I would be interested to see how newer vehicles power ports are wired, what gauge wire, and how many different circuits share the same fuse.
I've seen the '10 amp maximum' on newer vehicles power ports, and often think what non van dweller item is going to even approach 120 watts. Gps, Tablets and Cell phones are likely the 3 most common things and they do not exceed 25 to 30 watts.
The Ciggy plugs are convenient for sure, however the fact remains that they are a poor spring loaded connection dependent of the the springs exerting enough pressure over enough surface area to make good electrical contact. The springs nor contacts, are not made from a highly conductive metal, little about the design is about achieving a great connection mechanically and electrically, and while they might handle 10 amps for a short duration, 10 amps for longer times is going to heat the contacts, causing more resistance, more voltage drop. Many devices will still require the same wattage at that lower voltage, so the amps actually increase as voltage decreases, causing more voltage drop and more heating, until something gives.
So In the interest of not wasting battery power heating up copper wires and ciggy plugs, elimination of ciggy plugs on devices capable of drawing more than 5 amps is wise. When setting up ciggy plugs in a system, one should get the higher quality plugs, like the Blue seas or Marinco. These can be bought with a mating male end which has an O Ring, which is designed to seal the seated connector from water intrusion, in boats, but it also keeps the plug from working loose. When those ground springs on the sides, and that nipple spring on the tip are making good firm contact, then the connector is likely good for passing 15 amps safely. But add some vibration to an older ciggy plug whose springs have weakened from repeated compression and heating cycles, and the plug can push its way out just far enough that the connection is just barely held, and things go downhill quickly from there.
How many of you can always seem to push your ciggy plug in a little deeper? Does it stay there or instantly back its way out?
How many of you have ever cleaned the inside of your ciggy plugs receptacles. The sides and tip mating surfaces can get quite ugly with dust and heat and other crap.
The quality of the male ends of the ciggy plugs also varies widely. I found that the most capable male ends were those that did not incorporate fuses into them. But they still developed issues. I like how ciggy plugs you can just pull them out 1/4 inch to disconnect them electrically, but the side springs are still compressed, and over time they lose their ability to grasp the sides of the receptacle.
The basics of lead acid batteries have not changed in a hundred years and will not. The composition of the lead paste on the plates and the separators are constantly being improved upon, and companies like Trojan and US Battery are constantly flaming each other as to who has the most durable golf cart battery, and will do anything to get that step ahead and convince the golf courses to choose their batteries over the competition. One would hope this tech filters down to the marine and other pseudo 'deep cycle' batteries but by and large it does not. The interior of a GC battery and a marine battery are so different, it is astounding.
Look at the pics in this article to see the difference for yourself:
http://www.pbase.com/mainecruising/deep_cycle_battery
The 12 volt car jar batteries are all compromises, even if they say marine or deep cycle on them. They simply are not built anywhere near as durable or heavy duty as a golf cart battery. But that deep cycle sticker sure sells them and inspires confidence of the consumer, falsely, and that equals more profit for the top brass and a new shiny rock for baby.
In the last 15 years, the trend in batteries, like everything else, has been to cheapen it as much as possible for maximum profit. It is not about making the best product, it is about maximizing profit. This is a delicate balance of manufacturing and materials costs vs warranty returns, and this second part is the hard part, because somebody can buy a battery, run it dead, leave it for two months, then stomp their feet and act surprised when it cannot be recharged, and go get a new one under warranty. 100% user error that the seller has to cover.
This mostly applies to starting batteries, but then the marketers got in on the act and started putting 'deep cycle' in larger text next to the 'Marine' lettering, and presto, the public thinks a marine battery is a deep cycleable battery and is thus imparted with magical powers.
If one weighs a group 24 starting battery and weighs a group 24 marine battery, one will find very little weight difference. The Marine battery should have thicker plates, weigh more and have lower CCA figures, in addition to the threaded posts as well as the standard automotive posts. Will the marine battery actually weigh the 15% more as it should, or does it just cost 15% more?
Stevesway, In regards to your setup, a MSW Inverter powering a battery charger is nothing new. While many things have absolutely no issue being powered on MSW, others run a bit hotter on them. You could be shortening the life of the charger using this method.
The main reason people with trailers use the inverter on engine battery powering a battery charger feeding trailer batteries is the Voltage drop, AND the vehicle regulator dropping voltages to the mid to high 13's when it believes the starting battery is full.
If the vehicle decided that 13.7v is all that is required, and there is 1V drop over the wiring, then the 12.7v battery in the trailer gets nothing at all. So the inverter powering a battery charger that tries to get the battery upto 14.7v is about a zillion times more effective.
Your rear powerport, powering an inverter powering a battery charger which is only providing 2.x amps to the trailer batteries is extremely inefficient, regardless of what you think your battery needs are. The inverter is likely only 80% efficient, the charger is likely only 80% efficient at best, and Alternator amps are not free as so many people like to think. Each 25 Amps the alternator makes requires about 1 engine horsepower. So while it is hardly going to cause you to notice poorer MPG, this setup of yours is going to negatively affect your MPG to some small degree.
MSW inverter will likely cause the battery charger to run hotter, shortening its life. Inverters are also electrically Noisy. I have read reports that a MSW inverters and PSW inverters being run off of the engine battery actually caused engine computer glitches, and in some cases outright stalling and undrivability. I have not experienced this personally, but then again I rarely run an inverter at the same time the engine is running.
So your post kind of indicates you are proud of this setup, however there is nothing to be proud of. It is extremely inefficient and there are problems lurking around every aspect of it like great white sharks spying seals on the surface waiting for an opportunity to strike. If that Ciggy plug works its way loose while powering the inverter, then something in the inverter or the battery charger can take exception to this and release the magic blue smoke. This might not happen the first time it happens, but is cumulative.
If you smoke the battery charger, where is the economy in that? Not only do you no longer have a battery charger, but you need to buy a new one.
http://www.amazon.com/Keeper-KTA141...sim_263_1?ie=UTF8&refRID=147ND97WNXYBJX94R5M6
The product listed above will vastly increase the charging amps to trailer batteries, and costs less than a new battery charger, or inverter, or paying an automotive electrician to find out why your rear ciggy plug/powerport no longer works despite the fuse still being good.
if you are serious about using an inverter to power a battery charger, then eliminate the powerport. wire the inverter right to the engine battery, run an 120V extension cord to the charger, and run it on the 12 amp setting. At least that way some charging will occur.
2 amps is nothing to a depleted battery. This whole double conversion process for only two amp charge rate is mystifying.
As much as I dislike Ciggy plugs, you would likely get more than 2 amps by a double ended Ciggy plug with 14 awg wire between rear powerport and trailer ciggy plug receptacle, and not risk your inverter or battery charger in the process, for 2 peasly amps.
