Split charge relay burnt out

[ghost123uk]

Oldie, if the leisure battery is nearly fully charged would it take less of a strain on the relay so it could work as just a trickle charge?

On behalf of OBG = Yes, that is how it works, a flat leisure will "pull" a hefty current, lessening as it charges up. Once it is charged it will only pull a small amount of current, from the alternator, via the relay.

A flat leisure battery can pull over 30 Amps initially This quite quickly drops to more normal charging levels, but it's there for long enough to burn out a low power relay. btw, it does say on that website you linked to "Not suitable for newer caravans with refrigerators drawing above 15 amps" so perhaps your leisure battery had dropped to lower than usual, in which case it would easily exceed that. Perhaps it's on it's way out too, that would cause it to go flat quicker and then draw excessive current.

So, two things to do = replace that relay with a tougher one, and keep an eye on the resting voltage of the leisure battery, as in measure it after no van use for a day or more. Less than 12.6 volts and it's either on it's way out, or you have a parasitic current drain.

[CovKid]

Would concur with that. This is why 40amp relay should be a minimum and ideally twice that. Many kits fall far short of that. I've got fat battery cables everywhere now plus an 80amp relay and proper fuses where they should be (now in WIKI). After all, it all needs to be in place for good lights too. It actually works out cheaper to make up your own kit when going heavy-duty. I think my relay cost all of a £1 off an auto jumble and it was a Bosch one at that. Cable was £36 but includes run from alternator to starter and there to battery, and finally dash. Thats a LOT of cable but reasonable for a reel. Voltage drop is virtually non-existent.

[kit]

Thanks I will investigate what appears to be a heavy red cable running into a large household type ceramic fuse next to the leisure battery that at one time was connected to the main battery Looks like I will have plenty to do when the rain stops

[California Dreamin]

You are quite right..that 15amp relay has rather remarkably buzzed along for the last 15 years by luck rather than design, the low capacity supply wiring offering resistance and some protection to the relay contacts...it was just a matter of time, and in this case the relay did rather well considering its limitations, it could have just as easily melted the wires as it did the relay....and that is really the point, as I'm sure none of us wants that.
Put simply, wiring, connections and relays should always be rated well above current draw (save that of short circuits of course) and fusing below any of the circuits components.
As pointed out, my own tests have revealed amp flow initially into the mid 30's on a single leisure battery setup (80amp leisure, 70 amp starter batteries) so I agree with the minimum recommendation being a 40amp relay.

However, it won't really be good enough just to change the relay without also changing some of the wiring to suit.

Min 40amp wiring
Min 35 amp link wires (between batteries)
30 amp fuse (close to the starter battery positive post)

Martin

[Smcknighty]

Any recommended wiring suppliers?

[California Dreamin]

These guys have it all:

http://www.autoelectricsupplies.co.uk/" onclick="window.open(this.href);return false;


Martin

[Smcknighty]

Nice. Thanks