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Develop ultra capacitor power supply and LiFePO4 battery power supply
Develop ultra capacitor power supply and LiFePO4 battery power supply
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Old 11th September 2018, 12:06 PM   #31
sumotan is online now sumotan  Indonesia
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I assume that different brands of LifePo4 life capacitors will have different sound Ian ?
This looks very interesting question pls, if we feed the LifePo4 supplies individually to say 5 locations, how is the battery drain being controlled as current consumption will vary.

Thks Ian
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Old 11th September 2018, 03:37 PM   #32
iancanada is offline iancanada  Canada
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Develop ultra capacitor power supply and LiFePO4 battery power supply
@sumotan

It's a very good question.

LifePO4 battery has pretty good power capacity. I have an A123 26650 cell for powering my McDualXO with a pair of OCXO. For years I charge them every 7 to 10 days without having any problem. It would be more than 24 hours for continuous run. The current was around 100mA.

Though LifePo4 battery cells can deliver up to 50A huge current, however, as a kind of chemical battery, any kind of over dis-charge will cause damage to them in some degree, as well as possible damage to the audio gears. So, solutions have to be taken into design consideration:

1. There will be a programmable timer to turn off the LifePO4 battery power supply when time is up, just in case of forgot doing so;

2. An isolated monitoring circuit will be implemented for over dis-charge protection. When dis-charge voltage is lower than the threshold, say 3.15V, the controller will switch it to charging state automatically.

On-board controller will take care of all these kinds of jobs.

BTW, I use A123 26650, I'm very happy with the sound quality.
https://www.batteryspace.com/prod-specs/6610.pdf

Regards,
Ian
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Old 11th September 2018, 03:45 PM   #33
sumotan is online now sumotan  Indonesia
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Thank you kindly for the explanation Ian

Cheers
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Old 12th September 2018, 09:52 PM   #34
wtnh is offline wtnh  United States
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Quote:
Originally Posted by iancanada View Post
@sumotan

It's a very good question.

LifePO4 battery has pretty good power capacity. I have an A123 26650 cell for powering my McDualXO with a pair of OCXO. For years I charge them every 7 to 10 days without having any problem. It would be more than 24 hours for continuous run. The current was around 100mA.

Though LifePo4 battery cells can deliver up to 50A huge current, however, as a kind of chemical battery, any kind of over dis-charge will cause damage to them in some degree, as well as possible damage to the audio gears. So, solutions have to be taken into design consideration:

1. There will be a programmable timer to turn off the LifePO4 battery power supply when time is up, just in case of forgot doing so;

2. An isolated monitoring circuit will be implemented for over dis-charge protection. When dis-charge voltage is lower than the threshold, say 3.15V, the controller will switch it to charging state automatically.

On-board controller will take care of all these kinds of jobs.

BTW, I use A123 26650, I'm very happy with the sound quality.
https://www.batteryspace.com/prod-specs/6610.pdf

Regards,
Ian
Hi Ian - I am looking forward to your progress on this. Just as a reference, I built a quick and dirty LiPO supply for my Allo isolator and Boss DAC. The Raspberry Pi is powered by a 5 volt linear supply (which also powers the battery charging module). 2 relays are used to switch the LiPOs between parallel for charging and series for powering the isolator. A third relay switches the power out to the isolator between battery and unregulated power, so that the isolator and DAC are totally galvanically isolated from the Pi.

The relays are controlled by a GPIO pin which goes high when the player is active (it is running PiCorePlayer). When the player is quiescent, the batteries are switched into charge mode. This works well enough so that the batteries always have enough charge for extended listening.

This is pretty simplistic, so for my next project, I would like to implement your idea.

Pictures (one is the custom PCB I made for this) and schematic attached for anyone who wants to duplicate.

Regards

Whit
Attached Images
File Type: jpg DSC_0044.jpg (1.04 MB, 1561 views)
File Type: png PCB.png (130.6 KB, 1568 views)
File Type: png Schematic_Battery-Charging-Circuit_Sheet-1_20180727103356.png (78.2 KB, 1569 views)
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Old 13th September 2018, 07:42 PM   #35
hellokitty123 is offline hellokitty123  United States
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Ian, why not just do Regulator -> LifePO4 -> Super capacitor?
The regulator will keep the battery and the capacitor charged 100% of the time and the battery+capacitor act as low impedance power delivery while also filtering out the remaining noise from the regulator.
The best of all worlds.
I never understood why people want to place a battery or super cap before the regulator.

Last edited by hellokitty123; 13th September 2018 at 07:51 PM.
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Old 13th September 2018, 09:06 PM   #36
analog_sa is offline analog_sa  Europe
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Quote:
Originally Posted by hellokitty123 View Post
Ian, why not just do Regulator -> LifePO4 -> Super capacitor?
The regulator will keep the battery and the capacitor charged 100% of the time and the battery+capacitor act as low impedance power delivery while also filtering out the remaining noise from the regulator.
The best of all worlds.
I never understood why people want to place a battery or super cap before the regulator.
Using batteries as a capacitor replacement is easy and gives excellent results. But unlike Ian's project it does not provide a galvanic or noise isolation. Combining batteries with supercaps, otoh...not sure what that achieves.
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Old 13th September 2018, 11:06 PM   #37
hellokitty123 is offline hellokitty123  United States
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Galvanic isolation can still be had. I'm currently using 7.2v Nicad batteries to power the 5V regulator circuits.
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Old 13th September 2018, 11:51 PM   #38
hellokitty123 is offline hellokitty123  United States
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I'm just curious as to what LifePO4 batteries or super caps add to the equation that regulators don't.
If you slap relays in between them you are going to add a lot of HF inductance between the supply and ground. Plus what little information I could find about LifePO4 and super cap impedance at RF was not very useful.
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Old 14th September 2018, 12:33 AM   #39
wtnh is offline wtnh  United States
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Quote:
Originally Posted by hellokitty123 View Post
Galvanic isolation can still be had. I'm currently using 7.2v Nicad batteries to power the 5V regulator circuits.
Nicads have pretty low power density and limited charge/discharge life cycles. Not sure what the noise factor is, but you should consider lithium chemistry.

Cheers

Whit
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Old 14th September 2018, 12:41 AM   #40
hellokitty123 is offline hellokitty123  United States
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Yeah I know, couldn't find any lithium battery packs in the right voltage so I went for some Nicad RC batteries on ebay. They are post regulated twice so noise is irrelevant.
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