Caravan wiring diagram

Submitted: Wednesday, May 07, 2008 at 11:51

Member - Drew T (Melbourne)

I have just bought an old caravan to park on a bush block (no mains 240v). I intend to set it up as a stand-alone 12v solar/AGM system ... but with provision for connecting to the 4WD (aux bty &/or alternator chaging) or genie (eu10i & smartcharger) on the (hopefully) rare occassions the AGM has discharged too much (ie: 50%).

After a bit of research (Dereks diagram under 'caravan & camper wiring' on this site, searching this forum (lots of good discussion), Plasmatronics technical articles, Collyn Rivers books etc etc, I have has a first go at a circuit diagram. In particular I want to be able to monitor the net state-of-charge of the caravan AGM (ie including the contribution of external charging sources .. hence why I have used a PL20 & shunt) & a simple way of preventing the solar-charging from interfering with the rare times that i might need to use an external 12v charging source (car alternator or smartcharger).

Interestingly I have found there is a lot of good info out there but not many actual circuit diagrams that I could 'copy'. Maybe there's a legal issue if you have problems based on someones 'published' circuit diagram?

Hence I would welcome any suggestions for improving/correcting my circuit diagram (eg: a better way to automatically disconnect the solar when external 12V charging commencesImage Could Not Be Found
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Reply By: Matt(WA) - Wednesday, May 07, 2008 at 13:13

Wednesday, May 07, 2008 at 13:13
Mate, thats a good diagram. is there any chance of you being able to email me a copy please? My email is matthew.brook1@three.com.au I am setting up my van for traveling but thats exactly what I am after. Thanks in advance
Matt
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Follow Up By: DesF - Wednesday, May 07, 2008 at 13:21

Wednesday, May 07, 2008 at 13:21
Hi you can right click the picture and click "Save picture" and save it to your PC ( My Documents) , Easy, Cheers Des.
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Follow Up By: Matt(WA) - Wednesday, May 07, 2008 at 13:25

Wednesday, May 07, 2008 at 13:25
Cool, got it. Thanks for that.
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Follow Up By: Member - Doug T (FNQ) - Wednesday, May 07, 2008 at 15:27

Wednesday, May 07, 2008 at 15:27
DesF is right but you need to left click it first or it will be too small

.
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Reply By: Robin Miller - Wednesday, May 07, 2008 at 13:41

Wednesday, May 07, 2008 at 13:41
Hi Drew

Couple of comments, but first I can't actually read some of the text on your circuit so questions may seem dumb.

I could not see the reason for the switch in the positive lead from the solar panel, sometimes I have used a plug/socket here though which allows for easy disconnection of panel.

Your circuit shows external charging sources as going thru secondary wires to the battery.
I would make these a direct connection to the battery terminals which helps prevent external loads from changing the voltage seen by any smart charger.

You seem to have a couple of breakers to many , e.g. the 1500w inverter has 2 breaker and a shunt in addition to the inverters own on/off switch and protection. These could limit the output from the inverter unnecessarily as inverter needs a solid battery connection.

You don't seem to be using the PL20 load terminal - this allows
programmed load disconnection if for example battery volts gets low.
Robin Miller
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Follow Up By: Member - Doug T (FNQ) - Wednesday, May 07, 2008 at 15:30

Wednesday, May 07, 2008 at 15:30
Some mothers do ave em , left click the bloody photo .

.
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Follow Up By: Robin Miller - Wednesday, May 07, 2008 at 15:43

Wednesday, May 07, 2008 at 15:43
THanks Doug , I do know that one but resolution is not quite there to read all the text.
Robin Miller
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Follow Up By: Member - Doug T (FNQ) - Wednesday, May 07, 2008 at 16:07

Wednesday, May 07, 2008 at 16:07
Robin
I did a left click which enlarges the photo, then downloaded it, I can read it all .

,
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Follow Up By: Member - Drew T (Melbourne) - Wednesday, May 07, 2008 at 16:25

Wednesday, May 07, 2008 at 16:25
thanks for the feedback Robin.

