Club 80-90 Forums

hi guys ive been observing my volt meter and over the past few weeks it seems to have got less and less coming through to the 2nd battery from the split charge. with the voltmeter on me starter batt its kickin out 14ish, but when i flick it over to me 2nd its kickin out 12.3.

ive got a tester on the relay its reading the 14 goin in and just a tad under on the other side. when i followed it back to the fusebox its only giving me 12.3 and its melting the fuse but not blowing it and its kinda hot too? Why is it only melting the fuse and not blowing it ? im confused.com

Sounds like you have underrated cables to your leisure - minimum I would recommend would be 80A cables/60A fuse, preferably 100A/80A. If your leisure battery is flat it will draw 80A+ when your relay kicks in. I use a 160A intelligent relay, 140A cable and 100A fuse for a 110Ah battery.Saves having voltage drop to the leisure therefore more efficient charging.

thx for the info. how think/gauge is 80A cable? the relay i have is the one recommended on wiki from maplins 40A i think? i just dont understand this amp stuff to be honest

I agree under rated cables. current is too much causing overheating.
Worryingly this is the second mention I have had of blade type fuses melting under load rather than blowing. here is some of my wiring and to give you an idea of spec the cable feeding the home made busbars just fits 20mm conduit. The busbars are 1/8 thick copper an inch wide. The studblock terminals are 8mm. 12vdc resetable trips the earthing cables are, if I remember correctly 10mm and 6mm. The smallest cables there which are the control feeds to the relays are capable of carrying 16 amps. This system has been trouble free for nearly four years. Its not what is required to do the job, or in some cases what is barely adequate it is what will do the job properly, which is wh yI should take OBG's advice and uprate the cables and fuses, and possibly the relay too.

hixsy wrote:thx for the info. how think/gauge is 80A cable? the relay i have is the one recommended on wiki from maplins 40A i think? i just dont understand this amp stuff to be honest

Amps = watts/volts eg a 48 watt 12 volt load consumes 4 amps, a 3 kilowatt electric fire consumes 12 amps or thereabouts depending on the fluctuation of the mains voltage that day. This is Ohms law, it can be written as V = IR. You can also swing it round, If you know any two you can work out the third. Once you have done you energy audit to know how much current you will be consuming you can work out the size of cabling you need to do a job, this is electrical engineering at its most basic.

cripes ! thats a lot of wires man !

ok 2moro i upgrade the wire and see wat happens. also get me 2nd battery charged up.

how is it possible to melt the fuse without it blowing by the way ?

Hi Hixsy, thats only partly finished I need to get a shot of it done which I may well do tomorrow, I will PM the finished article if you are onterested. Sorry back to your question. If it heats up gradually along the length of the wire BECAUSE the wire isnt up to the continous current going down it THEN things start to melt, If that fuse had been in a cable capable of carring the load believe me it would have blown, therefore the cable was acting as a resistor and heating up, geat was then being transferred to the fuse which started to melt.
Does that make sense? Its like when fifty people try to run through a small space, but instead of the people getting hurt the wire insulation gets hurt. I have seen insulation that looks like candle wax from dashfires and cab fires. many lorries used to be written off cos of electrical fires, not economical to rewire them, however if you doing nothing all winter and have the know how it is lucratrive.
Fir the biggest possible relay the biggest possible cables and the heaviest duty terminals, its like giving the battery the M1.
HTH
Richard
PM if you like I wired up a friends lathe the other week, he was in Lincoln, I was in Hereford and we had two laptops one webcam and a cordless phone.

I have always advocated installing a hefty charging system but several people on here say that the 40A relay setup will do - you are the second person to my knowledge that has found that it is insufficient.
People think that you are only going to be drawing current from the alternator but it is also drawn from the battery so it could be well in excess of 100A if the leisure is very low.
Get flexible 120A welding cable from ebay, a smartcom intelligent relay to switch a big 120A relay or a 100+A intelligent relay (rare but available) - you are talking starter motor sized cables.
The fuse melting is a strange phenomenon that I find worrying - possibly it is cheap far eastern imports with poor manufacturing that is the problem.

Oldiebut goodie wrote:I have always advocated installing a hefty charging system but several people on here say that the 40A relay setup will do - you are the second person to my knowledge that has found that it is insufficient.
People think that you are only going to be drawing current from the alternator but it is also drawn from the battery so it could be well in excess of 100A if the leisure is very low.
Get flexible 120A welding cable from ebay, a smartcom intelligent relay to switch a big 120A relay or a 100+A intelligent relay (rare but available) - you are talking starter motor sized cables.
The fuse melting is a strange phenomenon that I find worrying - possibly it is cheap far eastern imports with poor manufacturing that is the problem.

And if you have difficulty following OBGs advice, cant find the tackle, havent got crimpers to handle the terminals I am in Worcester a lot of the time, thirty miles away. with notice I can bring gear, there is a large carpark in the marina with good lighting. You have tried hard to get your motor right, dont risk a fire over inadequate cabling. I dont have main starter cable around I am afraid but I have most everything else.
BTW I dont drink.

thanks again guys, ill order the stuff and if i blow meself up i might just take your offer for the help cafnod.

ill let ya know wat happens with it.

p.s. they were cheap fuses to be honest

BOL, be careful, you can do nasty things with twelve volt dc. Its not just mains thats dangerous. Always remove rings and other jewelry, gold is especially conductive, I saw one friend put a 150 amps through his wedding ring with a welder. Another mangaed to wedge his hand against a steel wagon bulkhead with ring acting as conductor between it, the spanner and the live terminal of a pair o truck batteries. ALWAYS DISCONNECT EARTH FIRST.

Can vouch for using hefty cable between batteries. Mines rated up to 100amp and only because I followed the recommendations on here. Also if your leisure drops down a great deal (ie its not in the flush of youth), the demand will be greater than one that is pretty new. Avoid cheap relays too.By cheap I mean ones where the cover pops off easily. I believe the maplins one is fine though.

I was taught at a very early age ( I've been at sea and fishing since the age of 5) by my grandfather when fishing - no watches, no rings, no buttons - any of them in a net and you are overboard or finger ripped off. Also worked in a machine shop on lathes in the 70's - everyone had long hair.
You guessed it - we had to wear hats with hair nets.
Loose cuffs are another favourite with rotating machinery.

jumper cable wire good ? seems cheaper than buying by the metre ? plus they red and black too !

where can i get some terminal fixings/push connectors that will take that sort of thick wire ?

the battery is a few weeks old too

As long as they are not the puny aluminium ones - flexible ones are best and easier to route inside the van.(sometimes the pound shops have them - but usually they are the stiff ones) Terminals available on fleabay like everything else, sized to fit whatever cable you use.Or somewhere like http://www.vehicle-wiring-products.eu/V ... termls.php I recommend soldering them on.