Hood adhered solar

[moorefc]

Good idea on the alternator thermal control. Driving will mitigate the heating. Had an experience in Mexico airing up two vehicles in 90deg sun, engine idling, 50+amp compressor, 130? amp Ford alternator...Next morning alternator was not charging. Long story short limped to border 100mi north, replaced alternator, and found after rebuilding, two blown rectifier diodes.. replaced with 200amp diodes...

The rub with lithium is they can charge at crazy rates, so not having a dc dc or limiter causes stresses our vehicles were never designed for...In diysolarforum there is a long thread on folks trying to not use a "standard" dc dc solution. Oh that added complexity makes the decision harder...I say that as an EEE and former German car owner...

[posplayr]

Originally Posted by moorefc

Good idea on the alternator thermal control. Driving will mitigate the heating. Had an experience in Mexico airing up two vehicles in 90deg sun, engine idling, 50+amp compressor, 130? amp Ford alternator...Next morning alternator was not charging. Long story short limped to border 100mi north, replaced alternator, and found after rebuilding, two blown rectifier diodes.. replaced with 200amp diodes...

The rub with lithium is they can charge at crazy rates, so not having a dc dc or limiter causes stresses our vehicles were never designed for...In diysolarforum there is a long thread on folks trying to not use a "standard" dc dc solution. Oh that added complexity makes the decision harder...I say that as an EEE and former German car owner...

So after watching that video of the smoking alternator from delivering 65A at 1500 RPM, I became keenly aware of the thermal issues .

So one issue is not knowing how complex to make this, and the other is not having an actual threshold limit for thermal shut down. So I found this thread where the Class B RV'ers are dealing with the same issue of Renogy DC-to-DC charger control.

https://www.classbforum.com/forums/f...way-11572.html

The upshot is that they are shooting for 225 degF shut off limits where 250-270 deg F is survivable but end-of-life accelerating. They are trying to achieve thermal management by controlling D+/LC by start battery voltage sensing. So this really helps me pic a good thermal limit. I was going to try 85 degC or 176 but that apparently is too low. However, with smarter controls I should be able to run at that lower limit but it will have obvious charging limitations at idle.

At this point you have to ask "Do I really need the convenience of full capacity charging at idle when it means running my alternator up to 250 degF?" I think not!

It defies comprehension that the Renogy charger will suck the juice out of the start battery down to 8V just because the engine is running???? So while voltage-based thermal control is a big step forward against the atrocious Renogy design, it does fall short of the most obvious direct thermal sensing.

This is the logic that a couple of members apparently used using an aftermarket voltage sense product. They needed two of them to achieve this control.

What I will try in the RV is as follows:
or D+:Function 3

• Power on at 13.2 volts, 30 second activation delay
• Power off at 12.8 volts, 5 second deactivation delay

This should turn on the DC-DC 30 seconds after the alternator starts spinning and off 5 seconds after it stops

For LC+:Function 4.
Power on between 12.8 and 13.1 volts,

• 0 activation delay,
• 5 second deactivation delay.

This should immediately reduce the total load by 30 amps if the alternator gets overtaxed and restore it 5 seconds after it recovers. I might adjust the higher voltage limit up after I make some observations in the field.

So I decided to implement this voltage-based control along with thermal shut down using an Arduino product (see initial concept attached).

Conceptually the red 3 way rocker is a 40A auto mode select (up to II) and half power 20A (down to I) control with built in voltage and thermal controls. The rocker does not directly control D+ and LC+. Those are controlled through a combination of the rocker, voltage sense logic and thermal sense shutdown. I will be able to mimick the relay logic I posted before where in thermal shutdown the rocker lights go off and the rocker appears inoperable but the LED is on but now with a flashing status. I guess I could flash both LOL; it's just software at this point.

So when you select Auto (40A) if the voltage drops then it will automatically follow the logic to drop to 20A using LC and will shut off completely is it drops further. There LED will warn with slow flash and fast flash depending upon 20A or OFF.

When in 20A half power, the same voltage limits apply except you never let it go to 40A and the LED will indicate if voltage or thermal shut downs occurred.

So maybe I have three flashing speeds.

• Voltage below 13.2 is slow flash
• Voltage below 12.8 is fast flash
• Thermal shutdown is very fast flash.

I was considering bringing in RPM but it seems from this thread that voltage-based control is good enough provided the thermal is also added. One of the reasons for the long delays they implement is probably because a simple voltage sense is problematic if it does not consider the load.

