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Old 08-30-2017, 01:06 AM   #1
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Default Underhood generator testing

I have the underhood generator (GU) option on a 2016 210 (Chevy Express). This is actually a 270 amp Nations high output alternator controlled by a Balmar MC-614 regulator and a 2500 watt inverter/charger.

To test the GU performance I installed clip-on current transducers on both the alternator output and the inverter input so I can monitor current both with and without the underhood generator running.

The Balmar regulator uses the alternator temp sensor feature to reduce the alternator output when it gets hot.

What I have found is on days when the temp is say 80 degrees or more, the underhood generator starts out producing the required output at idle, say 160 amps when using the convection oven and an induction cook top at the same time. But, after say, 15 minutes, the Balmar regulator reduces the alternator output to approx 80 amps (50%) for a few minutes, then increases to 160 amps, then reduces again, to keep alternator temp from getting too high. This continues during the rest of cooking the meal, and uses some battery capacity.

Just FYI, after heavy loads in hot weather, you will want to idle for awhile to recharge your batteries to recover power consumed when the GU power was reduced due to high alternator temperature.
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Old 08-30-2017, 01:24 AM   #2
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Thanks for the data.

We discussed Balmar temperature throttling a bit about a year ago. I posted some data I collected concerning charging a large, low-SOC battery while driving on a hot day here:

http://www.classbforum.com/forums/f2...html#post46481

The second of the following two graphs shows the kind of temperature modulation that you have described:

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Old 08-30-2017, 01:54 AM   #3
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Awesome data!

What is interesting here is the advertised "3500 watt" GU might reach this level cold, at 60 mph. The highest power I have reached at idle is 160 amps at 13.5 volts, about 2200 watts. The highest power I have reached when driving is 220 amps at 13.5 volts, about 3000 watts.

We still like our Roadtrek!
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Old 08-30-2017, 02:02 AM   #4
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Just a couple of side notes.

The stock Roadtrek alternator wiring connects the Balmar voltage sense wire at the alternator B+ post. I disconected this, and ran a sense wire back to the junction of the 2 battery banks. This noticeably improved the alternator response to high inverter loads.

Also the Balmar battery setting was on deep cycle flooded, I changed to deep cycle gel.

I found out that the Chevy Express has a high idle option. Using the cruise control you can raise idle to 1200 rpm. This would be useful when cooking a meal on a warm day. I called a dealer and this could be programmed into the cruise computer for about $200. Has anyone done this?

I put a stick on the gas pedal against the seat to hold rpms at 1200 for now when cooking a meal and also need AC.
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Old 08-30-2017, 02:33 AM   #5
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Quote:
Originally Posted by prfleming View Post
To test the GU performance I installed clip-on current transducers on both the alternator output and the inverter input so I can monitor current both with and without the underhood generator running.
How and where are you reading these values?
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Old 08-30-2017, 02:35 AM   #6
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As Avanti said, quite a bit of discussion about the 280 amp alternator really netting about 165 amps on average at speed, much lower at idle, which is definitely something folks should know. When you try to run AC at idle, you don't get enough to keep up when it is hot, as you have seen and get the death spiral. Roadtrek should be giving folks accurate expectations IMO, as they don't give you any monitoring to let you know you are going dead.

We are somewhat "lucky" to have a 2007 Chevy, that is just before they started using the PCM controlled alternators. Since the alternator takes care of itself, we can parallel on a second alternator without messing up the PCM. We settled on a 280 amp and a 250 amp Nations in parallel, controlled by an Ample Power regulator, that lets me set two switch controlled turn down output levels. It does not have alternator temp sensing so I had to set the turn downs properly to protect the alternators, which I monitor with a thermocouple gauge setup. We haven't had a chance to check it under all conditions, but we can get 280 amps continuous on the high setting and about 180 at the low setting. It goes to about 180 and 110 at idle. The full 280 will rarely be used as the battery temp climbs very quickly at that output, and we never need that much power to run anything. It would only be used for a 15 minute run to recover a days worth of use on a trip to the dump station or trailhead. The 180 amp setting keeps them at good temp, and the batteries don't get too hot either, but do go up about 15* above ambient. So basically, we have 530 amps of alternator to get 280 amps in bursts or 180 continuous with our 440ah of AGM. If it was lithium, we could use high output all the time if we wished, as they would keep cool at driving speed, but that is a lot of load at idle. Obviously, the alternator ratings only apply for about 1 minute of real world use, and then you go to the real rating of about 60% of the given one.
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Old 08-30-2017, 02:46 AM   #7
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Cruising7388, I'll post some pics of my current monitoring setup.

Booster, very cool adding the second alt. Yes, I was not happy not knowing what currents and loads were doing with just the stock battery led display. I have also added the Balmar SmartGauge battery monitor which I find really useful to keep track of SoC.
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Old 08-30-2017, 06:13 AM   #8
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Quote:
Originally Posted by prfleming View Post
I found out that the Chevy Express has a high idle option. Using the cruise control you can raise idle to 1200 rpm. This would be useful when cooking a meal on a warm day. I called a dealer and this could be programmed into the cruise computer for about $200. Has anyone done this?

I put a stick on the gas pedal against the seat to hold rpms at 1200 for now when cooking a meal and also need AC.
The high idle option is typically implemented during production. Did the dealer indicate that this could be accomplished post production by reflashing the computer?
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Old 08-30-2017, 11:22 AM   #9
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I posted some info on the Chevy cruise control fast idle here: http://www.classbforum.com/forums/f8...html#post11996

It's worth trying to see if it is already enabled.
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Old 08-30-2017, 12:29 PM   #10
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Quote:
Originally Posted by cruising7388 View Post
The high idle option is typically implemented during production. Did the dealer indicate that this could be accomplished post production by reflashing the computer?
Here is the upfitter bulletin, I called a local dealer and when they looked this up, they said it can be done on my 2016 Express 6.0L gas.

https://www.gmupfitter.com/files/med...lletin_82b.pdf
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