There has been a lot of conflicting advice here on the
BOG, from well meaning people, but giving advice that varies according to their specific experience and application. Many times they are correct from their Professional background, but still wrong in the application of the science in practical terms and specifications vary on AC and DC wire sizes for instance. NO WAY.!!.. Yes, sorry, just the way it is... One might want to question WHY we at
Bushtracker do things like we do, and go to the Source to understand this.
For instance, there is a huge discrepancy on wire size and what it means in terms of physical dimensions. Let me digress a moment. It used to be all in the Imperial or American Gauge system. As an example 10 gauge which is roughly equivalent to our 6mm. Now that is confusing enough, because the larger the number, the smaller the wire. 10 gauge is smaller than 8 guage, and 10 gauge is nearly twice the size of 16 gauge… (The same goes for shotgun barrels for those of you familiar with them still on the gauge system). Anyway, next was the Metric conversion from Imperial, changing over to milimeter wire size. Originally that was the overall size of the wire INCLUDING insulation… That proved to be fraught with problems, thickness of insulation and so on; so that changed to CROSS SECTIONAL DIAMETER of wire….
Think that is the “be all end all”? NO AGAIN… Sorry…. AC voltage wire, (Alternating Current) household and industrial mains power, has a cross sectional diameter in 6mm wire size of about 6mm. So an AC Electrician, Electrical Engineer, or household Electrical Contractor will tell you that…. HOWEVER, Automotive Electrical, Automotive and Marine Electrical stranded wire, which is our field, has a different cross sectional diameter…
Sorry, just the way it is. I get tired of arguing with well meaning people asserting their view, so sometimes I just let it go by the wayside. But, in our field, Automotive and Marine Electrical wire has a different cross sectional diameter. Do not let it bother you or concern you in any manner but it is true. 6mm is actually a CSD of 4.59 mm square. 8mm for instance, is roughly the old 8 gauge for those thinking in the old system, and has a CSD of 7.91 mm square… Confused? Fine, good, don’t be concerned, and don’t worry about it all. Leave it to us, we have made an Institution of
Bushtracker and will do the right thing. No worries… Why would we not....???
Now HERE IS THE BIT THAT RELATES TO YOU: An example that is relative to
Bushtracker is the wire size from the tow vehicle to the van batteries. We want NO more than 8mm, even prefer 6mm, from the tow vehicle batteries back to the Anderson Plug and 7 pin plug. Not two circuits of twin sheathed, only one… “Oh those Guys don’t know what they are doing at
Bushtracker, that will result in a voltage drop…” EXACTLY!!.... AND EXACTLY WHAT WE WANT BY DESIGN. Well meaning people are listening to “Experts” and want 10mm or larger battery cable sized stuff back to a 50 amp Anderson plug to get the full alternator capability back to the van batteries… From now on, we VOID the battery Warranty if anyone demands this as it will cook (overcharge) the van batteries. And little known to many is: It will grossly shorten the life of the alternator as well. I have killed two Toyota Alternators and a Ford Alternator trying to do just that… Here is the WHY of it all:
First of all your Alternator has a regulator that is set at something between 14.8 and 15 volts. Our Maintenance Free battery, and for that matter any Gel or AGM sealed type battery has charging limits of about 14.4 volts maximum. WE WANT THE .5 VOLT DROP by design. Why our choice of charging wire limits in the 6mm or maybe 8mm in the tow vehicle if the distance is long enough, is this throttles back the amperage flow to the van batteries, and will result in a voltage drop of about .5 of a volt by design.. KISS Engineering, Keep It Simple Silly... Yes you could do it with a Diode or in line additional voltage regulator, but this introduces other problems that are unnecessary. You can kill a Maintenance Free Battery if you use larger cable, as the voltages will run too high on the output of the tow vehicles alternator.
Yes some Electrical Engineering type will tell you that a simple way to do it is to run a large inline Diode, which has the side effect of giving you about a 1/2 volt drop with a 40 to 60 amp diode; but it will block the voltage from coming back from the van and this is a major disadvantage in some applications like using the van solar to help power an additional fridge in the tow vehicle. You need to understand we do what we do for very good reasons.. Trust us to do it in the most efficient way, and ask yourself "Why would we not?"
