Help With Cz20 Battery Pack Wiring!!!!

[PimentoUK]

Not quite right, Joe, a couple of diodes are missing. I was going to wait for DB1000 to reply before posting up some design details. Seems like I'd better do it now ... it would be useful to other folks, anyway.

Update1:

Here's the electrical wiring diagram for the 4-cell board. The two diodes are general-purpose 1 Amp silicon diodes, probably 1N4001 , you could substitute other types, including 1N4002 / 1N4003 / 1N4004.

If you go with the simpler "dual 9V batteries" arrangement, the diodes are not needed, see diagram attached.

Update2:

Here's a pic of the battery holder sold on eBay.

And a Pic showing the PCB tracking of the board. Simple enough that it could be copied by cutting blank copper-clad GRP board with a sharp knife and a metal ruler.

And a pic showing how a simple dual-PP3 board could be made by hand.

[Joe Beechnut OBN]

Thank you.. I was setting here for a hour looking this thing over...I knew there would have to be something to keep the batteries balanced. This was my other picture but I was confused that the two far right negatives went thru diodes to a positive out. Then the two far left positive went to a Negative out. I see now I had the batteries backwards. Crazy but I love puzzles like this.

 

[PimentoUK]

The primary purpose of the diodes is to prevent a 'strong' pair of batteries charging-up a 'weak' pair. Primary batteries generally don't care for being recharged ( except in specific ways ) , so diodes block charging current flow. In practice, a strong battery-pair will be drained first, until the voltage starts to match that of the weak pair, then they discharge together in a balanced way, a convenient secondary effect.

It would technically be better to use Schottky diodes in this circuit. They behave much the same as regular p-n junction silicon types, but they have a lower forwards voltage drop, typically 0.40V , versus 0.70 V. This would allow the batteries to be discharged that little bit more, before the detector stopped functioning. A suitable common type would be the 1N5818.

[locator]

On 5/25/2021 at 9:16 PM, Badger-NH said:

Is this what you are looking for?   https://www.ebay.com/itm/252678175953

Or is that the guy who ripped you off? I see no bad ratings for the seller. $40 + shipping is a bit steep though.

Apparently, he sells all kinds of Fisher stuff as well as other brands.  https://www.ebay.com/str/dmoutstandingbargainxchange

 

Did some business with dmobx in the past and all I can say is it was a pleasure, and if I am in the need for some parts I'd buy from him, no doubt.