DC charger project in LA

[TravelHabit]

While finishing my Victron Muliplus installation I started dreaming of a DC-DC converter project for our 2022 GD 22RBE. Initially I looked into buying a stand-alone generator for charging off grid but my dream was to avoid that extra weight and hassle by using the TV alternator as my generator. Why not have the ability to plug into the TV at a campsite to recharge the batteries when needed? It seemed like the perfect solution. It seemed straightforward.

Unfortunately I did not have the advantage of this forum so it took quite a bit of research to work towards getting it right. It’s now essentially complete and for those that asked I’m now posting what I did. Sorry it got a bit long. I also recommend reading what Yoda and howson did (see this link). Both were very interesting reading. I just happened on them after googling for solar info (my current project ). My installation is different in a couple of key respects but also very similar.

As did the others, I quickly eliminated a direct connection and a simple isolator (see this youTube video: “How to not blow up your Alternator when charging Lithium” by Victron Energy). After looking at Redarc, Victron, and other manufactures, I was drawn to the Renogy DC1212-40 and DC1212-60 units. I started tracking prices with camelcamelcamel.com while trying to figure out what my TV electrical system could do. Before even completing that investigation both units went on sale at Amazon ($136 for the 40A charger and $177 for the 60A charger) so I bought both (last October) with the intent on returning one. More on this later.

The next key decision was cable and cable routing. To determine the size of cable I needed to determine the DC voltage drop from the TV battery to the charger and used the Blue Sea Circuit Wizard as my calculator (link CIrcuitWizard). The chart in Yoda’s first post cited above provides basically the same information in a chart format. Now, according to the Renogy specifications the DC1212 can handle an input voltage of 8V to 16V. That is, when providing the needed input current within this input voltage range, the output of the charger will provide the rated DC output current (40A or 60A) at the selected output voltage (determined by a DIP setting on the unit). What is great about the DC1212 is that, if needed, it will boost a voltage if it is below the selected output voltage. In my case this is 14.6V as recommended by my battery manufacturer (Lion Energy). My Battery/Alternator measurement is ~14.4V. So the unit will automatically compensate for the ~0.2 voltage difference as well as the voltage drop due to cable losses.

From an electrical point-of-view it is important to remember that a lower voltage input comes at a efficiency cost in terms of needed current from the TV. The greater the voltage drop from the vehicle battery the greater the draw on the alternator. Assuming worst case cable losses, Renogy told me that the 60A unit could pull 95A from the TV. That is quite a load on the alternator! So the question of which DC1212 to choose then comes down to cable size/length and alternator capability.

I struggled with the alternator question quite a bit (and still do). My alternator is nominally a Denso model 421000-703 rated at 230AMP. This is what’s known as a ‘smart’ alternator that can adjust output to demand. This would imply I’m in charger nirvana and could be fine with the Renogy 60A unit and relatively small AWG cable. Unfortunately, this is not the case since, as the automotive folks here know, the 230 AMPs is a rating at some operating point that is above idle.

After searching for many many hours online for specs or guidance on this I engaged both Renogy and Denso on the question. For Denso I asked the question: what is model 421000-703’s continuous duty rating at 750RPM and what happens if the load is greater than this rating? For Renogy I asked the question: how does your unit respond to insufficient input AMPs? Does it proportionally reduce it’s output? They seemed to be straightforward questions. But they both led to many back and forth emails so apparently not. Denso has surprising limitations on what they are allowed to say. After several emails with them I was transferred to someone more senior who confirmed that he and Denso USA do not have visibility to any specifications/drawings (though we both agreed they existed). So no joy there. The only useful tidbit I got is that Chrysler typically rates their alternator capability at 2000RPM. For Renogy there seemed to be major English difficulty; the emails I got were very confusing. Essentially they seemed to be telling me the charger would not harm the alternator but also recommended using the DC1212 feature to cut the charging rate to 30A when needed! I never got clarification on how they were actually ensuring the charger did not harm the alternator. It is possible that they could have a logic board that reduces the charge current as the alternator current output (charger input) drops. But that still is an open question. The one clear point I did get is the possible draw of 95A for the 60A model. This was consistent with the 90A fuse recommendation in their manual.

