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Author Topic: Multiple (battery/inverter) power sources in a small audio system - ground ?'s  (Read 4086 times)

MattLeonard

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I often power small sound systems (speakers-on-stick size) with a LiFeP04 batteries/inverter setup - great for off-grid events. Usually, this is a 3kw inverter (so reliably a single 20a circuit). But for some slightly larger events - I'd like to use a 2nd inverter/battery setup that I could use - basically creating a 2nd circuit option.  Ideally - this could mean one inverter per side of PA, or PA on one circuit and monitors/backline on the 2nd.

-What are some considerations/best practices I should be thinking about if using (2) fully independent power sources?

-I know on traditional gennies a bonding kit is the norm - and while I could bond the chassis of multiple inverters together, I don't have the ability to sync phase. What are the real-world implications here?

-Could I physically isolate parts of the system that are on different power sources? i.e. - using wireless transmitter/receivers so that no physical path (copper or human) is possible between components?

I'd much rather than multiple 3kw inverters for modularity/redundancy than a single 6kw unit if possible. Thanks for any advice!





Grounding between them?
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Stephen Swaffer

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I would bond the chassis together.  Basically, code calls for anything that "could be energized" to be bonded to a common ground to avoid "potential" (as in voltage) differences.

Why would syncing phase matter?  Does any of your equipment NOT convert the AC to DC before using it?



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Steve Swaffer

Riley Casey

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Speaking of Lithium battery power inverters what kind of run time are you getting with what kind of audio system? I'e been looking at these for small powered mixer & speaker on stick voice systems.

https://www.amazon.com/gp/product/B07SM5HBK1/ref=ox_sc_act_image_1?smid=AZF6YB7UVA7OU&psc=1

Steve-White

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I'm thinking about putting together an inverter setup for garden/gazebo weddings instead of the inverter genny.  It's pretty quiet and at 100' away with a large cart tipped on it's side is inaudible.  But, a battery inverter would be faster setup and tear down and that's the name of the game.

Thinking something with quick change out battery packs in case of a problem or long run time is needed.

That Jackery 518WH looks pretty good.  Packaged up, probably want two of them - better solution anyway than a single rig with spare battery packs.  Should have plenty of grunt to run a wedding ceremony size PA for 45 minutes or so, much of which is idle time on the system.

For the OP, heed what Stephen posted about bonding.  Absolutely positively bond multiple portable power sources together well.  That's a huge safety precaution.
« Last Edit: August 06, 2021, 10:12:44 PM by Steve-White »
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MattLeonard

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I'm thinking about putting together an inverter setup for garden/gazebo weddings instead of the inverter genny.  It's pretty quiet and at 100' away with a large cart tipped on it's side is inaudible.  But, a battery inverter would be faster setup and tear down and that's the name of the game.

Thinking something with quick change out battery packs in case of a problem or long run time is needed.

That Jackery 518WH looks pretty good.  Packaged up, probably want two of them - better solution anyway than a single rig with spare battery packs.  Should have plenty of grunt to run a wedding ceremony size PA for 45 minutes or so, much of which is idle time on the system.

For the OP, heed what Stephen posted about bonding.  Absolutely positively bond multiple portable power sources together well.  That's a huge safety precaution.

 I think the small Jackery-size units are very limiting to what you can run - be cautious of the consumer-level inverter units that may not really be able to output the wattage the claim, at least not reliably, or handle transients in dynamic music.  And that won't deliver their full stated capacity either. Plan for a solid buffer on all specs. It really depends on the program material and volume - most Class D amplifier/powered speakers are very, very efficient and sip power.

The smallest inverter I use is a 1500w unit, and I've comfortably run 3 QSC k10.2's on that - at full (but not clipping/limiting) volume. I have done 4 (not at full volume) but have also had the inverter going into protect on some peaks. I ran a pair of Yamaha DXS subs and DZR tops (with a small mixer and pair of Sennheiser wireless) last night on my 3,000 water inverter - full volume, and it didn't blink.


