Battery power

[Chris V]

I have a couple of bits of kit like a DAC that run on 12 volt 'Wallmart' power supplies, but have very low power demands.

These power supplies seem also to be the switching type which get a worse press than the linear.

So I fancy going to battery power using say a rechargeable 7amp lead acid battery.

Here is my initial problem.

The power supplies deliver 12 volts but batteries normally deliver about 13 volts. Is this going to damage the DAC if so do I need to put a voltage regulator in the system?

[PeterSt]

Hey Chris,

I don't think anything can be in there that does not allow the 13V. However, no guarantee of course. What you can anyway do, is get youself a infrared temperature meter, measure the heat of the components inside before the battery appliance, and do the same afterwards. If there's a component (chip) that is rather hot before the change, it could be a regulator (for e.g. 5V) and that one could now get too hot when it is fed with 13V instead of 12V.
Don't ask me what s "too hot" because it depends on the component. Also, I don't like 40C already (while 100++ is easily allowed for most components).

Do not make the mistake that you (later) think that for 16V and 17V counts the same, because that certainly won't be true. Or more in battery-realm : 24V and 26V. That too has fair chance of going wrong (think of existing (possible) capacitor voltages).

Good luck !
Peter

[CoenP]

I have a couple of bits of kit like a DAC that run on 12 volt 'Wallmart' power supplies, but have very low power demands.

These power supplies seem also to be the switching type which get a worse press than the linear.

So I fancy going to battery power using say a rechargeable 7amp lead acid battery.

Here is my initial problem.

The power supplies deliver 12 volts but batteries normally deliver about 13 volts. Is this going to damage the DAC if so do I need to put a voltage regulator in the system?

Hi Chris,

A few words to set the expectations.
Lead acid is in principle a bad idea for audio. Its discharge is very noisy. Maybe there are specific implementations with low noise, but for the usual purposes this is not a requirement.
Also the voltage reduces during discharge, you will only hit the design or optimum voltage (and related circuit optimization) only for a very brief moment. Expect your sound quality to drift.
You could use the batteries with a wide input DC-DC converter, but then you re on the switching path again (which is not bad per se).

I would recommend a good linear supply, which should not be so hard to find for 12V.

regards, Coen

[Chris V]

Thanks guys for the prompt responses.

I have read that different batteries 'sound' different, and there are other rechargeable alternatives including Ni Cad and lithium phosphate. Would these be a better choice?

Scientifically its an interesting finding that a lead acid battery sounds noisy, as its just a chemical reaction, but I guess it might be the ever changing formation of hydrogen bubbles on the plates that causes variability.

Peter, I like the IR temp sensor idea - its another toy to play with

Coen, if you wouldn't mind I would like the name of that 12 volt linear supply as a fall back measure.

[CoenP]

Hi Chris,

something like this could work:

http://www.ebay.co.uk/itm/TALEMA-25VA-Linear-Power-supply-DC5V-DC9V-DC12V-DC15V-PSU-for-choose-L154-22-/121643341873

Must be many more offerings cheaper and more expensive.

I've got the HDPLEX 100W (VA) unit for my PC, which also has a fixed 12V out (and also a 19V for the laptop). That unit is somewhat more expensive of course.


regards, Coen

[Chris V]

Thanks Coen, that model on Ebay looks good and has had a good review.