/ Camper electrics

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yarbles 08 Sep 2019

About to start camper conversion, hoping for advice on electrics before I start cutting holes / ordering bits:

Intention so far is:

Leisure battery connected by VSR to car battery

Terminal spur off leisure battery to allow charger connection from mains and possible future connection of solar panel

Inverter

12v and 240v socket panel to be connected to both 12v and 240v (Inverter) supplies

Lighting off the 12v system

Questions:

Any obvious problems with the above?

Id like to put an isolator switch in for the leisure battery so I can turn the system off (and rely on solar only for charging) but best I can find has a 100A capacity, the relay has 140A capacity. Can anyone advise what current the leisure battery could draw if depleted (ie max current the wire could take)? Would this 100A switch be sufficient?

Is an inverter necessary? how often / what appliances do you use a 240v supply for? What capacity inverter is recommended?

Id like to bond the solar panel directly to the roof so it is as flat as possible - are there any systems which allow this? Is this possible? Its metal (ie not a pop top).

Fuses? Sizes and locations?

Any other tips / recommendations?

Thanks!

elsewhere 08 Sep 2019
In reply to yarbles:

> About to start camper conversion, hoping for advice on electrics before I start cutting holes / ordering bits:

> Intention so far is:

> Leisure battery connected by VSR to car battery

> Terminal spur off leisure battery to allow charger connection from mains and possible future connection of solar panel

> Inverter

> 12v and 240v socket panel to be connected to both 12v and 240v (Inverter) supplies

> Lighting off the 12v system

> Questions:

> Any obvious problems with the above?

> Id like to put an isolator switch in for the leisure battery so I can turn the system off (and rely on solar only for charging) but best I can find has a 100A capacity, the relay has 140A capacity. Can anyone advise what current the leisure battery could draw if depleted (ie max current the wire could take)? Would this 100A switch be sufficient?

Charging current typically much less 100A. Battery about 100Ah charged at 10A over period of hours rather than less than 1 hour at 100A?

jimtitt 08 Sep 2019
In reply to yarbles:

You can buy 12v battery selector switches (isolators) rated for 350A constant 1500A peak, I fitted a few over the years. Completely unescessary for your application, anything would do really.

elsewhere 08 Sep 2019
In reply to elsewhere:

> Charging current typically much less 100A. Battery about 100Ah charged at 10A over period of hours rather than less than 1 hour at 100A?

I've slightly misread your post. Isolator needs to cope with max charging current (10 A?) and max load (depends on your gadgets & lighting etc) and max solar cell output. Max solar output is rating or less as solar output cannot exceed simultaneously charging flat battery and supplying maximum load.

Hooo 08 Sep 2019
In reply to elsewhere:

Yarbles is right, the isolator needs to be able to cope with about 100A. This is in case the leisure battery is dead and the starter battery fully charged when you close the switch. You will get a very large current at first. This situation is best avoided for the health of your batteries, but you need to allow for it. 100A should be fine. You should put a 100A fuse at each end of the cable linking the batteries for safety anyway, so your switch will be protected. The cable should be 25mm2 to cope with this, which is pretty fat.

Most people wouldn't bother with an isolator switch. If you have a VSR you can disable it by disconnecting the ground, and this will stop it closing. Same effect as your isolator but with a little switch. I've done this in my van.

Hooo 08 Sep 2019
In reply to yarbles:

Is an inverter necessary? That all depends on what you want to do. I have one but have only ever used it for charging daughters laptop. Not exactly vital piece of kit!

Hooo 08 Sep 2019
In reply to yarbles:

For solar, you can get semi-flexible panels that you stick direct to the van roof. They are not quite as cheap, efficient  and reliable as rigid panels, but they are popular because of the neat easy fitment. Just have a think about how you will get it off if it fails. I've stuck mine to a sheet of ally on hinges, so that I can tilt it towards the sun.

RBonney 08 Sep 2019
In reply to yarbles:

I found this link really good.

https://www.switchpanel.co.uk/how-to-wire-up-your-camper.html

I basically copied that. I got the biggest battery and solar panel I could and never come close to running out of juice. But when I used the inverter for a small blender the lights dimmed. 

wintertree 08 Sep 2019
In reply to yarbles:

These batteries can deliver massive currents.  Your worst case isn’t a depleted leisure battery - it’s a depleted leisure battery and all leisure loads on vs a full vehicle battery and ~100 A from the alternator - so at least 200 A.  Obviously that’s not a normal situation but if it happens you don’t want to start a fire.