If you want consumer form factor and ease - look at Bluetti or Delta Pro - both are releasing new units right now that are nextg-gen in terms of features, weight, energy density etc.  And they have expandable battery options - which is clutch
.

For more power at lower cost - DIIYsomething if you have basic electrical comfort. I have a pair of milkcrates that each hold ~2500wh of lithium-ion batteries. With an Anderson SB175 quick-connect cable - I can connect that to any of my inverters (mounted on plywood that sits nicely on top of the crate) and its module and light.  A more "pro looking" option would be to build  into a Pelican or similar)
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Riley Casey

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My question would be how long did you run the systems you described and for what kind of program material? Rock bands vs spoken word are going to be radically different power consumption.  I've also found this unit with socketed battery packs which looks much more applicable to what we do.

https://egopowerplus.com/nexus-portable-power-station/

...
The smallest inverter I use is a 1500w unit, and I've comfortably run 3 QSC k10.2's on that - at full (but not clipping/limiting) volume. I have done 4 (not at full volume) but have also had the inverter going into protect on some peaks. I ran a pair of Yamaha DXS subs and DZR tops (with a small mixer and pair of Sennheiser wireless) last night on my 3,000 water inverter - full volume, and it didn't blink.


If you want consumer form factor and ease - look at Bluetti or Delta Pro - both are releasing new units right now that are nextg-gen in terms of features, weight, energy density etc.  And they have expandable battery options - which is clutch
.

For more power at lower cost - DIIYsomething if you have basic electrical comfort. I have a pair of milkcrates that each hold ~2500wh of lithium-ion batteries. With an Anderson SB175 quick-connect cable - I can connect that to any of my inverters (mounted on plywood that sits nicely on top of the crate) and its module and light.  A more "pro looking" option would be to build  into a Pelican or similar)

Steve-White

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I think the small Jackery-size units are very limiting to what you can run - be cautious of the consumer-level inverter units that may not really be able to output the wattage the claim, at least not reliably, or handle transients in dynamic music.  And that won't deliver their full stated capacity either. Plan for a solid buffer on all specs. It really depends on the program material and volume - most Class D amplifier/powered speakers are very, very efficient and sip power.

The smallest inverter I use is a 1500w unit, and I've comfortably run 3 QSC k10.2's on that - at full (but not clipping/limiting) volume. I have done 4 (not at full volume) but have also had the inverter going into protect on some peaks. I ran a pair of Yamaha DXS subs and DZR tops (with a small mixer and pair of Sennheiser wireless) last night on my 3,000 water inverter - full volume, and it didn't blink.

If you want consumer form factor and ease - look at Bluetti or Delta Pro - both are releasing new units right now that are nextg-gen in terms of features, weight, energy density etc.  And they have expandable battery options - which is clutch.

For more power at lower cost - DIIYsomething if you have basic electrical comfort. I have a pair of milkcrates that each hold ~2500wh of lithium-ion batteries. With an Anderson SB175 quick-connect cable - I can connect that to any of my inverters (mounted on plywood that sits nicely on top of the crate) and its module and light.  A more "pro looking" option would be to build  into a Pelican or similar)

Exactly for the DIY option.  I looked at the packaged up units again and the first thing that came to mind was putting them into the truck.  They would need to be cased up.  I had a couple of those little generators that are in a nice little rounded form factor with molded in handle.  Gone.  I use all full frame generators now for both fuel capacity and packing with other gear.

Yeah, it will be custom for sure with replaceable battery packs and probably fit into a standard 19" road case for integration both while in use and in the truck.

What inverters are you using?  What batteries?
« Last Edit: August 07, 2021, 01:04:57 PM by Steve-White »
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MattLeonard

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Exactly for the DIY option.  I looked at the packaged up units again and the first thing that came to mind was putting them into the truck.  They would need to be cased up.  I had a couple of those little generators that are in a nice little rounded form factor with molded in handle.  Gone.  I use all full frame generators now for both fuel capacity and packing with other gear.

