Using battery power to go off the City's power grid

@sbayne Oh that should be fun! I think I'll do that! Thanks for the suggestion! Is there a limit to how many pictures can be posted? 

Many audiophiles (myself included) consistently focus on earth grounds, grounding, and "clean" power. Yes, that's important, to maintain low noise floors (as earth grounds can also act as bonding conductors, which is also good), but what many times gets overlooked (IMO) are AC neutrals. Many times you can lower AC power total harmonic distortion (THD) by maintaining clean neutrals (and sometimes even oversizing them).

Let's take for example a dedicated 20 amp circuit, exclusively used for audio equipment. If you only plugged in one piece of audio equipment to that circuit, the THD on that circuit would probably be at 1% or lower (a good sign of clean power). Start plugging in more equipment to that "dedicated" circuit (especially equipment with switching power supplies), and the THD on that circuit is almost guaranteed to rise in value. The *neutral* bears the burden of equipment with poor power factors. There is a whole science behind this.

When electrical building engineers design an electrical system for a building, (if they're smart) neutrals, and balancing 3 phase electrical systems, are paid close attention to (neutrals especially). The story revolving around The First Interstate Tower (now called the Aon Center) fire in 1988 in Los Angeles has many times been reported as electrically related. Here's what Wikipedia says about that: "The fire's origin has been attributed to overloading of the building's electrical system by reactive distortion of lighting circuit currents." I'm not sure reactive current was fully understood in 1988, as computers were just starting to be the norm in office buildings, along with electronic fluorescent ballasts. It is rumored that the building had a lot of personal computers in the building, which all had switching power supplies (along with the numerous electronic fluorescent ballasts), which possibly/probably overloaded undersized neutrals (probably because the 3 phase power was not balanced correctly).

Times have changed, and switching power supplies are being built with better designs these days (energy star), and have better power factors (a perfect power factor is 1.0 or 100%). A perfect power factor means the piece of equipment is using all of its power, efficiently. There are however still a lot of switching power supplies (and electronic ballast fluorescent lighting) out there that have poor power factors, and high THD. 

So when establishing (utility powered) AC circuits for audio, have as many dedicated AC circuits as you can, and make sure that each circuit has a dedicated neutral, along with a dedicated isolated ground (no daisy chaining neutrals). I realize this can be costly, and quickly fill up a circuit breaker panel (technical term being Load Center), but it will keep AC circuit THD at low levels, which is the key to maintaining high quality noise free utility AC power.

Personally, besides trying to keep my neutrals clean, I also employ Equitech balanced AC power (Google that), isolation transformers, and Tripp Lite Ultra Isobar surge protectors to keep my noise floors as low as they can be. Good luck everyone.    

When you're really serious about power quality:

Fluke 43B/003 Power Quality Analyzer

Even though this model is now discontinued, you can still find them used on ebay. This unit will display the 60 Hz waveform (in addition to many other things), AND, give you a THD figure. With this meter (I've had one in the past), you might be surprised to find out that your home/apartment/condo utilityAC power is cleaner than you think it is. As many of you are already aware, AC line THD is a good indication of how clean your power is. 

Some of you could skip over all of the hassle of setting up separate components of batteries and inverters by simply purchasing UPS' which contain both of these components all in one package. Many models include metering too. Here's the thing about UPS' - there are typically two types; standard (or line interactive), and double-conversion. A standard UPS only transfers power to batteries when a power outage is experienced. In this situation, one specification to note is transfer time. That is the time it takes for a standard UPS to switch from utility power, to battery power. Sometimes that time can be 10 milliseconds, or higher. In a typical broadcast application (I'm a former Radio Broadcast Engineer), I used UPS' in many broadcast situations to momentarily supply power to broadcast gear, until a generator kicked in (after the loss of utility power) and took over. Sometimes this 10 millisecond (ms) transfer time was not quick enough, so many pieces of electronic microprocessor based equipment would lock up. What a pain. I then began using double-conversion type UPS'. This is a type of UPS that is *always* on battery power, with no transfer time. It sounds like with all of the batteries and inverters you're setting up, you're in a way creating a double-conversion UPS. Lead-acid batteries were the norm with UPS', but now many are utilizing Lithium Ion batteries. Here's an example of a double-conversion UPS:

UPS' come in a wide range of volt-amp outputs (easily converted to watts via website volt-amps to watts calculators). Another added plus of a double-conversion UPS is since it's always on line, it protects your equipment during momentary (and longer) utility power outages. All of my home audio equipment (TV's too) has been on a double-conversion UPS for years now. A word of caution though if you go searching for a double-conversion UPS; make sure to read the fine print. Some manufacturers use different terms for double-conversion. Key words being - no transfer time. 

