I have a bridge rectifier (because it was what was readily available as an integrated part) rated at 150A which I'm using to protect against intermittent reverse current (battery draining) in an automotive alternator:

image of part with schematic on label

Since there is no isolation between input and output ground, I just have it wired up using one diode (two terminals unconnected). Is there any better way to set this up? Would it make more sense to wire the alternator output to both "AC" inputs just to spread the current over two diodes?

I'm aware there are downsides to this whole setup, but it seems minimally viable for the time being until I feel like making a complete fix.


1 Answer 1


It make sense to wire both AC inputs, that is, 2 parallel diodes. The current will be splitted in 2 diodes (maybe not exactly 50%) and the voltage drop will be a little lower, and also lower power losses. Simplified parameters of these diodes are VFO=0.8 V, and RF= 3.8 mohm. Conecting 2 diodes will reduce resistance RF to 1.9 mohm . For better current distribution, connect individual wires from both AC inputs to alternator output, so wires resistance will contribute to current sharing.

  • \$\begingroup\$ Thanks for adding that final recommendation. I actually have two wires already running there, one of them currently unused, because I replaced it to rule out deteriorated wire as a cause of earlier problems. Hooking it up will in some ways be easier than bridging right at the rectifier terminals. \$\endgroup\$ Commented Sep 21, 2021 at 16:45
  • \$\begingroup\$ Sadly the output post is too short to get both cables on it and still have the nut grab, and I didn't want to risk stripping it keeping trying. But with the two AC input posts just wired together, the heat has gone way down and the battery voltage rises much faster to the expected level after cranking. \$\endgroup\$ Commented Sep 21, 2021 at 17:51

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