Trying to understand my split charging system

[MagicWagon]

Hi.
I am new to the forum, having finally found myself a decent (I hope) T25 after a 2 year search. It's in good condition in the important places, but will need some fettling and tweaking. This is my first post, but no doubt will be the first of many over the coming months and years.

As the title suggests, i'm trying to understand if my split charging/leisure battery is all wired up correctly.
I found the fuse to the leisure battery is blown. I don't have a replacement but will try to get one tomorrow. However, I find that the internal lights, sink pump, water meter and fridge all work, but only when the ignition is turned on.
My assumption was that the leisure equipment should only work off of the leisure battery, to avoid discharging the main battery, and therefore should not currently work at all with the leisure battery effectively disconnected. At the moment they are all working off the main battery. Is this correct, or do I have a wiring issue ?
Also, can anyone tell me the correct size of fuse for the leisure battery? It's a bullet/continental type, a yellow one which I think is therefore 5amp, but some diagrams I've seen show it should be 30 amp.
Finally, the four fuses for internal lights, sink pump, water meter and fridge are all 30amp. Is this correct ? IT sounds a bit high.

[California Dreamin]

What conversion have you got?
It certainly sounds like something is wrong but who can second guess how yours is wired if its none standard retrofitted split charge system.

Normally the split charge fuse is 25 - 30 amps but that depends on whether the wiring is above that rating. (the fuse should always be rated less than the thinnest wire)

As for the four fuses? I agree, Lights, pump, water meter....all relatively low consumers (the pump perhaps the highest of the three) but all under 8 amps (the pump maybe on that limit).

Martin

[Ruralman]

Hi MagicWagon,
I've just put in a new split charge system, Sergy was also running many systems off the starter battery and the split charger was suspect so I bought anew system:-

http://www.leisurebatterysystems.co.uk/ ... .html#p470" onclick="window.open(this.href);return false;

There are 60amp fuses between the VSR and each battery, my next move is to transfer all the leisure wiring onto the leisure battery having already removed it from the starter battery.
Regards
Keith

[Smiffo]

Mine worked a similar way when I got it.
The split charge relay was wired to the ignition, rather than the exciter wire from alternator.

( I assume you meant that all leisure circuit aspects work when ignition is switched on, and not just specifically when engine is running? You will need to clarify that bit, as it should all work with the engine running, even if the leisure battery is removed. )

It will depend on what conversion you have I suppose, but it sounds like - on first impressions - yours is wired like mine was.

Very easy to sort.
If yours is relay operated under the driver seat ( RHD ) then you will hear relay click when you turn the key to the on position.
Basically it seems like the relay - if it is a relay setup - activates and so `tees` both the leisure and starter battery together when ignition is turned on, rather than activating when current is fed via the blue exciter wire from the alternator.

That would explain the operation you are describing anyway, although I could be way off base.

This won't drain your starter battery unless you leave the ignition on when parked and using leisure circuit ( pump, lights etc ) as the relay will isolate the starter battery when ignition is turned off.
You will however find that the leisure battery and starter are both used together at the point of cranking if it is wired like I think it is.

[MagicWagon]

Thanks for the replies.
My wagon is a 1981auto sleeper 2l Aircooled.
I replaced the leisure battery fuse with a 25a one (although I might put a smaller one in as I don't know how to find out the rating of the wire).
Now the lights etc work with ignition off and the leisure battery charges OK.
I might run with it as-is for now as I'm not too clear on what to disconnect and how to connect to the exciter wire. Also I guess it could be a benefit in emergency to be able to briefly use the starter battery for internal lights by turning the ignition on.
Do you think with the ignition on it would use both batteries for leisure? That might not be so good. How could I check this?
Also, how could I check if both batteries are used for starting? I guess that could be a pro or a con, but as the LB wires are much thinner that might be bad if it draws starting current through them. How could I go about finding out ? Wouldn't the fuse blow if that were the case ?

