Best Deep cycle marine batteries for mobile PA system

[Seth Shonefeld]

You sure 1000W is enough for all the amps plus the PA?

Also what batteries are you going to use? A 1000W inverter at 12V needs about 84A to operate at 1000W. Keep in mind a 1000W inverter will probably have a 2000W surge capacity; I believe this means double the current.

The highest capacity battery I could find is rated 370AH at 20hrs (Duracell SLI6V370S). If I understand the rating, it means the battery can provide 370AH over 20 hours; 370/20= 18.5A per hour. Keep in mind you need two of these batteries to get 12V and they weigh 113lbs each and cost about $300. The page I found says this battery has 190 minutes of reserve capacity at 75A. 75x12=900W. I believe "reserve capacity" is how long a fully charged battery can provide the rated current at 80F before it discharges to 10.5V.

I used this page for AH and reserve capacity definitions: Battery Basics - Guide to Batteries | BatteryStuff

It's not going to be 1k +a PA. It's going to be a bit less than 1k or the PA. I'm letting the players use their own amps until we have the right PA and convince them to use it. Actually, the calculations around this stuff are not precise. It has to be field tested.

Using 2 6v golf cart batteries wired in series to bump them to 12v. Golf cart batteries deliver 230 amphrs.

195 amp hours needed to run 500watts for 4 hours. The amps will likely draw more like > 500 watts. For instance, my amp(biggest) draws a peak of 330 at 8ohms of 250max delivery. Rms will be closer to ~200. (~ = roughly) Also new solid state, pretty efficient. (Again without making yiu read the whole thread, I'm insisting everybody use solid state for the moment). Other amps, 2 or 3, all half the size, ~100 apiece RMS is actually conservately generous wattage draw. Hoping to be able to hit the 4-hour mark with these amps. That's the goal. 230amp hr battery/ies discharge/s to around 85% at 190 amphrs.

Wish me luck!

 

[Seth Shonefeld]

Get ready to spend some money.
I hate outdoor gigs.
Good luck.

So far I have spent less than half what I would need to for a presumably equivalent Li power delivery system and also less than what I would for a decent gas generator, which I'm trying to avoid. But yes, I have spent some money. Outdoor gigs can be a drag, but in the time of Covid we adapt. I live in SF where like many places, all the cool restaurants have closed down.

I was walking through my old neighborhood and came upon an old restaurant I LOVED where, funny we should be on the topic, I used to play.

Like all the restaurants scraping by, this one was no longer serving. BUT, this innovative guy transformed the space into a market, an essential business. He's open and business is thriving. My point is, we adapt or we stop doing what we do, thingz like playing music.

 

[Playbyear]

It's not going to be 1k +a PA. It's going to be a bit less than 1k or the PA. I'm letting the players use their own amps until we have the right PA and convince them to use it. Actually, the calculations around this stuff are not precise. It has to be field tested.

Using 2 6v golf cart batteries wired in series to bump them to 12v. Golf cart batteries deliver 230 amphrs.

195 amp hours needed to run 500watts for 4 hours. The amps will likely draw more like > 500 watts. For instance, my amp(biggest) draws a peak of 330 at 8ohms of 250max delivery. Rms will be closer to ~200. (~ = roughly) Also new solid state, pretty efficient. (Again without making yiu read the whole thread, I'm insisting everybody use solid state for the moment). Other amps, 2 or 3, all half the size, ~100 apiece RMS is actually conservately generous wattage draw. Hoping to be able to hit the 4-hour mark with these amps. That's the goal. 230amp hr battery/ies discharge/s to around 85% at 190 amphrs.

Wish me luck!

I think you'll be ok. The actual power consumption in use is usually much lower than the name plate wattage of the amps.

I would kill the power on breaks to stop any draw and let the batteries cool down.

 

[Seth Shonefeld]

I think you'll be ok. The actual power consumption in use is usually much lower than the name plate wattage of the amps.

I would kill the power on breaks to stop any draw and let the batteries cool down.

Definitely!

 

[Downunderwonder]

But they are not as powerful as the gear we play through. That is the trade off. All the stuff you listed here is like 30 or 60 watts, and comes with a mic. My amp is 250 at 8 ohms. Why sacrifice that to play at boombox volume?