In the end I still cannot get any sold information on alternator capability. If anyone has good way to determine a continuous duty alternator capability at ~750RPM, I’d love to hear it.

After some time I was able to find an AMP v. RPM curve on the Denso site for what appeared to be the next lowest product line of alternators:

Using this as a guide and scaling it with the assumption that my 230A rating is at 2000RPM, it suggests I could get 86A at the jeep idle of ~750 RPM. No idea if this is a continuous duty capability or not (or even a legit extrapolation). Again, any inputs on that are appreciated. In any case, based on all this, it appeared that choosing the 60A model (and a possible 95A draw) might not be advisable.

So back to the cable size and alternator in deciding between 40A or 60A. This is one area where I deviate from other installations I’ve seen posted here. In my case the TV is a 2021 Jeep Grand Cherokee so the battery is below the passenger seat. As a result the needed cable the length between the TV battery and the charger is a little less than 35’. In the DC world this means the total round trip length is ~70’. To help the alternator out as much as possible, improve the charger efficiency, and still hoping to go with the 60A charger, I decided to keep the voltage drop as low as possible. The closer I could get to the charger output voltage the less strain to the alternator at idle. With a 4-4.9% drop the Blue Sea calculator advises 2/0 cable (assuming 70-80A draw at 12V). At a 3- 3.9% voltage drop it advises 3/0 cable. For 5-5.9% it advises 0 AWG. Checking out pricing on Amazon, the price differential for TemCo 1/0 and 2/0 welders cable (this link) was just $40 (35’ red plus 25’ black) so I elected to go with the 2/0. Routing this 9/16” diameter cable under the jeep was another matter altogether and took quite a bit of doing! So for my installation, based on the 2/0 cable, the charger will have to boost the input voltage by ~1V. Unfortunately I have no information on what that value will actually do in terms of needed alternator current but I do know that 2/0 is the largest size I'd recommend based on my install difficulty.

Another factor that helped me decide on getting 2/0 cable is that, judging by visual comparison, Jeep used this gauge for their battery installation. The negative battery terminal has a 6-8” run directly to a Jeep frame termination whereas the positive terminal has a much longer run to the engine compartment, the alternator, and the fuse box. Both using 2/0 cable! More importantly, the fact that the negative terminal is connected directly to the frame means that everything on the Jeep must be wired with this assumption. In particular the startup CCA draw from the battery is designed to work though the frame, which means the frame and engine grounding must be wired accordingly. This observation allowed me extra confidence in terminating the negative cable run from the trailer to the rear part of the frame (saving me the difficult task of a separate 2/0 run to the battery and ~10’ of cable).

I did not use 2/0 for the run between the charger and the trailer battery though. Since that was so short, and independent from TV and alternator considerations, I just used 4 AWG as indicated in the Renogy manual. Here is the install. Note I had to reshape the lugs for the 2/0 input connection to provide adequate seperation. I intend to add shrink tube insulation to further isolate these two.


For fusing, the Renogy manual recommends a fuse on the hot line between the unit and the trailer (house) battery. It also recommends a fuse between the auto battery and the unit. For the 60A unit these are 75A (or close) and 90A (or close) fuses respectively. They don’t recommend a specific type of fuse (AMG, slow blow, class T, etc.) so I went with the Tocas 70 Amp and 90A Surface-Mount Circuit Breakers from Amazon. I wanted a breakers vs a fixed fuse so I could shut down the circuit manually.


...To be continued on next post...