[Mocki]

im not auto sleep expert, but sounds like its not wired correctly at all.....

the leisure battery should only charge when the engine is running, the split charge should be controlled by the blue wire from the alternator,
so it only switches once the alternator is charging.
however it was common on a few early conversions to control the relay from the ignition.

chances are your fuse was blown because the leisure battery was too flat and tried to draw more than the fuse was rated at on start up.

have a read of the wiki, all the info you need is there, including on how to change the feedpoint for your interior lights and radio over to the leisure battery

[Ruralman]

On Sergy's new set up the VSR (voltage sensing relay) senses when the alternator is charging the battery's
Not only will the split charge relay system recharge the leisure battery while the engine is running it will also stop current being drawn from the starter battery when the engine is switched off (ensuring you will be able to start your vehicle) should the leisure/auxiliary bank run out of power.
The relays usually cut in at around 13.7 volts, making sure the starter battery is at full charge first, and cut out at around 12.8 volts (figures may differ slighly on some relays) ensuring that the starter battery cannot be discharged when the leisure battery is out of power and that your vehicle will always start!
Regards
Keith

[Smiffo]

im not auto sleep expert, but sounds like its not wired correctly at all.....

the leisure battery should only charge when the engine is running, the split charge should be controlled by the blue wire from the alternator,
so it only switches once the alternator is charging.
however it was common on a few early conversions to control the relay from the ignition.

chances are your fuse was blown because the leisure battery was too flat and tried to draw more than the fuse was rated at on start up.

have a read of the wiki, all the info you need is there, including on how to change the feedpoint for your interior lights and radio over to the leisure battery

Yes what Moki says - prob why fuse blew.

You know it doesn't draw from starter battery with ignition off, because leisure circuit wouldn't work with leisure battery disconnected unless the ignition was on.

When you turn ignition on, but before cranking, do you hear the relay click under your driver seat ?
( if it's Right Hand Drive)

[Mocki]

On Sergy's new set up the VSR (voltage sensing relay) senses when the alternator is charging the battery's
Not only will the split charge relay system recharge the leisure battery while the engine is running it will also stop current being drawn from the starter battery when the engine is switched off (ensuring you will be able to start your vehicle) should the leisure/auxiliary bank run out of power.
The relays usually cut in at around 13.7 volts, making sure the starter battery is at full charge first, and cut out at around 12.8 volts (figures may differ slighly on some relays) ensuring that the starter battery cannot be discharged when the leisure battery is out of power and that your vehicle will always start!
Regards
Keith

sorry to say you are sadly mislead with the way the VSR works....... almost as soon as your alternator light goes out the voltage at the starter battery will be up to, or above the 13.7v point so the leisure battery will start to charge straight away , just like it would with a much cheaper simple alternator triggered relay , all you paid the extra for was NOT having to make that trigger connection...

[CovKid]

Indeed, that and a sometimes increased current capacity with some VSRs. Really, the only major step beyond the 'dumb' relay is DC - DC chargers and they're not cheap.

[ghost123uk]

Re the more simple "relay activated via the ignition switch" system. Agreed that it's less than ideal if the leisure battery is in circuit during cranking, but how about if one switched the relay from the output of the load reduction relay? Then, during cranking, the relay would be temporarily off

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Really, the only major step beyond the 'dumb' relay is DC - DC chargers and they're not cheap.

Or my "poor man's Sterling" system, but we won't go into that here eh (it does work well though )



:

[CovKid]

Thats not cheap either - once you add it all up. I'm still on the hunt for a circuit that does a moderately better job than a blunt relay that doesn't cost the earth. Must be something out there.

[ghost123uk]

Thats not cheap either - once you add it all up. I'm still on the hunt for a circuit that does a moderately better job than a blunt relay that doesn't cost the earth. Must be something out there.

Well, whilst it's not a "smart charger" as per mine, if you want cheap, and I know you and I love cheap, how about using one of these = 12 volt to up to 35 Volt DC converter. It could be set to output 14.5 Volts to the leisure battery, and fed via the normal split charge relay should do a good job.

Only £2.79 too (Chinese taking over the world again )

[Oldiebut goodie]

Ages ago I suggested using a couple of the 600w ones of those to give better voltage to the headlights but no one seemed interested. They are £11 each but save having to run new cables and/or relays.
The only problem with using them for 14.5v is that the performance may not be too good as you may be putting in, say, 13.7 to 14v and increasing to 14.5v and years ago I read the specs for these and they needed a couple of volts difference to work correctly.(this may have changed in the last few years ) I haven't tested this though. Fine if you only have 12 - 12.5v to start with.

[ghost123uk]

The only problem with using them for 14.5v is that the performance may not be too good as you may be putting in, say, 13.7 to 14v and increasing to 14.5v and years ago I read the specs for these and they needed a couple of volts difference to work correctly

I think you are probably correct there -
I should have thought of that, but I have dreadful cold at the moment