Battery Power Supply

[jkeny]

That ingredient in all these batteries that confers such high performance is the surface area of their anodes - this gives a much wider area for the chemical reaction that generates the voltage. With a much wider area it can deliver much higher instantaneous current delivery (internal impedance is very low) & the 'electrical noise' of the chemical reaction is much less. (The LiFePO4 forms into nano particles which confers this much higher anode surface area - the Li-titanate oxide does the same. Don't know how much more surface area compared to LiFePO4 but it seems to be the case)

This was what attracted me to the LiFePO4 batteries initially - I reckoned they should be much quieter & more stable than previous battery technology in the role I was intending to use them for - digital audio 3.3V supplies. Digital chips take large gulps of current very quickly at high frequencies - just what these batteries should be good at. Of course theory is one thing & practise another - but they have proven themselves in this role.

It also explains why putting a regulator after batteries can somewhat negate these benefits - making the current delivery noisier & slower. It also shows that the usual factors which are judged to characterise an excellent voltage regulator are missing something or not taking all the dynamic aspects of current delivery into account. I've seen people rave about the latest low noise regulators & yet when I have bypassed them & used a battery directly driving the circuits it has resulted in a very large audible improvement

[jrling]

https://www.ev-power.eu/LTO-Tech/
confirms what you say, but not a direct comparison with A123 26650 LiFe which have patented nano crystal anodes.

The effect and benefit of this alteration and inclusion of lithium-titanate nanocrystals is that the surface area of the anode of the Lithium-Titanate battery is about 100 square meters per gram in contrast to the only 3 square meters per gram that Li-Ion batteries hold. The result of the lithium-titanate nanocrystals with their enlarged surface area is that electrons are able to enter and leave the anode much more rapidly, leading to fast recharging and enhanced lifetimes of the battery.

But what tells me that LTO is 'better' is the low ESR. A123 26650 are rated at 6mOhm and these LTO at 0.6 mOhm. A 10 fold improvement. That would translate, as you say, into a theoretical 10 times quicker response to current demand from digital circuits.

Longevity and speed of charging is also massively better.

I had better stop or you will think I am selling them!!

[jkeny]

https://www.ev-power.eu/LTO-Tech/
confirms what you say, but not a direct comparison with A123 26650 LiFe which have patented nano crystal anodes.

The effect and benefit of this alteration and inclusion of lithium-titanate nanocrystals is that the surface area of the anode of the Lithium-Titanate battery is about 100 square meters per gram in contrast to the only 3 square meters per gram that Li-Ion batteries hold. The result of the lithium-titanate nanocrystals with their enlarged surface area is that electrons are able to enter and leave the anode much more rapidly, leading to fast recharging and enhanced lifetimes of the battery.

But what tells me that LTO is 'better' is the low ESR. A123 26650 are rated at 6mOhm and these LTO at 0.6 mOhm. A 10 fold improvement. That would translate, as you say, into a theoretical 10 times quicker response to current demand from digital circuits.

Longevity and speed of charging is also massively better.

I had better stop or you will think I am selling them!!

Yes, the low internal impedance is the giveaway measurement but we also have to be careful about whether this translates into 'better in use' as the wires that carry this current to the device will have a part to play in the current delivery at the actual PS pins of a chip, for instance. The impedance & inductance of the wire being used will determine the lower ESR limit that has an audible effect - going below this should make no improvement.

[jkeny]

You might be interested in the just launched ISO-PS an isolated power supply using LiFePO4 batteries
Outputs one or two 3.3V independent supplies or combined to give one 6.6V supply (other voltages can be considered - just ask) - perfect for pwerig many audio devices - see my signature for website
Internal battery chargers are isolated from power supply so no bleed through of noise from leakage currents or ground loops
Fully automatic - just plug in & forget

[wushuliu]

Not sure if this a good deal or not, but may be worth taking a look at for battery. Ships worldwide.

https://www.ebay.com/itm/4-HEADWAY-3812 ... SwUYNaS8aC

[jrling]

That does look a good deal if you are in USA.
Headway are a reputable brand.
Shipping though adds a lot to the cost and for Europe you have to factor in Import Duty and VAT as well as high shipping cost.

A123 like to make a big deal of their nanophosphate technology, but I doubt it would make much difference for our audio application.

[jkeny]

Seems LiFePO4 has a contender for best power source
http://www.diyaudio.com/forums/pc-based ... 78596.html

A number of people are reporting it sounds better, faster than LiFePO4 - the best PS solution so far
http://www.diyaudio.com/forums/digital- ... 81627.html

Ultracaps.
This is the best power supply I have tried so far! For reference: I already tried Salas Reflecor D with all avaliable modes, LT3042 and LifePo4. From those three LifePo4 was the best, however kind of too "slow" to my taste. Ultracaps beats them all. PRAT and silence is just gorgeous.

