Stupidist Plan yet to save gas -- muzzling the alternator

Has there been some trend of supersizing car alternators since the last time I checked?

Back when I was driving cars with alternators, it seemed like 65 or 80 amps might be typical. You might upgrade to a 90 or 120 amp if you had a reason. Maybe in a bigger vehicle / truck you'd see higher than that.

A gen 3 Prius DC/DC converter is rated 120 amps.

 

electrical loading is no joke when it comes to gaining or losing mpg.

A failing brake actuator in a Gen 2 can make the car lose 3-4 mpg from the hydraulic pump running every 7 or 8 seconds.
A failing 12v battery will be similar if it needs to stay "on charge" at a higher rate than normal.
Just like the AC will drain significant MPG depending on whether it's used or not, and at what setting.
There's a reason many versions of exercise equipment use alternator style loads to provide resistance.
If someone wanted to get crazy with mpg on a Gen 2, they could even add a temperature controller to the inverter cooling pump circuit since there's really no need for it to run continuously, small load or not.

 

See: gen 3 (where it isn't just a temperature-controlled on/off, it's a variable-speed pump).

 

Hey Chappy, have been curious about this as a new hybrid owner: when did electrically-controlled / -powered ICE coolant pumps debut on Pruises? Seems genius considering how many things in a hybrid depend on ideal temperatures... but want to know if they've been a failure point before, esp on higher-mile examples (like the coolant circuit thru either exhaust or catalyst, iirc -- 2nd? 3rd-gen? Hope those aren't still being used).

 

Meanwhile, I've seen people with sailboats put alternators on their diesel engines that can pump a up near 300amps into their battery storage while auto manufactures are sending a few amps to charge their 12v while its running and being drained down.

 

and what? it's pretty much the same thing as a diesel generator. Does a sailboat diesel engine not use fuel? There's a huge difference in fuel consumption between the engine idling and when it runs with a "300 amp" load.

People put oversized alternators on cars all the time to compensate for added electrical loads. Many ice car models have different size alternators based on the option package on the car. Special Service Police vehicles come with oversize alternators from the OEM.

Auto manufacturers have some of the best engineers in the world, and they actually specialize in automobile systems. Yet, you seem to think manufacturers are stupid, and you know more. Good luck with that........

 

In a Prius, anyway, the DC/DC converter doesn't "send" any particular number of amps to charge their 12v. It puts a certain voltage on the 12-volt system, and the 12V battery takes whatever current it will at that voltage.

When the DC/DC converter is putting 14.7 V on the bus, the battery will take serious current, especially if it is substantially discharged. The current drops off as the battery gets closer to charged, and drops off more when the car chooses to reduce the DC/DC converter output to 13.6.

Gen 1 and gen 2 had a belt-driven engine water pump, and a 12-volt single-speed inverter cooling pump that's always on with the car's IG circuits. Because the belt-driven engine pump would stop when the engine did, these gens also had a separate electric pump to keep the coolant flowing through the heater core when you were using heat.

Gen 3 introduced a 12-volt, variable-speed engine water pump, thus getting rid of the last thing needing a belt, and also getting rid of the separate heater-core electric pump, and at the same time changed the inverter cooling pump to a 12-volt variable-speed type like the new engine pump (though smaller).

I have heard of very few problems with the newer, variable-speed inverter cooling pump. If anything, it seems to have been more reliable than gen 2's inverter cooling pump, which is kinda known for letting the magic smoke out from time to time (often in a way that blows the AM2 fuse and stops the car).

The electric engine pump, which is larger and works harder, has been more of a mixed bag. Mine is still going at 200k+, but there are a lot of reports of earlier failure.

 

Similar 5th gen topic?

Solution to 12V issues? Disconnect 12v negative terminal sensor plug | PriusChat

 

You could watch with a voltmeter and see whether the Subaru control algorithm raises the 12-volt voltage when you turn the headlights on. If it does, that increased voltage could increase the charging of the 12-volt battery.

The gen 3 Prius does boost the DC/DC converter output voltage when some electrical loads are turned on (as has been observed in other threads). So there's precedent for the idea that the Subaru might do something similar.

The question is the kind to be answered by seeing what the car does, not by pondering it in an armchair.

 

I've heard talk that Subaru factory batteries are undersized. Since modulating the alternator isn't a new feature, I'd suspect that first.