'23 Toyota Tacoma "Smart" Alternator defeating DC-DC Converter

Maxcamp

Looking for Victron settings from someone who has a comparable setup please.

After a lot of work wiring up a DC-DC converter and 6awg wire and fuses from truck to camper, it looked good in initial testing.  First day on road proved we're getting NO charging.  The crazily variable output of the Tacoma 'Smart' Alternator cycles within seconds from 13.6/13.7 v down to 5-6v and possibly to zero.  
using: www.amazon.com/Orion-Tr-12-30A-Isolated-Charger-Booster/dp/B07ZKG396Y
40A inline fuses between truck battery and Anderson connectors to Tab DC-DC Charger. (Yes Victron manual calls for 60A but my battery terminal fuses are also 40A.)

Hours of testing today at idle and at 2500RPM elicited this cycling of truck output below acceptable voltage ranges for the DC charger.  
Truck output averages 13.8 to 13.9v with engine running; 13.1v engine off.  
Victron is set to re-start charging at 13.6v.
Victron came set to stop charging below a 13.8v threshold, lowered it to various settings at 13.2, 12, or even 5.
Below 12v it just blows the 40a inline fuse as it is milking the truck battery.

Victron putting out 23-9-17-15-12-6-0 amps output on the Victron Monitor as fast as you can read.  Stays zero.... then maybe a minute later repeats cycle.  Voltmeter on truck input to Victron reads 13.3-13.4v input with a fixed voltmeter.  An auto-ranging voltmeter cannot settle down but seems to indicate voltage keeps cycling to 5-6v or even zero very briefly.  This is the Smart Alternator at work?

Looking for Victron settings from someone who specifically has overcome this Smart Alternator issue.
Alternatively, someone who has successfully replaced such an Alternator with no-name or high output alternator.
It has been suggested the Alternator is not the issue but the Tacoma ECU (computer) regulates this cycling.

Horigan

Have you tried turning the headlights on?  I've heard that kicks the alternator into high output mode.

Grumpy_G

That does not sound right. The smart alternator varies its output somewhat gradually (unless Toyota is different from everybody else) and even if the alternator itself drops the voltage to nothing the system should have battery voltage. From how I read your post you wired the trailer charge connection directly to the battery. Compare the voltage at the battery terminals with what you are seeing at the victron input, and if you have some long wire at hand measure the voltage drop between the battery positive and the victron input positive, then do the same for the negative side.

Maxcamp

Truck battery at rest 12.6V.  Running at idle or 2500 rpm both 13.9V.  Getting 13.9V at rear bumper Anderson terminals and at input to Victron converter.  Autoranging meter fluctuates hundredths but these are pretty close.

Amperage at truck negative ground lead with no accessories 12.6Amps; all accessories runing 33.75A.  So the Tacoma 130A alternator has lots of capacity available.

Victron input is 13.8V to 13.9V, no detectable voltage loss over the 6awg wiring from truck.
Victron output is *programmed* at 14.4v and reads this when I cut out the Tab battery terminal breakers.  When I snap on the Tab battery terminal brakers the output reads the same as the tab battery, roughly 13.3V at moment.  I used the Inverter to draw down the battery from 100% to 85% for the purpose of testing DC charging.

20A Victron DC charger behavior continues to cycle between starting to charge and promptly plummeting to zero charging for a minute, then repeating.

if I set the Victron to Engine Shutdown detection ON (the default to keep from draining your auto battery) the Victron high draw is a brief instant of perhaps 22 amps that dwindles down to zero with a few seconds.

If I set the Victron to Engine Shutdown OFF the Victron high draw is a brief instant of 35 to 37 amps that dwindles down wotihin a few seconds.  After two or three cycles this pops the 40A engine compartment resettable breaker.

Again, if someone with a 3rd gen. 2016 through 2024 Tacoma that should have the same alternator, and has a Victron DC charger, can pass along their Victron settings I'd be grateful.  Here is what I have at the moment:

Grumpy_G

I realize you're looking for a simple setting to solve the issue but there are two things working against you:

The smart alternator drops the voltage down to 12.5V if the PCM deems the battery fully charged. You would have to set the lockout lower than that to avoid it kicking in while driving but that means the battery would be discharged when the engine is off until the lockout voltage is reached. The correct fix would be to put a relay into the power feed for the rear connector which is controlled by a wire from an ignition power source.

The basic function of a DC-DC converter is to use lower voltage and higher current to generate a higher voltage with a lower current. Some back of the napkin math with your max output voltage of 14.4V and worst case 12.5V on the input side and the 87% efficiency of the converter comes out to ~1.3 times higher current on the input side vs the output side, 38-39A. Basic rule for breakers is 125% of continuous load so the breaker should be at least 50A, better the recommended 60A.

GatorEgg

Look into what the folks with REDARC dc-dc are doing.  It’s the “go to” for Tacoma folks.  Good info from them.

Blueespy

I don't think it's your alternator.  I ran power from the battery through a heavy duty on/off and fuse to a plug on the back bumper.  DC-DC is mounted inside the front tub of our 400.  Connect seven pin, connect Anderson/Harris plugs, start vehicle, turn on head lights, check power light on DC-DC is on.  For us, we have to have the head lights on.