[TravelHabit]

The Renogy manual also points out the unit can be controlled by two voltage signals from the TV battery (~12V). There are many other posts here explaining the feature where the unit won’t start charging until it sees a signal on the “D+” input. However, in addition to that, the unit also has the interesting feature where it’s output can be reduced by 50% when a signal is put on the “LC” input terminal.

Because of the continued uncertainty with the alternator capability, the strong desire to have the ability to charge at 60A, and the need to get the installation moving forward, this secondary feature was the tipping point that caused me to finally select installation of the 60A unit for testing. I figured that, worst case, I could always get a solid 30A of charge most of the time and 60A while driving.
Of course, I wanted full control. I decided that it would be great to have a selector switch inside the Jeep so while driving I could manually toggle the unit on/off as well as to select either 30A or 60A. So, in addition to routing a 2/0 cable I also routed a 16AWG 2-wire cable for connection to the Renogy. This gives me the nice option of turning off or reducing the charge current when towing up steep grades or other times the engine was being worked hard.

Of course to do this I had to run a separately fused input line from the fuse box (in the engine compartment) to the driver and then, from there, run a 2-wire line from the selector switch back to the trailer. The line from the ignition circuit was accomplished with the Electop 12V Car Add-a-circuit Fuse TAP (this link) and some work to route a wire through the firewall into the driver area. I'ts hard to see in the photo so I'll note in the photo below that I used a 5A fuse for the tapped line (a 16AWG wire) vs the 20A original fuse. For others with a jeep I'll note the fuse type is a MICRO2 (not a MINI ATM). I found that out the hard way :(.


The actual switch turned out to be a trial and error situation. Initially I purchased a Single-Pole-Double-Throw for this at Amazon (see SPDT link) . This switch allows one to take the ignition output voltage (only live when the vehicle is on) and route it to either the D+ or the LC line (or no output at all). Well after some testing it didn’t work. It turns out the Renogy manual (and the email correspondence I had) is confusing on this point. What is really needed is a Double-Pole-Double-Throw switch (see DPDT link). That is, to work at the 50% output both the D+ and LC inputs have to be energized. The LC input alone won’t work. Below is the final switch install. It also shows how I had to wire the DPDT switch to work properly. The ignition signal goes to the middle contact. The wire going to LC is attached to the upper left contact and the wire to D+ is attached to the upper right contact.




The last part of the installation was choosing the best way to provide a connection between the TV and trailer. I wanted something that would be water-resistant and handle both the high current as well as the D+/LC signal connections. After doing some research I came across the Anderson SBSX-75A connectors (see this link) which are rated to 120A. These looked to be the perfect solution for one connector that did it all. The SBSX-75A even has a latching feature to hold a mated connection in place – a great feature while driving. Unfortunately they have not hit the market yet. Not giving up, I contacted Anderson directly to inquire about them. I was very fortunate in that they offered to provide me pre-market samples to test. It took a month or so but they finally arrived. I’ll be using those to replace the standard powerpole connectors I have now. Pretty neat.

So now with the wiring, fusing, connectors, and charger in place I’m ready to go. However, I’m still concerned about whether my alternator will stand up to a high load at idle so I’ve done some initial testing and plan to do more. I’ll post the initial results when I can.

[howson]

TravelHabit -- that's quite the write-up (thanks). The only thing I can think of that you wasn't addressed is that the vehicle, used as a generator, won't have much air movement through the engine compartment. Not sure how that will affect things...it's a from-the-hip observation. Many others here are much more qualified to talk to that point if (or if it's not) a concern.

Only other point I'll add is your focus on not smoking the alternator is why I like having control, from the driver's seat, of when the Renogy is providing power to the battery bank. If stuck in traffic or other situation, I'll turn my lights off (or to Auto if at night) effectively killing the D+ signal thus removing the output from the Renogy.

Look forward to reading your test results.

[Jkwilson]

Interesting read. Your estimate of 86A available at 750RPM doesn’t seem to take into account the power used by the engine and supporting electronics. That can be significant.

