Proposed dual battery wiring.

[Cage]

I think I'm getting down to the nitty gritty with the dual battery set-up for my camper trailer to run an EvaKool 55L fridge, some low output lighting and a charging point for phone etc.

I'll be using the CTEK D250S Dual DC/DC charger and a Fullriver 120AH AGM battery in a lockable toolbox mounted on the trailer mudguard.

I've decided to do the wiring myself and have read umpteen dozen threads, here and elsewhere, on the right cable to use, with 'experts' proclaiming that you need anything from 6mm Auto cable to 2B&S cable, with the general consensus being that for long runs (mine will be about 12m) 6B&S is the minimum to counter voltage drop.

One seller was offering a ready made kit with 50amp Anderson plugs and a 60amp circuit breaker, and with my very shaky understanding of this elecktrickery stuff it seems to me that the Anderson plug would go into melt down before the circuit breaker tripped.

While doing my price searching I've noticed that 4B&S cable is not that much dearer than 6B&S cable and that is what I've decided to use, with an 80amp circuit breaker at each battery, or would 50amp be better, and 120amp Anderson plugs. The Tycab 4B&S cable is rated at 108amps at 30°C.
I'll use a 50amp Anderson plug to pick up the lead from a solar panel to the D250S charger.

This set-up may be over-kill but I'd rather err that way than the other.

Any comments from those knowledgeable in the auto electrical field would be much appreciated.

Thanks

Cage

[WomblingFree]

4B&S - good
80 amp breaker. You are protecting the cable not the equipment connected to it. Use smaller fuses at the equipment end as reqd.
4B&S is rated to some 350amps when used as a starter cable (short term use) so restricting it with a 50 amp breaker is pointless. The circuit breaker will also act as a bit of a current limiting device so upping to 80 or 100amps will also help your voltage drop a tiny little bit.

[armbrup]

Personally I would not use an Anderson plug between a trailer and car.

I have seen 2 instances recently where the Anderson plug has detached from external force such as grass etc hitting the lead and then the Anderson plug disintegrates from dragging along the ground. These were 50 amp Anderson plugs.

I earned a nice wine in Mornington Wildlife sanctuary on the GRR from having a spare Anderson plug to give to a bloke whose fridge was defunct from no power. I am a fan of Anderson Plugs but no longer for car to trailer applications.

Supercheap do a 50amp 2 pin plug that is positively locked with a flap like a seven pin trailer plug.

Really if you have a DC/DC charger you should not worry too much about voltage drop as they of course are limited to whatever amperage you buy eg 10 or 20 and boost up to 13.9 or whatever. Seeing the amperage draw will probably not exceed 30 amps if you buy a 20 amp one then you are really into overkill. I think 6B&S with 50 amp plugs is fine.
Similarly you don't need 80 amp circuit breakers.
But hey its up to you, but 2B&S x2 is pretty heavy and stiff to manage and the weight from the trailer to the car may put a strain on an Anderson Plug in the bumper..
If I were in your position I would probably run 4B&s to the back of the car( which I have done) then into a splitter box down to say 6B&S or 8B&S for the rest of the run. I run 8 B&S to my fridge in the back of the car and merit plugs in the rear bumper to run my camper lights.
Regards Philip A

[Cage]

Thanks for the replies.

After reading the CTEK manual I found that it has a boost function to keep the voltage at 14.4v so voltage drop is not a big problem.

Consequently I've ordered 6B&S cabling and 50 amp circuit breakers. I'm also looking at fitting a fuse block with appropriate fuses for the various outlets.

This electrickery stuff is not one of my forte's so I've done my research and hope to get it right, first time. There is some very misleading info out there in cyber land, all of it well intended, but some of it possibly dangerous.

I've also ordered a Trailer Vision mounting pack for the Anderson plugs and it has a lock-in feature.

Cheers

[robcaz]

You will find 50 amp andersons & 6B&S twin core sheathed cable will suit your circumstances running in conjunction with the Ctek over your intended distance. Anything larger is definately overkill & wasted money.

Stick with genuine andersons as there are plenty of copies around that just do not live up to the conditions. Ebay sellers have them as anderson 'style'.

[WomblingFree]

Thanks for the replies.

After reading the CTEK manual I found that it has a boost function to keep the voltage at 14.4v so voltage drop is not a big problem.

Consequently I've ordered 6B&S cabling and 50 amp circuit breakers. I'm also looking at fitting a fuse block with appropriate fuses for the various outlets.

This electrickery stuff is not one of my forte's so I've done my research and hope to get it right, first time. There is some very misleading info out there in cyber land, all of it well intended, but some of it possibly dangerous.

I've also ordered a Trailer Vision mounting pack for the Anderson plugs and it has a lock-in feature.

