Hiow to replace wall wart on step up with battery

I've been thinking of trying to replace the wall wart on the Benz Lukaschek step up with some form of battery power supply. Has anyone done this or have any ideas about how it might be done?
Thanks for any input.
If it is a DC power supply, it would be easy. Just read how many volts the existing one supplies and the wattage and get enough batteries to equal it and wire them in series or parralel.
Rouvin: I have the same phono unit: version T-8.
I would like to hear any suggestions you come up with as well.
I have always wondered, looking at the plug-in wire and wall wart, if an "upgrade" or "mod" to this part of the design could be an improvement. Also, does anyone know if there is much difference, if at all, between versions T-8 and T-9?
Thanks. This sounds almost too easy to be true, but I'll start looking into this
I haven't heard them side by side in the same system, but there is a bit of opinion on the two on Ausio Asylum:


...always something newer or better....
I did a lot of research on this when I built a battery supply for my Naim CDX2. I'll assume you have basic electronic skills and a multimeter. You'll need a system of switches or connectors so you can switch the batteries from the preamp to the charger.

To determine what size battery supply you need you first need the voltage output of the supply (obvious) and also the current draw to determine the capacity of the batteries you need/want. Higher capacity batteries will last longer will cost more.

Once you figure the current draw multiply that by how many hours you want it to last between charges to get the capacity in amp/hours.

Next determine what type of batteries. Go here http://www.buchmann.ca/toc.asp to get a good overview but you are basically looking at a few things:

1. cost, this includes the initial cost, how many charge cycles they can take before needing replacement, and the cost of a charger.

2. Ease of maintenance, what efforts are required to charge and maintain a proper charge for maximum life

3. Discharge charecteristics, do they maintain their voltage until depleted or does it begin to drop as soon as they are loaded down?

You are looking at NiCad, NiMH, and sealed lead acid (SLA). Disposables are cheaper up front but too expensive in the long run.

I settled on NiCad. Cheaper in the long run because they have the most discharge/charge cycles if properly maintained. The most finicky about this though and short life if not properly maintained with a quality (read $150) automated charger/discharger, but you can use it to maintain your other NiCads too. The memory thing is pretty much a thing of the past and not a concern at all if properly maintained. They also maintain a steady voltage until almost completely discharged and like a deep discharge if you don't run them until dead, which can kill them. That is not likely IF you remeber to turn it off when not listening since it will begin to distort when they get too low.

SLA are cheap to buy and easy to charge so you see them used a lot, but the voltage drops as soon as you start to use them and they don't last as long, especially if you deep discharge them repeatedly. They are best for short bursts of high current like starting your car and then being topped off again.

NiMh are good and second to NiCad for your needs but about half as many charge cycles and generally a bit more expenseive, and you still need the good charger.

Go here to compare prices. http://www.robotmarketplace.com/

Good luck. It made a significant improvement to my CD player which was no slouch to begin with.
Thanks for the info on the parameters I should be considering, Herman. A great help. Since the Naim you modified was presumably an AC unit (as is the Lukaschek)and most battery power is DC, does this add an additional parameter I should be looking into?
What I am also considering is a way to bypass most of the DIY aspects of this by using the battery supply of another step up unit, such as, the Phonomena, thinking that replacing only the connector from the unit to the Lukaschek would be easier overall. So, I'm looking for output info on the Phonomena battery pack.
The output to Lukaschek is 24V 250mA, AC.
Thanks for any info or ideas.
ALL audio equipment runs internally on DC. Most take the AC from the wall and convert it internally to DC, easily done. A scarce few don't have this AC to DC conversion and run solely off batteries. Some, like the Phonomena can run off either.

I didn't really modify the Naim. It has a plug on the back that accepts an external DC supply that Naim makes to the tune off about $4,500. It is not a battery supply but a much better AC-DC supply that bypasses the internal CDX2 supply. Using that plug it is easy to apply the same voltage that the expensive Naim supply has but use batteries.

That is similar to the Phonomena only the Phonomena external supply has batteries and a charger. The preamp has an internal AC to DC converter, or you can buy the external battery supply and the internal AC - DC is disabled.

In your case, the Benz AC to DC conversion is done in the external supply (there isn't one internally) and this DC is applied to the phono stage. This makes it easier for you since you can use the same plug to supply DC from batteries instead of the external supply.

Unfortunately the Phonomena battery supply doesn't have enough voltage for your Benz. It has 16 NimHi batteries so in series that is 16 x 1.25V = 20 volts at full charge and closer to 19V (16 x 1.2v) when it is being used, and your supply is 24V. I would use 20 batteries since they do drop a bit from the fully charged 1.25 V so 20 x 1.2V = 24 volts, perfect.

If the preamp draws 250 mA then an 1100mAh battery pack (about $100) will get you around 4 hours and a 3000 mAh pack (around $150) will give you 12 hours. Not Bad. Add a charger with supply for a few hundred with a few connectors and switches and you are in business.
Once again, thanks for all the info.

But it does leave me a bit confused. The limits of my electrical understanding must have been reached, so if this seems too elementary, bear with me.

I don't understand how the AC to DC conversion is done externally to the Lukaschek if the output from the WW is marked "24V 250mA, AC," rather than "24V 250mA,DC." The Lukaschek case, itself, is marked "24V, 3 VA" above the input connector -- a further confusing item for me.

Many of the WW's I have for, admittedly less complex, devices are marked DC on the output description. That makes it clear to me that these devices operate internally on DC.

I also e-m'd the distributor of the Phonomena and Benz about the output of the Phonomena, and their reply was that the Benz is AC while the Phonomena was DC.

So how does this all fit together? I understand what you have written about battery choice, etc. It also makes sense to me that the conversion from AC to DC for the Lukaschek would take place outside of the unit itself because of its small size. The output info on the WW and what's printed on the case of the Lukaschek, though.... The case of the Lukaschek is metal, and I assume that it is supposed to operate, at least partially, as a heat sink. It stays warm to the touch

I guess it's clear that the background issue is that I am concerned about frying this in some way, and this leads me to proceed with caution in what I might actually be a rather straightforward process.

So, what am I missing?

You are missing nothing, I was wrong. Sorry. I looked at some websites for info on the Benz and for some reason gathered that the supply to it was DC. I now look and see that it says right on the front of the unit that it is AC 24V 3VA.

The only way you are going to run this off batteries is to go inside the unit, figure out where DC regulators are, and feed DC from the batteries directly to the regulators. I doubt you want to do that.
At least, I did manage to learn a good bit from this dialogue. You are right that feeding DC from the batteries directly to the regulators is something tht I don't want to attempt. Seemed like such a good idea, though....