 24 batteries, each 2V, 625AH, all in series.

If you tried to do this at 12V, you would need 2500AH of 12V battery.

The other reason for using 48V is that the battery bank current will also be lower, allowing for more reasonable wire sizes.
1kW at 12V would be 83A. At 48V it would be just above 20A.

First, this is only fairly simple if you understand it, I am trying to understand, LOL! Questions:

Should I be looking to use a 48 V system and forget about 12 V for this application?

Is 3kWh the same as 3KWH?

You say 3kWh is 625 AH at 48 V. My thoughts were to use "2" 3000 W inverters 1 for FOH and 1 for the monitor system, back line, soundboard, etc. So, for each inverter that would equal 312 AH per inverter or "12" 2 V battery's wired in series per inverter. Correct?

EDIT: Or would that be "24" 2 volt battery's for each inverter?

Where do you get the 2 V battery's? What brand? Are they Lithium Ion? (I think I would prefer that), would I have to build this battery pack or would the battery company build it?

You stated "you should try not to run your battery pack down by more than 20% per use before recharging". That means, 80% charge would still be left in the battery bank, not 20% remaining, correct?

You say using a 48 V system will allow more reasonable wire sizes. Is that from the panels to the battery, the battery to the inverter or both places. What size are you thinking?

Thanks for all the help on this!

[posplayr]

Fairly simple. Assume first a 48V battery bank (it will be harder to build with a 12V battery bank.)
3kWh is 62.5AH at 48 volts. You should try not to run your battery bank down by more than 20% per use before recharging, so your 48v battery bank would need to be 625AH.

It is hard to get 625AH batteries except at 2V each, so one solution would be 24 batteries, each 2V, 625AH, all in series.

If you tried to do this at 12V, you would need 2500AH of 12V battery.

The other reason for using 48V is that the battery bank current will also be lower, allowing for more reasonable wire sizes.
1kW at 12V would be 83A. At 48V it would be just above 20A.

Isn't 62.5Kw-hr/.2=312.5 Kw-hr?

[inetdog]

Now the BIG question: If in fact my sound system would draw 3 KWH in a 5 hour period how would I calculate how big of a battery bank I would need? Thanks!

EDIT: I should say that 3 KWH is for my whole system. If I was running "2 3000" watt inverters each one would be using 1.5 KWH per inverter for 5 hours. How big of a battery bank (or AH) would I need to draw 1.5 KWH for 5 hours.

Fairly simple. Assume first a 48V battery bank (it will be harder to build with a 12V battery bank.)
3kWh is 62.5AH at 48 volts. You should try not to run your battery bank down by more than 20% per use before recharging, so your 48v battery bank would need to be 625AH.

It is hard to get 625AH batteries except at 2V each, so one solution would be 24 batteries, each 2V, 625AH, all in series.

If you tried to do this at 12V, you would need 2500AH of 12V battery.

The other reason for using 48V is that the battery bank current will also be lower, allowing for more reasonable wire sizes.
1kW at 12V would be 83A. At 48V it would be just above 20A.

[SolarSoundMan]

I got the P3-4460 Kill A Watt meter yesterday at Home Depot, a $30 unit with different functions, amps, volts, watts, KWH, cost, etc. I had a show tonight but operated another bands PA system, so I thought I would take the P3 with me to give an idea of what this system would put out. These were not powered speakers I was running tonight like my system posted in post #1. The speakers were powered from separate rack mounted amps for each frequency range. Probably using more power than my powered speakers.

Due to the way things were setup I was not able to check the KWH of the bass and mid amps for FOH or the backline instruments such as the bass guitar amp, and 2 guitar amps, and fiddle amp. I was able to check the KWH of the Monitor amps, hi end amp (for FOH), sound board, EQ, CD player, and effects unit. I had the system on for 5 hours it used 1.5 KWH.

I realize this isn't exactly the same as my system but does give an idea of what I could expect with my system. I am going to say in round figures my system with everything I have listed and running for 5 hours would be around 3 KWH, maybe less?

Now the BIG question: If in fact my sound system would draw 3 KWH in a 5 hour period how would I calculate how big of a battery bank I would need? Thanks!

EDIT: I should say that 3 KWH is for my whole system. If I was running "2 3000" watt inverters each one would be using 1.5 KWH per inverter for 5 hours. How big of a battery bank (or AH) would I need to draw 1.5 KWH for 5 hours.

[SolarSoundMan]

Your current drain is going to vary hugely. What you need to know is the average power.
The P3 will tell you that on the KWH function over some operating time at power. Bruce Roe

Thanks Bruce! I just called Home Depot and they have the P3 in stock. I am going to get it today and will update my usage to this thread as I know it. Thanks very much for the tip on this! This seems to make sense knowing how much power I am drawing and then apply that to how big a battery bank I would need, why couldnt i think of that, duh. I would rep you but I don't know if there is that function or even how to do it if there is, thanks again!

[bcroe]

Thanks Bruce for making me remember I forgot to put how much power it is drawing. I had a guy check my 26,000 watt system this weekend during a pretty loud performance. I was using a double pole 30 amp breaker and he said one leg was drawing 8 amps and the other 7 amps.

I would think the system I have listed above is drawing less power than the big system that was tested this past weekend. The smaller system is only 6000 watts. So, I am going to say the 6000 watts system is drawing 5 amps or less per leg meaning 5 amps for FOH and 5 amps for the monitors and backline.

Your current drain is going to vary hugely. What you need to know is the average power.
The P3 will tell you that on the KWH function over some operating time at power. Bruce Roe

[SolarSoundMan]

I mean the big orange store (Home Depot), similar to Big Blue (Lowes, not IBM).
Other interesting nicknames are Harbor Fright (Harbor Freight) and FleaBay (eBay).

Thanks for the clarity on that!

[inetdog]

This one at Home Depot is the Kill-A-Watt EZ Meter P3-4460, I am not sure which one you mean when you say the big orange one?

I mean the big orange store (Home Depot), similar to Big Blue (Lowes, not IBM).
Other interesting nicknames are Harbor Fright (Harbor Freight) and FleaBay (eBay).

[SolarSoundMan]

The Big Orange model should work just fine for you.
Also look into the DC clamp-on ammeter from Sears. A great buy at about $60.

One of the problems with just measuring Amps is that it may show a high number for an unloaded transformer because of the inductive current (not in phase with voltage) that does not actually demand any power from the inverter.
The KAW shows both actual watts and the complex power, VA (volts times amps without regard to phase.)

This one at Home Depot is the Kill-A-Watt EZ Meter P3-4460, I am not sure which one you mean when you say the big orange one?

[inetdog]

This sounds like a great idea! Do you have a model # to reference? I googled Killawatt meter and one for Home Depot came up. Pretty cheap and looks simple to use too! I will look into getting one of these, thanks for the tip on that!

The Big Orange model should work just fine for you.
Also look into the DC clamp-on ammeter from Sears. A great buy at about $60.

One of the problems with just measuring Amps is that it may show a high number for an unloaded transformer because of the inductive current (not in phase with voltage) that does not actually demand any power from the inverter.
The KAW shows both actual watts and the complex power, VA (volts times amps without regard to phase.)