Cable lay out & recomendations

Submitted: Tuesday, Mar 28, 2006 at 17:05
ThreadID: 32266 Views:3627 Replies:4 FollowUps:16
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Im new to all the electrical side of camping but am getting older(46) and require some comforts. I intend to wire up my camp trailer from my ute.In my trailer I have 2 x 6volt Deep cycle 220Ah batteries which will be hooked up in series(12v). I want to run a cable from the altenator/Battery via a ARB solinoid to the the battery bank in the trailer using anderson plugs(what size).The local auto electrician said to run 2bs cable(sounds Big to me) but didnt say if I should run a negative as well.I will also be using 110 watt solar power via a smart regulator and plan on adding a Ctek 2500 charger(25 amp) when I add another 220 Ah battery array.I have a GMC 750w generator and a 2kva dunlite.I know it sounds like a lot of power but the trailer will proably be used as a power supply on a bush block at some stage.
So my question is how would I best do the wiring with fuses and curcuit breakers etc and will my generators run my charger efficiently. Any advise or experience would be appreciated.Im a brewer by trade so if you want to exchage advise Im happy to do that.
Thanks Niffty
Perth WA
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Reply By: Member - Mike DID - Tuesday, Mar 28, 2006 at 19:39

Tuesday, Mar 28, 2006 at 19:39
The minimum cable size would be 4 B&S and you will Positive and Earth because you will not a good connection throught the Towball.

An Anderson SB50 Connector should be adequate, since they can handle more than 50 amp intermittently. You could have another Anderson connector inside the Trailer for connecting Generator etc.

The advantage of using the 50 amp size is that it is becoming the standard among 4WDs for Trailer Power.

You will need a fuse (60 amps) on the Positive lead at BOTH ends close to where it connects to the battery.

For Fridges etc I prefer the smaller Anderson Powerpoles - 30 amp.

Is there a beer better than Redback ? :-)

AnswerID: 163498

Follow Up By: Niffty - Tuesday, Mar 28, 2006 at 20:50

Tuesday, Mar 28, 2006 at 20:50
Hi Mike
Thanks for the info .From what you have said I assume that the anderson sb 50 will fit the 2BS cable( rated at 255 amp) ?Can I run the earth from the body or do I need to start closer to the battery?And does a circuit breaker do the same job as a fuse. I have a 50 A(may be not enough?) circuit breaker, which I believe will reset if things are ok, is this right.I have not heard of the power poles, what do they do?I will check out your link now.
There is one beer better than redback its the one I make! A true Bavarian wheat beer. If you head this way let me know 4-5 weeks in advance and I will prove it!
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Follow Up By: Member - Mike DID - Tuesday, Mar 28, 2006 at 21:14

Tuesday, Mar 28, 2006 at 21:14
The Powerpole is a smaller connector that can take 30 amps. One big benefit is that it is genderless like the SB50.

The SB50 can only take 6G - you would need to add ashort adapter tail.

. . . aaaahhhh a Haefeweizen,

FollowupID: 418243

Follow Up By: Niffty - Tuesday, Mar 28, 2006 at 21:19

Tuesday, Mar 28, 2006 at 21:19
Ahhh You know your beers!!Do you brew or do you comsume with a passion?
FollowupID: 418245

Follow Up By: Member - Mike DID - Tuesday, Mar 28, 2006 at 21:24

Tuesday, Mar 28, 2006 at 21:24
I'll leave brewing to the experts - Redoak Brewery in Sydney do a very nice Haefeweizen.

FollowupID: 418248

Reply By: Sand Man (SA) - Tuesday, Mar 28, 2006 at 20:35

Tuesday, Mar 28, 2006 at 20:35

Even though you intend to wire up the battery bank via an ARB Solenoid, I would suggest you will need something at the trailer end to bump up the voltage enough to charge the batteries, regardless of the size of cable and the use of the Anderson Connectors. A voltage of between 14.4 and 14.8 is required to fully charge the batteries. This is of course, if you intend to provide battery charging whilst travelling.

It doesn't take much of a voltage drop to restrict the charging current. For this very reason a common practice is to include something such as an Arrid TwinCharge unit located at the trailer end, close to the battery bank.

The twinCharge will accept an input voltage as low as 8 volts and will bump this up to the nominal voltage (14.4-14.8) to provide a full charging voltage. This reduces the gauge of the cable required from the vehicle.

The Arrid TwinCharge BCTC20 sells for about $300 and I believe, in kit form, include a pair of 50 amp Anderson Connectors.