The golden rule - make sure you fuse the circuit to less than the rating of the switches, wires and relays in it.  So if you use a 100 A switch you want something like an 80 A mega fuse in there.  I’d put a 200 A switch in with a 150 A fuse - https://www.12voltplanet.co.uk/battery-isolator-changeover-switches.html - see also their fusing guide.

I’d fuse the battery-battery link on each end as close as I could to each battery.

Although I’d probably not do any of that - I’d probably use a smart DC to DC charger from the vehicle to the leisure battery to look after both and to prevent silly currents.  At that point I’d probably fit a lithium leisure battery.  I’d keep a jump lead around in case I ever wanted to start the vehicle from the leisure battery.  Whatever you do make sure the 0V line is equally beefy.  

henwardian 08 Sep 2019
In reply to yarbles: 

> Questions:

> Any obvious problems with the above?

Nope.

> Id like to put an isolator switch in for the leisure battery so I can turn the system off (and rely on solar only for charging) but best I can find has a 100A capacity, the relay has 140A capacity. Can anyone advise what current the leisure battery could draw if depleted (ie max current the wire could take)? Would this 100A switch be sufficient?

100A is already overkill. I've done silly direct connections with the vehicle battery and alternator when 2 leisure batteries are fully discharged and it has never yet blown the 30A fuse I use.

> Is an inverter necessary? how often / what appliances do you use a 240v supply for? What capacity inverter is recommended?

100W, get a pure sine wave one. You are always going to have at least one DC thing that you can only charge with a 240v AC socket (maybe a laptop), so it is very useful to have. Pure sine because some things like induction charging (electric toothbrush for e.g.) don't work with a crappy distorted wave. If you need more than 100W, it's probably not something you should run from one leisure battery.

> Id like to bond the solar panel directly to the roof so it is as flat as possible - are there any systems which allow this? Is this possible? Its metal (ie not a pop top).

You can stick the flexible panels direct to the roof easily and securely with Sticks Like Shi* or some equivalent. But, THEY WILL OVERHEAT AND BREAK, so don't do this. Whatever type you buy, leave space under them for air to circulate.

> Fuses? Sizes and locations?

Maybe 15A for the inverter, 30A for anything to do with charging the battery, lights depends on what you use but probably 3A or 5A, 5A for USB sockets. If in doubt, use physics (P=IV etc etc) or look on the product for its suggested fuse, many things may come already fused.

You should have a fuse for every circuit that comes off the battery and a master fuse between the battery and the point where it splits into separate circuits. Every connection between battery/solar panels/VSR should also be fused. You can never have too many fuses, they cost nothing, take a minute to replace and may stop your van catching fire one day.

​​​

> Any other tips / recommendations?

Check how thick your wires need to be and then make them a bit thicker just to be safe.

Use beefy connectors and make sure you have a big, good area of contact when you make connections in your wires. (Melted a connector and wasted hours searching for the problem myself once).

You might want a water pump.

You might want a fridge, vans get very hot very quickly and veg and meat dies just as quickly.

Stuff will break for no good reason. Many components, campervan specific or otherwise, are just unreliable and badly made, so be prepared to use you voltmeter and powers of deduction to locate problems and fix them as they arrive. Carrying a basic kit of some spare wire, connectors and screwdrivers in the van is a good idea.

> Thanks!

jimtitt 09 Sep 2019
In reply to wintertree:

> These batteries can deliver massive currents.  Your worst case isn’t a depleted leisure battery - it’s a depleted leisure battery and all leisure loads on vs a full vehicle battery and ~100 A from the alternator - so at least 200 A.  Obviously that’s not a normal situation but if it happens you don’t want to start a fire.

> The golden rule - make sure you fuse the circuit to less than the rating of the switches, wires and relays in it.  So if you use a 100 A switch you want something like an 80 A mega fuse in there.  I’d put a 200 A switch in with a 150 A fuse - https://www.12voltplanet.co.uk/battery-isolator-changeover-switches.html - see also their fusing guide.

