Power Pt. 2: How-To run component off of batteries

Rob Babcock · « **on:** 14 Dec 2004, 03:43 am »

Okay, this was touched upon previously, but how would I go about hypothetically, running a component off of battery power? I'm talking a source component, not an amp. Just what would one need (ie obviously batteries of some sort, probably car batteries) and how would one implement it?

I'm thinking along the lines of running a CD/DVD transport from batteries. Will this be difficult to do?

Occam · « **Reply #1 on:** 14 Dec 2004, 04:57 pm »

Rob,

The first thing would be examining the extant powersupply and determining what voltages/currents are provided. With your example of a DVD/CDP player/transport, typically is powered by a switching powersuppy. This is actually good in that switching supplies a usually physically isolated from the rest of the circuitry, and one could (if the schematic were unavailable) actually find specifically what voltages are generated. (I'm assuming your intent is to improve the circuit and eliminate those noise artefacts generated by the PS, otherwise the smartass answer would be use a battery to an DC to AC inverter

)

But a dvd transport presents some problems as (I think)? you'd require a +5v for the digital electronics, +9 or +12v for the transport, and -25v for the electroluminescent display. The first 2 might be implemented with 2 series connected 6v SLA batteries, some zener diodes as shunt regulators (capacitive bypassed zeners in the 5-6v region are quite quiet) or simply use resistors and caps, but the electoluminescent display could(or not) be problematic..... nor am I familiar with the typical ps switching converters used in EL displays, but your display might be driven with an application specific chip that can be driven with a +5.
The analog output ps, usually 12-18v + and -, might be ignored if the player is to be used only as a transport.

The bottom line is you need to find out what the powersupply is outputing.
A schematic would really be helpful.

Please realize my comments are based upon absolutely no hands on experience..... and I answered because no one else stepped up to the plate.

A solid state preamp or certain PWM, Class D, poweramps are far more straightforward. There obviously are portable/car DVD players available which have already addressed these issues but I'm assuming you're talking about converting an existing mains powered unit.

Rob Babcock · « **Reply #2 on:** 14 Dec 2004, 10:14 pm »

Thanks, Occam. In a roundabout way I'm interested in implementing (or trying) your "smartass reply", but for the same reason you surmised. I'm curious just what type/brand inverter to use- I've read that some provide really crappy power.

I'm only at the research stage so far, but it's something I'd like to try down the road.

JoshK · « **Reply #3 on:** 15 Dec 2004, 01:57 am »

I am not sure I would bother with the smartass approach. Seems like loosing the forest for the trees to me.

Rob Babcock · « **Reply #4 on:** 15 Dec 2004, 02:09 am »

The idea for me would be too get off the grid. I figure the best power filtration & voltage regulation would to unplug and go with batteries. I'm basically trying to compare the costs & benefits of massive power treatment vs running the most vulnerable components off of batteries. Of course, bypassing the PS is a benefit, too.

Occam · « **Reply #5 on:** 15 Dec 2004, 06:40 am »

Rob,

I think the point Josh was trying to make is that an inverter, even a perfect sinewave one, while eliminating whatever harmonics, distortion, rfi, etc... that might be mains bourne, does not address the fact that voltages suplied directly to a component (all voltages supplied by batteries serving as the sole powersupply) is quite hard to better. Though it can be done by some designers, but certainly not me.....

That being said, there are dc/ac inverters with actually address quality issues and delivery varying degees of minimal distortion of sinewaves as regulated voltages.

http://www.oksolar.com/inverters/selecting_the_right_inverter.html
http://www.wholesalesolar.com/inverters.html

And actually, if you want technical expertise on dc/ac inverters, tallk to an Aussie. If you want to know practitcal application of wind and solar, and how to turn it into AC, same goes.

But no, these are not audiophile specific products, but a developing technology, programmed PWM, quite similar to Class 'D' amps, will soon be addressing those issues at minimal incrementall cost. A specifically programed PIC computer (with stored 'solved' Chebycheff Polynomials), controlling an H-Bridge, a ferrite hf transformer, a CMC and a bunch of caps would ideally provide a straightforward, efficient, and high quality solution. And as far as I know, you can't currently buy one.....

Occam · « **Reply #6 on:** 18 Dec 2004, 12:36 am »

Just a further comment. If one were to have a true sinewave inverter (these are really quasi sine wave generators, in the same sense that a Class D amplifier is a quasi anolog amplifier, in that if that 'stairstep' is fine enough, those high frequency switching artefacts are easily filtered out.) an EI transformer might do wonders. Soooo, if you've got one of these inverters, a OneAC might truly do wonders. The EI transformers in these isolation transformers have low bandwitdth, and for line filtering this is exactly what you want. These switching inverters are going to put out a 60hz fundamental, and no doubt a bunch of switching hash, unfiltered, that is perfectly adequate for sensitive use, computers, copiers etc... but not 'audiophile' use. But an isolation transformer with properly sized capacitor before and after (just like the output of a Tripath amp, except you're using the inductance of the transformer instead of a torroid inductor) should clean things up quite substantially.

Please, please don't go out and spend your hard earned dollars to try this. If you happen to have access to such an inverter [Samlex, Exeltech or GoPower, something putting out <2%THD] and an isolation transformer, I'm simply wondering how well this would work....