Stromtank Battery Supply / Sine Wave Converter

[Ron Resnick]

The idea of powering an entire audio system with a big battery pack has waxed and waned over the years. Now we have offered to us the Stromtank device from Germany, claimed to be designed by a co-founder of MBL.

The one time I compared a preamp which can switch between an internal battery pack and the AC line I found the internal battery pack to provide smoother, "quieter" sound.

I am in the process of planning a comprehensive electrical upgrade to my listening room (JPS in-wall cable, new subpanel, new outlets, possible Torus isolation transformer, new ground system, etc.). But before I go down that road I want to consider the Stromtank.

For the price of the traditional comprehensive electrical infrastructure upgrade one could purchase one or even two Stromtanks.

The Stromtank specs state that it can output momentarily 2800VA (about 23 amps at 120 VAC). But some amps can have instantaneous current peaks higher than that current level, I think. (This is why fanatics use 100 amp isolation transformers for their systems.)

One could use a Stromtank for each channel, and a third Stromtank for the front end. All together that would provide 69 amps on a peak basis for the system, which should be enough.

One problem with battery power in the past has been the high output impedance of the battery pack output. The Stromtank claims to solve this particular problem by using many batteries, resulting in a low output impedance.

Is the Stromtank a viable or even superior alternative to the traditional audiophile electrical infrastructure upgrade?

How do we know the sine wave converter (isn't this really an inverter?) is not generating some sort of noise or distortion of its own?

Is there any reason to believe that the traditional electrical infrastructure upgrade would provide better AC to the Stromtank and thus allow the Stromtank itself to "sound" better when ultimately sending AC to the audio equipment?

 

[asiufy]

Hi Ron,

Last time I inquired the D'Agostino folks (US distributors) about the Stromtank, they told me there's actually a beefier version in the pipeline, as the first (initial) unit couldn't cope with a pair of D'Agostino monoblocs. When we had a unit in the store, that was indeed the case, as the unit would disarm on peaks and dynamic bits.

Like most designers, Dan is not a fan of tweaks and assorted voodoo, but according to him, the Stromtank is a solid investment, and does provide a significant upgrade, that's significantly easier than doing an entirely new electrical installation.


cheers,
alex

 

[Folsom]

I'm not personally a fan. Yes it works but as far as sounding better? Undetectable improvement from what I could tell when paired with D'Agostino and Wilson speakers. In no way did it seem to shine over anything else in anyway I could note. Vinnie Rossi's LIO is a better reference for a storage device success. But perhaps the Strombank could be improved. I will say it can deliver big power but the very crest of it isn't as sharp.

In general I prefer AC over batteries. Batteries can sound very good, but I have under no circumstance thought of them as the last word in fidelity that's possible. I prefer the Surgex over batteries, and it's only a step towards what's possible. I'm usually searching for realistic gusto which I find with AC devices.

AC untreated isn't something I'm for, however, just I prefer AC treated over DC (maybe treated).

 

[amirm]

Funny you should mention SurgeX as they are also coming up with a large UPS like Stromtank. They showed a prototype at CEDIA this year:

 

[Ron Resnick]

Unless carefully designed with audiophile sensibilities in mind can't an inverter generate noise or distortion of its own?

 

[amirm]

Sure. The sine wave inverter works by modulating a square wave as the carrier using a sine wave. That sine wave is often generated using rough samples in a table as the controller lacks the computing power to generate it on the fly. The square wave carrier will then need to be filtered and that is challenging to do well because of the high switching power.

A sine wave inverter can be thought of as a high power amplifier and with it, have a THD rating. I plan to do an in-depth analysis of them compared to mains power. For now, yes, you can do a good or crappy job of generating that sine wave. The response can also be load dependent with distortion levels varying depending on how much power you extract from it.

I just looked up the spec on Stromtank and it is rated at 2% THD which is the same as my lab grade AC supply.

 

[Folsom]

Unless carefully designed with audiophile sensibilities in mind can't an inverter generate noise or distortion of its own?

I don't know if the same engineers that worked on SurgeX's small units designed that UPC device, but if so I'd put my money down that it's considerably better than the StromTank; so long as a clean output was intentional. (He's probably a better EE than Dan, whom didn't design the StromTank anyway)

Using battery power removes the noise from the wall, but it can increase system generated noise depending on it's spec's, to varying degrees. Measures to remove system noise sharing and RF pickup from the cables themselves are still a good idea. I like my individual components to be isolated from each other - ones with smaller transformers generate common mode noise for example (all small transformers do this).