For example, compare 13.2V with charging OFF v.s. 12.8 with charging ON. It might be the first you do not want to charge (low RPM) and the second is perfectly acceptable with a large 40A charging load. This is where the logic can be refined with software flexibility. Since it is an Arduino family product you just need a laptop and USB cable to reprogram it.

[moorefc]

Haven't explored Renogy, only Victon and Kisae, but thermally assuming the power diodes are the most sensitive item, FWIW in the mil/industrial world semicondutors are burned in and life tested at 125C ambient, and rated power....Monitoring case on a alternator is a guessing game regarding actual semiconductor temps. The diodes rating will dictate their tolerance, and commercial generally tends to be 80C or so... If I remember in the video they did do an IR sense on the catastrophic temp, but do you know the rated current of the diodes in that alternator vs the load? One obvious aide is to not charge at idle (hot days?). How does one remember that after a couple years when someone else is driving the van. So safeguards...conversely 40amp is not a huge alternator load....
Cheers

[posplayr]

Originally Posted by moorefc

Haven't explored Renogy, only Victon and Kisae, but thermally assuming the power diodes are the most sensitive item, FWIW in the mil/industrial world semicondutors are burned in and life tested at 125C ambient, and rated power....Monitoring case on a alternator is a guessing game regarding actual semiconductor temps. If I remember in the video they did do an IR sense on the catastrophic temp, but do you know the rated current of the diodes in that alternator vs the load? One obvious aide is to not charge at idle (hot days?). How does one remember that after a couple years when someone else is driving the van. So safeguards...conversely 40amp is not a huge alternator load....
Cheers

The extended temp commercial is +85 degC which is safe in this application because automotive is going to be much higher. As you suggest what is important is what temperature and where. Power ratings are usually junction temperature not ambient.

A 125 degC burn in is probably non-operational for power electronics. The thermal cycles are meant to stress the traces to promote any infant mortalities. So for example using the VNQ660 HSS I have the spec sheet for, it has a 150 degC junction temperature rating for a 10 amp part. The thermal rise can be much higher than the 25 degree margin for 125 degC burn in.

I do agree it is going to be hard to predict what the thermal limit for a particular sense location should be and then what thermal switch to pick to get that range. That is why having real hard data (as reported) using IR sensor really helps to reduce the uncertainty because those are going to be soak temps at the case which is where I am measuring/mounting the thermal switch.

In the video, there used a Flir IR video sensor. presumably looking at the control module at the back of the alternator. I was going to be lazy and mount the thermal switch on the top of the case (tap a small screw hole) but now I realize I probably need to pull the alternator and mount it in the screw hole on the back. Use the attached picture for reference, I assume the diodes and any control electronics is in that module in the back?

These are available every 5 degC but it is not really clear what the real cut-off temps are. One reference I read claims there is only a +/-5 degC error bound whereas the spec sheet using +/15 deg above 1-00 degC. Something I need to test after I get some samples in.

https://www.amazon.com/-/es/termosta...7PDY9VVQ&psc=1

Anyway, in the link I sent, they are assuming case temperature I assume because it is al measured data and probably not an analytic model of junction temperature. The diodes should be pretty robust (although your failed) but I would start worrying about epoxy winding as well.

Any way my approach is to start on the low side (e.g. 85-95 DegC) and if I'm bothered enough (by low RPM performance) increase temp as necessary. If I mount on the case, it is going to be pretty close to the thermal measurement reported. Junction temps do not really enter into the observations.

[moorefc]

See the pic for the blown diodes, inside back of alternator...So sensing from back of alternator would be most sensitive.....Rebuilding the <100K OE with larger diodes, etc seemed better than running a reman alternator....

[cotrailhead]

Originally Posted by Clarkboulder

Thanks COTRAILHEAD! That sounds like a good option although I am a noob to all of this so I have a lot to learn. (I only know bikes!)
How do you initially charge those batteries? Is that charged via engine or solar or electric hook up?
I’d love to learn how this could replace the generator (as it seems it could) and how and what converting to this option looks like. I just have no idea where to start with it. I only ever really want to power the microwave and an occasional induction hot plate or other basic appliance or plug in lights. Lugging around a generator seems silly for that as does the heavy solar panels just to top off the two house AGM batteries. That combo is over 160lbs.

