2019 Tacoma Alternator - Is It “Smart”

By smart I mean: varies its output voltage according to the battery’s state of charge so as to minimize engine load and optimize fuel economy.

I am installing a lithium house battery as part of my camper build out. The answer to the question will inform how I go about it.

Thanks.

 

I don’t think it is, if it were then there would be talk about having to get the computer reset when you get a new battery. Also usually the smart alts are on cars that have the stop/start feature when you’re in stop and go traffic

 

i dunno, toss a meter on it?

 

A 12V lithium battery should have a Battery Management System integral to the battery to ensure the proper state of charge. If the one you are purchasing doesn't come with a BMS, get a different battery.

 

im reading anywhere from 12.65 - 13.2 on my short drive to work. From my phone app. If it dips below 11.6 the charging line shuts off.

 

I put a meter on it. With the engine off: 12.52v. With the engine cranked: 13.45v. After the engine had been running for 15 minutes: 13.36v. I had just driven the truck for 50 miles so the battery should have been fully charged. If I understand correctly then a smart alternator would have dropped the voltage into the 11 -> 12 volt range. Hence I conclude: not smart.

 

@computeruser6 I have a Battleborn battery and a redarc BMS. The BMS needs to know whether or not the engine is running and hence whether or not it can charge the house battery from the engine (i.e. not drain the cranking battery). For a “normal” alternator it can do this by sensing the voltage level at the cranking battery. Otherwise a separate input must be wired. Hence my question here.

 

No automotive alternator is designed to produce 11-12V during operation.

 

The third gen Tacomas to technically have a "smart" alternator. However it functions in a way that provides the factory lead acid battery with the correct voltage to charge while not overcharging which would result in extra strain on the alternator and decreased fuel economy. The third gen Tacomas are under much stricter regulations for fuel economy which lead Toyota to switch to a computer controller alternator that will only output the needed voltage and current to charge the battery efficiency. You can not charge a lithium battery with a simple solenoid, a dc-dc charge such as a RedArc bddc1225d is required to step up the charging voltage to the house battery as well as balance the lithium properly to make the charging safe. Lithiums charged improperly can result in thermal runaway and a fire.
Where are you planning on mounting the house battery?

 

I had the hood open the other day and the Alternator explained the Declaration of Independence, so it must be pretty smart...

 

From Battle Born's Manual it appears that the BMS will ensure the battery is properly charged to prevent damage; you should just be able to drop it in and have it charged by the alternator without issue.

 

So this is weird and I don't know exactly how to explain it, but thought it was relevant to the 'is it "smart"' question. I read though this thread earlier today as just installed a dual battery system in my taco about a week ago. I had just begun researching about the difference between DC-DC chargers and smart battery isolators to determine if my isolator was enough or if I needed to invest in a DC-DC charger for the system. I didn't realize that the tacoma's alternator was smart and worked in this way, so I decided I would just conduct a similar test on my system to see just how the "smart" alternator would react to charging my second battery. My setup is an Optima Red Top Group 34 Start Battery, an Optima Yellow Top Group 34 Accessory Battery, and the Keyline 140A Smart Battery Isolator.

Before I started the truck I checked the Voltage on the batteries:
Red Top: 12.42V
Yellow Top: 12.34V
I started the truck and immediately checked the voltage again:
Red: 13.91V
Yellow: 13.94V
I then turned all the auxilary lights, as well as the fridge/freezer attempting to cool to -8 F, and a 1000W power inverter running a 1500W heat gun on the lowest setting. All these accessories powered by the yellow top second battery. I watched the voltage in both batteries decrease as the accessories slowly drained the battery system until about 20 minutes in. The start battery hit 12.4 volts and the isolator stopped allowing charge to the second battery(also 12.4V)(side note: the isolator im using cuts off at 12.4V and back on again at 13.3V). But then the start battery jumped back up to 13.5V for a second and back down to 12.4V allowing the isolator to allow charge to the second battery again for about 5 seconds and then shut off again and instantly repeat this process. This went on for almost 10 minutes as I watched and wondered what the hell this "smart" alternator was thinking to create this cycle. Then then the start and second battery voltages shot back up to 13.6V each and stayed that way for the next 15 minutes.

So maybe someone here can explain this?? Because I can't. My conclusion from all my forum reading, youtube watching, and this 45 minutes spent watching a couple volt meters. I will probably just end up upgrading my alternator with a custom high output one from excessive amperage since my batteries are AGM and can be charged more than the stock alternator is able to
, beefing up my isolator to the Renogy 200A, and eventually adding a 100W or 80W solar panel to the roof. Unless someone else knows a reason to do otherwise haha.

 

Interesting..

I read the relevant sections in the SM ref charging, but there is no real "in depth" discussion on exactly how the O/P is controlled.

Was your truck idling the whole time you conducted the above tests? Did the RPM change on it's own to coincide with changes in the battery voltage you read?

There's a description of a charging system load test in the SM, and the RPM it's done at is 2000.

Also, here's a snippit from the 2GR new features PDF:



Also, the stock alternator DOES communicate with the ECM via LIN (basically serial data connection). Unless the aftermarket alternator you buy can do the same thing, you're going to set a DTC and have a CEL in your cluster, along with the annoying charging system error message.

 

So, you want to know why the system is giving the results you are seeing?
Your battery combiner/ charging relay is 'short cycling'.

Here is a Blue Sea article discussing it more effectively than I: https://www.bluesea.com/support/art...ensitive_Relays_and_Automatic_Charging_Relays

So you have some lights, a fridge, and heat gun (low) running.

