Power Bank that is always connected to a charger - effective?

[Ron Kuper]

Hi all,

In measurements threads, an option to use a power bank for USB powered DACs is mentioned.

The advantage - stable power.
The disadvantage - having to charge the power bank from use to use / time to time.

I wonder -
1. Do we know if, while connected to a wall charger, the power bank still isolates the connected devices and power them from the battery?

2. Assuming the power bank has enough juice to hold the usual listening session time, are there any disadvantages for simply having it always connected to a charger and save the trouble of remembering to connect/disconnect it at the end of each session?

What do you say?


Ron

 

[DonH56]

Disclaimer: I do not know any details about any specific power banks.

When charging a battery source is likely to be noisier than usual and the charging circuit is rarely isolated so I would expect more problems with things like ground loops and line-coupled noise (from hot, neutral, and/or safety grond paths). Charging circuits can be cheap and dirty (noisy) especially when not intended to be used when the battery bank is employed. Batteries also have finite recharge cycles and a constant trickle charge can reduce their lifetime. I would not leave the charger connected.

But, I would design a power supply and component power integrity network that obviated the need for batteries, which aren't all that great a power source anyway.

FWIWFM -- take with block of salt! - Don

 

[Ron Kuper]

You are right about doing it right with a good power supply... Just a bummer that they can be overpriced.

Here is an explanation I've found about the OP, doesn't look good for the cause:

http://blog.ravpower.com/2017/10/danger-and-damage-of-pass-through-technology-for-batteries/


I guess a reverse logic which would charge smartly to extend battery life and disconnect chargeing when power is drawn from battery could have been a better solution for audio. Probably won't happen and it does it would come with the "Audiophile" tax...

 

[DonH56]

Smart chargers are readily available that help keep the battery conditioned. I am not sure why someone has not built a circuit that uses a relay to completely disconnect the battery from the line when in use and not charging, but I think disconnecting the safety ground would violate various electrical codes. For those that believe any connection to the wall adds noise then simply removing any connection is the only tenable solution.

 

[Speedskater]

but I think disconnecting the safety ground would violate various electrical codes.

If it got it's AC power thru a double insulated wall wort, it wouldn't have a Safety Ground wire.

 

[Ron Kuper]

simply removing any connection is the only tenable solution.

But extremely inconvenient.

I think disconnecting the safety ground would violate various electrical codes.

Non of the usb chargers (inc. originals from LG, Samsung, Apple...) have a ground pin. All are just 2 pins.

 

[amirm]

I wonder -
1. Do we know if, while connected to a wall charger, the power bank still isolates the connected devices and power them from the battery?

Do they run that way? I always assumed when you were charging them, they would not supply power. If they do, I can measure it with and without charger and see if there is a difference.

 

[DonH56]

Inconvenient, yes, but that is potentially the price audiophiles who want complete isolation must pay.

Was not thinking about the two-wire solutions; true, no safety ground, so presumably they could switch both sides of the line to completely isolate the output. But someone would actually have to implement that circuit.

 

[Ron Kuper]

Do they run that way? I always assumed when you were charging them, they would not supply power. If they do, I can measure it with and without charger and see if there is a difference.

Apparently some do.

Definitely won't hurt to measure


Btw speaking of batteries, when you test USB power from your laptop... Isn't it sort of battery powered?

 

[amirm]

Btw speaking of batteries, when you test USB power from your laptop... Isn't it sort of battery powered?

It is usually plugged in because I don't want to drain the battery during long tests. I have tested it with laptop battery alone in some specific reviews where that was brought up and it made no difference.

 

[Guermantes]

Somewhat related: There was some interest in using power banks with pass-through charging as a UPS for the RPi. If power was cut to the charger, then it would continue to power the Pi until power was restored. There were some reviews but mostly they found that the power banks would not switch cleanly from battery recharge mode to device charging mode and thus caused the Pi to reset.

The reviews did, however, identify some pass-through chargers which may be helpful to the current topic. Here is one comparison:
http://blog.myombox.com/connected-o...ries-for-raspberry-pi-smartphones-and-tablets

 

[amirm]

Very cool. I may get one to measure.

 

[Occamsrazor]

A 12v option.... http://www.powerinspired.com/product-range/ipower-dc-ups-system/