Sorry it took so long to respond. The lithium house batteries in the van are connected to an inverter charger by mppsolar (USA stock) from eBay. If I ever wanted to add solar to the setup I could very easily. But, because my van is mainly a weekend warrior, all I do is plug it in at the house for a few hours, let it charge up, then it is ready for the next weekend.

[Scalf77]

This seems to have gone down a rat hole , and pretty much lost any information based on the original topic, Hood adhered solar panels. I agree with the basic statement that heat and panels don't match. That said the hood adhered panels are using ETFE panels and PERC cells. Will this address the issue of sticking on top of a heated engine. I haven't tried it, but they have at least tried to address some of the basic problems with their design choices. These panels will also cut the glare you would see on a standard panel. In fact they may have less glare then your waxed hood. If you needed space and can get by the price, it could be a option. I would like to see some real world results, just not enough to stick some on my Transit. Also they need to branch out on vehicles or at least give dimensions of the ones they do sell.

Now, to add to the rat hole. Hot temperatures and idle will always be a culprit to destroy a alternator. One of the benefits of the voltage monitoring ACR's was to disconnect as the voltage dropped. I saw this happen fairly regular when running my starcool air-conditioner , pull up to light at idle with full air running, charging a depleting low house battery and the load would be very high.

I can see that the additional load of an air compressor would be a big hit, I do wonder what type of isolator/separator/ACR you had? Unfortunately Sportsmobile is notorious for wiring the separators and ACR's wrong.

I find the renogy DC to DC charger issue a little perplexing. Granted I am not a big fan of renogy, but if you put a 40 amp DC to DC charger on your rig, you should make sure that the alternator can sustain that with max loads at worst case idle conditions. I expect they do have some voltage disconnect, which might also be exasperated if choosing smart alternator setting. But after that they have limited smarts as far as protection.

While the KISAE is true to their name Keep It Simple Alternative Energy, they do have some nice features. First they are one of the few that have a settable current output. So even if you get the 50 amp version you can dial it back to a lower output. It also does a system check every three mins, and if the start battery voltage is two low it will throttle back on it's own. My standard install procedure is to start a 40 amps, with van idling, lights on bright, air condition and fans on high. If I see the voltage of the van battery drop I would throttle it back to where it won't. If not I might go to 45 or 50 amps. This would mean that any other heavy load would be off of the house battery system. While they may consume all of the amperage coming from the DC to DC charger, it shouldn't be a hit to the alternator. Of course your house battery charge would be taking a hit.

Sterling power has the ability to monitor alternator temp on their DC to DC chargers.


I'm certainly not against your ideas and info, I enjoy a good over engineered solution. It might be a good time to step back and define the problem. Certainly monitoring the alternator temp would be a good start, but again if you are off designing something to cutback the output of your charger in this condition, maybe stepping up to a higher output alternator would be a better solution.

[posplayr]

Originally Posted by moorefc

See the pic for the blown diodes, inside back of alternator...So sensing from back of alternator would be most sensitive.....Rebuilding the <100K OE with larger diodes, etc seemed better than running a reman alternator....

So I see the diodes are buried inside. Obviously the weak link. The epoxy showing no discoloration means it can really take the heat.

The only conductive heat path out is to a 200+ degF engine so forced air cooling is the only way heat can get out. With the mass of that stator, I suspect that the whole alternator gets very hot with relatively insignificant temperature gradients.

[posplayr]

Originally Posted by Scalf77

This seems to have gone down a rat hole , and pretty much lost any information based on the original topic, Hood adhered solar panels.

I think the hood-mounted solar panel idea went out the window way back in this thread shifting to increased Lithium battery banks and the natural follow-on of DC to DC charging pf LiFePO4.

Some of the main problems are well defined like "Don't burn up your alternator". This is true whether Renogy or Victron two of the most popular brand on the market. Victron has a whole youtube tutorial series on the subject.

A brute force solution is a larger alternator perhaps but as has been shown (in various links), more finesseful control of the DC-DC charging can yield more satisfactory results while avoiding burning out the stock alternators .

[moorefc]

Yep the subject wandered...thought about that but it seemed to flow...The diode issue actually may not have been related to the separator (was a 1315 and now is blue sea), but was clipped to the starter batt....If it had been connected to the house, there may have had better 200ah buffering even tho the 1315 was closed...I should look at the voltage drop across there under high current....Now when airing up is done with some dwell time...