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Old 08-30-2017, 02:06 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, 02:24 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, 02:54 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, 03:02 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, 03:33 AM   #5
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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, 03:35 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, 03:46 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, 07:13 AM   #8
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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, 12:22 PM   #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, 01:29 PM   #10
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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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Old 08-30-2017, 01:41 PM   #11
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I looked at a fast idle aftermarket setup for our 07 Chevy, and it was available. I don't recall the supplier, however, and it was pretty expensive at about $500 IIRC. We decided to pass on it as we determined that we didn't want to bug folks with a racing engine to charge batteries. At normal idle the Chevy is nearly silent, so much less intrusive, but we never really do that either, as we haven't run out of battery capacity. We are good for over 5 days just on the batteries. We always seem to get enough sun or perhaps a short trip to the dump station, trail head, or store, and 15 minutes gives us a days power back, or more.
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Old 08-30-2017, 04:38 PM   #12
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A stick is a lot cheaper than $200! I am sure a cheap mechanical throttle option could be engineered.
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Old 08-31-2017, 12:26 AM   #13
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Originally Posted by cruising7388 View Post
How and where are you reading these values?
Here is a pic showing the inverter current clamp-on (left) and alternator current clamp-on (right) and the Balmar voltage sense wire with 5 amp inline fuse. I used phone cord and RJ11 connectors for ease of hookup and testing for the 2 current clips. The cables run to the cab where I have the displays.

Here is the current transducer I used, it is a 500 amp to 4-20 ma current loop. The 4-20 ma output is good for long runs, and eliminates voltage drop errors.

https://www.amazon.com/gp/aw/d/B00LM...ent+transducer
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Old 08-31-2017, 02:49 AM   #14
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Originally Posted by prfleming View Post
Here is a pic showing the inverter current clamp-on (left) and alternator current clamp-on (right) and the Balmar voltage sense wire with 5 amp inline fuse. I used phone cord and RJ11 connectors for ease of hookup and testing for the 2 current clips. The cables run to the cab where I have the displays.

Here is the current transducer I used, it is a 500 amp to 4-20 ma current loop. The 4-20 ma output is good for long runs, and eliminates voltage drop errors.

https://www.amazon.com/gp/aw/d/B00LM...ent+transducer
The split core feature is a real plus. Where did you route the telco wiring to and what metering did you employ to get a coherent amp delivery display?
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Old 08-31-2017, 03:59 PM   #15
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The split core feature is a real plus. Where did you route the telco wiring to and what metering did you employ to get a coherent amp delivery display?
Right, there are a few more bits needed to use 4-20 ma control loop monitoring. These are typically powered with 24V DC, so I used this DC to DC converter mounted inside the display box to supply 24V.

https://www.amazon.com/gp/product/B0...reative=390957

Also needed are 4-20 ma current to voltage converters to drive a 4 digit voltage display. I used converters similar to these (mounted inside the display box) and these displays.

https://www.amazon.com/gp/product/B0...reative=390957

https://www.amazon.com/SainSmart-Cur...reative=390957

The 4-20 ma current to voltage converters have a zero and range adjustment, I calibrated both current clamps using a hand held clamp-on current meter and my battery load tester and tested at 100, 200, 300, 400 amps for accuracy.

To answer your specific question, using std phone cord, the clamp-on current transducer is powered with 24V, and provides the 4-20 ma current signal back to the display box where it is converted to a voltage and shown on the 4 digit displays. You ignore the decimal, I adjusted 5.00 volts to equal 500 amps, so for example 1.65 volts equals 165 amps. It didn't cost much, and I needed a winter project to get me through to summer...
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Old 09-02-2017, 09:21 PM   #16
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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.
Took our 20917 PC to Chebby and they did program the high idle which activates at 1200 rpm. But following the instructions, we are not able to adjust the high idle rpm up or down.
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Old 09-07-2017, 12:52 AM   #17
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I thought you can charge AGM batteries at 20% of capacity. So how are you using the 180 amps? It does make a good case for lithium battery bank. That is a lot of amps in a short period.
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Old 09-07-2017, 12:55 AM   #18
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My understanding was that using high idle was more about the emission system not getting fouled up. Maybe if one does some hwy driving for a while it is not so necessary.
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Old 09-07-2017, 05:19 PM   #19
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I thought you can charge AGM batteries at 20% of capacity. So how are you using the 180 amps? It does make a good case for lithium battery bank. That is a lot of amps in a short period.
Lead acid batteries self regulate to some degree. You could make 500A available to them for example but they'll only take what they'll accept at a given voltage. I do agree with limiting the charging current to what the manufacturer recommends if the system allows for it as it would likely extend the life of the batteries.
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Old 09-07-2017, 05:25 PM   #20
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My understanding was that using high idle was more about the emission system not getting fouled up. Maybe if one does some hwy driving for a while it is not so necessary.
My understanding is that fast idle allows for:

Increased Air Conditioning for stationary operation.
Increased Electrical Output for stationary operation.
Increased Vehicle Heating for stationary operation.
Prevents "wet stacking" - unburned fuel contaminating the engine oil.

This current topic is about a gas engine Chevy van but here's some info re: Sprinter diesels. 5 years ago I sent an inquiry to Sprinter Engineering and their response indicated that fast idle does not eliminate DPF & EGR related problems.

Direct copy paste from that email:

Quote:
Per your request, with the SCR technology of our engines, we do not recommend idling a Sprinter for longer periods than 2.5 - 3 hours.

Even with the high idle engaged, you should not exceed the aforementioned times to avoid clogging the DPF or damages to the EGR valve.

Fyi, the fuel consumption is .4 - . 5gal. per hour of idling.
Back then, on this forum, we wondered if gas engine Class B's might be the better choice if extending idle times were expected.
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