Charging Leisure Battery.

[eckerB]

Hi guys,I had a problem a while back with the charging to the LB as the fuse kept blowing(30A).I tested the LB and decided to get a new one as it was going duff.At the same time I up-graded the wiring to thicker wire and the relay from a 30A to a 70A.The 30A fuse is still blowing and I wondered if I should put a higher rated one inline.When the engine is started the voltage reading at the start battery is 14.45V then drops after half hour to 14.23V.I have checked the state of the batteries and the alternator via a meter and the results look o.k.The start battery is 70A and the LB is 75A.I am baffled as to why the fuse blows as soon as the engine is started.Any help would be really appreciated,don`t have much hair left as it is!Thanks in advance,Eric.

[francophile1947]

If your leisure battery is low, the 30A fuse isn't big enough. As your wiring is 70A, I would try a 60A fuse.
If your leisure battery isn't flat, then you've got another problem that'll need someone with more knowledge than me

[eckerB]

Thanks for the reply.The wiring is about 30A-40A.The reading off the LB is 12.6V and it was new a few weeks ago.

[Duxass]

I presume your alternator is not putting out too much thereby blowing your fuse?

[eckerB]

I did notice that the revs dropped after about one minute as if the alternator was under load.I wonder if the start battery is about to pack up,although everything works fine.No probs with the lights dimming or starting up,no dash lights flashing?

[g8dhe]

The fuses are there to PROTECT THE CABLE not the battery / relay / electronics / alternator etc. If the wiring is only rated for 30Amps then a fuse of about 25Amps is about right, if its 40Amps then 30 Amps would be about right. Likewise the Relay should be rated higher than the expected wiring rating by about 20%-30% at minimum, as the relay will have to connect the circuit at the point of when the highest surge current is flowing! I would suggest a 40Amp relay is the minimum you want or if you use less then expect to replace the relay occasionally

It sounds like you have something causing the L/B to discharge when the car is parked, thus when you go to start it up there is a surge of current which blows the fuse.

[Jaws]

Several possibilities here but some more information might be useful. Clearly if your fuses keep blowing there is too much current flowing one way or the other!

What sort of set up do you have for the charging relay?

It sounds like a short or heavy load somewhere when the relay activates. The alternator electrics are pretty robust. If the batteries are up to scratch it has to be a wiring problem

Changes in tick over speed are quite normal according to the load.

[eckerB]

Thanks for the reply Geoff,there is nothing on the LB battery that is left on when I leave the motor,at least not to my knowledge.I just wondered if a higher rated fuse would be o.k. and not cause any damage.

[eckerB]

The info on the charge wire is,from the start battery to the inline fuse(30A) then to the relay then to the LB.The switching for the relay is,positive to the fuse box,negative to the start battery.The new wire for the charging is 30A-35A.the previous wire was a lot thinner and the relay was 30A.I measured the voltage on the LB and it is 12.5V.Thanks for the help.

P.S. the sliding door switch for the rear roof light does`nt work,could this be shorting out?

[g8dhe]

The info on the charge wire is,from the start battery to the inline fuse(30A) then to the relay then to the LB.The switching for the relay is,positive to the fuse box,negative to the start battery.The new wire for the charging is 30A-35A.the previous wire was a lot thinner and the relay was 30A.I measured the voltage on the LB and it is 12.5V.Thanks for the help.

P.S. the sliding door switch for the rear roof light does`nt work,could this be shorting out?

Unless the Relay is mounted on the L/B then there ought to be another in-line fuse between the relay and the L/B.

As regards the light switch any fault like that could be the cause of a problem, it might be that the switch isn't disconnecting entirely and there is a constant load on the L/B without the light actually lighting up. Its worth checking the current being drawn from the L/B whilst everything is supposedly switched OFF any significant draw over say 50mA I like to understand myself (small currents will be the stay alive for the radio and the door switching circuits). Do you have a meter to measure he current with ?

[Jaws]

OK, that sounds like a reasonable set up but I return to my original point: if the fuses are blowing it's because too much current is flowing. Not likely that the door switch is the entire problem although as Geoff says if it's flattening the LB then a surge as the relay closes might explain the problem. But if you have a shorted lighting circuit I'm sure another fuse would have blown before your charger circuit one

Again, as Geoff says there should be a fuse on both sides of the charging relay: 50amps with 100amp cable in my case. You also mention relay operated from positive on fuse box? Surely it should only operate from positive on BATTERY.

My set up uses positive from starter battery via input lead and negative from SB via separate thin lead direct to SB -ve terminal.

The relay needs to "know" the state of the starter battery to work correctly: connect it directly to it if possible

{Edit because I misspelt Ffoge twice!}

[g8dhe]

There are three ways of controlling the charging relay;

• Using a Voltage Sensitive Relay, this senses when the S/B is being charged by the alternator and switches in when the voltage exceeds about 13.8-14 volts.
• Switched via the Ignition ON, but not during Starter motor or in the Ancillary position.
• From the Alternator charge circuit itself - not seen that yet on a Bongo.

[eckerB]

Thanks for all your replies guys.I have been checking a few things out and the rear door switch for the roof light is on the start battery circuit and it`s now working o.k!The positive switching wire from the fuse box for the relay is activating the relay circuit,but I think it`s not deactivating as the ignition key is turned to start the engine?So,as I see it,the relay is constantly live when starting the engine and putting load on the relay,thus blowing the fuse.Does this sound if this is the problem and do I need to relocate the switching wire for the relay.Where on the ignition would I put the connection and how do I get to it?Can I connect it to the thin wire from the alternator? Again,many thanks,your time and input is really appreciated.Eric.

[eckerB]

Just finished checking as to what is on the L/B circuit and I can only see that the fridge is on it!That`s switched off.The radio/window-blinds are on the S/B circuit.Me thinks they need changing over?Got this from a friend,looks the business,would this be a bit big at 100A-Relay,and 70A wire,50A fuses as my batteries are S/B-70A and L/B-75A?
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 2070642948 (Expensive?)

Thanks for your replies,Eric.

[321Away]

100Amps is a bit big, with a dead flat LB there is a momentary current spike of 50-60A,which is why you usually see maxi blade fuses (the biggest type) as they are capable of taking more than their stated rating for a few seconds
Its better to over rate your equipment than under!

there are different schools of thought when it comes to waht should be on the LB and how it should be done,so not touching that 1 lol

The battery ratings your stating are the sustained rates 70AH/75AH etc, your batteries are capable of outputting 100's of amps in an instant, the 70AH (amp hour) means your battery can output a load of 1A for 70 hours, or 70Amps for 1 hour etc before reaching DOD (depth of discharge) or being dead!
Julian