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I have a friend who has a MTH  PRR S1 20-3107-1 who wants to convert from battery to BCR. The engine has a battery tray made for 2 1 1/2 volt rechargeable batterys. Is a BCR a direct replacement or do you have to switch polarities because of original batteries? I've read about the need to switch polarities, but am confused as to which PS2 engines this applies to. Any help appreciated.

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No switching of polarities for PS2 3V.

Red is positive, Black is negative.

You are referring to 9V battery snaps often associated with PS2 5V systems and PS1. The problem with that connector system is, it flip flops each connection. That is why a store purchased wire connector meant to plug into a battery becomes reverse polarity when you try to make it be the connector of the capacitors as the battery replacement.

Again, the problem may be- a few of the early PS2 3V systems used AA or AAA battery holders rather than battery packs. Further, those connector systems may not have a modular plug mid harness for the newer "pack" style batteries that terminate in a connector.

So, you may find yourself either soldering or splicing connectors to take an off the shelf "BCR2"

designed for PS2 3V systems into the existing wiring going to that battery tray system.

A solution would be to buy the matching newer PS2 3V charging harness that would plug between the PS2 board and your BCR2 with no soldering. Find that harness using "charging" and then refine with "3V"

bcr2 ver 3 trans


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Last edited by Vernon Barry

Vernon, I think you nailed it, this S1 is shown as a mid year 2003 delivery. It has to be one of the earliest 3 volt engines. My friend said the connectors from the 3 volt BCR DID NOT match the connector on the board. So can the leads from the battery tray be used by soldering them to the BCR? Red to red and black to black? Then plug BCR to board.

Last edited by spudder

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