Safe for my TV alternator?

kolmansoifer · May 11

Hi all,

2021 320s BD.
I recently replaced my stock lead acid with 2 x 100 ah Battle Borns.
I added a Vic 100/20 charge controller for a 220 watt suitcase panel and will continue to use my stock Vic 75/10 for the roof panel.
I'm super happy with how the project turned out and I had a ton of fun - and everything seems to work!

Is my 2021 Tacoma's stock alternator in danger due to this upgrade?
I did not add a DC to DC charger.

Thanks for any info,
KS

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Horigan · May 12

I would add a DC to DC. One, to protect you're alternator and two, to prevent your Tab battery discharging and over-charging your TV battery when the engine is off. I would pull the fuse in your 12V line to the trailer until you get the DC to DC.

donmontalvo · May 12

Not sure about Toyota Tacomas, but on my 2021 JLUR, removing the fuse would disable the trailer's electric brake system.

I was mistaken, posted a correction.

pthomas745 · May 12

When lithium batteries first came on the scene, there were lots of comments and discussions about "burning down your vehicles alternator". Victron had a video from 2013 that they only took down a year or so ago showing a "burning alternator" and a lithium battery.

Since these battery types have become the overwhelming battery of choice in millions of different applications, these fears seem to have disappeared.

elbolillo · May 12

With factory installed 7 pin the amp loss between the gauge of wire and distance will not allow for enough power to burn up a alternator.

Maxcamp · May 13

On your 3rd gen Taco the 10 ga 12v charge pin is only active with ignition on.
Confirmed on my 2023. I leave the trailer connected when stopped.
https://www.tacomaworld.com/threads/7-pin-trailer-connector-wiring-diagram.455153/page-2#post-26018393

If your charging system needs 14.x to fully charge, the Taco puts out 13.3 to 13.4v which will not balance lithium batteries. The ten gauge TV wire will limit amperage. I got little to no charging on my 2021 to two 100ah Battleborns.

While I installed a Victron Orion TR-Smart 30A DC to DC converter in the Tab (and TV 4ga wiring w/70A breakers), I still get poor charging (averages 7 amp hours) due to the Taco computer directing the "smart" alternator to constantly cycle from 13.4v down to ZERO volts multiple times a minute. This fools the DC converter (I tried three brands!) into thinking the engine shut off and trips charging off for tens of seconds each minute. Very frustrating. You can watch the Victron Monitor spin down from 30A charging to 25..21..18..15..etc to zero very quickly and stay at zero for tens of seconds before restarting cycle.

No solution after many posts here and on Tacoma World forum.

Others with variant systems have reported no known problems however none have stated they use the Victron charger or monitor output with a DC ammeter and/or Victron monitor.

Tacoma World reports you cannot overcome the TV computer issue with a non-smart alternator; generates errors elsewhere.

I would love an alternate solution. Let us know how you make out.

Horigan · May 13

donmontalvo said:

Not sure about Toyota Tacomas, but on my 2021 JLUR, removing the fuse would disable the trailer's electric brake system.

The way my Highlander is wired, there are separate brake control and 12V wires going to the trailer. I pulled the 12V fuse. The trailer should have the battery switch on during towing to provide braking 12V power, particularly for the emergency brake system. My brakes still work with the 12V fuse pulled.

Marceline · May 13

Maxcamp said:

On your 3rd gen Taco the 10 ga 12v charge pin is only active with ignition on.
Confirmed on my 2023. I leave the trailer connected when stopped.
https://www.tacomaworld.com/threads/7-pin-trailer-connector-wiring-diagram.455153/page-2#post-26018393

If your charging system needs 14.x to fully charge, the Taco puts out 13.3 to 13.4v which will not balance lithium batteries. The ten gauge TV wire will limit amperage. I got little to no charging on my 2021 to two 100ah Battleborns.

While I installed a Victron Orion TR-Smart 30A DC to DC converter in the Tab (and TV 4ga wiring w/70A breakers), I still get poor charging (averages 7 amp hours) due to the Taco computer directing the "smart" alternator to constantly cycle from 13.4v down to ZERO volts multiple times a minute. This fools the DC converter (I tried three brands!) into thinking the engine shut off and trips charging off for tens of seconds each minute. Very frustrating. You can watch the Victron Monitor spin down from 30A charging to 25..21..18..15..etc to zero very quickly and stay at zero for tens of seconds before restarting cycle.