You need POWER or you need less noise.

 

[Wasnex]

It's not going to be 1k +a PA. It's going to be a bit less than 1k or the PA. I'm letting the players use their own amps until we have the right PA and convince them to use it. Actually, the calculations around this stuff are not precise. It has to be field tested.

Using 2 6v golf cart batteries wired in series to bump them to 12v. Golf cart batteries deliver 230 amphrs.

195 amp hours needed to run 500watts for 4 hours. The amps will likely draw more like > 500 watts. For instance, my amp(biggest) draws a peak of 330 at 8ohms of 250max delivery. Rms will be closer to ~200. (~ = roughly) Also new solid state, pretty efficient. (Again without making yiu read the whole thread, I'm insisting everybody use solid state for the moment). Other amps, 2 or 3, all half the size, ~100 apiece RMS is actually conservately generous wattage draw. Hoping to be able to hit the 4-hour mark with these amps. That's the goal. 230amp hr battery/ies discharge/s to around 85% at 190 amphrs.

Wish me luck!

It's not the power of the PA you need to worry about. It's the total power requirement. FYI I have the entire thread.

In trying to deduce what Amp Hours mean I read several pages and there was some conflict in the definition, or at least the way I understood it.

Most of the pages I found say Amp Hours relates to how many amps a battery can produce for a certain time duration before it reaches it's minimum charge. Based on most definitions I read, one would assume that the battery I referenced, which is rated for 370AH at 20 hrs, is capable of continuous current of 370A for 20 hours. In other words 370A for each of 20 hours. I don't believe this is accurate.

The Reserve Capacity rating of the battery made me explore further. The reserve capacity rating says this battery can only produce 75A for 190 minutes which is well under 370 amps per hour. If you look at the page I linked for the definitions, the disconnect is because the standard rating is for 20 hours and the AH rating is the total amps the battery can produce over the entire 20-hour period. In other words the battery can produce 370/20=18.5A continuously for 20 hours. At least that is the way I understand the specs.

So based on this, we know how long the 370AH battery will last based on a range of continuous current draws. At 18.5A it is expected to last 20hrs, and at 75A it is expected to last for 3hrs 10 minutes. 75A at 12V=900W. I believe a good inverter is about 90% efficient at full load, and the voltage will vary with the batteries state of charge, so the available wattage at the 75A discharge rate should be adjusted for these factors.

The voltage should start at about 12.7V resting. A 12V system that has reached 11.9V resting is considered fully discharged.

The inverter will probably have a lower operating limit ranging something like 9.5 to 10.5V. In order to get long life out of the batteries, I suggest you don't push the rig until it shuts down. This is my reasoning behind installing a volt meter. The confusing part here is to determine the difference between the resting voltage and working voltage, because the battery's voltage will sag under load, and the inverters I looked at pull <1.4A with no load.

Keep in mind, while the batteries are discharged their plates are being damaged due to sulfation, so you want to charge the batteries at the earliest opportunity. Also to extend the batteries service life, you will want a battery charger that will sense the voltage and reduce current as the battery's state of charge approaches 100%.

I believe it is very possible that your rig will provide power for over 4 hours as long as you keep the total wattage at a reasonable level.

I found a Duracell 230AH battery (SLIGC115). The reserve capacity is listed at 115 minutes at 75A. So this battery could produce ~900W continuous for 1 hour 55 minutes.

 

[Playbyear]

The amps are never at the max power consumption for long. You would have to input a continuous sine wave to bring them to a 100% duty cycle. Figure a 25% duty cycle for power requirement.

 

[Wasnex]

The amps are never at the max power consumption for long. You would have to input a continuous sine wave to bring them to a 100% duty cycle. Figure a 25% duty cycle for power requirement.

Yes I agree. But if the 1000W inverter is pushed close to it's peak capacity of 2000W, the average power/current requirements will still be fairly high.

By the time you account for the power requirements of a bass amp, guitar amp, keyboard amp, keyboard, mixer, outboard gear, multiple power amps, etc, it's very easy to start getting up into the 2KW range.

Even if they duty cycle is only 25%, if the power system is pushed this hard the battery will be discharged rather quickly.

