Fire! Thank god for smoke alarm... (2 Viewers)

[Chossy]

Hey everyone,

I had a particularly scary situation earlier today. Smoke started pouring out the USB charging socket in one of these typical 12v control panels. It looks like the USB socket has gone wild. Fortunately smoke alarm kicked in. The fridge was on and the USB was in use to charge a phone say 8 amps total draw? the fridge I think draws 6amps when the compressor kicks in, and usb socket say 2.1a. The control panel comes with individual 15a fuses on each switch and I think I have a 15a fuse in the main supply to the control panel as well.
Can anyone tell me why it would melt like this? loose connection? faulty USB socket? crap manufacturing all the wiring etc. is legit and was checked by leccy neighbour.

 

[Mikey RV]

Looks a mess, but could have been a lot worse.

 

[DavidG58]

Very confused here, were you running the fridge off USB

Are the USB’s self fit or original with motorhome ?

Glad it all came out OK though

 

[Chossy]

The fridge was running on it's own switch, and a phone was also charging using the usb chargin port on the control panel. The USB's are part of the control panel. The whole control panel is 'self fit'.

 

[ivorantony]

Because you are drawing 8 amps from a socket designed for 2.2 amps,

Ok ignore what I just posted,

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[DBK]

USB chargers have been known to fail before.

 

[MisterB]

I also think having fuses rated twice as high as the expected current didn't help ... Some fuses don't actually operate until higher than their rating.

 

[Chossy]

Fuses are the right size for the wires, it should be 20/30a max on the wires, 15a for protection. My question is why the protection didn't kick in... and why could it draw more than the expected 8a

 

[autorouter]

If the circuitry in the USB socket failed then it could have been trying to draw a large current - large, but not a complete short circuit. For example about 15A. The fuse would be quite happy to supply 15A, that's what it is designed to do, it won't blow until the current rises to maybe 20A.

However 15A at 12V is 180 watts, so somehow up to 180 watts was being produced in the USB socket and its wiring. That wiring looks thin, as if you were expecting the current to be only 2 or 3 amps. It would have been better protected by a 5A fuse.

 

[oldiesontour]

If the usb is the typical 2.1 amp at 5v output that is a draw of under 1 amp so although your 15amp fuse may protect the wire it is vastly oversized Others may disagree but I always use a fuse to suit the known load (which will of course be below the wire rating)where possible ...no reason not to as you have seen those 14 to maybe 19 extra unnecessary amps can generate a lot of heat

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[activecampers]

USB can melt/catch fire at 2A.....

(don't ask how I know, but there is a reason I have a new phone! - Due to water rather than anything else, but 2A shorted can generate enough heat to melt plastic with no fuse blow (3A fuse in this case as covering 2x USB 2.1A sockets) - fuses do not and cannot protect heat generation/melt at 2A (unless you luckily short L+N together and blow it)

Those cheap 12v/USB control panels are crap. I've got lots of them (custom design but the same connectors) but they are crap. I'd not use them for any high draw 12v things, like fans or whatever, the connections/resistance is to high and I've had one melt @ 5A. (I now use the alternative 12v sockets in the same mounting (forget the name - HELA?) - but clips in and better connections.

12v-USB I only use branded chargers after incidents over the years - the unbranded chinese aren't worth the risk and the ones with those control panels are (or where when I bought) cheap and nasty. Cheap design and a simple fault/overheat/melt - all at low current= the mess above.

(I'd also have the fridge separate - its not just the current draw, but also the compressor startup spikes and the voltage drop when that happens, and usually you'd wire that with oversized cable to prevent fridge startup issues when battery is a little weak)

Regardless, yes, keep smoke alarms tested and working!!

 

[activecampers]

If the usb is the typical 2.1 amp at 5v output that is a draw of under 1 amp so although your 15amp fuse may protect the wire it is vastly oversized Others may disagree but I always use a fuse to suit the known load (which will of course be below the wire rating)where possible ...no reason not to as you have seen those 14 to maybe 19 extra unnecessary amps can generate a lot of heat

Agree totally, and it may help, but I've seen USB & 12v melt to similar mess (no flames though) at "operational current" levels which won't blow fuse.

 

[oldiesontour]

USB can melt/catch fire at 2A.....

(don't ask how I know, but there is a reason I have a new phone! - Due to water rather than anything else, but 2A shorted can generate enough heat to melt plastic with no fuse blow (3A fuse in this case as covering 2x USB 2.1A sockets) - fuses do not and cannot protect heat generation/melt at 2A (unless you luckily short L+N together and blow it)

Those cheap 12v/USB control panels are crap. I've got lots of them (custom design but the same connectors) but they are crap. I'd not use them for any high draw 12v things, like fans or whatever, the connections/resistance is to high and I've had one melt @ 5A. (I now use the alternative 12v sockets in the same mounting (forget the name - HELA?) - but clips in and better connections.

12v-USB I only use branded chargers after incidents over the years - the unbranded chinese aren't worth the risk and the ones with those control panels are (or where when I bought) cheap and nasty. Cheap design and a simple fault/overheat/melt - all at low current= the mess above.

(I'd also have the fridge separate - its not just the current draw, but also the compressor startup spikes and the voltage drop when that happens, and usually you'd wire that with oversized cable to prevent fridge startup issues when battery is a little weak)

Regardless, yes, keep smoke alarms tested and working!!

