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Author Topic: Multiple (battery/inverter) power sources in a small audio system - ground ?'s  (Read 4087 times)

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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