It really depends largely upon how the sound gear will be run. What I typically see with under powered systems is they are pushed beyond their limits, so the sound is audibly distorted. Of course when you push the amps into clipping the duty cycle percent goes higher.

 

[Playbyear]

If the power requirement in the first post of thread were 1100 watts "nameplate" , 25% duty cycle is 275 watts continuous draw. So figure 300 watts or 25 amps continuous draw on the batteries. If so, it's cake...he's got it.

 

[Downunderwonder]

My band with a 250w SS Trace a 50W tube Marshall a 30w SS guitar amp and a vocal PA could pop a 10A 240V breaker. Go figure.

 

[Eli_Kyiv]

could pop a 10A 240V breaker

240V * 10A = 2400 VA, which could be, like, 2000 - 2200 watt, depending of the power factor.

 

[DirtDog]

It's not the power of the PA you need to worry about. It's the total power requirement. FYI I have the entire thread.

In trying to deduce what Amp Hours mean I read several pages and there was some conflict in the definition, or at least the way I understood it.

Most of the pages I found say Amp Hours relates to how many amps a battery can produce for a certain time duration before it reaches it's minimum charge. Based on most definitions I read, one would assume that the battery I referenced, which is rated for 370AH at 20 hrs, is capable of continuous current of 370A for 20 hours. In other words 370A for each of 20 hours. I don't believe this is accurate.

The Reserve Capacity rating of the battery made me explore further. The reserve capacity rating says this battery can only produce 75A for 190 minutes which is well under 370 amps per hour. If you look at the page I linked for the definitions, the disconnect is because the standard rating is for 20 hours and the AH rating is the total amps the battery can produce over the entire 20-hour period. In other words the battery can produce 370/20=18.5A continuously for 20 hours. At least that is the way I understand the specs.

So based on this, we know how long the 370AH battery will last based on a range of continuous current draws. At 18.5A it is expected to last 20hrs, and at 75A it is expected to last for 3hrs 10 minutes. 75A at 12V=900W. I believe a good inverter is about 90% efficient at full load, and the voltage will vary with the batteries state of charge, so the available wattage at the 75A discharge rate should be adjusted for these factors.

The voltage should start at about 12.7V resting. A 12V system that has reached 11.9V resting is considered fully discharged.

The inverter will probably have a lower operating limit ranging something like 9.5 to 10.5V. In order to get long life out of the batteries, I suggest you don't push the rig until it shuts down. This is my reasoning behind installing a volt meter. The confusing part here is to determine the difference between the resting voltage and working voltage, because the battery's voltage will sag under load, and the inverters I looked at pull <1.4A with no load.

Keep in mind, while the batteries are discharged their plates are being damaged due to sulfation, so you want to charge the batteries at the earliest opportunity. Also to extend the batteries service life, you will want a battery charger that will sense the voltage and reduce current as the battery's state of charge approaches 100%.

I believe it is very possible that your rig will provide power for over 4 hours as long as you keep the total wattage at a reasonable level.

I found a Duracell 230AH battery (SLIGC115). The reserve capacity is listed at 115 minutes at 75A. So this battery could produce ~900W continuous for 1 hour 55 minutes.

Good summary @Wasnex.

I beleive your read of Ah is correct.

So, 2 6V batteries wired in series for 12V DC, inverted and transformed to 110/120V AC. - there's GOT to be some current/capacity difference there, right?

P(W) = V(V) × I(A)

How does transforming current from 12V power supply into 110/120V circuit work - in terms of the resulting power (watts) or current (amps)? Is there a 10-fold current loss or 10-fold current gain - all things being equal.

My current understanding is that voltage decreases the current available.

 

[DirtDog]

I don't get it. Are you using the inverter to keep the batteries topped up or something else?

A 1500w inverter will supply 12.5A of current to your circuit. What's the total draw of all the things you want to power? 1000w PA amp, a couple of xx watt instrument amplifiers, maybe some pedals???

If you're drawing from the batteries (uncertain how you're going from DC to AC), what's the capacity of those batteries in Ah (amp-hours)? If you want to power a 1000W amp (12A, at peak anyways) for 4 hours, you'll need 48 Ah capacity in those batteries. Rough order of magnitude, anyways.

