Van Wiring System Off Of Leisure Battery

[PEG]

Decreased charge time, surely! B2BC's used to be expensive but are perhaps better value now and the better charging performance worth the investment. I still tend to think in marine terms where an engine might run for 12 hours a day and there might be charging current available from somewhere - genset, aux or propulsion, for much of the daily load cycle. As such it's not so important to get charge into the service batteries quite as fast. In wiring terms the only real difference is that it will require more substantial negative connections than the low-current sensing wire of the relay. It will also probably require free airspace for cooling.

OT but does anyone remember Lucas 4BD split charge diodes in oilfilled cans like ignition coils? Found a few of those in my old service stock the other day dating from the mid 70s, including a pos-earth (common cathode) one. Only any good with a battery sensed regulator of course, and sure enough there were battery sensed 4TRs, 14TRs etc in the kit. And even a NOS 3AW warning light relay for the venerable 11AC. But I digress...

I do,vaguely,the 11ac was standard on some Jags,and various small Perkins,etc...what a mass of components,compared to today's gear.
Control units,field relays,and a bumble-bees heart of an alternator buzzing away at the end!

I appreciate your scenario re split charge relays,but with limited depletion,and use by your good self,problems would be rare.

In situations where there is not a "dedicated" charge alternator,as such,say just a vehicles standard fitment,and the aux batteries are flattened by a liverie's kid's laptop and lighting use...the 40A it tries to pull when that relay closes,plus the vehicles ancillary use,just murders the poor alternator.

Found one 2 year old MAN 18 tonne truck,with a 45A alternator as standard! Retro-fitting a 120A upgrade,was £850,12A current limited B2B unit was £70,so,customer had change for a new Stubben (saddle)

As a kid,i used to stalk an old auto-electrician,he had a very bad hunchback,and temper to match,but i learned many things...one was his reluctance to clip a Durite ammeter on,when testing charge rates,preferring to ask "can yer keep yer 'and on the casing,more than a couple of seconds?" ...a "yep" would mean no further discussion

As for my lock gate analogy,it IS possible to open them against a filled lock,or the upper level...just requires a Yale strongback or pull-lift,slung across the gate beam ends...don't ask...all i remember was THAT was the easy bit,removing all the old safes and shopping trolleys obstructing the sluices was a messy pain

 

[Lucien Nunes]

Still some confusion there. You do not need a fuse box on the AC output of the inverter, the 230V loads should plug directly into its 13A output socket. Whether you provide any additional AC earthing / grounding depends on how the inverter is internally configured, we cannot answer that without knowing and on small low cost units they don't tend to tell you in the blurb like they do on professional ones. You can test it with a meter.

The term 'earth' in 12V vehicle wiring, such as 'earth connection' or 'negative earth' simply means 'common return conductor' and has nothing to do with safety earthing. Using the vehicle chassis or 'earth' as one pole of the circuit is simply an economy measure to save cable. Whereas the term 'earth' in mains voltage 230V wiring means 'safety equipotential conductor' and has nothing to do with carrying the operating current of the device. Two very different things.

I don't understand your 'four wires' bit at all.

Those battery terminals are OK-ish but the cables need to fill the terminal before you do up the screws otherwise they will just fall out again. There are better versions of the same, or ones with a captive terminal bolt and nut to which you can connect a crimped lug. Or you can get pre-made cables with crimped terminals.

Very rough sketch attached of what I think you're trying to achieve

 

[Radventures]

Thanks Lucien.

By four wires I mean the two LEDS circuits & two mains circuits. (I realise now I only have one LED drawn, but there will in fact be two on separate switches).

I don't understand why I don't need a fuse - shouldn't each of the LED/mains circuits be fused? Could you kindly explain that to me?

Thanks for clearing up my earthing confusion. How then, shall I earth the inverter? Photo attached.

 

[Lucien Nunes]

Compared to household mains supplies which can deliver thousands of amps in the event of a short-circuit, the maximum output of a 600W inverter is around 2.6A. It simply does not have the capability to produce higher currents, and for its own protection against damage it will shut down if overloaded or short-circuited. The smallest fuse any piece of mains electrical equipment normally requires for adequate protection is 3A, most are fine with being protected at 13A or 16A. As the inverter output cannot reach this level, there will never be enough current to blow such fuses hence no point adding them.

You attach a pic of the B2BC but ask about the inverter earthing. When you have the inverter you can double-check the internal connection of the output socket earth pin by measuring its resistance to the case and DC input negative. There will then be some debate about the best configuration according to what kind of wiring you propose to connect to the output.

 

[Radventures]

I opted for a 1200w inverter in the end, as I didn't want to worry about overloading it. So the maximum output would be around 5A and should still be fine. Thanks.

Yeah, I can't explain that one away - it had been a long day! There will either be 2/3m of cable between the starter battery and leisure battery and >1m cable from the leisure battery to the inverter, or it will be the other way round. It depends on how I can rejig the space for the leisure battery under the bonnet.

 

[Lucien Nunes]

I expect that will do fine for your requirements, given the size of the unit and its terminals I would be sceptical about its ability to support 1200W for very long. Keep the cables short and fat consistent with keeping the inverter cool.

If you want to think about earthing on the 230V side, you will need to measure the resistance from the earth contact in that evil multi-hole socket to the neutral contact, the DC input and the case (I note it doesn't have a separate earth terminal.) What you do then will be a matter for discussion, there might not be one single recommended method as there are pros and cons of floating supplies etc. Or you could do what most people do and ignore it completely as an insignificant risk with so few pieces of equipment connected.

 

[Deleted member 26818]

A fuse box might be useful as a distribution point.

 

[Radventures]

I missed these - thanks for chipping in. Insignificant risk = no hassle in my books.

Could you clarify what you mean by a distribution point spinlondon? Do you simply mean a means to distribute more sockets etc in the future should I wish to?

 

[Deleted member 26818]

No I mean as shown, in your drawing.
A method to distribute the 4 (3 shown) circuits you intend installing.

 

[Radventures]

Okay sure. Logistically, I was wondering how I'm going to turn a single live wire from the fuse box into four and it makes sense to use the fuse box as you suggest, but do I need another part. Like I know you can get 2,3,4 way battery terminals - is there something similar I need here?