[DarnDave]

TravelHabit very interesting. One question or observation I have is related to the alternator output. It is possible that the alternator and engine are operating at different speeds. The diameter of the pulley on the alternator would dictate the actual rotation speed-smaller would be faster and larger would be slower. Don't know if changing the pulley size would help you get the desired result.

[NickinCO]

This might have been answered already but can't you just put the D+ wire to the positive input connection to get it's power? Then if it's plugged in it's charging. Then put the 50% power reduction option onto an outfitter switch? FWIW when I had a sterling 60A charger in my van with a 230A alternator if the van was on it was on. Traffic, idling, etc. Never had an issue. This was a 2017 Promaster.

[Yoda]

TravelHabit
You don't list your tow vehicle and trailer information - that would be very helpful

I have a new F350 coming with the HD 397A alternator (s) set up ( 240A plus 157A alternators). The ford 240 is rated at 132A at 583 rpm. My dealer pulled the information out of thier truck service/specification manual. The tech would probably use the information for testing. If you have a Ford I have posted the ratings at idle for several alternators in my thread.. BTW I am pulling my D+ signal from my trailer clearance lights. I always run with lights on. So when lights are on the DC-DC will be on (assuming I have the up fitter switch on)

Give your truck dealer a call and ask thier service department (service manager) to check thier service manual for your alternator. Somewhere should be the test procedure and baseline output at idle. Given what you have found, the only way you can run your DC-DC at 60A is when you at speed on the road with your current alternator. At idle it may overload you system on the 60A setting. Have you considered upgrading your alternator?

You 2/0 cable is a whole lot beefier than the 2 awg I am running, but I have the big alternator set up so I used the 10% non critical column on the Blue Sea chart and a few ampacity tables to verify my choice.
https://www.usawire-cable.com/pdfs/nec%20ampacities.pdf
https://www.cerrowire.com/products/r...pacity-charts/

I know you have already done your install (Great job ) , but I thought the information might help others.

Trying to help

Keith

[TravelHabit]

OK so I finally got to running a real stress test on my 60A DC-DC set up (my prior testing was only over a short period of time). Turns out there appears to be nothing to worry about.


I ran the test with the jeep Grand Cherokee at idle for 3 hours 15 min. During the test the Renogy switch at the driver was set to output the full 60A (i.e. ignition voltage only on the D+ terminal and nothing on the LC terminal). I calibrated the background current to be 0.39A with the Renogy off. Immediately on turn on to the 60A selection the voltage steps up from ~13V to ~13.4V:


Whats odd about this voltage is that the dip switch selection is set for a 14.6 V output (SW5 off and SW1-4 on). More on that later. To check the Victron bluetooth shunt measurements I also decided to use my voltmeter and measured the voltage both on the Renogy input (left image below) and output (right image below). That was about 40min into the test (~2:55PM). At that time the voltage was ~13.8V.


More interesting to me is the efficiency of the Renogy at producing the output. That is, the current draw a the input and output of the unit. I did this both early in the test and then later. In both cases the results were essentially the same. A ~72A input current produced ~56.6A output. Because the draw was measured at 0.4A with the Renogy off we can estimate the Renogy actually produced ~57A.


Since the output is a significant 3A below the rated output I contacted Renogy to see why. This time I got Andrew who seemed far more knowledgeable. His response:

"The reason you may not be getting the full 60 amps could be due to a few things, the battery may heat during charging, resulting in certain loss. At the same time, due to the BMS system inside the battery, the battery may not reach full load. It is recommended to discharge for a period of time before charging. The DC-DC charger is also tested under perfect conditions, which may not always be obtainable outside of the testing area."

Since this output was measured at the beginning of the charge cycle I don't think it could be from the Lithium battery bank being hot (or even warm since it was a relatively cool 60 deg at the test start). From the screenshots above the discharge was down to ~35% so the Lithium batteries were not really close to being full. Also, I was told by Lion Energy that the battery could accept 100A charge current each so it would be odd if the BMS would be the factor. I didn't push it further.

