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Did I screw up my power converter? Answered

my motorhome has a115v ac to 12v dc with a split transformer, the 2 outer leads went to press in diodes and the middle lead went to neg or pos.(cant remember witch)  it is 40amp converter. one of the diodes was bad and i was only getting 6 volts out so i replaced them both with 40 amp 600 volt ZENER diodes. Are the zener diodes the wrong type to use, all seemed good except my neg and pos polarity were reversed coming out of the power converter, I reversed the terminals at the hook up so polarity would be correct.  Could this discharge my battery when its not connected to 115v.

                                                                                            Thank you, Duncan

7 Replies

dsr. (author)2012-04-14

Sorry the may not have been zener diodes, this is what I used to replace both diodes with. SI Indutrial Rectifier, stud mount
PRV- 600V max. Ifsm-500amp max. IF- 40Amp max
VF-1.2V@ 40Amp typ. DO5 cathode to case.
Made by: NTE Electronics Inc Part # NTE5994

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steveastrouk (author)dsr.2012-04-14

PRV = Peak Reverse Voltage - in other words, what's the highest voltage you can put across them backwards.

So, just rectifier diodes. Pictures, and a wiring diagram might help.


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steveastrouk (author)2012-04-14

Zeners are EMPHATICALLY not the right choice...

And I ain't seen any that big anyway !

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Toby Robb (author)2012-04-13

He means a centre tap transformer and a rectifier bridge. You should get 6 volts AC from the centre tap to each of the outer windings I`d say. From outside tap to outside tap is probably 12 volts AC. If you are only using bulbs AC would be fine, but if u need DC current you have to rectify it with diodes. Often u can buy a bridge rectifier in a package. Maybe you will need to mount a heat sink to it if you are drawing a lot of current, as well as some filtering capacitors.

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iceng (author)Toby Robb2012-04-13

a power transformer rectifier with a secondary output center tapped
transformer = xfmr does only need 2 diodes.
I call that a battery charger not a converter.


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iceng (author)2012-04-13
Wow do you have difficulties;
  • I don't believe there are 40 amp  600 volt Zener diodes.
  • Yes, Zener diodes are wrong to use in this case.
  • Split transformer makes no sense.
  • Press in diodes exist to be easily cooled and rarely fail.
  • Press in Zener diodes are almost unknown
  • Diodes can regrettably be of reverse polarity :-(
  • Never mess with polarity reversing of a converter on your own !
  • Whenever you play reverse games you can set battery discharge into action.
Please take your RV to a good service garage because what you describe can be more then a damaged converter maybe even a high
current fire hazard.
  1. I have an RV and there is an on board AC Line to 12VDC charger for 2 batteries.
  2. The RV battery lights and the Engine Start and road lights battery.
  3. The diodes that charge the batteries individually are both anodes hooked to the charger + output and the other lead of one diode the cathode goes to + battery one while the other diode lead cathode goes to the + battery two.
How did you determine which diode was bad ??
How did you determine there was a problem with any diode ?


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Awesome-aniac (author)2012-04-13

Zener diodes were not the correct choice.

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