That all sounds great but I'd rather have an over-spec alternator than have to monitor alternator temperatures personally, or chance losing charging capacity due to an overload. A 60A fuse only means that the wiring is expected to handle more than 60A, and the load is expected to draw less; it doesn't really indicate actual load. I would expect 40A out, same voltage in and out, would draw 42A to 44A for a reasonably efficient regulator.

I think the inverter power being derated by Toyota from 400W (in park) to 100W (in drive) is indicative of how much (or little) power is available from the alternator. I agree, in a lot of cases the stock alternator is probably fine for this application. I'm still going to hold out for the DC Power alternator, just because I want the extra capacity, and may add more loads later.

Thanks for sharing your solution. It sounds very useful for a lot of users.

I think I dropped in on this thread after you already made your decision, but I had a question for my own learning.

You say “rather have an over spec alternator than have to monitor alternator temperatures”.

Would the heat build in the alternator (vs the wires, if the wires were not insufficient) in the case that the charging rate of your system exceeded the available current of the stock alternator? Would there just be a voltage drop? Both?

If there are options for multiple alternators on the 4Runner, I’ve toyed with the idea of having one be a 24V alternator (seen some up to 150A) to charge accessory batteries more efficiently.


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Interesting questions and options!

24V alternator: I'd be interested in this, but given the problems fitting a new higher-capacity alternator, I suspect adding a second alternator would be crazy hard. I don't want to add a 24V-12V DC/DC for the rest of the electronics, change to a 24V starter, etc. This could be a great option at home, on a boat, or in a larger vehicle.

The available current from the stock alternator, after subtracting loads for the stock devices, is an open question. I regard the information that Toyota restricts the load on the stock inverter to 100W when driving, but allows 400W when in park, to indicate that the available current may be pretty low (100W) in some cases. Toyota almost certainly built in margin on that, but I suspect it's not more than 100%, so 200W max when driving. Several things could happen:

* The voltage from the alternator could drop so low that the starter battery might start to supply current, which would be Bad (draining the starter battery).
* The big 140A fuse that protects the alternator and its wiring could open. Replacing it is a PITA.
* The alternator could overheat if not monitored (hot day, slow speed, high load).

In general, running electronics below their ratings (usually power, but also temps, and depth of discharge and peak charge level for some batteries) prolongs the life of the electronics. Electromechanical devices like alternators also generally benefit from lower loading. A nominal 270 amp alternator that can maintain that output at a certain ambient temperature, should be a lot cooler and last longer than a 130 amp alternator for the same output, all other factors being equal (no fair comparing an oil-cooled device against an air-cooled one, for example).
@4RExplorer 's approach is perfectly valid in a "let's see what works" approach to the problem. But as he's said, he's be careful about what he runs when charging; I'd rather not have to track alternator temps, or chance losing charging capacity even with an automatic system to watch the alternator temperatures and output current.

Does that help or did I go sideways on your question?

@4RExplorer
@scfw0x0f
@2021nightshade4x4



Not sure if you missed it earlier in this thread..but I did just install the DC power alternator....and it works great.

Here is the install thread
High Power Alternator install

Yes, and thanks for breaking that trail! I’m holding off until @DCPower_Anthony issues official instructions; my mechanic is more likely to be willing to work from those than from a post here. I do electrics, mostly, and leave the really funky wrenching to others.