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aopsahl7 avatar image
aopsahl7 asked

Onan P4500IDF Auto Start/Stop With Cerbo GX (Elevation Module)

All -

I have been working with my friends at AM Solar on a little bit of a square hole round peg problem.

I have an off grid cabin with all Victron equipment and some panels on the roof. I cannot add more solar due to restrictions, but I want to have a small generator that can boost back up the batteries if we get a big snow storm etc.

I am well aware of the fact that there are generators out there that are designed for this, but due to budget and low power needs I have selected the Cummins P400iDF (portable) to be my generator. With that said, I want to auto/start/stop with the CERBO.

My plan is to use the Elevation AGS, which has been proven to work with the Cerbo. However, wiring it to this particular generator is where I am looking for more information. I believe @Cleaver has figured this out and I would love his/her help as well as any others. Here is the schematic of the Elevation unit as well as the schematic for the generator.


Screenshot 2023-04-26 at 2.31.45 PM.png


Screenshot 2023-04-26 at 5.31.20 PM.png


Screenshot 2023-04-26 at 5.30.46 PM.png

cerbo gxgenerator auto start
screenshot-2023-04-26-at-53046-pm.png (148.4 KiB)
screenshot-2023-04-26-at-53120-pm.png (694.2 KiB)
screenshot-2023-04-26-at-23145-pm.png (49.6 KiB)
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5 Answers
Paul B avatar image
Paul B answered ·

you maybe able to do this with just using the cerbo relay one the picture MAY WORK, this will depend if there are any issues with keeping the buttons pressed all the time. I am guessing that pin 5 on the switch is the stop command. you would have to unplug the cerbo plug if you wanted to do a manual start at the generator.

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1682559283508.png (353.8 KiB)
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cleaver avatar image cleaver commented ·
I tried that. it didn't work for me. But try turning the switch on and just holding button.

I added to my comment below what I had to do to wire the remote start. It allows the generator to stay in sync with cerbo.

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aopsahl7 avatar image
aopsahl7 answered ·

Thanks Paul. I see what you are thinking. I have no idea if the start switch being held during all operation would be a problem or not.

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Paul B avatar image Paul B commented ·
you should be able to test that - it will work or it wont, so test and see if you hear any funny (bad) nosies ie starter holding in etc. if all seems ok give it a go
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aopsahl7 avatar image
aopsahl7 answered ·

Seems reasonable to me. Voltage coming out of the Cerbo relay is 12v yes? Going to simulate with a 12v source before taking up to the cabin.

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Paul B avatar image Paul B commented ·
no voltage coming out of the relay it depends on what you connect to the common, terminal
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cleaver avatar image
cleaver answered ·

I will post what all I added to the generator and the relays I used for the momentary pulse for push button start.

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aopsahl7 avatar image aopsahl7 commented ·
THANK YOU!
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cleaver avatar image cleaver aopsahl7 commented ·

So to begin I need to know how your generator works. I use the 4500i, so the only difference I see is yours has propane option.


So to begin I had to install 2 micro relays in the generator itself. one for the switch to close the circuit to supply power. The second to close the momentary contact for the push button. (I thought I had pictures of the wiring but I just have the before pics.)


All power and signal wires are fed from the RV (this makes sure the battery on the generator is fully charged when it is needed to run.

The cerbo has to have 2 relays hooked to the generator relay. These are a programable relay (Directed Electronic 528T) One setup to pulse when the cerbo relay closes and on setup to pulse when it opens. These relays were very popular for car alarms in the day. you can adjust for pulse time and control for negative or positive pulse. (i used negative on both )

So 3 wires from RV to generator.

1. constant 12 vdc

2. Negative (cerbo relay switched) (generator relay)

3. Pulse wire that is connected to both 528T pulse relays.

** the 528T's will be setup opposite. one will pulse when closed and the other will pulse when the cerbo relay opens**

(I originally had this setup for a different generator) for cummins you only need 1X528T relay. Setup to pulse when closed. Because when the cerbo relay opens it will turn off the master switch relay in the generator.


I found a couple of pics but they do not show anything after the wiring mods.

the on/off switch in the generator is 2 pole. you need to install 2 micro relays that operate from the same signal wire. one to be normally open and the other to close.

1. generator shuts down when power for relays is removed (normally closed)

2. power is supplied to the momentary start button and remote start.(normally open)

(my generator power switch is powered and illuminated so it will kill the start battery if left powered)

the 528T needs to be set just long enough for the generator to recognize signal. having it set to long seems to trigger a diagnostic mode and switch would flash a blink code. If it will not start play with the time setting on the 528T

the relays and 528T cost approx 50.00CDN. just the 4 wire signal and weather pack plugs were the expensive parts.




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cleaver avatar image
cleaver answered ·

528T wiring.pdf

Here is the 528T wiring


528t-wiring.pdf (101.3 KiB)
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