Power Sources

It all depends on what you want. I have run large cable from the auxillery battery in my LC100 to the rear to an Anderson plug and then down the camper trailer to power up the battery and charge it whilst I am traveling. Works fantastically if you ask me.

Warm Regards
Turtle

Hi mate, never mind all those expensive dual battery systems, just head down to your closest super cheap auto and get yourself their battery isolator kit, about $95 bucks and you can do it yourself, all it is a voltage sensitive relay that charges your back battery off the front batt until the front batt gets down to 12V... Very easily installed and very cheap... just hook upto one of the spare pins on your trailer plug :) Isolator is good for 200A DV12V

Justin

Good to see that a number of you have been able to post an answer or suggestion to my question. Its just ashame that half of them are aimed at ripping someones post apart. A simple be careful doing this stuff yourself would have been sufficient or even some suggestion on how to do it.

Cipher, NO that post was meant in support of you..."ripping" was meant to say that they were basically getting stuck into your post....I appreciate your suggestions and help. As I said I have no experience and am not going to get out the front tomorrow and start wiring up....lol

Thanks mate :)

Cram ,type in dual battery into the search function ,also try batteries /charging /wire size /voltage drop , ect ect . allow youself a few days reading and then you will be able to see what you need and dont need ,,

Hi Cram, Very interesting reading lol. I have a 2002 Prado I ran 6mm twin core in condute down the inside of the LH chassis rail to a HD 2 pin plug on the bumper, then on to the battery on the trailer. Just make sure you fuse it at the car battery and on the trailer befor the battery.( I used 30a at both ends) I have no problems with this set up sofar, hope this helps.

Steve

Here is what I have done to fix my problem. It is available for anyone to rip apart... I don't care. It works for me.
I used 35mm2 cable, black and red. Run the full length with a 50a circuit breaker as close to each battery as possible. An Anderson plug between the trailer and car.
The end result... no voltage drop, fully secure and safe with the battery on my trailer getting full charge whilst driving.
Hope this helps you.

Warm Regards
Turtle

cram,
There are a myriad of ways of doing this job.

At the simplest level you can parallel the battery in your car with the battery in your camper.
Down side of this one is you must remember to disconnect the camper from the car when stationary. If you don't disconnect you risk having a dead flat starter battery in the car. Also, vehicle alternators aren’t designed to fully charge storage batteries.

From there you can move onto simple relay or solenoid or switch based isolators. These work by installing a manually operated connection between the two batteries. When the engine is running you parallel the camper and the car. When the engine is off you break the connection.
Down side, same as above.

Next step up the tree is an automatic voltage sensing type of device. These devices sense the voltage of the vehicle starting battery. Once the starting battery reaches a preset voltage or state of charge they connect the trailer battery into the circuit. The system then starts to charge the camper battery.
Down side, Vehicle alternators aren’t designed to fully charge storage batteries.

Beyond these you’re getting into the realm of smart charging systems with 3 or 4 stage charge algorithms. These systems offer true 100% charge of your auxiliary batteries and also perform some smart battery maintenance. These are a whole topic unto themselves!

A final thing to note is,
Because the camper battery and car battery are so far apart in 12 Volt terms the cables and connectors need to be as large as possible to minimise voltage drop.
The only plug brand worth looking at for this project are Anderson Plugs and anything smaller than 100 Amps is at best useless. Why do I say that? These larger plugs are the only ones that will accept a cable size that minimises your voltage drop at the camper battery and therefore maximises your charge.
My favourite cable for these applications is Double Insulated Welding Cable of a minimum 25mmsq. Note: Cable should always be measured by the conductor area or diameter of the conductor, never the overall diameter of the cable including insulation.

Note: The trailer lighting plug is totally unsuitable for this project.

Hope this helps,

Geoff.

Cram

Here's my suggestion.

Battery - put in an AGM battery, costs a bit more but it will last longer and charge quicker without needing a $300 voltage booster. Commonly used brands that don't cost a fortune are Fullriver and Remco.

Wiring - nothing less than 4 Gauge - this means that the Copper diameter is at least 6mm and outer diameter of 10mm.
Site Link

Connector - if you use an Anderson SB50 there is a good chance that if you ever need to exchange power with another camper, you will have the same Connector - this is becoming the standard. BUT it is not weather proof and even though the contacts are silver you will still have corrosion if it is wet with 12 volts on it. The contact surface will not work well for long if they are covered in dirt. Ensure that it is sealed with Neutral-cure silicon around the cable entry and mounting screws and it has a Rubber Plug when not in use.
Site Link

Fuse - you must have a Fuse or Circuit Breaker (less than 70 amps) in the Plus wire at BOTH the engine compartment and the Trailer Battery.
Site Link

Battery Isolator - dozens to choose from.