Cheers

Yes the Ctek will make up for voltage drop but the more drop you introduce, the harder the Ctek has to work to bring it up again. That produces heat which is not very clever in the outback where the Ctek is already running hot just at ambient temperature without heating itself up further trying to boost your volts. In electronics, heat means premature failure then you have no battery.

The breaker is there to protect the cable, not the gear you attach to it. How did you come up with a 50amp value?
If you run one circuit with a little breaker then the first little surge (just plugging in your fridge) can pop the breaker and remove power from everything.
You don't say how you intend to use your truck but lets pretend you are off in the outback and days away from replacement supplies. Your Chinese USB charger that is connected to your nice new fuse block fails and takes out the little 50 amp breaker which means your fridge has gone off but you don't know that until the food starts warming up and going off.
Cheap circuit breakers work by heating up and bending bi-metallic strips. You have already warmed it up to a very high value by having it engine bay so it doesn't take much of a surge to trip it.
The sensible thing to do is run two circuits, one just for the fridge with an appropriate sized breaker or fuse rated to the cable and not to the fridge. Your fridge should have another fuse in it to protect itself against shorts.
The second cable is for all the other stuff you have decided to incorporate, also properly rated.

If you are dead set on using a small breaker then do yourself a favor and fit a fuse instead. You will be changing it for a larger size later on so this will make things easier for you.
This electrickery stuff is one of my forte's as I'm an electronics engineer but obviously its up to you.

[robcaz]

On page 24 of the Ctek D250S Dual manual it lists recommended cable sizes to length run & also circuit breaker sizes http://www.ctek.com/Archive/ProductManu ... UAL_EN.pdf

This is a good diagram to show your circuit breaker placement between the batteries & the charger http://www.jtsonline.com.au/media/wysiw ... d250s4.JPG

The best are the manual reset circuit breakers http://www.narva.com.au/products/browse/high-amp-manual

I have run thermal breakers in my 12volt system http://www.narva.com.au/products/browse/plastic-manual

I used a six blade fuse box to run my accessory outlets through with a connection from the positive & negative on the battery. Each outlet has its own positive & negative connection with a blade fuse http://www.campertrailers.org/redarcbcdcinstall13.JPG

You can find a write up of how I went about installing a Redarc BCDC1225 into our camper with a wiring diagram http://www.campertrailers.org/bcdc1225_install.htm

[Cage]

Thanks for the replies.


If you are dead set on using a small breaker then do yourself a favor and fit a fuse instead. You will be changing it for a larger size later on so this will make things easier for you.
This electrickery stuff is one of my forte's as I'm an electronics engineer but obviously its up to you.

OK, this Fuse/Circuit Breaker stuff is making my head hurt.

If I'm reading your posts correctly, you seem to advocate a minimum of 80/100 amp C/B's on 6B&S cable.

If I'm using 50 amp Anderson plugs would that not then make the Anderson plug the weak link and go into meltdown before a 100 amp thermal circuit breaker tripped?

The purpose of this exercise is to run my fridge while on the move, and to keep the auxiliary battery topped up so I can get a couple of days careful use from it when away from mains power.

[robcaz]

Hi Cage,

Assuming the cable length from your vehicles alternator to the camper trailer batteries is 10 metres, the manual recommends a 10mm sq/AWG 8/8 B&S size cable with a 30 amp circuit breaker.

8 B&S is the next size down from 6 B&S. It is best to use the 6 B&S over that distance to avoid voltage drop.

The cable conversion chart on Collyn Rivers page shows you the relation between the sizes http://www.campertrailers.org/collyns_p ... Conversion

8 B&S cable is rated at 70 amps & the 6 B&S 100 amps.

The Ctek D250S Dual has a maximum output of 20 amps so if it exceeds this it will trip the 30 amp breaker. You are not putting 50 or 100 amps through the 6 B&S cable or 50 amp Anderson's, but using that size to avoid voltage drop over 10 metres.

The Redarc voltage drop calculator shows 0.28 volt drop using 6 B&S over 10 metres at 20 amps as opposed to 0.45 volt drop using 8 B&S http://www.redarc.com.au/handy-hints/ca ... calculator

[vincent]

Electrics are always a hot topic. Fusing, important fuse on your battery terminal first, I cannot emphasize this enough.It is best to fuse every circuit separately.Put an earth bar under your fusebox.Run always a positive and a negative to this point do not use the chassis as a return circuit.That are simply the basics. skimping on wiresize is false economy.Even a voltagedrop say of 0.5V which is seemingly insignificant in 240V terms makes your fridge working that much harder.Put an Ampmeter on it and you will be amazed how much more it draws.As far as circuit breakers are concerned I am not a fan of those.If you want to use them make sure they are breakers and do not automatically reset.In my Van. Supply Wire 2x16mm, Solarpanels 6mm. the rest 6mm. Yes Australia converted to metric a long time ago.