I did ask about the voltage being below the 14.6V setting and was told "Based on the screenshots you've provided, your battery is in the bulk state, and would be at the 13.5 volts until it reaches the absorption stage.". However after running the test for over 3hrs I never got to above 73% fully charged. My final screenshots at the end of the test show the voltage did seem to be increasing (13.6V near the end) while the Amps remain steady.

It was interesting to compare the measured-adjusted Amps into the battery (57A) to what the Victron calculated based on the shunt output. Clearly the Victron is providing a much more rosy pictures. No too surprising since the shunt is actually not measuring Ah or % at all. It does a fairly sophisticated calculation based on a range of factors. That said I would have expected it's calculations to be internally consistent so 63.4A vs 71A was a surprise. To really know the right number I probably should run the test to 100% and record the time then. This would eliminate Victron variables (it actually changes it definition of what 100% is at that point).



Finally, the real purpose of the test was to see how the alternator would handle this large draw continuously. I tried to ascertain this by measuring it's temperature at two points. I use my BGE grill temperature control device (flame boss). In addition to being able to handle high temperatures it has the ability to export the temperature profile of a cook. Perfect for this test! I used the grill clip attached to the fin of the alternator and I carefully stuck the meat probe further down into the alternator itself. Note these are relative temperatures. As Guest notes, the temperature deeper inside the alternator will be hotter. I do argue that since the alternator stator is primarily copper windings that the difference wont' be huge. In any case, the results are shown below.

For the first 10 min of the test I did not have the Renogy on. As you can see the temperature increased steadily until about 6-6 min into the test. At that point I heard the jeep cooling fan engage so, no surprise, the temperature started dropping. Then at about 10min I flipped the Renogy to the 60A setting. As you can see the temperature rises quickly to ~230 deg. For the remainder of the test it remains in this region. Although I don't have any real basis for doing so I'm going to assume the temperature around the diodes (the alternator week link) will be another 40-50 deg. hotter. So the real question is whether a constant 280 deg is bad for my alternator. After about 3 hrs I started feeling real comfortable that the alternator was handling the load just fine.

What does the crowd here think? Should I worry about early death of my alternator?

Plot of Temperature vs time with 15-point running average to smooth out somewhat the noisy measurements

..

[TravelHabit]

The key plot does not seem to have uploaded... so here it is:

Plot of Temperature vs time with 15-point running average to smooth out somewhat the noisy measurements

[TravelHabit]

TravelHabit very interesting. One question or observation I have is related to the alternator output. It is possible that the alternator and engine are operating at different speeds. The diameter of the pulley on the alternator would dictate the actual rotation speed-smaller would be faster and larger would be slower. Don't know if changing the pulley size would help you get the desired result.

I hadn't thought of that. In the end though the RPM number is really a relative number as far as damage goes which is why I decided to measure temperature. I'd be too uncomfortable about making any changes on the OEM pulley ratio to the engine. I'm sure there are a lot of factors the auto designers used to choose it!

[Guest]

TravelHabit Very nice job on the testing. Since you asked and since I have received information directly from Denso on their concerns, and that there still involves too many variables for my comfort such as varying ambient temps, varying under hood temps, TV battery condition and Lithium SOC (run test at low SOC for TV and RV) I would not do it with a 60amp unit at idle. However, you could force the TV electric fans on to help with alternator temperature but you would not want to do this with a cold engine since there are codes related to engine operating temp and warm up time, catalyst temp and so on. TV fans are not tied to alternator temperature. So to wait for engine warm up is another reason to buy a small Honda generator which will use far less fuel.