- i'm using the switch in the positive lead from the solar panel to manually disconnect the solar charging when externally charging from say car alternator or a smartcharger .. so the alternator/smartcharger do not confuse the solar charge as the battery voltage & hence cut back charging. I know i could fit relays to disconnect the solar (1 relay from car ignition for alternator & 1 from 240v source for smartcharger) but that seemed just a tad more complicated for my elec skills & in the case of the alternator would only work for that specific car. also, i only see the external charging as a rare occurence as i want to scale the solar/AGM to meet all my needs (touch-wood)

- I take your point about connecting the external charging sources direct to the battery .. i'll change on my diagram

- re inverter: ok, i see your point ... i will do away with the 2nd breaker next to the inverter

- re low-voltage disconnection: i only steered away from using this (load- to relay for + load) because I read in one of Collyn Rivers articles that I would then have to reprogram the PL20 using program 4 (instead of pre-programmed 1 for Gel/AGM) & this was not recommended unless you knew what you were doing (& I wasn't sure i was at that stage!!!!!). I'd be interested to know from anyone whether the re-programming is really that hard (as the actual circuit changes seem minor). either way i'll incorporate the low-voltage cutout into my circuit diagram & see what feedback i get re re-programming at PL20

thanks again
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Follow Up By: Robin Miller - Wednesday, May 07, 2008 at 16:41

Wednesday, May 07, 2008 at 16:41
Hi Drew

The programming , or rather the manual takes a bit of getting used to as its based on state logic - I managed to get thru it and programmed using program 4.

I would advise anyone who does it to throughly check the actual operation as in my case I wanted to shed a load across midnight and there was a flaw in the base code in a couple of areas, I believe after I advised the manufacturer that these were corrected in 2007 .


Robin Miller
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Follow Up By: wazzaaaa - Wednesday, May 07, 2008 at 19:11

Wednesday, May 07, 2008 at 19:11
Robin,
By connecting direct to the battery wouldn't that bypass the pl20 and so not allowing it to monitor amps going in?
Wazzaaaaa
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Follow Up By: wazzaaaa - Wednesday, May 07, 2008 at 19:12

Wednesday, May 07, 2008 at 19:12
I was referring to connecting the battery charger direct to the battery
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Follow Up By: Robin Miller - Wednesday, May 07, 2008 at 20:06

Wednesday, May 07, 2008 at 20:06
Hi Wazza

As the circuit is it's not intended to measure amps in thru the battery charger , it just measures amp hours in via the solar panel.

This is pretty much the normal use from what I have seen,
although other configurations are certainly possible.

The changes I am suggesting don't change the circuit configuration but just give lower impedances (resistances) which will make it hold up better under loads in both directions.

Robin Miller
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Follow Up By: wazzaaaa - Wednesday, May 07, 2008 at 20:25

Wednesday, May 07, 2008 at 20:25
Robin, I am in the process of wiring solar to my caravan and am still trying to get my head around Plasmatronics wiring diagram. Looking at the Pl20 & PL40 they count all amps in and out to give an accurate state of charge in amp hours hence my question. On looking at Drews 2nd diagram it appears it still is measuring amps as the neg. still runs through the regulator. I am still at the planing stage at the moment so this post interested me.
Thanks for the time replying.
Wazzaaaa
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Follow Up By: Robin Miller - Wednesday, May 07, 2008 at 21:30

Wednesday, May 07, 2008 at 21:30
Fun Project Wazzaa .

From the point of view of practical projects the only value I have really found from the PL20 Amp hour tallying is simply to know wether more has come in from the sun than has gone out.

I haven't found they they give an accurate state of charge of the battery , and just read the voltmeter reading it gives.

Personnaly unless you have a need for the exact type of logic control the PL20 has, I think its overpriced and not to easy to use.
For example I designed them into one of those roadside message signs you see about , because of perceived value of the monitoring but I don't expect them to go into a future upgrade.

Robin Miller
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Reply By: Affordable Batteries & Radiators - Wednesday, May 07, 2008 at 16:06

Wednesday, May 07, 2008 at 16:06
Here is a updated diagram I did for another customer. Note: It is designed for a Bi-Fold portable solar panel and does not have the solar regulator fitted to the van.