Yeah, it will be custom for sure with replaceable battery packs and probably fit into a standard 19" road case for integration both while in use and in the truck.

What inverters are you using?  What batteries?

I have 4 drop-in 12v (well, 14.4v LiFeP04) Lion UT-1300 batteries (2 per milk crate wired in series for a 24v system, along with  MRBF fuses - ~2500wh per crate), and then a few different inverters. While the robustness of a low-frequency inverter (previously had a Victron) are undoubtedly more reliable - I have some cheaper (Giandel) high-frequency units that I have had zero issues with, and they weigh less than half as much. All pure sine wave of course. The battery setup allows me to have (2) different rigs, or parallel the crates together to have longer run-time if needed.

As someone (Riley) above mentioned - power consumption varies dramatically based on the program material. I ran 2x DSX subs and 2x DZR tops (all efficient Class D amps) last night for 3 hours - lower/medium-volume hip-hop for 90 minutes and speech for 90 minutes.  I used just slightly over 1,000wh (I wasn't measuring peaks, unfortunately). A full-volume nonstop DJ would of course use more than a speech-heavy event which has a lot of idle time between content.

As far as rack-mount options - Gyll makes some rack-mount batteries for this purpose. I haven't seen inverters that rack-mount, but it wouldn't be hard to fashion something road-worthy. I just built a small plywood frame for my inverters, and the milk crates are robust enough (and lightweight) for my battery needs.
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Art Welter

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My question would be how long did you run the systems you described and for what kind of program material? Rock bands vs spoken word are going to be radically different power consumption.  I've also found this unit with socketed battery packs which looks much more applicable to what we do.

https://egopowerplus.com/nexus-portable-power-station/
Riley,

Regardless of quiescent vs peak vs long term music/voice average, the amount of power delivered can be measured in watt (or killowatt..) hours, the ability to deliver that power depends on the type and capacity of the storage battery.

The Nexus portable power station uses up to four of the EGO 56V ARC Lithium™ batteries, the largest being the 10Ah, 560 watt hours each, total of 2240 watt hours. For long term lithium battery life, probably don't want to use more than 80% between recharge, so figure around 1792 watt hours.

Matt Leonard's pair of ~2500 watt hour batteries total 5000 watt hours, 80% around 4000 watt hours, over double the run time, whatever is being run  ;).

Art



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Steve-White

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I can customize the rack mount in my shop.  It'll be a decision of battery and inverter in a case together with quick swap capability for the battery pack or separate battery packs in their own cases which will probably be the simplest way to go.  24V setup looks pretty good with 12V batteries in series.
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MattLeonard

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I can customize the rack mount in my shop.  It'll be a decision of battery and inverter in a case together with quick swap capability for the battery pack or separate battery packs in their own cases which will probably be the simplest way to go.  24V setup looks pretty good with 12V batteries in series.

I chose 24v as it was a nice balance of keeping the DC amperage draw reasonable at the AC scale I wanted to work at. I still run 2/0 cables everywhere (finding the Anderson SB175 2/0 components is a challenge!). And if I find the eventual need for a much bigger (6,000w+) inverter - I can run a 48v inverter by again combining my batteries in series. Though, I'd likely want a few more of them!

I want to 2nd what Art said - I hadn't seen those Nexus units, but like a lot of this sector - it seems like it has some dubious marketing. The marketing of 2,000w seems a bit disingenuous given those small battery packs. To pull 2,000 watts you are looking at a very high battery discharge rate - which will not just blow through the battery capacity quickly, it will mean a short lifespan for the batteries. The fact that the manual/specs don't offer anything about the # of battery cycles or lifespan says a lot - don't expect these to last long. Far better options from Bluetti or Ecoflow.

The DiySolarForum is a great resource for the latest tech, deals, ideas on all things solar, battery, inverter related.
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Steve-White

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Good 24V inverter is over a grand, then case and batteries + hardware.  Probably end up close to $2K for something decent with two battery packs.

