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.

 

As no one was quick enough to beg me not to post the next bit, here is your punishment ...

Part 2 for those who have just woken up face down on their keyboard

The next great idea was to lower that initial high charge voltage, the partially sulphated battery reached 14v very quickly, then a drop back to 13v and the alternator was no longer under high torque load ......
The bonus was, a much increased sale of replacement battery, great for the dealer servicing profit line and parts sales ....
Replacing the mechanical fan with electric fans also improved the fuel numbers, reduced load on the belt to drive the water pump, so you could use the back of the pulley to drive the pump and introduce the single serpentine belt that loops around the moon and back..... easier for the service tech to change so you increase drivebelt sales as well ......

The only fix, add a small maintenance charging session at least once a week to recharge the battery and maintain it is a better state of charge ..... or change to an LFP chemistry start battery, but out of the engine bay heat, and it will absorb that 14v until it is 98% charged, the 13v will hold it there, never need to replace a start battery again .....


The LFP is highlighted because not all lithium batteries are the same, but the LFP battery won't burst into flames if not cared for with kid gloves and a special battery management system (BMS) but something like these induction balancers are a good idea to fit to avoid a single cell overcharging and wrecking the battery if it's a sealed type with a built in BMS ...... that was actually designed for pushbike and toy battery capacities, not start battery/auxiliary batteries.

Naturally, the introduction of hybrid technology eliminated the alternator completely, along with the starter motor in a lot of cases ..... and even anything belt driven in a number of cases ..... the 12v aux batteries is still required, but using an LFP or Sodium ion battery and induction cell balancer is the answer to having a 12v battery that lasts longer than the traction battery .....

T1 Terry

EDIT: The induction 4 cell balancer is an HA02 battery equaliser, it says 48v but that just refers to balancing 4 x 12v batteries in series, they will balance 3.2vdc or even 2.8vdc cells in series