Edit- looking at some specs for golf cart batteries. $200 for a 6V 232 Ah battery seems like enough - although I don't know enough about how you'd make 6V power something at 120V. Do you need to hook up 20 of these in series? I'm dumb on this, please educate me.

So, using my golf cart battery spec above, with two wired in series, you get a 12V system with 464Ah of capacity. Use the transformer to get to 110/120V, you're looking at ~50Ah of capacity. Meaning you can get 50A for an hour, 25A for two hours, 12.5A for four hours, give or take, and so on. Say the OP has two powered PA speakers, a mixer, three instrument amp and a couple of pedal boards, he *might* be close to 15-20A of draw (at flat out). Meaning he's good for two hours of playing with a very good buffer for capacity - way more if he's drawing less amps with his equipment.

Can someone tell me if these calculations are correct?

Edit: sorry, just working through the theory (and practice) here....

 

[Downunderwonder]

y current understanding is that voltage decreases the current available.

the reason a lot of the world is on 240V is you get double the power out the socket for the current in your house wires. Current in the wires is what heats the wires up, not the voltage. Half the current = a lot less eldctrical fires.

This is why dragging a whole lot of power out of 12V worth of batteries needs a lot of thought! Not hard to cook the batteries if you get it wrong.

 

[Downunderwonder]

Deep cycle batteries are rated at 5A draw. If you go drawing 20A you get quite a lot less AH than the rating.

 

[Wasnex]

Good summary @Wasnex.

I beleive your read of Ah is correct.

So, 2 6V batteries wired in series for 12V DC, inverted and transformed to 110/120V AC. - there's GOT to be some current/capacity difference there, right?

P(W) = V(V) × I(A)

How does transforming current from 12V power supply into 110/120V circuit work - in terms of the resulting power (watts) or current (amps)? Is there a 10-fold current loss or 10-fold current gain - all things being equal.

My current understanding is that voltage decreases the current available.

Here is a basic inverter schematic.

Link Removed

Q1 and Q2 form an Oscillator. This puts AC on the transformer. The transformer steps up the Voltage from 12V to 120V. Conceptually the same amount of power that goes into the transformer primary should come out of the secondary. What this means is the the transformer is exchanging current for voltage. The formula for Power is (E x I = P) where E is voltage and I is current. So the primary is high current low voltage and the secondary is high voltage low current, but the power is the same in both.

The inverter specs I read said they were about 90% efficient at half load, so there is some real world losses in the circuit.

 

[Wasnex]

So, using my golf cart battery spec above, with two wired in series, you get a 12V system with 464Ah of capacity. Use the transformer to get to 110/120V, you're looking at ~50Ah of capacity. Meaning you can get 50A for an hour, 25A for two hours, 12.5A for four hours, give or take, and so on. Say the OP has two powered PA speakers, a mixer, three instrument amp and a couple of pedal boards, he *might* be close to 15-20A of draw (at flat out). Meaning he's good for two hours of playing with a very good buffer for capacity - way more if he's drawing less amps with his equipment.

Can someone tell me if these calculations are correct?

Edit: sorry, just working through the theory (and practice) here....

I am not an expert on this but I will do my best to try and make sense of it, without spouting .

I believe two 230AH batteries wired in series still gives you 230AH. This is rated over 20hrs so 230AH/20H=11.5A continous.

In a series circuit all the current passes through both batteries, so the current capacity stays the same. If you want to double the AH capacity you need additional batteries in parallel.

This is why earlier in the thread I suggested the possibility of series parallel. Series gives you 12V and adding additional series circuits in parallel increases the current potential.

Here is an example of three series circuits in parallel

This arrangement will double the voltage and triple the current capacity.

To get the Power, you multiply the available current by the voltage. I believe fully charged, the batteries will provide around 12.7V so 11.5Ax12.7V=146.5W. Remember 11.5A is for the 20hr rating. The battery can definitely provide more current but it will decrease service time.

On the secondary side of the transformer (inverter output) we have 120V and 146.5W. The formula is I=P/V so the current will be 146.5W/120=1.22A Disregarding losses, 1.22A at ~120V is the current level the battery and inverter can support for 20hrs. The time will need to be derated some because the inverter is not 100% efficient. Also keep in mind the voltage will decline a bit over time.