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AnswerID: 163521

Follow Up By: Niffty - Tuesday, Mar 28, 2006 at 21:00

Tuesday, Mar 28, 2006 at 21:00
Hi Sandman
All things come at a cost, In this case what powers the unit and what is the Amp consumption.Sounds to good to be True. Would it be cheaper to put a larger cable through?Its sounds like electrickery to me.But Im willing to learn.
Thanks Niffty
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Follow Up By: Member - Mike DID - Tuesday, Mar 28, 2006 at 21:19

Tuesday, Mar 28, 2006 at 21:19
It doesn't break any laws of nature. You might input 30 amps at 12 volts amd get out 22 amps at 14 volts.

Voltage drop is less of a problem with AGM's - I have charged mine fully with 13.8 volts - it just takes longer.

FollowupID: 418246

Follow Up By: Sand Man (SA) - Tuesday, Mar 28, 2006 at 22:01

Tuesday, Mar 28, 2006 at 22:01

I don't use one myself, but this technology is the most commonly adopted solution within the Caravan / Camper Industry.

What powers the unit?
The DC voltage from your vehicle's alternator.

What is the Amp consumption?
Whatever your battery bank in the camper can take, although the TwinCharge I mentioned has a maximum output to the batteries of 20 amps.

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Follow Up By: drivesafe - Tuesday, Mar 28, 2006 at 22:45

Tuesday, Mar 28, 2006 at 22:45
Sand Man, I supply both caravan and motor home manufactures and none of my customers use them. Thats not to say they aren’t being used but their benefits are limited to a very small portion of the market.

As pointed out, once the total battery capacity is 100 a/h or more, these devices are of very little advantage and then only where the battery bank has only been partially discharged.

An example, if a 200 a/h wet cell battery is discharged down to around 11 volts and then a 14 volt charge is applied, the battery can easily draw over 60 amps initially and over the next 4 hours will eventually drop to around 10 amp. These figures are based on experiments we have carried out on equipment we regularly work with.

The first hours charging drops the current draw to about 50 amps. The step up would take at least 2.5 hours to replace the same capacity.

It’s only when the battery has only had a small discharge that the step up will charge the battery to full charge quicker and then is still only a marginal improvement.

For the cost of one of these things, it would a greater advantage and a far cheaper cost to simply add another battery. At the end of the day you would have a much greater stored capacity, achieve in a much shorter time than these things could ever do.

And last but not least, most of these things are not very efficient so you are wasting power while using them.

Good quality high amp units that actually work, have a starting price of around $600 or $700
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Reply By: drivesafe - Tuesday, Mar 28, 2006 at 20:50

Tuesday, Mar 28, 2006 at 20:50
Hi Niffty, Mick DID pretty well covered it, but one suggestion I would put forward.

I have been fitting dual battery systems for nineteen years and started out fitting fuses on either end of the positive cable and with a very short period of time we found that fuses, no matter how big, will eventually blow and remember this was a good while ago and the systems being fitted today are much larger. The main problem with fuses is not some much that they blow, but that you usually don’t know that the fuse has blown until you discover that the auxiliary battery is flat.

You are far better of using auto reset circuit breakers they have the additional advantage of not only going open circuit during a short circuit event but they also act as current regulator when the current required for recharging the rear battery exceeds the designed current limit of the system.

Next, if you are planning on using the system for a fair time on the block, as you posted, then you might consider using more solar panels.

In the long run the solar panels may workout a lot cheaper than continually refilling the generator and are usually much more reliable.

One last point, with the size of batteries you are using, these voltage step devices will actually cause the batteries to take longer to recharge. They are only effective on battery capacities up to about 70 a/h and bigger capacities of 100 or more actually take longer to recharge as against just letting your alternator do the job.
AnswerID: 163526

Follow Up By: Niffty - Tuesday, Mar 28, 2006 at 21:15

Tuesday, Mar 28, 2006 at 21:15
Hi Drive safe,
Yes I think circuit breaker are the way to go!Is 50 amp ok?I will plan on setting up more solar panels as Im all for green power but its turning out to be an expensive project right now. Next year when I have ironed out the bugs I will add another 100 watts or so.The batteries I have at the moment are 6 volt 220 Amh wet cells Supercharge Deep cycle hooked up in series(12 V).Next step is 440 Amh bank minus the losses.I know I will have fun keeping this puppie charged, this is the reason for getting the good oil from people like you with experience.In the mean time im stuck with fossile fuel. Thanks Niffty
FollowupID: 418244

Reply By: Member - Norm C (QLD) - Tuesday, Mar 28, 2006 at 21:06

Tuesday, Mar 28, 2006 at 21:06
I think it has been pretty well covered. Cable size is the key. The fact that the cable is rated to 225Amps is not the point. You need heavy cable (heavier the better) to prevent the voltage drop referred to. I charge two 120AH AGMs on the CT via 25mm squared cable (two cables all the way from front to back) and a 175 Amp Anderson plug. I used the bigger plug as it may draw more than 50 Amps at times if the batteries are run down and as the cable was too big for the 50 Amp plug. I've also used 2B&S (I think) with a 50 Amp connector. Very tight fit and a bit fiddly and I'd say about 10% of the strands didn't get into the hole in the connector. Still better than using lighter cable IMO.