@jollygreenaudiophile2 mentioned a flywheel type system. Just in case some of you wanted to take a look at this type of energy storage system, here's one that I'm aware of (BTW, you can click on the link on the right hand side for a tutorial):

https://vyconenergy.com/products/ups/vdc-products/

I believe these are mainly used in data centers (and other broadcast applications) to cover the building load, while a generator is ramping up to full voltage, which will then take over the building load. I've never used one, or been part of a facility that had one, but it looks like they can take the place of many UPS'.

Here's another picture of the Fluke 43B:

Fluke 43B

>>>All of my home audio equipment (TV's too) has been on a double-conversion UPS for years now.<<<

Correction, my power hungry power amplifiers are surge protected, but not on the UPS. Only the low wattage consuming front end gear in my audio system is on the UPS. Even some of *that* front end gear is *even more* power conditioned after the double-conversion UPS. My headphone amp (Gustard H10) has a smaller dedicated 500VA balanced AC transformer from which it gets its power from, and my PC tower (yes, I still have one of those) which contains my Audioscience ASI5002 soundcard, also has a dedicated 500VA balanced AC transformer feeding it. I also use a dedicated isolation transformer for my CD players (of which I have two). I have the measuring devices to measure noise floors, and my amps receive a -95 dB SNR signal. In listening terms, of course that is a *very quiet* noise floor. THAT is the figure I pay most close attention to.   

Even though in my previous posts I have put a lot of emphasis on THD; maintaining a figure of 1%- 2% it's not always my numero uno priority. Just like many of you, my ears play a bigger part. For many years I've owned a Fluke 43b (like mentioned above), and was obsessively measuring THD on my AC lines. Since readings in my house were always within the 1%-3% range, I sold it, but I still stand behind the neutral theory, because in the electrical world, there's been so much discussion about it.

As I may have mentioned, I was Chief Engineer for numerous radio stations for over 30 years (try interconnecting 13 studios in the same building, which are all interconnected to each other, full of audio gear, and have an end result of no audio humming or buzzing - it's quite the challenge).

One time I took my Fluke 43b, and plugged it into a power strip which had at least 12 pieces of gear plugged into it, at one of the radio stations I was working at. This rack of gear was about 6 feet from the primary power service entrance for the building (lots of EMI I'm sure), directly under a 340' self supporting broadcast tower (lots of RFI). I was amazed(!!) when the Fluke revealed a THD of 0.3% at/on this powerstrip. In all my years of owning that Fluke 43b, I've never ever found a reading that was under 1%, anywhere, but of all places, in a rack full of gear, at a radio facility, directly under a broadcast tower. Now I think this had something to do with the rack being so close to the service point entrance. My theory on this is that the neutral feeding this rack had a very short distance to travel, and had little chance to inductively pick up noise via that short distance, which may be why it had such a low amount of THD. I was very happy to see this reading, as this rack contained the audio processor for the over the air (OTA) audio, and if I'm feeding AC to this audio processor, which has a 0.3% reading, glory be, all of the listeners of this radio station benefit.  

This is just one example of a Battery Room at a Data Center (ie, computer farm). These batteries are for mission critical UPS power. 

Typical UPS Battery Room at a Data Center

@curiousjim Mechanical hum or audio hum?

@curiousjim You may not be speaking to me directly, but just out of curiosity, are you referring to mechanical clicks, or audio clicks?

Since I'm more familiar with the UPS world, from experience, standard UPS' (themselves) will give off a mechanical hum, and most always a fan will kick on, when a loss of power is detected and they are called for action. but I've never heard any mechanical clicks emanating from them. Double-conversion UPS's (since they're always on battery power) will typically *always* emit some hum and fan noise, continuously (fans to keep the batteries and inverter circuitry cool). That's why I try to locate them away from quiet recording/broadcast studios, or my personal listening areas. I never hear any mechanical clicking noises emanating from them either. Not sure how many audiophiles use UPS' though.