Stress testing 12V Victron MultiPlus 3000 with EG4 LL batteries (heating issue)

[pabla007]

Current System Configuration​

1. 12V Victron MultiPlus 3000 - Quantity: 1
2. Lynx Distributor - Quantity: 1
3. Lynx Shunt VE.Can - Quantity: 1
4. Lynx Power In - Quantity: 1
5. 12V EG4 LL Batteries - Quantity: 4

Wiring and Connectivity​

• The "Lynx Power In" is connected to the "Lynx Shunt VE.Can".
• The "Lynx Shunt VE.Can" is connected to the "Lynx Distributor".
• The "Lynx Distributor" is connected to the MultiPlus.

Power and Safety​

• A 400-amp fuse is installed at the Lynx Power In, which is connected to the batteries.
• Four batteries are connected in parallel (each is an EG4 Lithium battery 12.8V (12V), 400AH, 5.12kWh with a 200A internal BMS).
• Wire size used is 2 gauge.
• A manual disconnect is installed between the battery and the Lynx Power In.
• The RV has a 30-amp system, with a 20-amp breaker dedicated to the air conditioner.

Testing and Observations​

• Conducted a stress test after installing a total of 20 kW in the RV.
• During testing, the following appliances were running: air conditioner, TV, lights, and refrigerator.
• Noticed the wire from the batteries to the manual disconnect was warm.
• The wire from the manual disconnect to the Lynx Power In was hot (not just warm).
• Ensured that the wire connections at the manual disconnect were not loose.

Questions​

1. Fuse Sizing: What size fuse should I be using given the current setup and the components involved?
2. Battery Connections: Do I need to install a fuse on each battery before connecting them to the bus bar? Currently, all four batteries are connected to a single 400-amp fuse at the Lynx Power In.
3. Cable Upgrade: Should I upgrade to 2/0 gauge cable to handle the load more efficiently, despite the high cost of copper?

Goal​

Seeking advice to improve the system and ensure safety to prevent any potential damage to the RV trailer.

 

[sunshine_eggo]

1. 1.25X wire rating rounded up to the nearest common size.
2. That is considered best practice. With a single 400A fuse, all wiring must be able to handle 400A/1.25 = 320A
3. 3000/12/.85 = 276A

2awg feels REALLY thin for this application.

It's worth opening the MP manual and looking at their recommendations for wiring. They recommend 2X 50mm^2 wires, which is the equivalent to 4/0.

 

[Brucey]

When you say 400A do you mean a class t fuse? Can you provide a picture of how it's wired up? What specific disconnect are you using?

 

[chicagoandy]

Your Multiplus can pull 3,000 watts. Divide that by 12V and you get 250 Amps, just for the inverter. Add additional amps for your other DC current.
AWG-2 cable is far too small for what could be 300 Amps.

The Victron Multiplus that you're using specifies two paralell runs of 50mm cable. The AWG equivalent of 50mm is 1/0 "one aught", and they're calling for a pair of them. And that doesn't even include any additional DC loads.

https://www.victronenergy.com/upload/documents/Manual-MultiPlus-3k-120V-(firmware-xxxx4xx)-EN.pdf

Reading the manuals are important, getting educated on wire-size is important.

You also haven't talked about what kind of fuses you have. That is critically important, as different fuse types have very different characteristics. Here is a good primer on fuse-types:

- note this video is produced by Explorist.life, which has an excellent series of building RV power systems.

Your questions:

1. Fuse Sizing: What size fuse should I be using given the current setup and the components involved?

RTFM. Victron recomments a 400amp fuse JUST for their Multiplus.

4 400 ah batteries in parallel can put out a MASSIVE amount of energy in case of a short-circuit. You MUST use a T-Class fuse to protect downstream components.

1. Battery Connections: Do I need to install a fuse on each battery before connecting them to the bus bar? Currently, all four batteries are connected to a single 400-amp fuse at the Lynx Power In.

Fuses should be placed as close as possible to the battery, not the bus-bar. You can put a Marine Rated Battery Fuse on each battery. (MRBF).

What this video on where to put fuses. :

1. Cable Upgrade: Should I upgrade to 2/0 gauge cable to handle the load more efficiently, despite the high cost of copper?

YES! If you can't afford the copper, you can't afford the RV. You can do a pair of 2/0 cables, or a single 4/0 cable.

 

[pabla007]

When you say 400A do you mean a class t fuse? Can you provide a picture of how it's wired up? What specific disconnect are you using?