If you don't want to do this yourself, tell an AutoElectrician EXACTLY what you want, rather than giving him a blank cheque.

Mike

Evening Cram...
Started to read your thread and figured it would be an "interesting one" so to speak...
Have NO intension of getting into a debate over who said what or who's right or wrong , but happy to tell what I did in the same situation...

First off, I too am qualified in the electrical industry although when it comes to this particular topic I did several months reading and research on the subject before deciding on my own path...

Firstly I installed a Redarc isolator under the bonnet of my patrol between the auxilary battery and the main cranking battery, from the auxilary battery I run all my extras within the vehicle such as 2 fridge points in the back and the uhf radio etc. At the rear of the vehicle I mounted a 150amp Anderson plug on the bumper in a protected area and ran double insulated 200amp cable directly to the auxilary battery. Note.. ALL wiring between batteries and to the back bumper are 200 amp cable. On the battery end I have an automatic 50amp circuit breaker for protection purposes. On the camper I ran the same cable from the Anderson plug that connects to the back of the car to the 2 deep cycle AGM 120amphr batteries I installed in the battery box (also with the 50amp circuit breakers for protection). From that point I dropped the cable size down (not sure what size) into a fusable link type setup to protect individual circuits I ran throughout the camper for various lighting freezer etc.

Reasons.... The voltage drop in small wires will prevent the camper from getting the maximum possible charge thus the reason for the 200amp cable to ensure no voltage drop, as for the 150 amp Anderson plug between the car and the camper... also to minimise the voltage drop also as mentioned earlier , the large cable simply wont fit into the smaller plugs and the larger plugs are very robust .

From the large cable I ran through the car I tapped into it at the rear corner panel and wired in 2 50amp Anderson plugs (1 on each side of the vehicle, and also protected with a seperate fuse) and from these I run my 2 fridges and 12v oven etc, all with the 50amp Anderson plugs. I also put one on my 12v compressor so it can run from my rear points also...

Something to consider with your camper batteries is, recharge time and how low they can be discharged before you start to damage them. Different brands/types of batteries have different characteristics. I went with the 120amphr Fullriver deepcycle batteries as they accept a very fast charge rate thus maximising the recharge durring travel and they can be discharged slightly lower than a lot of other brands, and then the price which was pretty good at the time for what we got (about $260 each).

Happy to supply more details or pictures if that can help (just drop me a line)

Some will say its over board some of my specks... not realy interested in the debate... this is simply what I did to ensure my system works the way I wanted it too while also allowing expansion on the elctrical side if ever wanted..

Hope that helps...
Boo

GeoffMc Cut me real deep mate, cut me real deep.

Disapointed, i never meant to offend anyone in this post, if i have a sincerly appologise. I did not mean to inflict my point of view to anyone rather share what i have done.

As for the comment about Sparkies sticking to AC, Not sure if you are aware but DC is also a major part of the whole kit and kaboodole.

Regardless of that, instead of saying my ideas were virtually 'crap' why not just say wouldnt this be a better way of doing it, instead of just purely insulting me.

As i said above i do appologise for losing my temper before, but alloy was really getting on my nerves as i was only trying to help and he kept getting stuck into me.

Justin

Cram,

I make no claim to knowing what I am doing with auto electrics ( my efforts usually end with a puff of smoke, a frying smell and a call for professional help). I have 210 Ah worth of batteries in the CT and I use the trailer plug (30A rating) with 8mm cable either side from a Redarc controller. Works well for my setup and you only need to have one plug on the back of the car Still, most advice suggests that there is no such thing as cable or sockets which are too heavy, so hefty cable and Anderson plugs seem to be the go.

I skipped most of the pathetic abuse in this thread, but no one seems to have suggested a 240v charger in addition to your car setup. A good three stage charger will give you battery power when 240v is available and help you to maintain your batteries when at home. I believe, and I could be shot down here, that a multi stage charger will do a better job of charging your batteries than simply relying on the alternator.

Anyhow, I am off to measure the voltage drop in my current setup as I am interested to see what I am losing by using the trailer plug.

Matt.

