Inverter and hot cables

Joined
Feb 14, 2021
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Milton Keynes, UK
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79,219
MH
Burstner Lyseo 727G
Exp
3 years 30,000 miles UK and Europe.. Campsites and off Grid.
I have a 1500w/3000 inverter. It is conncted to 3 leisure batteries (270amh). the negative cable funs from the bench seat behind the drivers seat to a battery under the driver seat - about 70cm? . The positive goes to the battery at the other end of the line- about 30cm. The cables are ticker than th ones supplied with the inverter. I was using it the other day and got a smell of electrical burning. I investigated and discovered that the negative (longer) cable was getting hot at the battery end. The connection to the battery wasn't the most secure so I improved this. I tried again and now it seems both ends get a little warm when using the toaster (950watt)

So what's the issue here - Cables to thin? Too long? Dodgy inverter? Dodgy toaster? (it is quite old)
 
Pulling over 80 amps out of your batteries is likely to create some heat for sure. Are the connectors you are using suitable for this power requirement?
 
Sounds like the loose connection you found was the root of your original problem. Connections add resistance so it’s important that they are well made.

If you’re pulling big amps, cables will get warm.

Ian
 
Look at the hot connection first
Could need crimping a bit tighter or even soldering
 
As has been said, it's a connection problem. If the cable was too thin, it would get hot evenly all the way along the cable. One of the concerns is that if heat is produced, that means there is a voltage drop at that point. Improving the connection will reduce the heat, and reduce the voltage drop too. Any heat wasted in the wiring and connections means less heat in the toaster.

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I have a 1500w/3000 inverter. It is conncted to 3 leisure batteries (270amh). the negative cable funs from the bench seat behind the drivers seat to a battery under the driver seat - about 70cm? . The positive goes to the battery at the other end of the line- about 30cm. The cables are ticker than th ones supplied with the inverter. I was using it the other day and got a smell of electrical burning. I investigated and discovered that the negative (longer) cable was getting hot at the battery end. The connection to the battery wasn't the most secure so I improved this. I tried again and now it seems both ends get a little warm when using the toaster (950watt)

So what's the issue here - Cables to thin? Too long? Dodgy inverter? Dodgy toaster? (it is quite old)
So the cables used are a bit thicker than the ones supplied? Fancy providing any actual sizes?
Also have you got any fuse protection for the cables (the inverter having an internal fuse is a separate thing. You need to provide cable protection).
If the cables are too warm to hold, then they are undersized for the job. If they are smelling they are severely undersized (and/or you have a connection issue as mentioned)
FWIW, the last inverter I fitted was a 1000W (actually a Victron 12/1200 Phoenix) and I used 35mm2 cable for that. Cables don't get warm. On my last camper, when I had the 2kW Hob running, the initial 50mm2 cables got a little too warm for comfort and I replaced with 70mm2 cables which eliminated the issue. That was a cable run of maybe 0.7M from battery bank to inverter.
 
Tight and good connection is very important especially as the amperage goes up it's not uncommon for a terminal post to be completely burnt off a truck starter battery with a loose connection !
 
So the cables used are a bit thicker than the ones supplied? Fancy providing any actual sizes?
Also have you got any fuse protection for the cables (the inverter having an internal fuse is a separate thing. You need to provide cable protection).
If the cables are too warm to hold, then they are undersized for the job. If they are smelling they are severely undersized (and/or you have a connection issue as mentioned)
FWIW, the last inverter I fitted was a 1000W (actually a Victron 12/1200 Phoenix) and I used 35mm2 cable for that. Cables don't get warm. On my last camper, when I had the 2kW Hob running, the initial 50mm2 cables got a little too warm for comfort and I replaced with 70mm2 cables which eliminated the issue. That was a cable run of maybe 0.7M from battery bank to inverter.

Yes, I was vague as I am away on a trip and don't remember precise size and it was some cable I had in my garage already. I do remember it being 2X the width of the original supplied cable so I assumed it would be an improvement. It's not hot now I have improved the connection - just vaguely warm I'd say.
 
Yes, I was vague as I am away on a trip and don't remember precise size and it was some cable I had in my garage already. I do remember it being 2X the width of the original supplied cable so I assumed it would be an improvement. It's not hot now I have improved the connection - just vaguely warm I'd say.
Just a comment on cables supplied with Inverters .... they are usually a) undersized; and b) aluminium, not copper, which makes them even more undersized! First thing usually to do with them is chuck them out!

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