Absolutely agree a lot of the very cheap Chinese stuff by design is running way to warm for comfort, unfortunately it is getting harder to find stuff in general that isn't the same thing rebranded so many old names reappearing,and others taken over by an importer not to mention copies,it's a shame as some of even the cheaper Chinese stuff is genuinely good value and quality I have a Chinese plate compactor nearly 20 yrs old done loads of work and still perfect,also a3kw generator same age had nothing but hard work and abuse still fine(both the honda copy engine) Unfortunately too many people rely on the name on the product or of the retailer and or assume expensive is good cheap is cr..p ,

 

[autorouter]

Absolutely agree a lot of the very cheap Chinese stuff by design is running way to warm for comfort, unfortunately it is getting harder to find stuff in general that isn't the same thing rebranded so many old names reappearing,and others taken over by an importer not to mention copies,it's a shame as some of even the cheaper Chinese stuff is genuinely good value and quality I have a Chinese plate compactor nearly 20 yrs old done loads of work and still perfect,also a3kw generator same age had nothing but hard work and abuse still fine(both the honda copy engine) Unfortunately too many people rely on the name on the product or of the retailer and or assume expensive is good cheap is cr..p ,

I agree too, I think the problems with a lot of the cheap unsafe stuff seemed to start after - let me think - about 2016 or so. What could possibly have happened then to allow this?

 

[activecampers]

I agree too, I think the problems with a lot of the cheap unsafe stuff seemed to start after - let me think - about 2016 or so. What could possibly have happened then to allow this?

lol - you think? Been going on for decades - just the ease of access though Ali/Wish/Temu/ebay has made it more common an available to the masses, rather than via "resellers" who check the quality. Its our own fault, we like cheap and we all shop by price. Nothing to do with politics, though I guess politicians adjust facts to fit a narrative.

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[Chossy]

Thanks everyone, I don't think the usb socket actually has it's own fuse... I will find out when my pal is back, but it looks to have 5 fuses yet it has five switches a 12v socket and the usb socket. There is no harm in dropping the individual fuses down to say 10 for the appliances and then 3 for the usb but I don't think it actually has a dedicated fuse. I'll present it to my neighbour and see what he thinks. I'm just keen to try to understand how it could happen and why for example a loose connection might lead to that 'spike' in draw.

 

[oldiesontour]

lol - you think? Been going on for decades - just the ease of access though Ali/Wish/Temu/ebay has made it more common an available to the masses, rather than via "resellers" who check the quality. Its our own fault, we like cheap and we all shop by price. Nothing to do with politics, though I guess politicians adjust facts to fit a narrative.

It happend before the Chinese came on the scene Japan started producing cheap rubbish.. motorcycle tyres made from recycled plastics...it was common if you bought a new bike to have the tyres and chain(think they made them out of chocolate)changed before leaving the shop,some of their bearings were made from the same useless material but very quickly they went up market and became world leaders in many industries ...just as china is doing now,but for the moment their is a lot of substandard stuff about that is taking enough of the market to kill off the established manufacturers or force them to lower quality and price ask any trade about old quality brand name tools and you hear they are not as good as they used to be I've personally heard it said about de walt ,Stanley and many more. so for now it's buyer Beware and smoke alarms ,first aid kits and fire extinguishers at the ready
( Whilst knowing they probably came out of a factory in. China.... hopefully one of the better ones)

 

[activecampers]

Thanks everyone, I don't think the usb socket actually has it's own fuse... I will find out when my pal is back, but it looks to have 5 fuses yet it has five switches a 12v socket and the usb socket. There is no harm in dropping the individual fuses down to say 10 for the appliances and then 3 for the usb but I don't think it actually has a dedicated fuse. I'll present it to my neighbour and see what he thinks. I'm just keen to try to understand how it could happen and why for example a loose connection might lead to that 'spike' in draw.

Loose connections or corroded connections (esp with spade connectors) will increase resistance, and power via a high(er) resistance path gets hot. Its how all electrical heaters work. So yes, loose wire, corrosion (rust/oxidisation) etc can get hot and do so WELL WITHIN the rated current.

As an example, I have a charger that pulls 7A load (@ 12v) via a 12v cigarette socket. With the cheap sockets that gets hot enough to burn and melt plastic. Changing to decent connections (ergo less resistance) then it stays cold. And as I posted, I melted a branded USB cable and a 3mth old new phone (doh) - all within rated current levels and fused correctly!!! (Though as I mentioned that was due to water in the plug causing a short/high resistance between cable & phone. Wires/charger all OK - just the high resitance point melted. I know water was not your issue, but highlighting same results within current limits. (this was on motorbike, and only knew when the phone started beeping via my headset with a USB "error" - stopped, and smelt burning and saw smoke at phone/cable connection and cable end too hot to touch)

So a fuse, even 2A, may not prevent the above issue if there is a fault and high resistance - though it may help.

 

[oldiesontour]

Thanks everyone, I don't think the usb socket actually has it's own fuse... I will find out when my pal is back, but it looks to have 5 fuses yet it has five switches a 12v socket and the usb socket. There is no harm in dropping the individual fuses down to say 10 for the appliances and then 3 for the usb but I don't think it actually has a dedicated fuse. I'll present it to my neighbour and see what he thinks. I'm just keen to try to understand how it could happen and why for example a loose connection might lead to that 'spike' in draw.

A loose connection is more likely to result in a build up heat due to the resistance created but the degree of heat is generally proportionate to the current being carried

 

[rolosroller]

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