My System may sound crude but I am using 4 ASWG from my main battery to a 175amp Anderson plug and 4ASWG to my auxillery battery on my caravan. There is an ignition operated soliniod rated at 100amps in the engine bay and an 80amp fuse int the engine bay and another near the auxillery battery.
The cable was purchased from Jaycar and the soliniod and fuses were purchased from a local auto electrician. The whole set up (DIY) cost me approximately $100.00. It all works very well. When not being used the caravan battery is kept fully charged by a small solar panel I baught from Supercheap.
This system has been in service now for about three years and give no trouble.
I don't know where some of these installations come up with very high prices using fancy gismos.
My only regret is that I did not use an AGM battery instead of a wet cell DSB

Unique to the world of Automotive cable, it is specified by the outside diameter of the insulation - a 6mm automotive wire will fit through a 6mm hole - it doesn't give you any other useful info about the wire.

AWG (American Wire Gauge) and B&S (Browne and Sharpe) are the same.

Mike

Mat has given some clues to efficient battery charging in message 12. “but no one seems to have suggested a 240v charger in addition to your car setup. A good three stage charger will give you battery power when 240v is available and help you to maintain your batteries when at home. I believe, and I could be shot down here, that a multi stage charger will do a better job of charging your batteries than simply relying on the alternator.”

Three (or four) stage battery chargers produce a higher voltage out put than an alternator over the complete bulk and absorption stages of battery charge. Why? Because competent battery engineers have established that is what is required to charge a battery to 100% of its rated capacity. Deep cycle batteries are generally stored in places that are not effected by the high temperatures. Thus charging voltages can be set higher without running into overcharging problems.

There are several ideas of “a fully charged battery.” To people providing power for use when there is no charging present fully charged means 100% capacity. To an auto electrician it means sufficient to get a vehicle started in Arctic winters and sufficient to prevent sulphation.

The under bonnet temperatures of a vehicle is probably the worst situation for lead acid batteries. Batteries have a wide rang maximum voltages over which a charger can operate. A battery at a working temperature of 50-70 degrees requires around 1V less to charge it than one working at Arctic temperatures. Alternators are built to charge a battery to 100% of rated capacity over these operating ranges. They have a temperature sensor to measure the temperature of the battery. You will find these in marine installations. How many vehicle electrical systems have you seen that incorporate this sensor – if you have one then you will have to re-glue it to the side of the new battery when you change them. Because of this problem alternator output voltages are turned down so that the battery will not be overcharged under any operating condition. The result is you will thus rarely get a battery charged to over 65-70% of its rated capacity. This is OK in auto situations as a battery charged over 60% will not sulphate and batteries will produce most of their rated cranking current at much lower capacities.

To cope with the ranges of temperatures mentioned in the previous paragraph alternator voltage regulators have built in temperature compensation. We have all observed alternator outputs of over 14V when we are measuring them in the back yard with the bonnet open. How many of you have closed the bonnet and gone for a drive lasting over ½ an hour whilst keeping an eye on the volt meter. Every vehicle I have owned has had an operating temperature system voltage of 13.4 to 13.8V. This is not sufficient to charge even an AGM battery to 100% capacity.

All using extremely heavy wiring and plugs will do is to get your battery closer to an auto electricians idea of “fully charged.” If you require your battery to be charged to 100% capacity then you need a booster that will give an output (over 14V) to match the specified charging voltage. Without a booster you will probably be operating your battery over a range of 20-70% instead of 50-100% which is not being kind to it. Before trips and when in caravan parks using a well matched three stage charger will be of great benefit. A multi stage charger will definitely do a better job of charging your batteries than simply relying on the alternator.

REMEMBER – BATTERIES DON'T JUST DIE – MOST ARE KILLED.

PeterD

For Fridges and battery-charging, most people seem to design for a 3% voltage drop.

Here is a table run length in feet based on 3% drop in a 12 volt system with Amps on the left and AWG(B&S) across the top.

www.freesunpower.com/wires_cables.php

Mike

Hi Cram,

If you are charging batteries that are not in use a 5 or 10W solar panel and regulator will keep your battery topped up (costs less than $150.) If the batteries are in use a bigger panel and regulator can give you the charge you need.

You can determine your solar and battery needs using this calculator:

AC and DC solar calculators and battery sizers

Of i am biased towards solar .. :)

Max
Information Manager
Energy Matters - Solar and Battery Sales
www.energymatters.com.au