When is it time to upgrade the alternator?

Hey all!

Im slowly adding auxiliary stuff to my taco. So far I’ve got my ARB single-output compressor and a set of Hella 500 driving lights. I plan on adding more in the future, including (but not limited to)

• Additional driving/spot/fog (going 100% halogen, no LED)
• A lighting setup for the camper shell (probably LED for this only)
• CB Radio (would have preferred GMRS but the club I found runs CB)
• Possibly a mini fridge or powered cooler
• An additional (or upgraded) compressor for when I get the front locked installed and to have a better way to inflate

I’m wondering how I will know, or at what point I need to upgrade the alternator.
Eventually I’d also like to run a secondary battery in the bed, deep cycle with an inverter. That’s down the road quite a bit. But how can I determine what the stock (but recently replaced) alternator can handle?


Sorry in advance if this is a dumb question, I’m just barely learning how to do my own electrical work. In the past I’ve been to afraid to touch wires. The Hellas were my first experience (which I’ll re-do soon b/c I did a poor job soldering) and just finished up the compressor today.

 

Just upgrade it and be done with it. I don’t think anyone knows at what exact point an upgrade is necessary. Just do it, one less thing to be concerned about.

 

Fair point. I guess that’s /thread.

 

Math out your loads, then look up the spec on your factory alternator, subtract 15% for headroom, and another 0-30% for age. Compare the two numbers.

To be real, the first gen didn't have a ton of headroom to begin with so if it's an old alternator, no better time than the present.

 

Start adding up your additional power draws. Think about constant vs intermittent draws. Things like a compressor might draw 20A when operating, but it is intermittent and can easily be run off the battery. A fridge is mostly intermittent and will draw maybe 5A -of more concern here is that it will run a lot when the truck is not running, so it becomes a "do I have enough battery" problem. Your Driving etc lights will be you biggest draw. Not sure what you have in mind, but maybe 20A or so. Your Alt is capable of 100+Amps. The truck might use half of it's capability if everything is running full tilt. With what you have in mind you are maybe half way to thinking about needing more power.

This thread has some interesting info on power draws. Note that his amp numbers are a running total, i.e. the last set of gear plus the new stuff etc...

https://www.tacomaworld.com/threads...-amp-draw-and-alternator-loads-tested.821385/

 

I got the upgraded alternator with the tow package. I run a winch along with some other stuff. Got a Northstar battery when the OEM battery went south.

 

^^^^ This.

If you're going to add all that stuff, don't waste time with all the math and looking for the tipping point. Just do it and don't worry.

What you might do is see if there is a long term quality electrical shop in your area. If so, drop by and chat with them about the upgrade. They 'may' be able to accomplish that with a rebuild of your existing unit, or at least give good direction on sourcing one.

I find my local rebuild shop to produce a much better product than the big box mass reman stuff.

 

It's always easy to say "Just upgrade it" when it's someone else's money being spent. lol

The way I look at this is:
If your truck's voltage stays above 13.8V when everything is on & running (including your truck's headlights, and also the A/C blower fan on Hi), the alternator is sufficient. If the voltage drops down to that of battery level (<13.0V), then the alt is not carrying the load and is drawing off the battery.

Your alt will put out less amps at engine idle speed. For most people, this shouldn't create an issue as long as it can carry the load at just above idle (1200 RPM or so), however if you spend a lot of time idling, then you'll probably still want to consider an upgraded alt (a smaller pulley for the alt can be another option in this scenario).

 

+1.

speaking as someone that routinely upgrades my vehicles with around 2,000 watts of audio gear, "just do it" is a horrible way to go about things.

i've never needed to replace an alternator on any of my vehicles.

also, many upgraded alternators will require a higher rpm in order to maintain the rated power output. i've seen a number of people get stuck with this, where they expect the upgraded alternator to make rated power while idling, but it only makes rated power at 1.5k-2.5k rpms...

the next questions i'd have is "how much of that will be running at the same time?" and "how much will be running 100% of the time?"

i think once you start digging into how often the devices are using power, most will fall well within the range of the factory alternator, when the truck is running.

but running power and non-running power are two very different animals.

non-running power requires appropriate battery sizing, as well as isolation/low voltage protection on the starting battery so that you can drain battery power, but still have enough juice to start the truck and leave from wherever was called 'home' for the night.

but that said, why halogen-only add-on lights? with led and hid tech, halogen tech has almost entirely stagnated since the early 90's. they're also one of the least efficient options for both power and output specifications.

 

I can see a wiring upgrade like a big 3. A really good battery with high CCA and a big reserve. A higher amp alternator should only be added if your battery is dying or there is a clear issue with charging. A multimeter can confirm if you are charging OK with all things running like lights and fridge on Etc.

 

Some of us, our eyes don't play well with the output of typical LED offroad lights (too much glare/too bluish).
HID is a great option if you don't have 2-way radios (or you don't drive in fringe FM reception areas much).
For me, halogen was the only practical option.
GOOD quality halogen lights do put out impressive amounts of light, especially deep into the distance (I have Hella 4000c driving lights wired w/relay). You are correct that they are inefficient compared to LED though.

 

Lots of good advice here, thank you for all your replies- don’t have time to read through all of it at the moment but did want to respond to the question of why I’m going with halogen lights.

Answer: it’s an aesthetic thing for me. It’s a truck from the 90s. In my opinion halogen lights look more appropriate, and it better matches the dream build I have in mind for my truck. I’m not terribly concerned about efficiency and I’m using high-end lights (will be all either Hella or KC), which will be enough for my purposes and will look the way I want it to.

 

fair enough.

i'd also highly recommend looking into lightforce halogens. if hella cornered the market mostly due to their marketing ability, lightforce did it on sheer willpower for designing the best optics they possibly could. very much the same as baja designs. given the bulb types, their designs transitioned well into the hid market, and they held a significant market share well into the led era with their superior halogen designs that still have a better reach than even many current mid-grade led options.