For the 57amps this may be due to the alternator putting out all it was capable of at the tested RPM and temperature. You can supply 12V to the field wire to rule this out. The battery BMS operates as a switch and would not regulate the current if its within the BMS acceptable limits. When I tested my 20amp Renogy I used a clamp type current meter where the 20amp Renogy controlled very tight to its output specification. The load on the TV was higher at around 27amp startup with a running current on the TV at 25amps.

I really admire what your after but in the auto industry this would be tested in the worse possible conditions for each hardware configuration and for extended intervals before the design or function would be released to production.

Jim

[TravelHabit]

TravelHabit
You don't list your tow vehicle and trailer information - that would be very helpful

I have a new F350 coming with the HD 397A alternator (s) set up ( 240A plus 157A alternators). The ford 240 is rated at 132A at 583 rpm. My dealer pulled the information out of thier truck service/specification manual. The tech would probably use the information for testing. If you have a Ford I have posted the ratings at idle for several alternators in my thread.. BTW I am pulling my D+ signal from my trailer clearance lights. I always run with lights on. So when lights are on the DC-DC will be on (assuming I have the up fitter switch on)

...
You 2/0 cable is a whole lot beefier than the 2 awg I am running, but I have the big alternator set up so I used the 10% non critical column on the Blue Sea chart and a few ampacity tables to verify my choice.
https://www.usawire-cable.com/pdfs/nec%20ampacities.pdf
https://www.cerrowire.com/products/r...pacity-charts/

I know you have already done your install (Great job ) , but I thought the information might help others.

Trying to help

Keith

Yoda My TV is a 2021 Jeep Grand Cherokee with the V8 5.7 HEMI and with all tow package upgrades (alternator is a Denso 230A heavy duty). The trailer is a 2022 GD 22RBE. Since the trailer UVW is ~1200 lb less than the jeep 7200 tow rating I was comfortable with this arrangement. Besides I had to meet my wife's constraints . She absolutely did not want a truck and also didn't want a large SUV.

I referenced the same USA-wire NEC ampacity-chart. One thing for folks to keep in mind is that there is an apparent difference in interpreting the max current values for DC current vs AC current. The NEC chart advises no more than 85A for AWG 4. Others state similar restrictions (here) . This is also consistent with my local codes for home construction and I've been following those recommendations for decades. However, for their AWG 4 welders cable, Temco advises limiting the current to "150 Max Amps (up to 50 feet) ... -58°F to +221°F." West marine allows 160 max Amps (links here and here). While DC the current is greatly influenced by length (and associated voltage drop), we also know, for typical use, length of AC wire is not really an issue. That said, I have not heard or read a good summary to explain fully the allowance for welders cable.

When I ran my test I could feel the warmth of the AWG 4 cable even though the length of the cable to the battery was short. The AWG 2/0 the cable at the Renogy input, and over it's length, remained cold even to the end of the test.

[TravelHabit]

TravelHabit ... you could force the TV electric fans on to help with alternator temperature ...

For the 57amps this may be due to the alternator putting out all it was capable of at the tested RPM and temperature. You can supply 12V to the field wire to rule this out. The battery BMS operates as a switch and would not regulate the current if its within the BMS acceptable limits. When I tested my 20amp Renogy I used a clamp type current meter where the 20amp Renogy controlled very tight to its output specification. The load on the TV was higher at around 27amp startup with a running current on the TV at 25amps.

I really admire what your after but in the auto industry this would be tested in the worse possible conditions for each hardware configuration and for extended intervals before the design or function would be released to production.

Jim

I agree that this was not done at the worst possible conditions so it all should be taken with a grain of salt. For example the ambient temperature should of been colder; ideally I would have liked to run the test at desert ambient conditions... Also as Jkwilson noted one must consider all the other loads the alternator is supporting (I had all selectable electronics turned off). It's interesting to realize that so many of the the after market modifications of our vehicles violate many of the design assumptions. In my research I had a good laugh to find a very large number of folks are stressing their alternators with very high power audio amplifiers. I guess it's a thing with the young crowd to see how loud they can get their upgraded audio electronics and speakers lol.