Bushtracker is without a doubt the best, we are an Institution, and constantly doing R&D trying to do it better... (The Rangers Lifestyle...Ha!)
Second problem, very large battery cable size from tow vehicle through to van, over works the Alternator, as they are not designed to be continuous duty alternators. Let me explain: Your tow vehicle alternator is designed to just run a short time with one or two batteries and the regulator will start throttling back the charge. It might be a 60 amp or even an 80 amp alternator, but it brings up the battery quickly so it runs on maximum output only a matter of a few minutes, then maybe it is throttled back to 40 amp output for ten minutes more, then 30, 20, and the final finishing voltage that can take hours might only be at an output dropping from 10 amps down to 5 amps or less. But if you run heavy cable back to a large Anderson Plug for the van, it has to run a maximum output too long when it is bringing up 6 batteries at a time. It reads them as one GIANT BATTERY of combined average voltage. Not only will it run the van batteries up too high... It will grossly shorten the life of the tow vehicles alternator as it is not designed to run at a “continuous duty cycle” charging five or more batteries up in the combined tow vehicle and caravan and it cannot dissipate that much heat running at full output struggling to bring up 300% or 400% of the Amp Hours in batteries that it was designed to do…. How do I know that? Well, in trying, I have killed several Toyota alternators and one Ford 7.3 Diesel alternator. Even more Yacht alternators on Marine Engines like Perkins, Detroit, even John Deere. The problem comes in with five batteries or more, where the alternator is running at maximum capacity for too long and it does not have the cooling capacity to do so and cooks itself. To do that you need what is called a “Continuous Duty Alternator” that is about TWO TO THREE TIMES the size (and five times the cost) of normal alternators and have to have a large heat sink and cooling fans to run flat out for a long time…
The KISS engineering to get around both problems is to restrict the wire size back to the van batteries to diminish the problem, which has worked well. Even if you put in the very large cable and plug, and even with the continuous duty alternator, you have the overcharging problem on the van batteries, that has to be overcome with a Diode that has a side affect of dropping the voltage that half volt difference. Even if you spend thousands and do all that, the diode keeps the voltage from coming back from the van, which is its true Engineering Function, so you cannot use the van extra solar to help power up a fridge in the tow vehicle. It is all just not worth the effort and expense… So, while well meaning people try and eliminate the small voltage drop that comes with smaller sized cable, it can actually work to their disadvantage to run the larger cable. People need to fully understand that we do what we do, for a reason. For most, I would suggest extra solar and not concentrate on the vehicle alternator so much..
The original design of the Anderson Plug: I originally incorporated the Anderson Plug concept into my own
Bushtracker van in 1997. This was the second van to move up to four panels and four batteries, to use the excess solar to power my 100 litre Trailblazer fridge in my tow Vehicle. Sometimes in a remote setting there was no where to go on a day trip, and the batteries in the tow vehicle needed a half day running to be charged up every other day, and so the Anderson Plug allowed the use of the excess solar in the
Bushtracker to run the fridge in the tow vehicle. There was also an added benefit, as the same condition of having to run the tow vehicle every other day for a half day to charge the batteries in the tow vehicle, existed in town. The Anderson Plug allowed me to use the battery charger to charge the second battery in the tow vehicle when plugged into 240v at a caravan park or for running on a generator, when there was nowhere to go on a long day trip. Our Anderson Plug and 6mm wire is enough to do that, positive and negative sides each. …. AND YOU HAVE DOUBLE THAT ANYWAY, AS YOU ALREADY HAVE A CHARGING CIRCUIT IN 6MM IN THE 7 PIN PLUG, so you end up with two 6mm charging circuits in the van. You do not want any more than that, or it works to your disadvantage…. Trust me, I try everything!
Hard to argue with what works... And if you try too hard with big cable and big Anderson Plugs, you create more problems that you solve, including shortening the life of both the maintenance free batteries and the alternators...
Cheers from a practical Ranger,
Semper Fidelis
