5 VDC battery supply - LTO batteries (Lithium Titanate - Toshiba) on ebay.

[JCMcNeil]

@JCMcNeil : Hi Chris ... So, now I have a bit more time and have read your post in detail. Sounds like you have been very active with implementing a solution(s) that appears to work to your satisfaction. Just a couple of comments:



* Depending on how you have implemented this I personally would consider breaking the connection with the laptop supply completely when playing music (you may already be doing this, of course). I've measured the noise spectrum on a couple of laptop PSUs and they may be very noisy - something that could spread to the shared GND (again depending on how you implemented your circuitry).

Do you mean break both power and ground connections between the charging source and batteries/ Ultracapacitors with 2 relays? If so, I already do that with a DPDT relay per supply. Or, if you mean disconnect the PS from the mains as well, I have not done that yet but am looking at doing both that and running the Arduino on batteries as well when music is playing.

That is also my impression. At least the Toshibas that I use also have a relatively high self-discharge rate which at one point in time caused many of the cells to completely self-discharge. Caused me to be quite discouraged until I learned that they could actually cope with this. So, just recharged them and they appear to be fine again.

I found many LTO discussion threads attesting to their robustness in the face of abuse. Good to hear your experience supports that.

As far as I understand Li-ion batteries' life-span deteriorate if they are charged from a charger with a high ripple level (basically a continuous charge/discharge while charging). I do not know if this is also the case for LTO batteries but, well, just wanted to mention it. I reckon your SMPS chargers could have a relatively high ripple level (?) ...

Maybe, I haven’t tested to see. Since they disconnect when music is playing, and given the aforementioned LTO robustness, I am not too concerned at this point.

My observation & choice as well. BTW ... I suppose that since you parallel the LTO & UC cells then you prefer the sound from the combined cells - or some other reason for doing this?

My blind listening tests favored the Ultracapacitor/LTO combination above those small 1.5AH LTO batteries alone. The UC board doesn’t last long enough disconnected to a charging source to be practical, but I also liked the sound of the combination at least as much as the UC’s alone … it was close enough to merit further testing at some point, though.

Well, now I don't know which balance board you have acquired but when I was searching for this (a couple of years ago) I did not find any with a balancing voltage that was below what I would consider an absolute maximum voltage for the individual cell (Li-ion cells). The balancing onset voltage typically was at ~ 4.2 to 4.3 volts - IMHO not suitable for float charging.

it at least a looks like the one on this DDDac blog post. It is working well for float charging so far. I was also encouraged by a thread that referenced successful use of supercapacitor balance boards for balancing LTO’s.

Hmmm, well ... Just FYI I have float charged my DAC's batteries (Li-ion and LiFePO4) for ~9 years now, constantly, and they appear to be working fine. I think that float charge voltage, cell temperature, PSU ripple, and discharge level are what matters most in terms of cell life span. And at least my Toshibas have an 80% retained capacity cycle life of more than 15.000 cycles. Should be enough to get me through life ...

Part of the reason for alternating the float charging between modules is to keep the opportunity open to balance batteries in series by charging each one in isolation…which I can’t do simultaneously unless I use separate charging sources with separate grounds. I haven’t crossed that bridge yet, though, in part because I sense I might want to incorporate voltage measurement and self adjusting charge time per cell with a feedback loop…a bit more complicated than I have felt I’ve had time for recently with an unrelated new business model launch going on concurrently.

I guess you know about much that better than I do ... As it is I have not read the thread so I wouldn't know about this. Might you post in the thread & ask? However, besides Ian Canada's battery supply (thread here on diya) there's also (at least) Andrea Mori's battery supply ( https://www.thewellaudio.com/twrps-lbs/ ) - don't know if you are familiar with this one? Just FYI in case this could also be interesting in your context ...

Yes, I’ve seen Andrea’s and Ian’s battery systems online. I have not personally experienced either, though, since I decided to figure out a system myself as a learning experience and to keep the door open for any innovation opportunities.

Well, will end here - wishing you a pleasant day, Chris

Jesper

cheers, Jasper, I appreciate the feedback and ideas.

chris

 

[gentlevoice]

Hi again, Chris ... You seem to be well underway with your own solutions & ideas so just a couple of brief comments:

Do you mean break both power and ground connections between the charging source and batteries/ Ultracapacitors with 2 relays? If so, I already do that with a DPDT relay per supply. Or, if you mean disconnect the PS from the mains as well, I have not done that yet but am looking at doing both that and running the Arduino on batteries as well when music is playing.

I actually did mean breaking both the GND and supply connection between the chargers and the batteries when playing music. However, entirely disconnecting from the mains sounds like an interesting idea as well. I reckon that the inter-audio-device voltage levels may benefit from this. If you try it out I'd appreciate your observations on this.

Part of the reason for alternating the float charging between modules is to keep the opportunity open to balance batteries in series by charging each one in isolation…which I can’t do simultaneously unless I use separate charging sources with separate grounds. I haven’t crossed that bridge yet, though, in part because I sense I might want to incorporate voltage measurement and self adjusting charge time per cell with a feedback loop…a bit more complicated than I have felt I’ve had time for recently with an unrelated new business model launch going on concurrently.

I use a very low noise balancing circuitry on each cell which balances the batteries to within ~ 10 mVs. In this way I don't need a charger per cell and, additionally, when the cells are not charged, the noise from the balancing circuitry essentially is "zero" (not possible but very low level). A relatively "simple" solution that appears to work well.

with an unrelated new business model launch going on concurrently.

Sounds like you could have something on your mind then Good luck with your business endeavors - & feel welcome to ask should you have more questions.

Cheers,

Jesper