Probably start there, and keep the small inverter generator for backup.

All suggestions and comments have been helpful - thanks gents.
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Riley Casey

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Drilling down on your observations about the differences between the Ego and the Bluetti. Is there some metric other than rated wattage you see as being a deal breaker on these two similarly priced units?  The Ego with two 7.5Ah batteries appears to provide 1800 watt hours at 120 VAC ( if amp hours times voltage is indeed a correct calculation in this application )  and the Bluetti is rated at 1000 watt hours . The removable batteries seems like a handy option at least for my applications but I'm curious where the dubious marketing is in this. Not doubting it, this is consumer targeted stuff after all, just trying to clarify.

https://www.bluettipower.com/products/bluetti-eb150-1500wh-1000w-portable-power-station

https://egopowerplus.com/nexus-portable-power-station/


...

I want to 2nd what Art said - I hadn't seen those Nexus units, but like a lot of this sector - it seems like it has some dubious marketing. The marketing of 2,000w seems a bit disingenuous given those small battery packs. To pull 2,000 watts you are looking at a very high battery discharge rate - which will not just blow through the battery capacity quickly, it will mean a short lifespan for the batteries. The fact that the manual/specs don't offer anything about the # of battery cycles or lifespan says a lot - don't expect these to last long. Far better options from Bluetti or Ecoflow.

...
« Last Edit: August 11, 2021, 11:55:11 AM by Riley Casey »
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MattLeonard

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Drilling down on your observations about the differences between the Ego and the Bluetti. Is there some metric other than rated wattage you see as being a deal breaker on these two similarly priced units?  The Ego with two 7.5Ah batteries appears to provide 1800 watt hours at 120 VAC ( if amp hours times voltage is indeed a correct calculation in this application )  and the Bluetti is rated at 1000 watt hours . The removable batteries seems like a handy option at least for my applications but I'm curious where the dubious marketing is in this. Not doubting it, this is consumer targeted stuff after all, just trying to clarify.

https://www.bluettipower.com/products/bluetti-eb150-1500wh-1000w-portable-power-station

https://egopowerplus.com/nexus-portable-power-station/

I admittedly haven't looked closely at the Ego units - but didn't see any specs about battery lifecycle rate - which is an instant red flag. Stuff like this sold at hardware stores that lacks robust 3rd party reviews  is marketed that way for a reason. Bluetti, EcoFlow (and others, like the Titan, or Inergy) have a more robust user base, more rigorous testing/stories, and more robust specs that are real-world tested.
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Stephen Swaffer

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Seems there should be an opportunity here for equipment builders.  The radio repeater we installed at my facility is designed for battery backup-just hook up a battery and it has an internal maintainer but it could run 24/7 on that battery power.  Seems like it is very inefficient to convert DC battery power to AC, with its attendant losses and noise, then convert back to DC with those inherent losses.

I saw a cartoon the other day of two gals looking at a clothesline "It uses the latest tech to dry clothes-wind a solar power".  Sometimes the hoops we jump through make you scratch your head.
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Steve Swaffer

Art Welter

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Drilling down on your observations about the differences between the Ego and the Bluetti. Is there some metric other than rated wattage you see as being a deal breaker on these two similarly priced units?  The Ego with two 7.5Ah batteries appears to provide 1800 watt hours at 120 VAC ( if amp hours times voltage is indeed a correct calculation in this application )  and the Bluetti is rated at 1000 watt hours . The removable batteries seems like a handy option at least for my applications but I'm curious where the dubious marketing is in this. Not doubting it, this is consumer targeted stuff after all, just trying to clarify.

https://www.bluettipower.com/products/bluetti-eb150-1500wh-1000w-portable-power-station

https://egopowerplus.com/nexus-portable-power-station/
Fully depleting two Ego 56v 7.5Ah batteries would only provide 2x420 watt hours, 840 total, 160 less than Bluetti specs.
If you are already using 56v packs, the option for other uses is a nice feature- I was surprised how fun electric chain saws are  :D
That said, if you want "real power" the much larger individual cells in the batteries like those that Matt uses are simply capable of far more C (discharge rate) than the little series of cells in the EGO and the like, which use similar cells as are used in laptop computers.