In the end that's why I added a switch near the drivers seat. Now I can intervene manually. BTW, I also had the same thought on holding off on any charging until the car was warm -- though I wasn't as concerned about the catalyst temp. as much as any initial spike load and waiting until TV battery was recharged to minimize those extra loads.

Though I did seriously consider buying one (even selected a model), I note that bringing a honda generator is not really an option for me. I do have to watch the weight of both my trailer and need to keep the Jeep rear axle weight below it's spec. If I had a dulie or even full up truck this wouldn't be an issue and a generator would actually be my choice. It certainty would have saved me a lot of work !!


I should also note that based on my initial test a couple of months ago, I actually was thinking/planning to add an extra fan! However, I'm not so sure I really need to do that now. In addition to my test, one rule of thumb I've heard from several different sources is that one should limit the idle alternator load to 1/2 it's rating which seems reasonable. Mine is 230A so my 72A draw is well withing that (0.5*230=115). Also the measured 230F is actually a lot lower than I expected. I my mind I thought 315F would be the max allowed temperature at the diodes. So my test shows there seems to be quite a bit of margin for any number of uncertainties and non-worst case test conditions. That said it's still an open question/possibility to add a fan particularly since putting a 12V fan directly above the alternator would be easy if I'm charging at a campsite.

Can you help me understand the suggestion to "supply 12V to the field wire to rule this out." Are you saying to put 12V on the D+ wire using an external battery rather than the TV starter battery? Agree the BMS operates as a switch and would not regulate the current. When I talked to the tech at Lion Energy he basically said the same thing.

So you got a solid 20A output? What clamp current meter did you use? In my case the missing 3A does still bother me a bit. My best guess is that the large current and the Jeep logic may have something to do with it as you also suggest. It's also possible that my clamp meter has a part to play (though I did calibrate it to 0). I did rev up the engine to a high RPM for a minute or so but the amps and voltage essentially stayed the same. Other than your suggestion above I'm at a loss to find the root cause.

[Guest]

TravelHabit I would not know the alternator failure rate of the young crowd loading up an alternator at extended idle so I have no answer other than auto systems are designed around their original intent. I could go into detail in how durability tests are ran in Detroit but state simply they are exhaustive and can last for months. So I'm cautious.
Alternator sizing is also part of the design. Your engine is being controlled to a specified idle speed where the load is changing based on the torque required to drive the alternator at various loads so no issues there. Depending in how you plan to use the system, underhood temps can become very high. For instance right after a tow underhood temps at idle will spike. Ambient temp can provide additional variation.

Not sure on the root cause of lower output but certain its not the BMS. The F terminal on the alternator is the field terminal where this controls the output of the alternator where there is no need to mess with that based on the elevated idle test
Heat kills everything over time, however it looks like you have determined you do not need a fan for extended idle at load. Now I'm left wondering why Denso raised the red flag?

Here is some information I ran across on rectifier bridge (diode temp).

https://www.sciencedirect.com/scienc...11379721000875

Interesting project,

Jim

[TravelHabit]

Thanks for the insight Jim. They quoted ">200 °C at maximum currents" in the article ... that's 392F!!!. I had no idea. I'm with you on being cautious though. Bottom line: I intend to keep a close eye on this as I learn more about my set up... particularly in hot stressing environments.

While it may not show up immediately, the article points out that consistent high temperatures will lead to a high failure rates. I wish I knew where the inflection point in that temp vs failure rate curve is. In any case, this is an important take away message for any folks out there who have installed the 60A, or are thinking about it. In my case the amount of time running my DC-DC charger is much less than the actual time we use the Jeep so that's in my favor. But it's no guarantee and other folks with a similar install should realize that going in.

BTW, I think those young folks should be more concerned about their ear drums vs. burning up an alternator. At least an alternator can be replaced lol.