They still seem to be chasing the 'pure' version of ultracapacitor power i.e. not being concurrently trickled charged but switching between powered banks of capacitors

I have some on order & will be assessing them

[gstew]

John & others...

The concurrent charging scenario is not dead. It did not win in Ian's early trials. I'll setting up some alternatives to try including pure Ultracap and some concurrent charging alternatives. I'm hopeful the latter can be made to equal or come very close to the pure UC setups.. I like the advantages of a steady and stable output voltage plus the overall configuration for an always-on setup becomes much simpler and less expensive if bank-switching is not required. Also it is easier to implement in a many multiple-rail setup as needed for most modern digital builds.

We shall see. I'll be publishing my results over there along with Ian's... and will point back to any developments here.

Greg in Mississippi

[jrling]

I have tried various DIY combos along these lines for powering my audio PC which runs off DC between 8-18VDC.
So different experience probably from using Ultracaps for running low power DACs or other PCBs.

But .... I bought 5 Maxwell 350F 'D' cells, same as in Ian's picture. I went for them because they have terminals you can easily solder with not too outrageously high wattage soldering iron and they cost about £8-9 in UK; the Maxwell 3000F Ultracaps are a lot more expensive @ c. £40-50 each. Much cheaper in USA I think where Maxwell are based. Keep off the cheap Chinese ones - many reports of all sorts of issues that can damage the equipment attached to the PSU.

Their nominal voltage is 2.7V. I wired them in series with a 1Kohm resistor bridging each cells terminals (as a bleeder resistor to balance them out). I read all sorts of warnings about cells getting out of balance with bad consequence, but with the bleeder resistors I have never found any of the 5 cells more than 0.1V out of balance.

One issue with Ultracaps is that if they discharge a lot or particularly completely to 0V, although that does not damage them at all, after all they are only a capacitor, when you recharge them, whatever you use to do the charging sees effectively a dead short and the Ultracaps pull very high current which overheats the charger. They need a high wattage low value resistor in series to start with to reduce the initial inrush to sensible levels.

The other issue (apart from shorting them!) is that they do not tolerate over voltage which will kill them.

Up until I bought the Ultrcaps, I had been powering my audio PC with A123 26650 LiFePO4 to great effect. 4 banks in parallel of 4 cells in series (13.2V). I float charged them with my Maplin XM21X linear PSU. It worked very well and made a material beneficial SQ improvement over using the XM21X direct to the PC.

In for a penny, in for a pound, I thought I'd try Maplin XM21X float charging the LiFePO4 batteries which in turn float charged the Ultracap bank and it gave another improvement in SQ over batteries on their own. They seem to be getting better and better and I suspect the Ultracaps take many tens of hours to fully bed in.

I have no switches, regulators, cell balancing board or other devices in the PSU chain. I connect the XM21X to the battery/Ultracap banks with a 2.5mm barrel connector for now (I know) and just unplug the Maplin when finished to prevent drain back through it and ditto with the output to the PC. Crude but it works for me. The batteries keep the Ultracaps fully charged for weeks of non-use as their self-discharge rating is very small.

As Greg says, keeping the batteries and Ultracaps at constant voltage in their optimal operating voltage parameters, is likely to minimise chemical noise in operation and maximise their life as neither are ever charging/discharging by more than a fraction all the time they are in use. Changing voltage through the switched bank approach is also like to produce changing output impedance with varied voltage.

[jkeny]

Thanks guys
@Greg, I didn't see Iancanada's report on the sonic difference between concurrently trickle charging the Maxwells Vs the purist approach. What % degradation did he experience & what did he use for trickle charging?

This to me represents the best approach & I'm willing to forgo a small degradation for the simplicity

@jrling - thanks for the report - what wattage 1K resistor do you use between caps? I presume this has to be sized according to what instantaneous current is likely to be drawn. I've seen reports of series Maxwells without these resistors holding their balance?

The bank switching is not a runner as far as I'm concerned - it requires a regulator on the output to maintain a constant voltage which defeats the purpose

I've seen talk of chemical reaction noise in batteries but when I first looked into A123 LiFePo4 batteries the characteristic that allowed such low internal impedance & hence high current delivery was the large surface area of the cathode by using iron nanophosphate i.e. very small particles. Along with other techniques they ensured that the ions move very quickly across the electrodes - hence the high power delivery. Anyway, all this means that there is very much less chemical reaction noise particularly when low currents are being drawn typical of DACs.

The idea of putting a battery behind the capacitors doesn't make a lot of sense to me either as we still need all the relays/switches to ensure the battery is isolated & prevented from being drained - do the ultracaps bring a significant upcheck in sonics?