Alternator amperage reserve for gen3

Starting this thread to setup a reference for future gen3 owners.

I am looking at upgrading my sound system but the first thing I will need to do determine how much amperage reserve. I have built many sounds systems in the past, some of them competition but most tuned to sound quality. Finding the vehicles amp reserve is always step one. I need to determine not only the amp draw of the different accessories but also the amperage output of the alternator at a given RPM. Failing to do so can not only cause problems with the sound system but it can also lead to some really nasty electrical and ECM issues down the road. Here is what I intend to post. If someone already has the info then please post it:

alternator model

amperage output map (mapping of the output of the alternator in relation to alternator RPM

size of alternator pulley

size of crank pulley

The pulley sizes will help determine the RPM of the alternator at a given engine RPM.

Amp draw of accessories

Amp draw of starter


As I find this info I will post it into this thread for folks that want to add electrical items to their taco.

 

Should be super helpful to know and be able to calculate how much draw different accessories will have so we don’t over do it.

 

Good luck, let us know.
I didnt find any of this info in service manual, on a previous trip down the rabbit hole.

 

I'm pretty sure I read somewhere that the models with the tow package have an alternator rated for 130 amps or something. Not sure, don't quote me on it

 

Yes the alternator is 130 amps on my rig but all 2018s have the tow package. I assume that all 2018s also have the same alternator. I looked it up in the toyota parts catalog and there is one alternator for both the 2017s and 2018s from what I could tell. I came up empty trying to find the output profile for this alternator. Parts wise it looks a lot like a 130D but I'm not going to assume anything. Looks like I'll be buying a carbon pile load tester to get the data I'm looking for. I'll be redoing an RV roof for a while so it will be a while until I can get back to this thread but trust me I will. Once I have the tester you'll get some baseline tests at idle for

I will be starting with regular ammeter readings to see how the alternator handles its current loads

+ baseline readings with nothing on
+ blower on low
+ blower on high
+ defrost
+ AC
+ radio
+ power window (one and then 4)
+ DLR lights
+ headlights
+ headlights with brights
+ AC and Radio
+ AC blower on low and radio and headlights
+ AC blower on high and radio and headlights

Once I have those readings I'll hook up the carbon pile tester, turn off all the accessories, and see what the max output of the alternator is at idle. I'll take 90% of that measured output and subtract the max accessory load to determine how much reserve I'll have for stereo upgrades. If there are other readings folks would like to see added, feel free to add them to the list. Hopefully I will be able to revisit this thread in a few weeks.

 

Did you end up running these tests? What were your findings?

Have a new system 900w RMS in my 2020 OR and am dealing with dimming lights and some noise on the lines when at low volume. Toying with the idea a new alternator and dual battery setup and am looking for as much info as possible before moving forward.

 

Subd would like to know this into myself

 

Anyone ever get this info? I’m trying to figure out if I can run a fridge and charge a portable battery out of my 12v plugs inside the cab. Any help would be greatly appreciated!

Fwiw fridge (massimo 40qt COSTCO special) probably draws around 45w while battery might draw up to 125w (undecided; looming at Bluetti AC50S & Jackery 500). I’m a beginner with electronics y’all so play nice please.