I've also got the 25Amp CTEK and a 1KVA Kipor. I've never measured it, or tried to calculate it, but I suspect I'm not getting the full 25Amps with the gennie. But it is a great charger and charges real fast when I have access to mains power.
AnswerID: 163530

Follow Up By: Marc - Tuesday, Mar 28, 2006 at 21:22

Tuesday, Mar 28, 2006 at 21:22
save money and go to bogas or a welding supplier and buy the 25mm2 battery lead from them. Its heaps cheaper
FollowupID: 418247

Follow Up By: Niffty - Tuesday, Mar 28, 2006 at 21:36

Tuesday, Mar 28, 2006 at 21:36
Hi Norm
The cable I am using between batteries Is 32 mm2 rating. the sparkie assures me there is only one size bigger.This I think will be standard for the whole run.I will have to use the 175 andersons i think.Where did you take your neg lead from? Battery / motor.I can get the ctek 2500 for $590 which is the best price I have had with paying for freight.
FollowupID: 418251

Follow Up By: V8 Troopie - Wednesday, Mar 29, 2006 at 00:40

Wednesday, Mar 29, 2006 at 00:40
What some seem to forget when quoting massive cable sizes is that there IS a limit of current that the car's alternator can supply.
I see little point going above the max alternator output minus the Amps required to run the car electrics.
Find out first just how much juice you have on tap to feed back to your trailer. Then make sure you are not overloading the alternator by trying to demand more than it can supply. You can actually limit the charging current to the trailer batteries by using sensible cable sizes. That way you ensure you do not accidentally cook your alternator.
FollowupID: 418280

Follow Up By: drivesafe - Wednesday, Mar 29, 2006 at 12:53

Wednesday, Mar 29, 2006 at 12:53
Hi V8, the advantage of thick cable is more related to reducing the voltage drop between the alternator at the front of a vehicle and the battery in the trailer.

The longer the length of cable that the power has to travel along, the greater the voltage drop is going to be and the only way to reduce voltage drop by any segnificant amount, is to increase the thickness of the cable.

The Circuit Breakers will protect everything from current overloads.
FollowupID: 418354

Follow Up By: Marc - Wednesday, Mar 29, 2006 at 12:54

Wednesday, Mar 29, 2006 at 12:54
what has been said is true but to ensure minimum loss over 6 to 7 metre to the trailer 25mm IS the way to go. I have taken a earth from the spare tyre holder with a lug and 8mm bolt and feed to the anderson from there. I have more than enough takeoffs from the battery
FollowupID: 418356

Follow Up By: V8 Troopie - Thursday, Mar 30, 2006 at 00:02

Thursday, Mar 30, 2006 at 00:02
Yeah, I know all about voltage drop, but its also dependent on the current flowing through the wire.
Now, if you are in the habit of flattening the trailer batteries regularly then a 25 sq mm cable might be the ticket.

But, if you are like me and look after the batteries, which at present are in a trailerable yacht, then a 6 sq mm cable is perfectly adequate. The cable (2 wires) runs from the battery to a socket at the back of the troopy and from there to the boat. This size cable had no trouble keeping the 90Ah boat battery full while towing the boat for 5 days (3000km), running a fridge inside the boat and the boats electrics when it was used as a caravan every night at roadside stops. I doubt that the current ever needed to exceed 10 Amps to keep the boat battery happy.

Marc, the steel body of the car is a worse conductor than a 6 sq mm cable would be to the battery negative or to the body end of the negative strap.
FollowupID: 418552

Follow Up By: drivesafe - Thursday, Mar 30, 2006 at 06:44

Thursday, Mar 30, 2006 at 06:44
Hi V8, if you are using as little power as you are then you will probably get away with such thin wire but the first time you, for what ever reason, use more power than usual, you will find that your set up will now take days to get your battery up to anywhere near fully charged.

With thin cable, the time required to recharge a battery dramatically increases because of the combination of thin cable and the current load required will cause such a voltage drop that the battery will literally take days before the charge state of the battery rises enough to allow the current level to drop and therefore have an increase in the charging voltage start to get the battery to get towards a full charge state.

If this was to be repeated on a regular basis, the life of the battery would be servilely shortened, furthermore in niffy’s case, it sounds like he is going to be using his batteries in a big way so the quicker he can get his batteries charged up the better and thin cable just won’t allow him to do that.
FollowupID: 418570

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