HELP...Split charge relay has melted the inline fuse holder

[Baldrick]

Hi all

Just typical :roll:! The first weekend when I've needed to use the leisure battery and I have a problem !

I have a Ring RCT360 split charge relay and it has managed to melt the cap on the end of the in line fuse. It isn't situated near anything hot so it hasn't had any external heat applied to it.

Got any ideas what it could be? Is it likely to have damaged anything else? The fuse is still intact, although I don't know what rating it is.

EDIT:
Sorry should have said that the wire with the inline fuse comes off the live terminal of the main battery and goes into the relay.

I could cut the wire and put another inline fuse in...but I'm worried that there is something wrong here.

Thanks

Andy

 

[sparkywig]

Sounds like either a very high resistance at that point or a very large overcurrent to generate that kind of heat.
Is the fuse tight in the carrier when done up?
Any loose connections?

 

[jacks906]

you need to find out the fuse rating too and try lowering it if its too high.

 

[six]

do you have anything runing off the lesuire battery? if the battery isnt charged and you run stuff off it, once you have the relay on (engine running) then current will be pulled through the chargin circuit melting the fuse and such.

does the split charrge have anthing inline to stop surging etc or is it a straight relay set up?

Whats the rating of the fuse and fuse holder? if unknown replace with knowns most, The wire in my kit was 5amp wire (30amp relay)

put in a fuse to suit, charge you lesuir battery properly then try again?

 

[matt-me]

do you have anything runing off the lesuire battery? if the battery isnt charged and you run stuff off it, once you have the relay on (engine running) then current will be pulled through the chargin circuit melting the fuse and such.

Is that right? What do you mean exactly and are you saying this might happen only if the leisure battery isn't charged?

Seems to defeat the point of having things wired on the leisure battary circuit, if, as you are suggesting it might melt fuses if you use those things when driving along? Like, say a propex heater? I want to use it when i may be driving in the winter and when camping, on cool nights, so I've wired it up to the leisure battery fuse board and can use it either when driving or not, is this wrong?

I would appreciate it if you could clarify what you mean.

Ta Al

 

[six]

Is that right? What do you mean exactly and are you saying this might happen only if the leisure battery isn't charged?

well what you have is batteries wired in parallel. When you place demand for some power, weaker cells(battery) will drain current from the stronger batteries.

Seems to defeat the point of having things wired on the leisure battary circuit, if, as you are suggesting it might melt fuses if you use those things when driving along? Like, say a propex heater? I want to use it when i may be driving in the winter and when camping, on cool nights, so I've wired it up to the leisure battery fuse board and can use it either when driving or not, is this wrong?

Well you gotta calculate what you have running from the battery. say you have a

200W stereo
a 80w fridge
propex heater 12W
20w of toys satnav phone fan etc charging etc

assume they are all working at max

thats 312W we know Watts / Volts = Current in amps 312/12 = 26Amps drawn
now most kits have a 5amp split charge wire and a 10A fuse.
So lets say you got a 100Ah battery, 100/26 =3.84hours. (simplified version)
that means in 3.84 hours the battery will be dead.. this is assuming its not being charged.

So in many cases then we are putting in max 5A to charge a battery.. taking 26 out.. so yes.. at some point the battery will discharge..

back to the problem of the melted fues holder.. imagine the battery is near flat.. you jump in start the van, its a hot day.. on goes the stereo.. on goes the fridge (mmm cold beer) on goes tomtom (in the lastest voice of terminator etc) thats a load 300W .. where does the circuit get 300W thats right off that split charge circuit the moment the relay closed..

your 10A fuse is nothing for the 25A demand,, maybe it didnt pop right sway? maybe there was crap in the holder or its a 5A rateed holder twith a 10A fuse.. my guess is that the demand was just under the fuse rating.. maybe 9A in a holder rated heat built up etc who know either way it would be worth checking that circuit and double check your draw and ratings.

maybe im way off but it works for me

 

[jacks906]

that is the reason i use one of these then you can use proper size cabling to batteries.

altho will cost more its bullet proof

dave

 

[faux]

You should only need a 10amp fuse and the wire needs to be comparable to the relay system you are using really. I use 30 amp relays with 30 amp wire and 10 amp fuses. The relay switches with the engine so there should not be any draw unless the engine is on and it should only draw at the rate of the the vans charging system.