Victron Energy MEGA-Fuse 400A​

 

[pabla007]

I notice my wire is 1/0, but after disconnect I believe is 2 AWG.

 

[pabla007]

Your Multiplus can pull 3,000 watts. Divide that by 12V and you get 250 Amps, just for the inverter. Add additional amps for your other DC current.
AWG-2 cable is far too small for what could be 300 Amps.

The Victron Multiplus that you're using specifies two paralell runs of 50mm cable. The AWG equivalent of 50mm is AWG-1, sometimes called 1/0 "one aught". AWG-1 is twice the thickness of AWG-2, and they're calling for a pair of them. And that doesn't even include any additional DC loads.

https://www.victronenergy.com/upload/documents/Manual-MultiPlus-3k-120V-(firmware-xxxx4xx)-EN.pdf

Reading the manuals are important, getting educated on wire-size is important.

You also haven't talked about what kind of fuses you have. That is critically important, as different fuse types have very different characteristics. Here is a good primer on fuse-types:

- note this video is produced by Explorist.life, which has an excellent series of building RV power systems.

Your questions:

1. Fuse Sizing: What size fuse should I be using given the current setup and the components involved?

RTFM. Victron recomments a 400amp fuse JUST for their Multiplus.

4 400 ah batteries in parallel can put out a MASSIVE amount of energy in case of a short-circuit. You MUST use a T-Class fuse to protect downstream components.

1. Battery Connections: Do I need to install a fuse on each battery before connecting them to the bus bar? Currently, all four batteries are connected to a single 400-amp fuse at the Lynx Power In.

Fuses should be placed as close as possible to the battery, not the bus-bar. You can put a Marine Rated Battery Fuse on each battery. (MRBF).

What this video on where to put fuses. :

1. Cable Upgrade: Should I upgrade to 2/0 gauge cable to handle the load more efficiently, despite the high cost of copper?

YES! If you can't afford the copper, you can't afford the RV. You can do a pair of 2/0 cables, or a single 4/0 cable.

Thank you for the video. I will be placing my fuse near the battery. I do have extra 2/0 cable red and black each 20 ft. I will double up each cable to make 4/0.

 

[Brucey]

Victron Energy MEGA-Fuse 400A​

Ok so a few more questions.

1) Have you converted your power in to act like a distributor (I e placed nuts and bolts in it to allow it to hold mega fuses?). Because out of the box the power in doesn't support fuses.

2) Or is this 400A mega fuse located in the distributor to the right of the shunt? Where the multiplus connects to the bus? If so that's fine for protection from an inverter failure but does nothing to mitigate the risk from the available current of the batteries.

If 2 is accurate, then best practice would be to mount a Class T fuse on that battery cable, prior to the shutoff switch, ideally as close to the batteries as possible. perhaps a combo of mrbfs on the terminals and then a class t prior to shutoff switch. Make sure the mrbfs you get are quality (blue sea systems etc). Don't go for the cheapest option on Amazon.

 

[DIYrich]

The Victron Multiplus that you're using specifies two paralell runs of 50mm cable. The AWG equivalent of 50mm is AWG-1, sometimes called 1/0 "one aught". AWG-1 is twice the thickness of AWG-2, and they're calling for a pair of them.

just for clarification for newbies: AWG 1/0 is the same as AWG 0, which is one size bigger than AWG 1.

 

[DIYrich]

I do have extra 2/0 cable red and black each 20 ft. I will double up each cable to make 4/0.

Note: two 2/0 cable does not "make" 4/0 cable.

 

[corn18]

Get rid of that cheap piece of crap disconnect and get a real one. Victron gear should not be associating with cheap kit. Blue Victron + Blue Sea Systems = Bluey goodness.

https://www.amazon.com/Blue-Sea-Systems-3001-Alternator/dp/B000THRMOG/ref=sr_1_5?crid=1XRK6Q1THZ9MB&dib=eyJ2IjoiMSJ9.iR1ccldpHzHSndmvI5CXnhTfl4p2r7FqJoW0inKgMvonw97hu2MVy8O6dNZRNiiuCmSyLzbX_YSi3sWyGlSaVFoZ_1TqTgWZu68IEbGzh39GZ8_Xr3Zt0IjhtKqqiYJS-JZO32L6-O-DnfKDsLHgRqGCNaymIOhaYNcei9LmwSuiqAQyNkcpufqGq7KHNGQEuHCK2a88G1vqrxT-qCw6L7BzF6xxGzpA1SViJqjilTc.1QFfhZuEuIP21rXWvpIk5DLhyPh7HnOuzKOhnud3GnY&dib_tag=se&keywords=blue+sea+systems+battery+disconnect+switch&qid=1715166139&sprefix=blue+sea+systems+battery+disconnect+switch%2Caps%2C218&sr=8-5

