Solar Power Sound System

[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?

[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!

[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]

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]

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

[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]

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.

[SolarSoundMan]

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

Thanks for trying to help clarify this and to help me understand, I really appreciate it! I see you have what looks to me like to different figures, 1 is 3 KWH the other, 3 kW, are these different values?

The P-4460 Kill A Watt meter I used to take the calculations is KWH (kilowatt hours). In 5 hours the monitor speaker system used 1.5 KWH. I couldn't check the font of house speaker system but was allowing 1.5 KWH during 5 hours run of time for it. Both the FOH & MSS each would use 1.5 KWH in 5 hours. I am trying to calculate how many amp hours of battery's FOR EACH SYSTEM that I would need.

From what the OP said (and how I understood it) using a 48 V system I would need 625 AH of battery's to run 3 KWH FOR 5 hours. Since each system uses 1.5 KWH is it OK to assume I would need 312.5 AH of battery's for each of these systems? OR, should I have 625 AH for each of the systems? Sorry for the thick skull on my shoulders but it is allot to understand,

[Naptown]

Actually much less than that
Do the off grid cAlculator in my sig line.
You actually used 1.5 kWh
At 48 volts that is 31.5 amp hours ( means the same thing but is how batteries are rated)
So as not to drain your batteries below 20% depth of discharge ( meaning 80% left in them at the end of a show) which increases battery life)
You would need about a 150 amp hour 48 volt battery.
Now a few more questions.
How many shows like this do you do per year. The 20% rule will get the most cycles out of them but they will die about year 5 or six anyway.
If you only do say 100 shows a year that is 600 cycles in that case you could use a smaller battery and go to say a 50% DOD.
that would take a much smaller battery ore like 75 amp hour battery.

[DanKegel]

... I would need 625 AH of battery's to run 3 KWH FOR 5 hours...

Hang on, you might still not get the difference between kilowatts and kilowatt-hours. Just to be sure:
kW is a measure of power.
kWh is a measure of energy; it's kilowatts times hours.
600 watts (or 0.6 kW) used for five hours totals 3 kWh.

watts = volts times amps
so amp hours = watt hours divided by volts

So 3kWh = 3000 Wh, if supplied by a 48 volt battery, equals 3000 Wh / 48 V = about 62.5 Amp-hours (assuming everything was 100% efficient).

If supplied by a 12 volt battery, it would equal 3000 Wh / 12 V = about 250 Amp-hours.

Make sense now?

[bcroe]

Actually much less than that
Do the off grid cAlculator in my sig line.
You actually used 1.5 kWh
At 48 volts that is 31.5 amp hours ( means the same thing but is how batteries are rated)
So as not to drain your batteries below 20% depth of discharge ( meaning 80% left in them at the end
of a show) which increases battery life) You would need about a 150 amp hour 48 volt battery.

Now a few more questions. How many shows like this do you do per year. The 20% rule will get the
most cycles out of them but they will die about year 5 or six anyway. If you only do say 100 shows a
year that is 600 cycles in that case you could use a smaller battery and go to say a 50% DOD.
that would take a much smaller battery ore like 75 amp hour battery.

Yes, and I'm trying to understand what this is really about. You will need to arrive with the batteries
fully charged in case the sun isn't available for the show. Adding solar panels could reduce the depth
of discharge and increase the number of battery cycles. But a small generator could recharge them
between shows without any panels; most battery systems require one as the last ditch "save the
batteries" anyway. I think the battery system complexity is to be justified by not needing to run a
generator during a show?

The 50% DOD instead of 20% may wear out the batteries sooner, but there are FEWER BATTERIES
to be replaced each time. In a thread a while back I estimated the long term $ savings was on the
order of 10%, replacing much larger batteries less often. That would be compensated by not needing
to haul such a huge battery all the time, not to mention reduced loss for other things that might go
wrong. Bruce Roe

[posplayr]

Yes, and I'm trying to understand what this is really about. You will need to arrive with the batteries
fully charged in case the sun isn't available for the show. Adding solar panels could reduce the depth
of discharge and increase the number of battery cycles. But a small generator could recharge them
between shows without any panels; most battery systems require one as the last ditch "save the
batteries" anyway. I think the battery system complexity is to be justified by not needing to run a
generator during a show?

The 50% DOD instead of 20% may wear out the batteries sooner, but there are FEWER BATTERIES
to be replaced each time. In a thread a while back I estimated the long term $ savings was on the
order of 10%, replacing much larger batteries less often. That would be compensated by not needing
to haul such a huge battery all the time, not to mention reduced loss for other things that might go
wrong. Bruce Roe

Yes it seems like getting a van with a battery array mounted in back that you can run the sound system, and install a battery charger so the thing charges up on the way back home. If necessary get a higher output alternator. No need for solar panels.

[DanKegel]

Yes it seems like getting a van with a battery array mounted in back that you can run the sound system, and install a battery charger so the thing charges up on the way back home. If necessary get a higher output alternator. No need for solar panels.

+1 for keeping it simple like that.

Solar might be useful if you were doing all-day or two-day events
and didn't want to make noise by running the van's engine to charge the batteries.

[SolarSoundMan]

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

The meter is reading in KWH over a 5 hour span, that being the case from what you say above this would be an average load of 600 watts per hour. I would rather have an inverter with more output than what I would need as I do have even bigger sound systems I may be able to use this solar power system with and use it at my home. My primary goal is to at least be able to run the sound system I am talking about in this thread for 5 hours.

[SolarSoundMan]

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



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.

Dan, thanks for the clarification on these things. I will now focus on a 48 V system. Thanks also for the links to these 2 V battery's. although I do need to have the battery bank be Mobil.