 

[Rodney Gold]

I use batteries to power my music room , a bank of 6 200ah deep cycle batteries and a luminous 7,5 kva pure sine wave inverter and solar panels or mains to charge the batts

Mostly used because we have bad power, brownouts , surges and rolling blackouts here in south africa

I have a master switch at my distribution board that I can throw to either make the feed to the room come from the mains or from the inverter.. makes no difference in sonics whichever one I use ..mains or regenerated power.

If I had a stable mains PS , I wouldnt bother to use batteries....
I use high efficiency amps ... Devialet.. so the effective 5-6kw output of the battery system is more than adequate
If I were running big power hungry amps like big krells or the like , I might have gone to 10kva ..
The system cost me around $4000 ... solar panels , inverter , batteries , installation and another sub distribution board for the battery system.

 

[Audiophile Bill]

Hi Ron,

It might be worth writing to Kevin @ Definitive Audio in U.K. (makers of Vox Olympian). They have long been proponents of a battery powered solution that they have developed over years. Theirs will be big budget and require a lot of space but it is likely to be very good - sorry I can't provide the details as I simply don't know.

 

[Audiophile Bill]

http://www.voxolympian.co.uk/

You can see the photo on this page

 

[rockitman]

I like the idea...if you move, your silent electrical grid comes you. I just read this review and this is my immediate concern:

It is possible to listen to music up to eight hours (depending on your equipment's power needs) before recharging processes start.

http://www.enjoythemusic.com/HIGH_END_2016/Stromtank/

So what if you are running class A amps that need an hour or two to warm up ? Right there your battery capacity has reduced 2 hours.

Does it charge and let you still listen via the AC power grid ?
How long do the battery cells last before they need to be replaced ? (They will lose their capacity to hold charge over time...all batteries do)
What is the cost to replace the old/worn out battery cells ?

I am definitely intrigued and want to learn more about it and see if it would work well with my system...(power hungry)

This review answers more questions...http://www.monoandstereo.com/2016/01/stromtank-ultimate-off-grid-power.html

very long life (> 20 years possible)

- up to 10,000 cycles – with low DOD (depth of discharge)

- 5 times more cycles than lead or lead-gel batteries

- up to 6,000 charge cycles at 60% DOD (equivalent to 16 years with a daily

charge/discharge, after that at least another 80% of battery capacity)

- 93% efficiency

- up to 100% DOD possible (90% effectively usable)

- high current capacity

- absolutely environmentally friendly and maintenance-free

- no fire hazard – explosion proof, since non-oxygen-reactive

- modular system concept - extendable at any time and interchangeable

- high safety standards confirmed by relevant certificates

- lightweight

maybe more answer here in the owners manual. I am still skeptical on whether it's a good match for my power hungry class A amps....1200 watts at idle.
http://www.audiosalon.com/pdf/owners_manual_STROMTANK.pdf

 

[rockitman]

For me, it would be good to know what calculations I need to make with my system to determine the battery operation listening time for my system. Also, it appears when you run down to 10% battery capacity, the system automatically goes back to "on grid" to charge the batteries. During this time, is one still able to listen to the system ? Will it sound at least as good or maybe better than just plugged into the grid without the StromTank ?

 

[Fiddle Faddle]

I have my reservations about inverters for AC - even "good" ones. They still have a decent harmonic distortion component and I often feel that people can get better results simply through highly advanced conditioning devices. Out of interest, here in Australia we have a proliferation of domestic inverters feeding power back into our electricity grid from domestic roof-top solar panels. There was a real "boom" in this several years back when the Government offered to actually pay people for the energy their inverters put back into the grid - look at my street and almost every house has roof panels and is feeding power back into the street via inverters.

As a result of this, our domestic energy grid has such a high harmonic distortion component thanks to being fed by dubious inverters that a certain university did a white paper on the problem! Forgetting about audio quality, every now and then it manifests itself with the power being so far out of spec, equipment and protection boards shut themselves down thinking the power is simply too bad to pass on to what is connected to them! For my own part, everything does sound better once there is no sun around (luckily storage batteries in this country are just too expensive so when the sun goes, no power gets fed from houses back into the grid and thus the power is cleaner).

So I am not a big fan but then again I understand the potential - but only if you can generate a better quality sine wave than a "good" power grid unpolluted by domestic inverter feed back.

 

[amirm]

Does it charge and let you still listen via the AC power grid ?

I am pretty sure I asked them this question and the answer is yes. The charger is a "back end" process so doesn't impact the inverter pulling power out of the battery (and charger) while supplying the AC power.