use 2/0 equal length cables for all your battery connections to the Lynx. Replace the lynx power in with a lynx distributor and use 250A fuses on each battery input (or just make the mod to turn your lynx power in into a lynx distributor). Use 4/0 cable from the lynx distributor output to the disconnect and the same size to the class T 400A and the inverter.

Doing this wrong in any way with 320A flowing about will heat stuff up to red hot fast. You have basically installed a welder in your RV. Guessing at these current levels can go wrong fast.

 

[pabla007]

Ok so a few more questions.

1) Have you converted your power in to act like a distributor (I e placed nuts and bolts in it to allow it to hold mega fuses?). Because out of the box the power in doesn't support fuses.

2) Or is this 400A mega fuse located in the distributor to the right of the shunt? Where the multiplus connects to the bus? If so that's fine for protection from an inverter failure but does nothing to

Get rid of that cheap piece of crap disconnect and get a real one. Victron gear should not be associating with cheap kit. Blue Victron + Blue Sea Systems = Bluey goodness.

https://www.amazon.com/Blue-Sea-Systems-3001-Alternator/dp/B000THRMOG/ref=sr_1_5?crid=1XRK6Q1THZ9MB&dib=eyJ2IjoiMSJ9.iR1ccldpHzHSndmvI5CXnhTfl4p2r7FqJoW0inKgMvonw97hu2MVy8O6dNZRNiiuCmSyLzbX_YSi3sWyGlSaVFoZ_1TqTgWZu68IEbGzh39GZ8_Xr3Zt0IjhtKqqiYJS-JZO32L6-O-DnfKDsLHgRqGCNaymIOhaYNcei9LmwSuiqAQyNkcpufqGq7KHNGQEuHCK2a88G1vqrxT-qCw6L7BzF6xxGzpA1SViJqjilTc.1QFfhZuEuIP21rXWvpIk5DLhyPh7HnOuzKOhnud3GnY&dib_tag=se&keywords=blue+sea+systems+battery+disconnect+switch&qid=1715166139&sprefix=blue+sea+systems+battery+disconnect+switch%2Caps%2C218&sr=8-5

use 2/0 equal length cables for all your battery connections to the Lynx. Replace the lynx power in with a lynx distributor and use 250A fuses on each battery input (or just make the mod to turn your lynx power in into a lynx distributor). Use 4/0 cable from the lynx distributor output to the disconnect and the same size to the class T 400A and the inverter.

Doing this wrong in any way with 320A flowing about will heat stuff up to red hot fast. You have basically installed a welder in your RV. Guessing at these current levels can go wrong fast.

I am placing order for following all item from Amazon so could I have my tomorrow or in a week.

1.Blue Sea Systems 3001 Heavy Duty Battery Switch with Alternator Field Disconnect, On-Off, Beige
2.4/0 Gauge - 15 Feet Black + 15 Feet Red Combo - EWCS Brand 100% Copper Premium Industrial Grade Extra Flexible Welding Cable 600 Volt
3.RIOCAN 10pcs 4/0 AWG-5/16”(M8) Ring Terminals Battery Lugs 0000 Gauge Battery Cable Ends Heavy Duty Wire Lugs Battery Cable Connector Copper Lugs…
4. Blue Sea Systems 5121 FUSE A3T (CLASS T) 400 AmpBlue Sea Systems 5121 FUSE A3T (CLASS T) 400 Amp
5. AMRB-5502 Blue Sea Class T Fuse Block w/Insulating Cover - 225 to 400AAMRB-5502 Blue Sea Class T Fuse Block w/Insulating Cover - 225 to 400A

mitigate the risk from the available current of the batteries.

If 2 is accurate, then best practice would be to mount a Class T fuse on that battery cable, prior to the shutoff switch, ideally as close to the batteries as possible. perhaps a combo of mrbfs on the terminals and then a class t prior to shutoff switch. Make sure the mrbfs you get are quality (blue sea systems etc). Don't go for the cheapest option on Amazon.

 

[Brucey]

I am placing order for following all item from Amazon so could I have my tomorrow or in a week.

