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jamesmcclatchey asked

DC Charger output

I have an isolated DC-DC Charger connected with 4 AWG wire from a tow vehicle to trailer. There is little to no voltage drop in the wiring. I have 400 watts of rooftop solar connected to a Smart Solar MPPT 100/30. Batteries are 2 Battleborn 270 AH GC3 Lithium. Please review the attached iPhone screen shots taken while underway on the highway in partly sunny weather. One is from VRM and the other from near simultaneous Victron Connect. I think I have gotten more from the Orion in the past. Now its maximum appears to be no more than 200 watts where I have seen 300 in the past. Why is the difference of 13 V from the DC-DC charger so different from the 13.83 volts from the solar charger? Are these 2 units conflicted with each other? Is there something I can do to increase the charger output?


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MPPT SmartSolarorion dc-dc
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kevgermany avatar image kevgermany ♦♦ commented ·

Guessing.

Looks as if the Orion isn't getting enough input power and there is load on its output which drops the voltage. Might be resistance in connectors/fuses as well.

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Bob K avatar image Bob K commented ·
An Input Voltage of 12.9v indicates you have a smart alternator. Please post your Engine Shutdown Detection settings. If those settings aren't correct for your vehicle, the Orion will automatically decrease its load as the Input Voltage drops (because of the smart alternator dialing back its output).
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jamesmcclatchey avatar image jamesmcclatchey Bob K commented ·

Engine shutdown detection

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ jamesmcclatchey commented ·

The Orion starts reducing the charging current if the input voltage gets near the shutdown voltage.

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Bob K avatar image Bob K jamesmcclatchey commented ·

Your Shutdown Voltage is set to 12.95. As your smart alternator reduces its voltage output down toward 12.9v, the Orion will reduce its load (i.e. amperage output) in order to attempt to keep from falling below the Shutdown Voltage. That's why you're seeing lower amperage output from the DC charger.

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Try reducing your Shutdown Voltage down to 12.8v. A fully charged lead acid battery sits at about 12.78v, so you won't want to go below that in order to prevent discharging the starter battery after you turn off the vehicle.

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jamesmcclatchey avatar image
jamesmcclatchey answered ·

Thanks for the responses. This makes sense. I will give it a try!

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Bob K avatar image Bob K commented ·

If adjusting the Shutdown Voltage downward doesn't make your alternator play nice with the DC Charger and output higher amperage, your next option is probably to wire up a Remote On-Off switched circuit (which will let you set your Shutdown Voltage even lower without discharging your starter batter when the vehicle is off). See my comment a few down in this thread: https://community.victronenergy.com/questions/229390/engine-start-detection-by-orion.html?childToView=229826#answer-229826

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jamesmcclatchey avatar image jamesmcclatchey Bob K commented ·
Just to tie things up, I reduced the Engine Shutdown Voltage to 12 V on the DC-DC Charger. A bit lower than the recommendations here, but it still detected the engine shutdown. I am getting full output now. Yesterday driving in full sun through west Texas, I was getting 350 watts from the DC Charger along with 150 watts from the solar. 500 watts into 2 Battleborn GC3 270 Amp-Hr Lithium batteries at 50% charge. Pretty cool!
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Bob K avatar image Bob K jamesmcclatchey commented ·

Excellent! If you don't have the Remote On-Off switch installed, just be careful. 12V is pretty much "dead" for a lead acid battery. With your Engine Shutdown Detection Shutdown voltage set at 12.0v, the DC Charger will almost always continue drawing on that battery until it reaches 12.0v and will leave you stranded with a dead starter battery.



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jamesmcclatchey avatar image jamesmcclatchey Bob K commented ·
Understood. I have checked to see if the Orion detects engine shutdown at the 12 volt setting. It does so. My guess is that the 30 amp draw from the battery in the tow vehicle (TV) with no alternator operating is enough to pull the apparent voltage at the Orion down below 12. There is 25 ft of 4 AWG wire (one way) between the TV battery and the Orion which creates about a 0.5 v drop at 30 amps so that mitigates the issue a bit.


Keep in mind that I generally keep a 350 watt refrigerator running when underway. A circumstance I will have to watch would be where the trailer batteries are near full charge and there is little or no current draw from the trailer. Such a low draw might keep the apparent voltage above the shutoff point.

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Bob K avatar image Bob K jamesmcclatchey commented ·

"There is 25 ft of 4 AWG wire (one way) between the TV battery and the Orion which creates about a 0.5 v drop at 30 amps so that mitigates the issue a bit."

Excellent point.

I mentioned "almost always" for the exact scenario you highlight: Sometimes the huge draw on a starter batt alone (when the alternator is not on) while the DC charger is in Bulk charge mode is enough to draw the starter batt voltage down below that 12v long enough (for more than 60 seconds) to get it to turn off before the DC charger can run its algorithm and back off on its load. I've seen it happen a couple times with my Tacoma. Normally, however, the DC charger is very proficient at reducing its load (so as to not drop below the Engine Shutdown voltage), even in Bulk charge mode, and running down my starter batt if the Tacoma is turned off.

The problem will arise more so when the DC Charger is in absorption or float mode. In that case, it's already putting a more gentle draw on the starter batt and the DC charger's algorithm will be much more proficient at reducing its load on the starter batt so that it doesn't fall below that 12v. It'll persist with that gentle draw until my starter batt is depleted.

So I basically just reworded everything you just said. My wife says I'm good at that. ;-)

This would be so much easier if auto manufacturers would just give us a switch to make the "smart" alternator output higher voltage, wouldn't it??


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