Note the inverter wiring is to suit the inverter and could be 200 amp cable in some cases.

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Reply By: Member - Drew T (Melbourne) - Wednesday, May 07, 2008 at 17:02

Wednesday, May 07, 2008 at 17:02
thanks for your feedback ... here is my updated diagram

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Follow Up By: Affordable Batteries & Radiators - Wednesday, May 07, 2008 at 17:13

Wednesday, May 07, 2008 at 17:13
Good.

You need a fuse on the smart charger and 12V input from the car and this car input should be 6 B&S if possible.

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Follow Up By: Member - Drew T (Melbourne) - Wednesday, May 07, 2008 at 17:50

Wednesday, May 07, 2008 at 17:50
thanks Derek .. i have added to the diagram
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Follow Up By: Angler - Wednesday, May 07, 2008 at 20:46

Wednesday, May 07, 2008 at 20:46
I wouldn't bother to put in the solar panel disconnect switch as most panels have a diode inbuilt to stop any back current.
I just left the panels connected in mine.

Pooley
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Follow Up By: Member - Drew T (Melbourne) - Wednesday, May 07, 2008 at 21:10

Wednesday, May 07, 2008 at 21:10
Angler, the disconnect switch is for a different reason ... to prevent the solar charge/voltage tricking the external charging sources into thinking the battery charge is higher than it really is & making them throttle back prematurely (well this is what i have read .. i'm no expert myself!!)
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Reply By: roblin - Wednesday, May 07, 2008 at 22:14

Wednesday, May 07, 2008 at 22:14
This is a minor point but when mixing 12volt systems and 240 volt systems (from your inverter) you should not be referring to the 12 volt negative path as an earth. They serve completely different functions in the two systems. Although car manufacturers choose to earth the negative of a car battery to the chassis, they still use separate negatives back to the battery for circuitry (at least in these modern days they do). There should be no reason to have to earth your battery negative to the caravan chassis unless you are going to use the chassis/bodywork as a return path. There is potential for you to introduce stray currents in the caravan body through doing this but, more importantly, if you have a 240volt breakdown to earth, there is potential for the 240volt source to creat havoc in your 12 volt system. Another question that I don't know is covered very well, is how do you REALLY earth the invertor 240volt output. Although the invertor is earthed to the chassis you now have a floating earth (in the caravan) with respect to the ground it stands on unless you intend to earth the van to the actual ground.
Maybe I am speaking through by backside but, whatever you do, ensure the applicable standards are followed and your 240volt wiring from the invertor is installed by a licensed electrician. I was one once bu have been away from the trade for awhile.

Cheers
Rob
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Follow Up By: Member - Drew T (Melbourne) - Thursday, May 08, 2008 at 08:08

Thursday, May 08, 2008 at 08:08
i am intending to wire each circuit directly back to 12v- (ie return wire back to the shunt). i was also going to earth the shunt to the chassis as an additional earth return for any 12v appliances that inherently earth themselves to the chassis when they are installed .. hence the 12v earth would be an additional earth return path only.

as for 240v earth i am not sure of this. i have had a quick read of thread 23356, an article at http://www.aroundoz.com/diy_archive/inverter.htm, and in Collyn Rivers book 'Motorhome Electrics'. I m not sure i am any wiser but in all honesty that is probably due to my level of electrical knowledge. It appears that my particular inverter (a Jaycar 500W pure-sine-wave with what i presume is a 12v earth) should be earthed to the caravan chassis. Do i simply not require a 240v earth if i am only using a single 240v appliance at a time?

is there really ever a requirement to earth the caravan with an earth stake?
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Follow Up By: Nomadic Navara - Friday, May 09, 2008 at 12:52

Friday, May 09, 2008 at 12:52
"Do i simply not require a 240v earth if i am only using a single 240v appliance at a time?"

The output of an inverter is floating. If you plug straight into the power socket on the inverter then just earthing the cabinet to the vans earth is sufficient. If you wire in some power points connected to the inverter then the electrician who install them will do it correctly.

