30v Battery substitute for Avo accessory

[avocollector]

I've just acquired an Avo 8 resistance range extension unit. This is NOT an Avo 8 but a separate unit requiring 4 x 30 volt batteries. Any suggestions for substitutes??

[Sinewave]

The only thing off the top of my head is for bench use, lab power supplies.

[Peter.N.]

4 x PP3 in series x 4?

Peter

8 blr121

[Dave Moll]

Originally Posted by Peter.N.

4 x PP3 in series x 4?

Or if undervoltage (27V) is preferable to overvoltage (36V), 3xPP3 x 4, especially as I find that modern cells can deliver more than their nominal voltage.

Another possibility may be four stacks of ten 3V button cells.

It would also depend on the amount of space available for batteries.

[TonyDuell]

The BLR123 (orignally B123) is a double-length BLR121/B121 as far as I know. In other words 20 of the cells that were used in the B121 wth the contacts on the ends.

Are the 4 batteries in this unit simply wired in series to give 120V, or is the thing tapped? If the former, perhaps 10 of those 12V key fob batteries could work.

[Refugee]

I would be tempted to use a V-core regulator from an old computer mother board with a tapped choke and three or four AA cells.

[duncanlowe]

In order to get an old geiger counter working, where the HT batteroies were no longer obtainable, I built packs using a number of button cells. I used ones with the same diameter as an AA cell and stacked them in a single AA holder. Depending which button cell you choose determines how many will fit and therefore the voltage. A double AA holder with 10 in each side for example will give you around your 30v.

[avocollector]

Thanks to everybody for your suggestions - not enough room for the 4 x PP3 ideas and I'd like to keep it mobile (so no mains device) - the 3volt button cells stacks look the most likely as they would fit in the space and are available cheaply from the discount shops. The original style batteries seem to be available but at some huge price (14 pounds??) each. Another possibility is a step up 'chopper' style power supply possibly powered by 2 x PP3 in parallel - just enough room for that - but the button cell approach appeals as simplest. Thanks again for the ideas.

[avocollector]

Originally Posted by TonyDuell

Are the 4 batteries in this unit simply wired in series to give 120V, or is the thing tapped? If the former, perhaps 10 of those 12V key fob batteries could work.

Wired in series to give 120 volts.

[avocollector]

Update - not only found an elcheapo source for 50 3v cells but ex prescription pill container neatly holds 20 of them them and fits exactly in the space for the old batteries - all I have to do is drill a coupe of holes in the pill containers and fit conductors of some sort. Will try and get some pics up when done.

[G6Tanuki]

I'm wondering if you could use a couple of brass paper-fasteners [the type that look like a rivet-head with two flat 'wings'] for your contacts? I used some of these as contacts in the past when making up a "bunch-of-rechargeable-AA-cells-in-a-plastic-pioe" battery.

[duncanlowe]

Originally Posted by G6Tanuki

I'm wondering if you could use a couple of brass paper-fasteners [the type that look like a rivet-head with two flat 'wings'] for your contacts?

Beware. I tried to do this but the only ones I could find were brass coloured steel. There must be some old stock real ones around but even when described as brass I never found any that actually were.

[avocollector]

Here's some pics of the unit, the containers (each holds 20 3v cells 2032's form memory and the containers in place - I drilled a large hole in each end of the container and used a nut to make contact with the spring.