At engine idle, I have to assume that your load requirement (about 1kw) exceeds your alternator output (at idle way less than 130amps x 12V) by a good margin.
Because the load exceeds the source (alternator) the voltage slowly sags. Eventually the load sag goes below the cutoff of your charging relay (or equivalent). This disconnects the load and house battery from the starting battery and charger. With the load disconnected from the starting battery and alternator, the starting battery voltage rises back to the charging level. This trips the charging relay to close, and reconnect the start battery to the house battery and load. Which sags the start battery again...

So you get a cyclical behavior. With your current setup, this is what will occur (eventually) whenever your load exceeds the charging supply.

If this is a very unlikely load, then this is no big deal in my opinion. (for example, for supplying a winch that draws huge current from both batteries, I wouldnt use a charging relay, i would use a manual switch or ML-ACR to force both batteries together.) What is a realistic load that you want to be able to support?

(Another way of saying it.. this is the expected behavior for the system you have designed. To protect the start battery function you are always having the truck charge the start battery and the house battery gets charging if the truck charging exceeds the load. To protect the start function, the start battery is being disconnected from the house load when the voltage sags.)

How often are you going to be drawing more load than the alternator can provide but you have the truck running to help? Is that a critical design requirement? When that happens does the system need to be able to handle it gracefully without manual control? Do you want the truck alternator to be able to slow the bleeding in the house battery when your load exceeds the charge capability?

What you really need to do is make some expected and worst case load usages.

For example on my dual battery truck, my house system is generally expected to provide about 100 watts max most of the time (for hours with truck off and with the truck on). In addition, when using the winch (about 3000 watts) I want to pull from both house and start batteries even though the voltage may sag, to reduce the sag as much as possible.

For these requirements, a single blue sea ML-ACR works well for me. For normal automatic mode, the ML-ACR will tie the batteries and charge both shortly after starting automatically without any user interaction. Under all typical usages (99% of the time), the ML ACR wont short cycle for me because my typical house load does not exceed the idle output of the alternator when the engine is running. For my setup, the ML ACR will short cycle when I use the winch with the truck running and the system in automatic. I dont want that, but winch usage is a very atypical load and I am fine with manual override when I do this operation.

Therefore when winching, locking the MLACR to manual tie is just part of the checklist for me to provide maximum winch power.

If you really think that the loads you were simulating are 'typical' and want the system to respond to them automatically, you will want to look into a DC to DC charger, but will need something with about 60-80+ amps at least to be able to get the most of your alternator and charge. Also note, DC-DC charger will not provide emergency starting, battery tie for winching, etc... you will want a manual battery tie switch if you want those options...

 

No it's not smart. Folks think because it won't recharge a AGM battery it's smart. Google "charging requirements for AGM batteries"
I'd plan on a additional charging plan like solar and tenders when not in use. Lithium is bad ass. I've talked to some folks that manufacture these dual battery, charging and monitoring kits and they are good for saving the truck battery from draining, and be able to drive home after a weekend of beer, busted fenders and flat tires, but you'll never be able to have disco lights, 3,000 watts of music and tiki torches out on the trail...lol. Ya Know? I'd keep it simple, or start searching for stacks of cash, and a used nuclear power plant. Lmao
Zim

 

@BigWhiteTRD
@MOC221_

Thanks for filling in the holes for me. That’s pretty much what I thought, just didn’t know if the alternator being “smart” or not had anything to do with why it cranked back up out of nowhere after short cycling. But I’m sorry if I led y’all to believe that those were intended to simulate normal loads for me. I cranked the fridge as cold as it gets, maxed out the inverter, and turned on all the lights to put a heavy load on the system just as a test. Normally I run the fridge around 35 F, use the inverter rarely to charge small accessories like batteries and Bluetooth speakers or occasionally a low power fan in the tent, and I power some small led camp lights. And I do all this on my deep cycle battery with the engine off. The fridge runs when I’m driving, but I never run the truck at idle and try to crank out power. I’m just learning more about all this dual battery system stuff. Reading and watching as much as I can but wanted to see how my system reacted. I will look into the ML-ACR as I plan on running a winch in the future and like the idea of being able to connect them manually for that. I’ll probably just stick with the smart isolator I’m using for now. Once I get my roof rack I plan on installing solar to supplement. Hoping the solar will make up for the last bit of charge to fill the AGMs. And I’m toying with the idea of downloading the vF Tuner Software from ovtuned for the 3rd gen taco when it’s released May 1st; just because it will apparently allow you to adjust the voltage regulator to allow the alternator to charge batteries up to 14.8V. See the thread on it here: https://www.tacomaworld.com/threads/vf-tuner-for-the-3-5l-tacoma.662948/

 

No problem. I was just trying to be helpful, sometimes it just becomes counterproductive I do realize.

If you are happy with your smart isolator, for winching adding the MLACR would probably be way overkill. I think this type of application should be fused and switched, so I would recommend looking at the blue sea 9001e switch, and probably some MRBF fuses... but just warning, they are large.
If you run the big wires, that can be used as a manual battery tie and winch power cutoff both...

https://www.bluesea.com/products/9001e/e-Series_Selector_Battery_Switch

https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

(I ran 1/0 wire for fore/aft winch power and battery tie, but I am prone to excessive overkill on wiring)

 

You definitely were helpful! And thanks for these links. That’s more or less what I thought the ML ACR was going to be, but after looking into it I think you’re right. Overkill for my needs. The switch and fuse would work great. Unfortunately the winch is a ways down the road, but those are going in the future mods list for sure.

 

And keep testing, it's the only to really know how your equipment will respond in real life...

 

Alternators output more than nominal battery voltage because the serve the electrical system so the battery doesn't have to.

Correct.

Personally I'm not interested in a smart alternator, or too much other additional complexity or expense to repair. I don't even want a smart key, dual zone AC or several other 'creature comforts' that seems to be the norm these days. And no, not a luddite. Worked in IT a few years, and IMHO there is a difference between useful technology and feel good technology.