Experimental engine generator setup

[booster]

Started the engine as I normally would, with it set on low alternator output and coach batteries disconnected. Let it idle down a bit (650rpm) and then connected the coach batteries. It flashed up to about 160amps and then started dropping, so I put it on high alternator output setting and it jumped to about 210amp. The thermocouples did not go nuts and seemed to work fine. It started out reading the 280 amp alternator about 10* hotter than the 250 amp one, but by the end of the test that had swapped, with the 250 reading about the same amount hotter than the 280.

After 20 minutes was in the process of swapping, and both read 188*, with the cheapo infrared thermometer giving 202* on both in the hottest points I could get to. It was running a constant 185amps at 13.3v at that time, at 545rpm engine and 1700 rpm alternator, hood up, 65* shop temp.

At 30 minutes it was running at 200/195 on the TCs and 215/202 on the temp gun, while running at 175amps and 13.3v.

I closed the hood, and as expected, both alternators got hotter by 40 minutes. Surprisingly, they held the 175amps and 13.3v, though, and went to 215/205 on the TCs and 224/215 on the temp gun. Temp was still climbing, and I also could hear the clutch fan on the engine starting to engage, so the engine was also warming. Nearly all engines run hotter with hood closed, so no surprise there. Water temp as holding at 195*, so not at cooling capacity yet.

Just for fun, I decided to see what the add on electric cooling fans would do to the whole thing. They pull about 30 amps total when running at good voltage, so pretty big fans. They will go to near 50 amps if voltage drops. As expected, the amps to the coach dropped by the 30 amps, so total amps and volts were essentially the same, just less to the coach and batteries available. The alternator temps started dropping in less than one minute and where down about a degree per minute for the 5 minutes I let them run. This is good to know, as the alternators were cooling and we still had 145 amps to the coach available.

All of the amp numbers are the amps going to the coach, but the engine and starting battery are also running off the two alternators, so that is going to be 20+ more amps of actual output being generated. That would put us at over 2600 watts at this idle speed and temps.

Bottom line so seems to indicate that when we are into the higher temperatures, the TCs read about 10-15* cooler than the hottest spots found on the cases, which is not all that surprising. As long as it stays fairly consistent, it is an easy allowance. I forgot to get a temp of the actual alternator output terminal temp, where Balmar senses temp, but the guess would be it would also be a bit lower than the case, as it has the huge heat sink of the cable on it and it hangs out in the inlet cooling air to the alternator.

What temp is OK is certainly uncertain, I think. Balmar uses 220* at the output terminal to trigger turndown, while DC Power rates stuff at 270* alternator, but don't say where that is taken, or even if it is internal or external. Gut says using 220* on the TCs will likely be very safe, but think I will try to get an output temp at the output terminal to see how that compares to the hottest case spots. I would also expect to get substantially different temps when driving than idling, but how much and which way will interesting. Our Chevy has both alternators behind the radiator, and the added 280 amp unit is also tucked low and gets less airflow, so the Sprinters and others that hang the alternator low in the front would certainly cool better, but be more vulnerable.

At this point, at least, or risk of damage or overheating should be very low, as we can continuously see the alternator and battery temps when driving, with the option of turning the output down or off, or the fans on, if we need to. Just need to learn how they react in the driving conditions and hot weather.

Time will tell, but so far very happy with the results.

Here is pic of the stuff that is related to alternator charging, all on the dash. Basically the two channel ammeter/single channel voltmeter, 4 channel TC thermometer, the control panel which also includes the cooling fan switch, and the Blue Sea remote disconnect for the coach.


This is the control panel, showing the regulator locked into absorption, on high output setting (still only a little over 9v to the field), fans off, and coach connected.




This is the TC thermometer showing individual alternator temps, battery temperature, and oil temperature (which I have always wanted to be able to see).



Here is the ammeter/voltmeter. The left amps are amps to the coach batteries, then voltage at the batteries, and then the total amps to the coach.

[booster]

I need to clarify a bit, as I misspoke about the voltage on the ammeter. It IS the voltage at the batteries and will read lower than setpoint, or running point, of the alternator, especially at higher amps, until near full . There is .5v+ drop in the cable when the amps get high.

What is sensed at the separator is the control voltage for the regulator. I did that to make sure that the starting battery didn't see extended amounts of time at near 15 volt, if the regulator was trying to hold the batteries at 14.4v even with the drop. In the early stages of the charging, I have seen very little difference in the amps to the batteries based on the .5v drop, but of course, the watts do go down somewhat. My bad .

