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01-05-2023, 02:19 PM #1
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EMS in front of MultiPlus ii, Technical questions
Currently I have the 50amp Progressive Industries box hardwired, it works very well. One thing we like is the LOW voltage shutoff; we get down to 108ish then it shuts off power when someones AC kicks in. Now I want to integrate the Victron MultiPlus ii unit. This is supposed to sense LOW voltage then make up the difference with battery power. I like this feature a lot. Now comes the problem; with the EMS in front of inverter, the inverter would never see the lower voltages as the EMS would not pass that thru. I spoke with PI today and he said there is no way to toggle the LOW voltage protection and to look at a surge/over voltage device for the pedestal. For the reasons I got the hardware unit, I prefer not to put anything on pedestal. It seems I have (3) options.
1. Don't use the boost feature of Multiplus.
2. Remove the hardware EMS unit and go "unprotected".
3. Get a lightning and overvoltage protector that is plugged inline with power cable INside the trailer.
I want to pursue #3 , but I am worried when the batteries are low I might choose to disable the inverter and now I have no LOW voltage protection. I was searching web to find a transfer switch, that the Multiplus would toggle, so when I use inverter, it would look like the below graphic, no luck. My idea is to use my existing EMS as "b" and a simple overvoltage "hang on the pedestal" as "A" and somehow setup Victron so if I use inverter, it toggles switch to EMS "A" and it would use the full protection of EMS "B" at all other times.
Anyone have suggestion on how to handle this ?
2022 GD 2970RL (soon to be "released")
2019 F350 Platinum, Shorter bed, Diesel, SRW, 3.55 rear, 55gal tank!
2016 F150 Platinum (traded in for F350 fall 2019)
2016 GD 2600rb (Sold)
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01-05-2023, 06:06 PM #2
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01-05-2023, 06:16 PM #3
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Thanx for pointing this out;
Fact 1: The EMS shuts off power to RV if is voltage < 108vAC. So if a Multiplus ii was after EMS (where it belongs) then Multiplus would never see the low voltage comming from EMS, it would not see any voltage and that would really clobber my batteries quick if the AC was running as it would do its best to keep outputting 120v all from battery when the shore power was mostly available.
Fact 2: You cannot put the EMS after the Multiplus ii; instructions clearly say this.
Fact 3: Without the EMS, if the voltage drops below 108vAC it will use batteries to bring voltage back to 120vAC. BUT without EMS I lose my surge and lightning protection.
Fact 4: According to Progressive Ind support, I cannot disable the low voltage shutoff in the EMS. If I could then I would and this forum post would not
be purposed.
Fact 5: Victron is fuzzy on what voltage protection it offers, if it protected against over voltage and lightning, then this forum post would not be purposed.
2022 GD 2970RL (soon to be "released")
2019 F350 Platinum, Shorter bed, Diesel, SRW, 3.55 rear, 55gal tank!
2016 F150 Platinum (traded in for F350 fall 2019)
2016 GD 2600rb (Sold)
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01-05-2023, 07:01 PM #4
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I didn’t think the boost feature worked that way?? I know it provides power (amps) from the batteries if you need more than is available from shore power I.E. plugged into a 15a circuit and need 20 etc.
Maybe it does both?
Using a autoformer in front of the ems will solve low voltage shutoff. That’s how I have mine wired. Autoformer—>ems—>multiplus.2021 Solitude 375 RES-R
2024 GMC Denali ultimate DRW
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01-05-2023, 08:14 PM #5
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1: Yes, if EMS disconnects shore power to due to low voltage, the MPII will start inverting if set to do so Automatically
2: Correct, there would be no reason to
3: This is incorrect. The MPII will do nothing with bucking the voltage. In fact, the MPII had it's own configurable internal low voltage disconnect. The MPII will NOT buck low voltage up from a low voltage situation. The Boost (power assist) merely supliments the A/C if the wattage load demand exceeds the A/ C capacity. For example you are on 30amp shore power but you want the inverter to assist if the demand exceeds 30amps temporarily.
4: Agree
5: Answered in 3 except for surge protection. It doesn't offer any surge protection. The MPII has an internal transfer switch only. Definitely recommend having a surge protector.
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01-05-2023, 08:45 PM #6
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Thanks to @A.Texas.Yankee and @JKellerJr for the clarification on Multiplus NOT bucking mains voltage; it boost current only. I wish I could find where I read about low voltage. I will look to design in an autoformer. I am not familiar with that device. Thanks to both.
UPDATE: Please read THIS post, does the Engineer say my #3 is correct ?Last edited by wudwork; 01-05-2023 at 08:57 PM.
2022 GD 2970RL (soon to be "released")
2019 F350 Platinum, Shorter bed, Diesel, SRW, 3.55 rear, 55gal tank!
2016 F150 Platinum (traded in for F350 fall 2019)
2016 GD 2600rb (Sold)
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01-05-2023, 08:53 PM #7
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https://hughesautoformers.com/
Here’s mine
2021 Solitude 375 RES-R
2024 GMC Denali ultimate DRW
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01-05-2023, 09:18 PM #8
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01-06-2023, 06:46 AM #9
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Yes, Dragonfly Energy is claiming the power assist feature of the MultiPlus will aid a low voltage source, according to the quote from Second Chance. I understood it to be like @A.Texas.Yankee mentioned, but I’m not far enough along in research/buy/install process to say yet. If it does, then a Quattro would achieve the goal in your original post by allowing u to eliminate the transfer switch.
Larry and JoAnna
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01-06-2023, 06:58 AM #10
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I will say I’m skeptical of what the Dragonfly guy says tho. You don’t just raise voltage without feeding back to the source, but you can “assist” it by not allowing it to drop further, which is what I understand Victron to be doing. Otherwise they would have to isolate the weak source by converting to a DC bus, then inverting the full power requirement. This is my speculation, not because I know for sure, so take it for what it’s worth.
Larry and JoAnna
‘23 Chevy 3500HD CCLB DRW High Country 6.6L Diesel, ‘22 Solitude 310GK-R, Hensley BD5
MORRyde 8k IS, QD8000 Genny, Dual 5kVA Quattros
Dual SOK 48V 100ah Server Rack Batts (10kWHr)
Re-pack bearings necessary?
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