No solution after many posts here and on Tacoma World forum.

Others with variant systems have reported no known problems however none have stated they use the Victron charger or monitor output with a DC ammeter and/or Victron monitor.

Tacoma World reports you cannot overcome the TV computer issue with a non-smart alternator; generates errors elsewhere.

I would love an alternate solution. Let us know how you make out.

Thanks for sharing this information. I have a second generation Tacoma (2015) and have been thinking of installing a DC-DC charger. Do you know if I would have the same issue? Or did this start with 3rd gen?

donmontalvo · May 13

Horigan said:

donmontalvo said:

Not sure about Toyota Tacomas, but on my 2021 JLUR, removing the fuse would disable the trailer's electric brake system.

The way my Highlander is wired, there are separate brake control and 12V wires going to the trailer. I pulled the 12V fuse. The trailer should have the battery switch on during towing to provide braking 12V power, particularly for the emergency brake system. My brakes still work with the 12V fuse pulled.

I stand corrected. I spent some time confirming the details with Jeep and Mopar, they are indeed separate on a Mopar tow connector.

4 (red) is Aux 12V and 2 (blue) is Electric Brakes.

My apologies.

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Maxcamp · May 14

@Marceline, I believe the 2cd Gen tacomas do not have the smart alternator issue. Replaced my former 2012 alternator with a larger capacity and there was no connection to the ECU.

WayneW · May 14

This question of lead acid and lithium batteries keeps coming up and I'm facing the same thing. I had a 2006 F-150 and I installed a Renogy DC-DC charger for our 2021 320 Boondock that has a 100ah LiTime lithium battery. Things worked great.

I just bought a used 2017 F-150 that has the smart alternator setup and I was wondering whether or not I should install the DC-DC charger in this truck. I currently have minimal charging through the 7-pin connector. The battery gets charged via the rooftop solar as well.

I found this informative video that answers several of the questions that I had regarding the alternator/lead acid/lithium battery charging situation. Perhaps it will help others.

https://www.youtube.com/watch?v=4pKyUMElVJo

However, there seem to be other issues, as @Maxcamp pointed out, that are still unanswered. I have my DC-DC charger wired so it's activated only when I turn on my lights. I connected an activation wire (required on the Renogy chargers) to the running light wires in the junction box of the trailer. I don't know if this would get around the issue that @Maxcamp has with his Taco or not.

donmontalvo · May 15

Today I tested as recommended, with the engine off. Using a tester connected to pin #4 (Aux 12V+ Charging) and pin #1 (Ground), and the tester lit up. So until I sort out whether to install a isolator relay or a DCtoDC, I will keep unplugging my Jeep when parked with the camper connected.

Not sure if I can install a second DCtoDC in my Jeep, since it has one as part of it's own off grid power kit, and then there's the additional cable to have to deal with when connecting and disconnecting the trailer.

https://donmontalvo.com/2022/03/27/main-line-overland-lifepo4-ftw/

Sharon_is_SAM · May 15

Besides adding a DC to DC charger which is the best long term fix, the easy fix to eliminate the risk of high current due to low resistance of the lithium battery is to either pull the fuse on the TV 12V charge wire or disconnect the + 12 V trailer pigtail wire in the junction box.

AnOldUR · May 15

Sharon_is_SAM said:

.... or disconnect the + 12 V trailer pigtail wire in the junction box.

We went this disconnect route. Additionally, I upgraded the rooftop solar on our 2020 320S to 310W this winter. On a recent two week trip with mostly rainy, cloudy conditions, the new panel kept our 200Ah of LiFePO4's in good shape without the need for any charging from the tow vehicle. This was with a 12V fridge and a little streaming video each night. In route we did a lot of Harvest Host stops and never disconnected anything.

elbolillo · May 15

Sharon_is_SAM said:

Besides adding a DC to DC charger which is the best long term fix, the easy fix to eliminate the risk of high current due to low resistance of the lithium battery is to either pull the fuse on the TV 12V charge wire or disconnect the + 12 V trailer pigtail wire in the junction box.

The only problem is, there isn’t a risk of high current due to low resistance of the lithium batteries via the standard 7-pin connections.

elbolillo · May 15

https://youtu.be/KXG7-EegNV0?si=Ne8gv_099tSuxyiq

Interesting video that helps explain some of the issues regarding DC to DC chargers

elbolillo · May 15

This site is also useful to calculate what a DC to DC charger might provide for charging: https://youtu.be/KXG7-EegNV0?si=Ne8gv_099tSuxyiq

As an example, I have a 400ah battery bank. If my bank was at 0% charge, it would take a 30a DC to DC charger over 13hrs to charge to full. With a OEM 7-pin wiring harness, there is no guarantee that the alternator could even provide the full 30a of charge.