To deliver 1800 watt hours, you would want four of the EGO 56v 10Ah, 560 watt hours each, total of 2240 watt hours, using 80% between recharge to preserve battery life would be 1800 (1792 actual) watt hours. If you did use that power in one hour, that would be 80% of it's 2k output capacity, which might be a concern on a hot day.

Art

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Art Welter

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Seems like it is very inefficient to convert DC battery power to AC, with its attendant losses and noise, then convert back to DC with those inherent losses.
Stephen,

Considering all the different voltage supplies needed for audio gear, the stored DC needs to be either boosted or cut in voltage, at similar losses as DC/AC inverters.

DC/AC inverters have reached very high efficiency, converting over 90%  (some near 98%) of DC into AC.
Even the cheap Harbor Freight units are very quiet, the switch rates are now at such a high frequency they are almost like sine waves.

Distributing 120v AC compared to 12v requires 10 times less copper...

Art

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Stephen Swaffer

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I am thinking more of a complete shift in thinking and standardizing on 24 VDC or 48 VDC or both.  If 24 V battery packs were standard, equipment could use combinations to satrt with 24 VDC, 24 +/- DC, 48 VDC or 48 +/- VDC.   In a small SOS system, two battery powered speaker and separate battery at FOH means no power distribution.  No 120 VAC running around in power cords eliminates a safety hazard.  Properly packaged, batteries at the speakers could even double as ballast for the stands.  There is already conversion going on on the load end-eliminating the conversion on the supply end is one less failure point-and one less investment/maintenance point.

Probably never do a medium-large stage that way-but for a lot of what I do outdoors it would be a huge selling point.
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Steve Swaffer

Steve-White

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I am thinking more of a complete shift in thinking and standardizing on 24 VDC or 48 VDC or both.  If 24 V battery packs were standard, equipment could use combinations to satrt with 24 VDC, 24 +/- DC, 48 VDC or 48 +/- VDC.   In a small SOS system, two battery powered speaker and separate battery at FOH means no power distribution.  No 120 VAC running around in power cords eliminates a safety hazard.  Properly packaged, batteries at the speakers could even double as ballast for the stands.  There is already conversion going on on the load end-eliminating the conversion on the supply end is one less failure point-and one less investment/maintenance point.

Probably never do a medium-large stage that way-but for a lot of what I do outdoors it would be a huge selling point.

You are right.  Smaller amps could be made to run from 24/48VDC or AC line pretty easily.  For wedding receptions, I have 36 par hex up-light cans to do perimeter lighting.  They are all battery WiFi lights and that is a selling point to my clientele - they are safe with children fully sealed on battery and LED so no heat either & IP54 rated.

Today safety is a selling point especially with families and children type events.
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MattLeonard

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You are right.  Smaller amps could be made to run from 24/48VDC or AC line pretty easily.  For wedding receptions, I have 36 par hex up-light cans to do perimeter lighting.  They are all battery WiFi lights and that is a selling point to my clientele - they are safe with children fully sealed on battery and LED so no heat either & IP54 rated.

Today safety is a selling point especially with families and children type events.

The Rock the Bike folks in the Bay Area have done something similar. They have bike-powered DC generators that can run blenders, but also modified some JBL PRX boxes to bypass the AC transformer, and run straight from their pedal-powered DC power source (pretty sure they have some capacitors in there for headroom/dynamics).  I've seen few events they have done - and while it's not a true full-range pro-level rig, for the small festivals and political events they do - it's a pretty slick setup. And people LOVE to pedal at these sorts of events, especially kids.


See: https://rockthebike.com/modified-jbl-loudspeakers/
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Re: Multiple (battery/inverter) power sources in a small audio system - ground ?'s
« Reply #19 on: August 12, 2021, 07:36:33 PM »


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