2023 Smart Alternator incompatible with DC-DC Charger

I've read that the windshield wiper fuse is a good candidate. Have not done this myself.

 

thank you will try that.
windshield washer 20amp , wiper 30amps

 

Dumb question - does the ‘smart alternator’ setting on the victron not help?

 

This is not a "smart" alternator issue imo. The alternator does not drop output to 7v. What I suspect is you have too much inductance in your cable going to a negative impedance load. I suspect this is also what is causing your fuses to blow. You cannot accurately see peak inrush currents and how low your input voltage is going without an oscope. As the voltage dips severely due to inductance in the lines, the dcdc will draw more and more current.

Also, the one minute reset cycle you are seeing is most likely an undervoltage reset time constant in the dcdc.

To prove this, do a quick test for me. Make a short cable with the same gauge wire, 6awg if i remember correctly, and hook it directly to the battery terminals. Now also have a short cable for the output to the battery you are trying to charge. This will prove whether or not it is an inductance issue and I have a few tips to fix that. Let me know.

 

I use the same victron dcdc charger in my trailer with a 2021 t4r. I also have 6awg marine grade wire ran from the battery to an anderson plug. I do experience a little voltage drop (~0.3v) but that is expected. I also run a 60a breaker on it at the battery and it hasnt blown. However, I have yet to experience any of these issues so i am intrigued. Admittedly, i am not a certified electrician some of this is a bit over my head.



i know inputs arent attached to dcdc in the pic.. it is from install but i ensure you, all is operational

 

The cable probably doesn't have much inductance but scoping the voltage could really help. This battery-operated scope is a great value for how cheap it is:

$117 HDS242 Oscilloscope, 40MHz Bandwidth 2CH Handheld Oscilloscope Multiumeter 2 in 1 Digital Oscillograph for Electronic Measurement, Circuit Design or Test

https://www.amazon.com/gp/aw/d/B09BV5C9XK?ref=ppx_pop_mob_b_asin_title&th=1

I also like the idea of reconnecting with different wires just to force some kinds of errors/problems to surface.

 

Not sure why you think it doesnt have a lot of inductance when what he is describing is around 20 ft x 2 (round trip) of length.

 

For parity, what frequency are you assuming? Agree scoping it could help.

 

It's a dcdc converter with some high di/dt transients. I am not worried about any frequency content on the input power lines. He isnt even able to start up his dcdc converter it sounds like. This has all the hallmarks of undervoltaging and resetting the dcdc.

 

Of course all this is assuming he can crimp properly.

 

Agreed about all sorts of spectral response but how much power lives in the reactance and how does it all average out. 20 ft of 6 AWG wire has 10 uH so you will start to see phase shift at several kHz due to the wire. Have wired high current switching units deep into a trailer and never had power factor show up, yet. Glad to see you know what you are describing, would bet the issue includes something else too.

 

Honestly this is all conjecture since OP needs to give us more info and pictures. Another quick test is to just bypass dcdc, and power up all your trailer lights with your main battery, essentially putting a known resistive load on it, so you can measure total round trip resistive voltage drops and rule out inductive voltage drops.

 

Totally agree, measuring resistance of a known load and running a load test through it with 12VDC would be a good place to start. A simple but useful known resistance could be at least one incandescent auto headlight to pull at least some power if you load test it.

 

Im wondering if OP will actually take our advice and troubleshoot. Itll be much cheaper than trying to buy a new alternator or dcdc.

 

I know the OP does not have a renogy but i found this on there dc to dc charger FAQ section.

This battery charger is designed to work with both conventional and smart alternators. However, because conventional alternators maintain a consistent voltage during charging, while smart alternators adjust their charging output based on operating conditions, it is necessary to connect the charger to the smart alternator using the IGN cable (ACC labeled) from the product through the Vehicle Ignition Port.

 

this is the same as the victron, how much voltage does the renogy/victron needs from the ignition fuse to tell the charger that the vehicle is on/off.

 

Is this Victorian isolated or non isolated

 

You can have the regulator changed on your stock alternator to a one wire just need to feed it power on ignition and you will have 14.8 volts this would effectively bypass the smart alternator function. I’m doing this with a rebuilt 180 amp Highlander alternator cranked up to 390 amps. No charge light on dash either!

 

Are you suggesting modifying the stock 120A alternator internals to bypass the LIN management. LIN is a digital signal instead of a steady state DC voltage. Was your Highlander alternator LIN controlled?

 

Tell me more! I don't know the details of the existing alternator... it's two wire? How hard is it to pull the alternator and swap? Looks hard to get to. Thinking I could swap in a modified one and if it creates computer issues swap the oem back.
Thanks for your input.