Sharon_is_SAM · May 15

The LiFePO4 BMS can be a weak point according to Will Prowse. So, if it fails, what protects the TV battery?

elbolillo · May 15

@Sharon_is_SAM There are a lot of things that possibly could fail. In a recent video by Will he specifically mentioned that BMS failures are extremely rare. Regardless, the wiring in your tow vehicle will not be able to pull the type of draws to cause harm to your TV battery. And there will be a fuse protecting your battery along the wiring for your 7-pin.

elbolillo · May 15

Here is a link to a video that clearly explains charging lithium through the 7-pin.

https://youtu.be/WblbzIQgNRE?si=K4uQoJdunkptjPT8

A DC to DC charger is not needed if you only connect through the 7-pin. To fully utilize the alternator for charging your batteries you would need a much heavier gauge dedicated wire run from your alternator to your trailer battery. This would be a situation where you might decide to install a DC to DC charger. However, you will still be limited to the amp rating of the charger. The higher the max amps he more expensive the DC to DC charger.

Sharon_is_SAM · May 16

@elbolillo - thanks for that video. It does make sense that between voltage drop and limited current due to a small wire gauge. the lithium battery does not present a risk to the tow vehicle battery. So your average 10 gauge charge wire will prevent excess current via charging or discharging of the lithium battery.

I watched another video where a commenter described a smoking alternator related to a high current using a lithium battery. They referenced the Victron bench demonstration. What is your best guess of the cause of that?

WayneW · May 16

@Sharon_is_SAM I’ve seen several critiques of the Victron video. They think the demo was “designed to fail.” They used a small alternator from a Citroen car, rated at something like 70 amps, not a more realistic alternator from an SUV or truck, which would be at least twice as big as that. They used large gauge wires to facilitate high amperage flow, not smaller gauge wires that are commonly found in 7-pin wiring, and they ran the test at fairly low rpm’s with no airflow, conditions that would not happen during normal use. Vehicle movement and fans would provide cooling.

Sharon_is_SAM · May 16

@WayneW Yes, I saw that criticism in this video that supports not adding a DC to DC charger: https://youtu.be/KXG7-EegNV0?si=hRenitg-WubpDwS6
Victron does have a vested interest in selling chargers. But, they are really best for those who travel longer distances who have time to charge a depleted battery. I can see the value, but installed solar in sunny locations may be adequate for some.

elbolillo · May 16

@Sharon_is_SAM That video from Victron is very deceiving. The first battery they used also doesn’t have a BMS. There are many ideal situations for using a DC to DC charger. For the vast majority of those towing a camper, there is very little benefit.

donmontalvo · May 17

I've been using ChatGPT to help dig for info, not sure if it is helpful.

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donmontalvo · May 17

AnOldUR said:

Sharon_is_SAM said:

.... or disconnect the + 12 V trailer pigtail wire in the junction box.

We went this disconnect route. Additionally, I upgraded the rooftop solar on our 2020 320S to 310W this winter. On a recent two week trip with mostly rainy, cloudy conditions, the new panel kept our 200Ah of LiFePO4's in good shape without the need for any charging from the tow vehicle. This was with a 12V fridge and a little streaming video each night. In route we did a lot of Harvest Host stops and never disconnected anything.

Our setup is nearly alike.

2024 T@B 320S Boondock Black Canyon camping trailer, came with 380W of flexible solar panels (due to the curved roof it is great on cloudy days; not so good on sunny days). I hang a 100W solar panel in the back of the camper, on sunny days it outperforms the 380W curved panels, not so god on cloudy days). With 200ah and 480 solar, boondocking has been awesome.

2021 JLUR tow vehicle with it's own off grid power that includes a DC to DC charger and 130W folding solar panel. It was built with the Mopar Tow Package, so it has a 240 AMP heavy duty alternator.

I haven't dug much into adding a DC to DC charger to the camper. Mostly because of the need to manage another thing to connect and disconnect at the hitch. But also because as I learn more about solar power, the more I understand that wiring distance matters. I also don't understand enough to know if there might be issues in having two DC to DC chargers connected to my JLUR.

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