How long do the battery cells last before they need to be replaced ? (They will lose their capacity to hold charge over time...all batteries do)

I did two battery conversions over the summer to the type of cell they are using. The number of cycles you get out of them depends on depth of discharge. If you pull them down 80% at a time, the cycle count is about 2000. This is highly temperature dependent so the actual number may vary. And the count is determined by the charge capacity dropping to certain number (about 80%). If you lightly discharge them, say 10 to 20%, the cycle count can be 6 to 8000.

What is the cost to replace the old/worn out battery cells ?

Depends on whether you can replace them yourself or have them do it. Stromtank runs at 48 volts with a capacity of 100 amp hour. 100 amp hour batteries are about $130 each. You would need 12 of them because they put out around 3.5 volts to 4 volts. 12 times $130 = $1560. These are hazardous parts so you get hit with $300 to $400 shipping depending on where you are. So rough number for good price for raw cells would be $2,000.

maybe more answer here in the owners manual. I am still skeptical on whether it's a good match for my power hungry class A amps....1200 watts at idle.
http://www.audiosalon.com/pdf/owners_manual_STROMTANK.pdf

Hmmm. I should have paid more attention to the output rating. This is what it says in the spec for S5000:

Continues power @ 25°C 700 VA
Power 30min. @ 25°C 1.200 VA
Power 3 sec. @ 25°C 2.800 VA

700 volt amps? That is nothing. You can't power anything but source devices or pre-amps. Depending on the power factor of your device, conversion from VA to watts is from 0.4 to 1.0 so maximum wattage could be as low as 300 watts and if you are lucky, up to 700 watts.

Is there a different unit than the S 5000???

 

[morricab]

The idea of powering an entire audio system with a big battery pack has waxed and waned over the years. Now we have offered to us the Stromtank device from Germany, claimed to be designed by a co-founder of MBL.

The one time I compared a preamp which can switch between an internal battery pack and the AC line I found the internal battery pack to provide smoother, "quieter" sound.

I am in the process of planning a comprehensive electrical upgrade to my listening room (JPS in-wall cable, new subpanel, new outlets, possible Torus isolation transformer, new ground system, etc.). But before I go down that road I want to consider the Stromtank.

For the price of the traditional comprehensive electrical infrastructure upgrade one could purchase one or even two Stromtanks.

The Stromtank specs state that it can output momentarily 2800VA (about 23 amps at 120 VAC). But some amps can have instantaneous current peaks higher than that current level, I think. (This is why fanatics use 100 amp isolation transformers for their systems.)

One could use a Stromtank for each channel, and a third Stromtank for the front end. All together that would provide 69 amps on a peak basis for the system, which should be enough.

One problem with battery power in the past has been the high output impedance of the battery pack output. The Stromtank claims to solve this particular problem by using many batteries, resulting in a low output impedance.

Is the Stromtank a viable or even superior alternative to the traditional audiophile electrical infrastructure upgrade?

How do we know the sine wave converter (isn't this really an inverter?) is not generating some sort of noise or distortion of its own?

Is there any reason to believe that the traditional electrical infrastructure upgrade would provide better AC to the Stromtank and thus allow the Stromtank itself to "sound" better when ultimately sending AC to the audio equipment?

Well, I use a power regenerator for my sources and that has an enormous improvement on their sound. Highs become grunge free and space in the recording benefits accorgingly. I would not recommend though for the power amps...everytime we have experimented with this it damages the dynamics and sometimes the bass power of the amps.

 

[LL21]

Well, I use a power regenerator for my sources and that has an enormous improvement on their sound. Highs become grunge free and space in the recording benefits accorgingly. I would not recommend though for the power amps...everytime we have experimented with this it damages the dynamics and sometimes the bass power of the amps.

Hi Morricab,

Which regenerator do you use? apologies if you've posted someplace earlier.

 

[Ron Resnick]

. . . Also, it appears when you run down to 10% battery capacity, the system automatically goes back to "on grid" to charge the batteries. During this time, is one still able to listen to the system?

I know the system can be played during charging.

 

[rockitman]

I know the system can be played during charging.

is this battery system only realistic for source components ? That in and of itself is still a great thing....more important than the power amps, imho.

 

[Ron Resnick]

It definitely is not supposed to be only for source components.

I think it has been demonstrated at shows powering the entire system.

 

[asiufy]

It is supposed to be used for an entire system, but as I said in my initial post, they're working on a beefier version that will handle more powerful amps, as the current version will not.