[jeslaughter]

What did you use for a test load?

[booster]

Originally Posted by jeslaughter

What did you use for a test load?

I was using our 1500 watt electric heater through the 2000 watt PSW Magnum inverter, plus there was always about 75 or more amps going to the batteries.

[booster]

Went out today and moved the TC from the through bolt of the case to the output post, like the Balmar temp sensor is to see how it compared. The temps on the TC thermometer looked very similar between the two locations, when compared to one I didn't move on the other alternator. The post might even have been little bit cooler.

I also tried to take the temp of the output post and got 240* while the TC read 180*, and then checked the case and it read the same, and then started reading different everytime I did it again. I removed the batteries and put them back in and the temps looked better, but I still was getting nearly 40* hotter on the laminations than the case, which I didn't notice yesterday, so I don't know what is up with that, but at least I got the same as the TC on the post and case sections.

I think it's time to get a better infrared temp gun than the Harbor Freight Anybody got a good recommendation? I am thinking Fluke or Omega at this point.

It would be interesting to see if anyone has taken, or could take, the temps of the laminations and case right next to it on both sides. I don't see how they could be that much different when the sit right together.

It is pretty obvious that even at the about 40% of rated output, the alternators get considerably hotter than going down the road, like in our trip test a couple of weeks ago. Less cooling air, lower alternator fan speed etc, definitely seem to take a toll. It is no wonder the factory systems get into the "death spiral" when running AC at idle, as they would be turned down and running very hot, at low rpm. The regulator would cycle to 50% for large amounts of time, so no way to keep up, I would think.

I think I will leave it with one sensor each place with them on the post on the 250 and frame on the 280 unit. For now, will use 220* as the cutoff on the temps based on the TC thermometer, which should be pretty safe. I do expect them to run cooler at speed by quite a bit, unless it is very hot out.

Hopefully, we are done until I a get a new temp gun, and bring it along on our, tentative, winter trip.

[jeslaughter]

Okay, the 75 amps is disturbing, that's a lot of power and power usually means heat. I seem to recall that you have 4 batteries so I would not expect the current to be so high for very long. Perhaps you meant to say 7.5 amps. John

[booster]

Originally Posted by jeslaughter

Okay, the 75 amps is disturbing, that's a lot of power and power usually means heat. I seem to recall that you have 4 batteries so I would not expect the current to be so high for very long. Perhaps you meant to say 7.5 amps. John

75 amps would be a lot for wet cells, but according to Lifeline our 440ah of AGM will pull upwards of 300 amps if down under 50%. What we have found is that you can't go that high for a charge from 20% SOC to the 60-65% where it starts to taper, as the batteries will get to hot. They seem to do OK at 250 amps for 15 minutes or so, and at 180 they usually will be able to do the 20-60% with a 20* temp rise in the batteries. Of course where the temp is when you start is a big deal, so if you are starting out at 105* you would go too high.

The acceptance on the batteries isn't down to 7.5 amps until they hit 95% full. 10 amps is 90% full, from what I saw today watching the 100 amp shore charger. .2 to .4 times the capacity of in amp hours (as amps) is what Lifeline likes for range of charging amps which is 88 to 176 amps for us, but they say faster is fine, as long as you are temperature controlled and also monitor the battery temps. .5C would 220 amps, and at 250 amps would be .56C. Lifeline has really upped the recommended amps for charging, especially for discharges of over 50% down, wanting a minimum of .2C in amps, or 88 amps in our case.

[booster]

I broke down and ordered a Fluke 62MAX+ tonight. Has adjustable emissivity and circular laser spot to show the sample location and size. We had a similar one where I used to work and the circular laser was really nice to have.

I also did a quick test to see if emissivity was as big an issue as the charts would indicate. The show anodized aluminum at about .5, and the Harbor freight is fixed at .95, which should have made it read about 1/2 of the actual reading. I painted a couple of places on the case, and laminations with flat black barbecue high temp paint, and checked the temp a room temp, not running. 75.5F on the paint, 75.5 on the bare aluminum right next to it, and 76.0 on the laminations, so certainly no where near what the chart would predict. The thermocouple on the post read 73.5*, so all easily within the accuracy of the instruments. I will heat it up tomorrow I think for a quick test, and then wait for the better thermometer to get here.

Perhaps electrical interference is affecting the Harbor Freight as some of the infrared units warm about not being too close, and I have to be or the spot size gets too big on the HF. Something is going on.