I would check:

good earth, wire rating, fuse rating, you have the correct terminals on split charge, all connections.

 

[Matt84]

Hi all,

Sorry to revive an old thread but this also happened to me recently, my leisure battery was run flat and then the relay wouldn't charge it, is there an answer to this other than don't let it run flat? Sometimes I'll leave my fridge on whilst we're at the beach etc....

The link from a couple of posts ago didn't work, but I guess it's just too old,

Any thoughts?

 

[jacks906]

Hi dude

What is the relay using to switch?

 

[KateLovesPurple]

Hi all,

Sorry to revive an old thread but this also happened to me recently, my leisure battery was run flat and then the relay wouldn't charge it, is there an answer to this other than don't let it run flat? Sometimes I'll leave my fridge on whilst we're at the beach etc....

The link from a couple of posts ago didn't work, but I guess it's just too old,

Any thoughts?

Without knowing all the details of your setup, it is difficult to say where the problem lies. Could be a couple of problems.

Are you using a deep cycle leisure battery or is it a normal car starter battery on your leisure circuit? If it is a car starter battery, they don't respond well to being totally discharged and may not charge from flat with a basic current applied to it, it may need a smart charger/conditioner to recover it.

or

If the battery was totally flat as you say, it may be the instant charging current pulled by the battery when you started the van may have been too much for your charge protection fuse and popped it.

 

[Matt84]

Hi,

Thanks for both your replies,

Firstly the relay is using the small blue wire off te top of the alternator (integral Regulator) to switch, I was under the impression this was the right one rather than the coil?

Secondly - It is supposed to be a proper deep cycle leisure battery therefore I think the latter is my issue.

Theres not much on it, a stock stereo, the westy lights (LED bulbs) and a 12V igloo coolbox, (think it's a 5A draw).

We drove to the beach from our campsite, (about 3 miles), when I left the bus the fridge was running but after a day on the beach it wasn't. Unsurprising really.

I only noticed something was wrong later... I started the engine I expected the fridge to come back on after an hour or so of driving, but it didn't! I then checked the inline fuse and it was almost melted, fuse (30A!) had blown though.

I can understand if the alternator can't charge a dead flat battery but surely there's a cut off alternative at 10V for example?

Thanks in advance,

Matt

 

[KateLovesPurple]

The blue wire is the correct trigger for the relay.

You say your fuse had melted? The fuse should just pop rather than melt. Has it actually blown or is it the holder that has melted? Check the fuse with a multimeter if necessary.

The fuse must be the weak point in the chain. If you have a 30A fuse, then your fuse holder, relay, cable and connectors MUST be rated at a higher current than that or you risk something burning out before the fuse does its job in protecting the circuit.

Sorry if it sounds like I am teaching you to suck eggs, but I don't know your skill set.

Good luck sorting it, if you need any more help just shout.

 

[Matt84]

Hi,

Yep, the fuse had blown, but just think a build up of heat didn't do it any favours, all my cable etc is rated to 35a so should be fine which is why I don't want to go any higher than 30a fuse.

I've had a look and I think a voltage sensing relay may be the answer - supposed to use voltage as the trigger to cut in and out rather than the current from the alternator,

Anyone used one?

http://www.the12voltshop.co.uk/Shop/music/relays/" onclick="window.open(this.href);return false;

Thanks again

 

[lard]

Assume that's the smartcom split charge - I used to run one, but my deep cycle charger broke it - when testing the battery prior to charging it (was charging main battery) it cycles between 0 and 14 volts for about 10 mins - the smartcom was clicking away every second and by the time I investigated it had clicked for the last time - my fault for being a numpty and not disconnecting the leisure battery before charging the main one! Worked fine before then and a good item, even had fridge terminal on it

 

[KateLovesPurple]

I had a smartcom one too (not any more). It failed somehow allowing my leisure battery to draw current from my main battery even when the engine wasn't running. Not good.