Need some help diagnosing what has happened

[HJEngland]

Today, I went outside and smelled a burning smell coming from my small solar system. The negative wire from the inverter to the battery had begun melting!

What would cause this? I have a very simple system of (1) Renogy 24v 320w solar panel, a Renogy Rover MPPT solar charger, a 2000w inverter, and a 12v 200 ah Renogy AGM battery. I have disconnected everything and removed the inverter.

I really am at a loss now... any insights would be much appreciated.

 

[Wjm1964]

What load were you pulling from the inverter at the time?

 

[HJEngland]

I'm not sure. It said 100% load, but I'm not sure how that can be-- the only thing on has been a Dometic refrigerator..

 

[Johno1066]

Looking at the picture it would appear that the lug got pretty hot from poor conductivity of the cable to lug. The cable only seems melted close to the lug, the rest of the cable looks OK.

 

[Ampster]

What would cause this?

A bad connection or too small of cable. A bad connection could simply be a lug with a hole too big for the stud reducing the contact surface area between the lug and the terminal on the inverter.

 

[HJEngland]

The inverter is still working but I'm scared to use it because of this damage. Is it safe to continue to use? If so, should I use larger cables? This is all very new to me.

 

[Ampster]

The inverter is still working but I'm scared to use it because of this damage. Is it safe to continue to use? If so, should I use larger cables?

The inverter would not likely be damaged. My guess is it was the connection as @Johno1066 suggested since it looked like the heat was restricted to the lug. Are the hole in the lug and the bolt on the terminal matched? Can you find a lug with more surface area? I would try making sure that connection is good and see if the issue resolves.

 

[HJEngland]

Thank you for this input-- I will check and see if I can get a better lug for the inverter terminal. I am feeling very defeated that I can't even manage the smallest of systems...

 

[Ampster]

I am feeling very defeated that I can't even manage the smallest of systems...

Each one of those situations are learning opportunities. I have been messing with Lithium batteris for twelve years and am still learning. The joy comes when the system is really humming and you know that you built it.

 

[HJEngland]

thank

Each one of those situations are learning opportunities. I have been messing with Lithium batteris for twelve years and am still learning. The joy comes when the system is really humming and you know that you built it.

thank you for the encouragement, I appreciate it.

 

[SamDeleted]

thank

thank you for the encouragement, I appreciate it.

Do you know what size cable you're using ?

 

[SamDeleted]

2000 watts ÷ 12v = 165amps

But you actually have to do the maths at the lowest voltage your batteries might get so:

2000w ÷ 10.5v = 190amps

So I'd go for 35mm² - rated up to 235amps

 

[SamDeleted]

Your cables look thick enough by eye ? Are they properly fused ?

It is possible it's a problem with your inverter not the cable or lug ..

 

[Johno1066]

Practically speaking a 12 volt battery is unlikely to put out more amps at 10.5 volts than at 12.6 unless you have a room full of 12 volt batteries. At 10.6 volts the batteries capacity is almost depleted so a cable that will carry 200 amps will be sufficient so a cross sectional area of 0.2" should do.

 

[JJJJ]

.

 

[HJEngland]

Your cables look thick enough by eye ? Are they properly fused ?

It is possible it's a problem with your inverter not the cable or lug ..

I contacted the manufacturer of the inverter. They said probably the lugs were not tight enough snd it caused that, but to mail the the unit and they will replace it,

 

[HJEngland]

Do you know what size cable you're using ?

I believe they are 6 awg-- they came with the inverter

 

[Crowz]

I ran 2/0 gauge wire on my 2000 watt aims inverter and that was a 24 volt model which meant I was pulling less amps than you are doing at 12 volts. I admit its considered overkill by any and all charts but the inverter is inside the house and the batteries are outside the house. I was not going to sleep without being safe on the inverter wires. All of the inverters I have bought or have seen in person that someone has bought that came with cables were not very well sized or made that well but thats my experience yours may vary. The 2/0 wire never even got warm to the touch at full load.

The cable could of had a bad connection at the inverter but it could of been an inferior crimp from looking at the cable picture you posted. Another reason to do your own cables. A hydraulic crimper off amazon is pretty cheap and makes perfect crimps every time from my experience. Again piece of mind.

As for the melting down since they are replacing it there may not be a reason to explore it further but the first thing I would of done with it showing 100% load like you mentioned and the load not being great enough to be 100% like you mentioned I would of unplugged the load with the inverter still running to see if the load dropped. If it didn't then there is a fault inside the inverter.

If the load displayed dropped after unplugging the load then the device plugged into the inverter has an issue that's pulling to much from the inverter.

Even if it turns out the load is to high the inverter should of shut off before melting the wires so that comes back around to the wires being undersized or a bad crimp or loose.

Besides the pinch on your wallet you can never go wrong over sizing battery to inverter wires

 

[SamDeleted]

I contacted the manufacturer of the inverter. They said probably the lugs were not tight enough snd it caused that, but to mail the the unit and they will replace it,

Good good that's ok then !

 

[Johno1066]

I would tend to think if there was a fault with the inverter that both cables would have shown signs of overheating.