[booster]

I think that most of the mystery of the craze readings I have been getting off the Harbor Freight temp gun are figured out. It doesn't appear to have much to do with the emissivity, or that kind of stuff.

Today, I went out to check what the black paint did compared to the bare aluminum, and found it wasn't much as I was taking temps as the alternators warmed up with about 130 amp output. Readings matched the TC thermometer fairly well. I turned up the output by adding a hotplate to the load side and got to about 190 amps to get the temps higher and nearer 200* and kept taking readings. The higher the readings, the more they mismatched the TC thermometer and the more the were inconsistent. At one point, the readings were approaching what I got yesterday, so I quit taking readings as I knew they were bad. As a reality check, I shot the temp on my brown Kennedy machinist tool chest, and got an amazing 120*F when I know it was at 66* like everything else in the garage. I then noticed that the temp gun was warmer than ambient from being around the engine. Not really hot, but warmer than body temp so maybe 100*F. As it cooled down the temp of the tool box dropped until it was at 66* after about 10 minutes.

This would seem to indicate that at least the HF temp gun is very, very, sensitive to ambient temp and heat gain. We are talking about being 30-40*F off at 200*F if the gun gets to 100*. I need to see if Fluke has any specs on that issue so I know if the new gun will do similar.

It would certainly indicate the need to get in and get your readings very quickly around anything hot like an engine, and check if it is reading right by shooting something like the tool chest before and after each reading to confirm accuracy.

I have confirmed that the laminations do run hotter than the case or post by about 15-30*. I think this is relatively normal as most of the reading and test results I have found would indicate that the winding will run up to 40* hotter than the case on most alternators. The windings and laminations are basically one unit, so they probably run near the same temperatures, and would be hotter than the case. It would also confirm the 220* output terminal temp that Balmar uses is pretty reasonable, as it is similar to case temps on our units, and if the windings were 40* hotter, they would still be under the 270* that many want to keep the windings and insulation under in their specs.

[booster]

I got the parts I needed yesterday and finished up the cleanup. Really not much, as all I did was replace the steel nuts on the alternator output with tow brass jam nuts, and move the oil temp TC to a bolt head on the remote hoses adapter, now that I know the the electrically isolated terminals I can build work fine to get rid of interference to the TC thermometer.

With the proper nuts on the outputs, I ran a better test on comparing the the temp on the alternator output to the case temp and the lamination temperature, using both the new Fluke temp gun and the Harbor Freight one. Up the entire warmup and running range, the output terminal ran significantly cooler than than the case temp at about 15* less up to 210* on the case. I moved the TC back to case drawbolt and now it within 5* of that the temp guns say.

Loaded it down with use though the inverter, and it did the same 180-190 amps at idle on the high output setting, and about 105 amps on the low setting, which is what I saw before, and it held to 200*+ alternator case temp. This all was at 545rpm engine, 1700rpm alternator which is pretty slow, so that is nice and no high idle needed.

The amps given are to the coach, and alternator output was 15 amps higher when I checked what the chassis and starting battery were using. That would net at over 200* for at least 1/2 hour to get to 200* on the alternators. Conditions were not harsh though as it was cool, hood up, and on stands.

12v adapter for the TC thermometer worked fine so it can run continuous if we want.

Being able to make it stay in absorption for as long as we want is essential to be able to get full, and when you release the lock in, it steps down to float in about 10 minutes as it slowly decreases.

As it looks right now, it is doing beyond what we had hoped for. Hopefully, it will perform as well when driving, which may actually let the alternators run cooler, and in the hot climates. Having the visible alternator temps and amps, will let us know that in real time when we get those conditions.

[BBQ]

.

Any updates?

[booster]

Our winter trip got cancelled due to DW getting ill, but a short late fall trip seemed to indicate all was working well. Spring is coming and we will be off to see how it does over time. I think we are looking at being able to recover upwards of 300ah with a 1.5 hour drive and good sun for another 5-8 hours on solar, and that is probably as good as it will get unless they put more hours in a day! This is assuming we take the AGMs to totally full, based on amps, which is a long process. If we just want to recover 250ah, to get us to 75% full from 20%, it would only be about 1.5 hours.

Our main interest was in the alternator temperatures, and at the 75* ambient we saw, all was good up to 185 amps of continuous charging, plus another 15-20 to run the van.

Happy so far, but it is still very early to know for sure.

[Twinbridges]

My Midwest automotive has the second compressor run from the engine, 16,000 btu's I think. Has control near the front that is thermostat controlled with fan switch. Works great.