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Reply By: jdbb - Thursday, May 08, 2008 at 07:22

Thursday, May 08, 2008 at 07:22
Hello Drew

Can you please post the latest version of your layout.

thanks John
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Follow Up By: Member - Drew T (Melbourne) - Thursday, May 08, 2008 at 08:11

Thursday, May 08, 2008 at 08:11
yes shall do in a few days once i have incorporated everyones feedback .. otherwise i'll be posting updates everyday!!

i also need to get additional feedback on the 12v vs 240v earthing issue raised above, which i had ignored up until now
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Reply By: ExplorOz - David & Michelle - Thursday, May 08, 2008 at 11:27

Thursday, May 08, 2008 at 11:27
Drew,

When you are complete and have the general tick of agreement of everyone we would be very happy to publish the diagram in one of the articles on the system, maybe a new article about caravan wiring we would of course attribute any information provided to yourself. I will mention this thread to Damian and get him to contact you about this in due course. Good work.
David (DM) & Michelle (MM)
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Reply By: Member - Drew T (Melbourne) - Friday, May 09, 2008 at 09:25

Friday, May 09, 2008 at 09:25
ok here is my latest diagram .. thanks for everyones comments. still happy for any final feedback (do i have enough fuses? wiring sizes? the contentious earthing issue? etc etc)
I have added a few explanatory comments to the diagram to explain why i have used certain components ... in most cases I want to keep it relatively simple and limit the cost!

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Follow Up By: Nomadic Navara - Friday, May 09, 2008 at 13:07

Friday, May 09, 2008 at 13:07
I would be inclined to keep the 3 way fridge separate from the battery circuit. If you have it switched on whilst you are charging from your multi stage charger then the fridge will take a lot or most (depending on the size of the charger) of the current available. Also if the battery reaches full charge the current drawn from the fridge will prevent the charger from dropping back to float charge (the fridge will be drawing 12 to 15 A and the chargers do not switch to float until the current drops below an amp or two.)

You are doing an extensive installation. Wiring the 3 way fridge directly to your tugs electrical system will be very little extra work. Please consider a separate feed for the fridge and keep it away from your vans battery system. You can wire this through a 12 pin trailer connector, also incorporate a relay in circuit, controlled from your ignition switch to protect your tugs starting battery.

PeterD

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Follow Up By: Member - Drew T (Melbourne) - Friday, May 09, 2008 at 18:56

Friday, May 09, 2008 at 18:56
PeterD .. I only ever intend to run the fridge on 12v when the van is being towed & I can't use gas. Hence an additional ignition activated relay to connect the fridge doesn't seem warranted (especially when different vehicles may be used to tow the van). I used the same logic re method of disconnecting the solar feed for the rare times I will be charging the van battery from car alternator or SmartCharger. That said I have re-worded my comment next to the fridge switch & made further notes in the 'Notes' section at the bottom to explain that others may wish to consider such relays.

thanks again for your feedback

updated diagram below ... again !

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Reply By: Member - Drew T (Melbourne) - Tuesday, May 13, 2008 at 14:21

Tuesday, May 13, 2008 at 14:21
ok here is my final diagram .. thanks again for the various feedback i received. In the end i simplified the diagram even further to save $$$ & reduced the number of cable runs for the 12v load so i didn't have as many cable runs around the van (but i did compensate by increasing the cable size!). Two particular areas where others may wish to vary from my diagram:
- addition of various relays etc to connect-disconnect various devices depending on whether the engine is running etc.
- keeping the fridge circuit completely separate

PS: I drew the diagram in MS powerpoint so if anyone wants a copy I will setup a link

cheers ... Drew T
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Follow Up By: jdbb - Tuesday, May 13, 2008 at 18:11

Tuesday, May 13, 2008 at 18:11
I would like to get a link to the file - my old eyes are finding it hard to read some of the words.
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Reply By: Member - Drew T (Melbourne) - Wednesday, May 14, 2008 at 22:07

Wednesday, May 14, 2008 at 22:07
ok heres a link
Drews caravan wiring diagram (powerpoint format)
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