1.Blue Sea Systems 3001 Heavy Duty Battery Switch with Alternator Field Disconnect, On-Off, Beige
2.4/0 Gauge - 15 Feet Black + 15 Feet Red Combo - EWCS Brand 100% Copper Premium Industrial Grade Extra Flexible Welding Cable 600 Volt
3.RIOCAN 10pcs 4/0 AWG-5/16”(M8) Ring Terminals Battery Lugs 0000 Gauge Battery Cable Ends Heavy Duty Wire Lugs Battery Cable Connector Copper Lugs…
4. Blue Sea Systems 5121 FUSE A3T (CLASS T) 400 AmpBlue Sea Systems 5121 FUSE A3T (CLASS T) 400 Amp
5. AMRB-5502 Blue Sea Class T Fuse Block w/Insulating Cover - 225 to 400AAMRB-5502 Blue Sea Class T Fuse Block w/Insulating Cover - 225 to 400A

that's pretty expensive for 30 feet of 4/0, maybe consider this for $229.

https://www.amazon.com/Welding-Battery-Flexible-Terminal-Connectors/dp/B01MD21MWL

 

[pabla007]

that's pretty expensive for 30 feet of 4/0, maybe consider this for $229.

https://www.amazon.com/Welding-Battery-Flexible-Terminal-Connectors/dp/B01MD21MWL

Thank you.

 

[chicagoandy]

I am placing order for following all item from Amazon so could I have my tomorrow or in a week.

1.Blue Sea Systems 3001 Heavy Duty Battery Switch with Alternator Field Disconnect, On-Off, Beige
2.4/0 Gauge - 15 Feet Black + 15 Feet Red Combo - EWCS Brand 100% Copper Premium Industrial Grade Extra Flexible Welding Cable 600 Volt
3.RIOCAN 10pcs 4/0 AWG-5/16”(M8) Ring Terminals Battery Lugs 0000 Gauge Battery Cable Ends Heavy Duty Wire Lugs Battery Cable Connector Copper Lugs…
4. Blue Sea Systems 5121 FUSE A3T (CLASS T) 400 AmpBlue Sea Systems 5121 FUSE A3T (CLASS T) 400 Amp
5. AMRB-5502 Blue Sea Class T Fuse Block w/Insulating Cover - 225 to 400AAMRB-5502 Blue Sea Class T Fuse Block w/Insulating Cover - 225 to 400A

Thanks for taking the advice and following through.

 

[pabla007]

Thanks everyone! I was worried when the wire got hot and wasn't sure if it was because of the cheap disconnect switch or if I needed a bigger wire. I appreciate the advice from those more knowledgeable, and I'll share updated pictures soon.

 

[pabla007]

I have implemented all the requested changes. I've included before and after pictures, each labeled accordingly. I installed a Class T fuse rated at 400 amps, and upgraded the cables to 4/0 gauge. There are now four fuses installed, each rated at 400 amps. Please let me know your thoughts.

 

[pabla007]

Following items were purchased from Amazon to complete my project.

* Blue Sea Systems 5121 FUSE A3T (CLASS T) 400 Amp ()​

* Blue Sea Systems 3001 Heavy Duty Battery Switch with Alternator Field Disconnect, On-Off, Beige ()​

* 4/0 Gauge 4/0 AWG Red 15 Feet + Black 15 Feet Welding Battery Pure Copper Flexible Cable + 10pcs of 3/8" Tinned Copper Cable Lug Terminal Connectors + 3 Feet Black Heat Shrink Tubing​

* AMRB-5502 Blue Sea Class T Fuse Block w/Insulating Cover - 225 to 400A​

* 4/0 AWG 3/8" Stud (10 pcs.), Heavy Duty Battery Ring Terminal, 0000 Gauge Connectors, 4/0 Battery Cable lugs, Copper Wire Lugs, Copper Ring Terminals, Bare Copper, Tubular Ring Terminal Connectors​

* AMZCNC Hammer Lug Crimper Tool - 0000 AWG Battery and Welding Cables( 8 AWG TO 4/0 Wire Gauge)​

*​

 

[chicagoandy]

Those are some impactful upgrades. I assume you didn't see any more hot connections?

What are the amps on the mega fuses in the lynx distributor?

 

[pabla007]

Those are some impactful upgrades. I assume you didn't see any more hot connections?

What are the amps on the mega fuses in the lynx distributor?

All of them are 400Amp