Question on the new diode cutouts

700rpm

700rpm

Well-known member
I have heard that the diode cutouts cause a continual drain on the battery when the car is shut off. Slow, but continual, so if you don't drive your car every day the cutout is not doing its job 100%, and your battery will die.

Is this true? :confused:
 
I have had a diode cutout for 30 +years and have no problem starting the car after 4-6 months sitting---and the battery is 14 years old and I have never used a charger except the time I left the ignition on for 3 months ---I used the best free parts I could find in the trash to make the cutout, perhaps the ones you buy aren't as good.
 
Well, it's not 'supposed to' (I bought one, but never put it on yet) but I did install a master switch under the seat to kill the entire vehicle when it's parked - as I don't drive mine every day either. and don't want to come home someday and find my barn burned down.;)
 
This is just a quick guess...

My guess is that the reverse leakage current of modern power diodes is about 1 mA (one thousands of an amp). I'm also guessing that the internal leakage current of a modern lead acid battery is about the same.

So I would say that leaving the battery in the car is about the same as leaving it on the shelf. It will run down in about the same time.

The spec sheet for the diode will give the exact reverse leakage current. If you have the part number, you can google it.
 
Our car sat for over 3 weeks without a charger, starting it, or disconnecting the battery. The battery wasn't even phased.
 
What newshirt said about battery IR (internal resistance) and diode RI (reverse current).
 
If you have a good original cut-out then why not just install one of Tom W. EVRs ?? I have not had good luck with the other cut-out style regulators.. The vendors would not stand behind them as I happen to think they were mismarked as to the ground.. I can't buy just one of anything.. There are expensive things too..
 
I just measured the entire leakage current of my car's wiring (by connecting an ammeter in place of the fuse on the starter). The total leakage, including that from my diode cutout and all the wiring, was 2.4 uA. That's 0.0024 mA!

If you drove on a rainy day and got some of the wiring damp, the resulting leakage would probably be many times larger than this. Likewise if the top of the battery was dirty.

Doug
 
I've got several model A's and some have sit for over three months with a diode installed in the old cut out and cranked right up . I install the diodes from Brattoins or Snyders myself and have never had a problem of any kind with any of them. Your best bet would be the Fun Projects can style regulator, it gives voltage regulation and installs in place of the cut out.
 
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