> I’d fuse the battery-battery link on each end as close as I could to each battery.

> Although I’d probably not do any of that - I’d probably use a smart DC to DC charger from the vehicle to the leisure battery to look after both and to prevent silly currents.  At that point I’d probably fit a lithium leisure battery.  I’d keep a jump lead around in case I ever wanted to start the vehicle from the leisure battery.  Whatever you do make sure the 0V line is equally beefy.  


Indeed, nowadays a DC-DC charger the way to go (essential with anything modern anyway) as they charge the extra battery better, protect the system and you don't need huge cables everywhere, caravan charging circuits are 2.5mm2 not 25mm2

wintertree 09 Sep 2019
In reply to RBonney:

One error in that - there should be a fuse on the 12 V battery charger wire near the battery.  Currently that wire is unprotected and if damage or incompetence happens and it’s shorted the battery could slag it and start a fire.  For a 20 A charger I’d use a 30 A fuse and 6 mm^2 wiring.

Remember - fuses protect the wiring from all sources of current.  Well, except the solar panel to charge controller wiring for which there’s nothing to gain from fusing.

Alasdair Fulton 09 Sep 2019
In reply to jimtitt:

> Indeed, nowadays a DC-DC charger the way to go (essential with anything modern anyway) as they charge the extra battery better, protect the system and you don't need huge cables everywhere, caravan charging circuits are 2.5mm2 not 25mm2

Further to this: check what type of alternator you have. Many of the newer types don't work well with VSRs.  I've never quite got the need for the isolator switch. We don't have one and I've never wished I did. 

Good info here on smart alternators:  https://www.12voltplanet.co.uk/auxiliary-battery-charging-in-vehicles-with-smart-alternators.html

Since you are going solar, just get one of these instead of a VSR and MPPT:  https://www.12voltplanet.co.uk/ctek-d250se-dual-input-dc-dc-charger-mppt-solar-controller.html

Post edited at 07:50
snoop6060 09 Sep 2019
In reply to Hooo:

You can get 12v laptop chargers. I have one for my ThinkPad but they are widely available. And it's fairly fast. 

Defo bin the invertor if you don't really need it. They are stupidly inefficient. I don't have one and only use 240v stuff when on hookup. Which in reality is only ever a hair dryer

Ciro 09 Sep 2019
In reply to yarbles:

I'd recommend joining the SBMCC - slightly stuffy forum at times but a wealth of information on all aspects of van building 🙂

Hooo 09 Sep 2019
In reply to snoop6060:

Yes, but an inverter is cheaper and more versatile. It's also permanently installed, so can't get lost like yet another laptop adaptor ( children involved).
Efficiency is about 90%, so not worth worrying about for this sort of load. I definitely won't be binning it, it might come in handy and doesn't waste any power if I'm not using it.
I haven't used EHU since I got solar. I probably wouldn't bother installing EHU if I was doing a conversion now.

Hooo 09 Sep 2019
In reply to Alasdair Fulton:

Good point about smart alternators.
If you have one, you need a B-B charger and the CTek one is well regarded. If you have an older van with a dumb alternator you can use a VSR and separate solar controller, which works out quite a bit cheaper.

In reply to yarbles:

We’re off to wales in our van this weekend, which I converted around 3 years ago. The two most critical thing for us looking at all the trips, has been the Eberspacher heater, and a 12V top loading compressor fridge freezer. The fridge was quite expensive (£600 ish), but keeps stuff properly cold, even on the move and even when switched off (really well insulated). Water pump and built in cooker and sink are up there too. 

For long stop overs, a hookup and 12v charger hard wired via a fused switch into the leisure battery makes life easier too. Conversions to allow you to swing the front seats right round are brilliant for creating more living space too.

fyi this

https://www.decathlon.co.uk/air-seconds-base-xl-inflatable-camping-shelter-id_8358157.html?gclid=CjwKCAjw8NfrBRA7EiwAfiVJpY7E5E2P8NhGxWVm9Bqg40mbpUozj3ijvzard18sVgOMErs36pfFqBoC4BkQAvD_BwE

is really popular on the VW forums. I got one, and it gives you such a lot of room to store mats etc. and researchers your place on the campsite if you have to drive to the crag.


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