If you pull more than 1.22A the service time will decrease. If you can find the data sheet for your battery it should provide the battery's AH ratings for different time durations. There may be engineering documents with charts that graph current draw VS time, but I haven't seen them.

I do not believe the current draw VS time relationship is linear so I don't believe the assumption "50A for an hour, 25A for two hours, 12.5A for four hours" is correct. If you can find a datasheet for your battery, it should provide various ratings like a 20hr rating and 5hr rating. It may also provide minutes to discharge at various current draws such as 75A, 56A, 25A.

Here is a battery spec sheet you can browse through for examples: https://www.driveduracell.com/pub/media/wysiwyg/Duracell_Spec_Sheet.pdf. Note that various batteries listed have different types of ratings. Obviously you will want to use the spec sheet for your specific battery.

I also found another informative article that suggested minimum resting voltage for a 12V deep cycle battery system should be 12.06V which equates to 50% charge. Deep Cycle Battery FAQ This is another factor that should be considered as discharging the batteries below 50% will significantly shorten their life span.

 

[D.A.R.K.]

Thought I'd add what I've done to this thread. I have a small, mobile battery rig that powers a pair of QSC K12's, pedal boards, a small mixer for an hour no problem.
It's built in a wheeled tool box. I have a small size Optima deep cycle battery, 750 CCA. There is just enough room for a second in the box (and a pair is 120 lbs- these batteries are heavy). One thing I've read up/ found is that you really need 2x the rated draw when powering up a lot of electronics- so I used a 3000 watt pure sine wave inverter so that we do up to standard 1500 watt draw max. I installed a fuse for protection as well as a shut off switch. I also have a ground spike that I can attach for safety. This rig cost under $500.00 to build. It runs great. haven't had any weird noise issues or failures. Initially it was put together for mobile projections, I have a 6500 lumen theater projector that lasts 30 minutes on a single battery at full charge (incandescent projectors are mad power hungry). This thing is also great for tailgating, festivals etc. I have a charger that hooks up to the 12v out on my truck, so we can re-charge the batteries while driving. Batteries have lasted 3 years so far without any noticeable loss in life.
Edit: woah, just checked the price of batteries and they have skyrocketed! I paid 189 for the one pictured, they are now 276.00...

 

[Wasnex]

View attachment 3902010 View attachment 3902011 Thought I'd add what I've done to this thread. I have a small, mobile battery rig that powers a pair of QSC K12's, pedal boards, a small mixer for an hour no problem.
It's built in a wheeled tool box. I have a small size Optima deep cycle battery, 750 CCA. There is just enough room for a second in the box (and a pair is 120 lbs- these batteries are heavy). One thing I've read up/ found is that you really need 2x the rated draw when powering up a lot of electronics- so I used a 3000 watt pure sine wave inverter so that we do up to standard 1500 watt draw max. I installed a fuse for protection as well as a shut off switch. I also have a ground spike that I can attach for safety. This rig cost under $500.00 to build. It runs great. haven't had any weird noise issues or failures. Initially it was put together for mobile projections, I have a 6500 lumen theater projector that lasts 30 minutes on a single battery at full charge (incandescent projectors are mad power hungry). This thing is also great for tailgating, festivals etc. I have a charger that hooks up to the 12v out on my truck, so we can re-charge the batteries while driving. Batteries have lasted 3 years so far without any noticeable loss in life.
Edit: woah, just checked the price of batteries and they have skyrocketed! I paid 189 for the one pictured, they are now 276.00...

Based on the provided info it looks like the model is D34M. Some additional specs: The C20 rating is 55AH, so 55/20= 2.75A continuous for 20hrs. Reserve capacity is 25A for 120M. 25x12=300W.

Spec came from this page: Link Removed

 

[D.A.R.K.]

Based on the provided info it looks like the model is D34M. Some additional specs: The C20 rating is 55AH, so 55/20= 2.75A continuous for 20hrs. Reserve capacity is 25A for 120M. 25x12=300W.

Spec came from this page: Link Removed

Cool, thanks! Run time a draw after start up has a lot to do with how hard you are pushing things for sure. I also wonder if a higher rated inverter is going to draw more power itself- However, due to that double power rating to start devices I figured it was better to go larger.