Melted positive battery terminal (1 Viewer)

Jan 11, 2023
7
0
Funster No
93,359
MH
Renault Master 2006
Hi all, first time here, hoping someone can help us understand what's gone wrong with our leisure battery system.

Today our inverter started beeping to say the battery power was too low. We turned it off and then found that the positive battery terminal on one of our 12v leisure batteries has melted.

We have 3x 12v batteries, wired in parallel, connected to our inverter which only runs an electric water heater every so often (3 times in the last month).
The cable us is 35mm.

It's the last battery in the circuit that's had the issue. The one connected to the inverter.

The positive cable from the battery to the inverter was very hot also.

Our power comes via split charge and solar.


We disconnected and removed the battery now. And will not connect the inverter again.

Just wondering whats gone on here, in case it's something that might happen again?

Any helpful thoughts/suggestions appreciated.
 
Dec 6, 2011
11,709
25,722
South Wales
Funster No
19,136
MH
Coach built Adria
Exp
Since 2007
Hi welcome.
To state the obvious something is drawing way over its intended current.
It also sounds as if you have no fuse in the line or way too big a fuse.
I would start looking for a potential short circuit.

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Kannon Fodda

LIFE MEMBER
Feb 26, 2019
2,622
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Seek and Ye May Find
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58,768
MH
Autotrail V-line 540
Exp
I Make Schoolboy Errors!
Look at how your wiring is arranged. Does it have all the connections to load from the one battery with the melted terminal, or are the connections spread with positive to load from one battery and negative to a different one?

Plenty of articles on the net but this one seems to explain a lot of the options:
 
Nov 2, 2022
386
428
Gloucestershire, UK
Funster No
92,219
MH
Burstner Eliseo C602
Exp
Since 2016
If it is a 200A fuse and the cable is 35mm2, the fuse should easily rupture in the case of a short circuit or other significant over current.
I think it is more likely a poor resistive connection has caused overheating. Was the inverter feed cable connected to the melted battery terminal post?
A photo would be helpful.
 
OP
OP
R
Jan 11, 2023
7
0
Funster No
93,359
MH
Renault Master 2006
If it is a 200A fuse and the cable is 35mm2, the fuse should easily rupture in the case of a short circuit or other significant over current.
I think it is more likely a poor resistive connection has caused overheating. Was the inverter feed cable connected to the melted battery terminal post?
A photo would be helpful.
IMG-20230111-WA0000.jpg
 

Abacist

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Oct 15, 2013
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You appear to have positive supply cables from each end of the battery and similar with the negative side.

You should take one positive terminal from one end of the battery bank and one negative from the other end of the battery bank so that the draw is through all three batteries and not just one which is what is happening from your picture.
 

Kannon Fodda

LIFE MEMBER
Feb 26, 2019
2,622
8,100
Seek and Ye May Find
Funster No
58,768
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Autotrail V-line 540
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I Make Schoolboy Errors!
You've reached the limit of your free posts. To post any more you will need to subscribe to the forum.

As Richard says, make sure everything is fully tight. The 200A load from your inverter tries to pull a lot of current.

BUT, the wiring is a poor arrangement if you are pulling that load with inverter connected both positive and negative to that bottom battery. It puts most of the strain on the one battery. You should try and have load on bottom and negative on the top battery (or vice versa).
 
May 7, 2016
7,356
11,905
West Sussex
Funster No
42,951
MH
Malibu Van 640 LE K
Exp
Since 2003
Is it possible that the end cell in the battery has failed and created enough heat to melt the terminal?
 
Nov 13, 2011
1,486
3,544
Lincolnshire
Funster No
18,889
MH
PVC
Exp
30 years
If it was mine, I would not use the overheated battery post any more. Remove the cable insure the connector is tight on the cable or replace by shortening the cable, then refit to the traditional taper post along with the other cables and make sure the connections are all tight.
I would also like to see protective covers on all those battery connections, an awful lot of short circuit risks with so many exposed connections.

Geoff
 
Aug 1, 2021
1,003
5,817
Pembrokeshire, UK
Funster No
83,135
MH
Auto-T Expedition 66
What wattage is the water heater that you are using with the batteries and inverter?

I'm guessing quite high, and you are therefore pulling far too much current for the batteries to safety supply.
 
Aug 6, 2021
92
143
Funster No
83,247
MH
panel van conversion
Any chance it's been overtightened and damaged something under the plastic casing?
 
OP
OP
R
Jan 11, 2023
7
0
Funster No
93,359
MH
Renault Master 2006
What wattage is the water heater that you are using with the batteries and inverter?

I'm guessing quite high, and you are therefore pulling far too much current for the batteries to safety supply.
It's a propex 10l electric water heater.
 

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OP
OP
R
Jan 11, 2023
7
0
Funster No
93,359
MH
Renault Master 2006
Hi all, thank you so much to everyone for your replies! So much better than the Facebook. We really appreciate your comments.

So we're pretty sure this is our fault for wiring incorrectly, as suggested.

We disconnected the battery and the inverter.

Should we dispose of the battery? Or could it still be used but via the other terminal as mentioned further up in te thread?

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Apr 27, 2016
6,929
8,095
Manchester
Funster No
42,762
MH
A class Hymer
Exp
Since the 80s
You appear to have positive supply cables from each end of the battery and similar with the negative side.

You should take one positive terminal from one end of the battery bank and one negative from the other end of the battery bank so that the draw is through all three batteries and not just one which is what is happening from your picture.
That is an improvement on the present arrangement. But not the best way for three batteries. The best way is to have three equal links from the positives to a common point, like a fuse or busbar, and pass all the loads and charging through that common point. And the same for the negatives.
 
Apr 27, 2016
6,929
8,095
Manchester
Funster No
42,762
MH
A class Hymer
Exp
Since the 80s
Any chance it's been overtightened and damaged something under the plastic casing?
Should be possible to test this. There is a substantial metal bar between the two connections of the double terminal. The resistance between the two connections of the double terminal should be very small. Too small for a standard multimeter to measure. but you could put a large known current (amps) through it, and measure the voltage drop in millivolts across it, then work out the resistance from that. It's known as the 4-wire ohms measurement method. You could compare the voltage drop across that terminal pair and one of the good pairs.
 

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