Maximum acceptable alternator leakage current

[dnb]

I have been engaged in a hunt for stray current consumption in the TVR when it's locked. I have found all of the components that consume current and managed to remove the undesirable ones to get the draw down to 51mA. This isn't too bad, all things considered.

One I can't remove is bugging me - the alternator consumes 5mA through the starter/alternator wire. I believe this to be parasitic losses through the diodes within the alternator. A quick look on the internet tells me that alternator parasitic loss is expected but it should be less than "a couple of mA". The 5mA is 10% of the total current consumption at the moment so while it's a small amount it is worth saving if possible since it means less worry about the battery being flat when I ignore the car for a couple of weeks.

I think mine is on the high side of acceptable, but I have no firm data to base this on and no desire to buy a new alternator on the off-chance of it being better when turned off. (Note the alternator appears to charge the battery nicely and there's no evidence of significant AC on the power supplies) Does anyone have a view on whether this consumption is normal for an alternator with a reasonable mileage, or is it showing early signs of failure?

Thanks

[anonymous-user]

imo, 5mA reverse diode leakage at room temp (say 25degC) would seem to be excessive. I'd expect it to be a LOT lower (sub 1mA probably)

[dnb]

Thanks. 5mA does seem excessive. I'll see if I can measure another alternator tomorrow to see what it does. Maybe it's time to get a new one.

[Blaster72]

As you say 50mA draw isn't unusual for any normal car. 5mA through the alternator diodes isn't anything to worry about either.

I'd say you'd struggle to get the normal draw for the whole car when off below 50 or so mA without actually disconnecting the battery.