NEW wiring sketch

[jimindenver]

I wonder who was the first to say that the sky is falling when it comes to alternators. Who was the first to hear it and spread the word until it became fact? It happens a lot, think Y2K. Yet the only ones affected by Y2K were those that prepared themselves and woke up New Years Day learning that they were scammed. Billions of dollars were spent because someone said the sky was falling.

You would think that RV manufactures that have been using the alternator to charge house batteries for decades would have stopped if they were having to replace alternators under warranty. That auto manufactures would be warning not to do it instead of building in the features that make it so you can charge from the 7 pin.

You would think that they would find a different solution if it were this massive problem like they did to keep the house batteries from draining the starter battery. Instead they keep building them the same way. Why is that? Are they that stupid?

I see more people worried about alternators than I hear of them failing. Yet a industry is being created around them using lithium batteries as a excuse when there have been batteries with less resistance for a long time.

I have created hundreds of designs and installed around 100 systems, many with isolators or solenoids. In four plus years not one customer has come to me saying that their alternator failed. I do tell them not to sit in a hot parking lot idling their engine to charge their batteries. That can burn up your alternator unlike running down the highway.

 

[bullfrog]

Mechanical parts wear, the more load you put on them the quicker they wear out, not just the alternator but the engine that turns it. My first learning experience about how much load even an old time generator can produce was when I attempted to polarize a VW generator using a drill press with the 1/2" or so shaft tightly in the drill press chuck spinning several hundred RPM holding the housing with one hand and grounded the field with a wire in the other hand. Fortunately we had a very high roof in the shop as the generator disappeared for several seconds and then took out a chunk of concrete floor several feet away. I was trying to figure out how the drill chuck could have loosened up when I realized it had not. The 1/2" shaft had broken flush with the front bearing in the generator case as part of the shaft was still in the chuck. After that the fan belt came off whenever a few extra horse power were needed to win drag races! In times past I carried a spare alternator and still do today for my older vehicles because they were a common part to fail. Vehicle manufacturers are doing every thing they can to increase fuel mileage by making lighter parts. I can't help but think they would not over build a charging system by several times just in case someone wanted to charge some extra batteries. Some alternators are very expensive and very expensive to replace, over $1,000 in some cases. You can buy a DC to DC charger now for less than $150 dollars but even better you can buy a small generator for less than $500. Why would you risk or spend more on maintenance of your primary vehicle when for less than $650 you could have a better solution insuring your batteries are charged daily and have more electrical power when you need it. The DC to DC charger's cost is probably saved in fuel and maintenance over the long run anyway even if you don't get the small generator as it will protect your vehicles charging system by limiting the load of charging the extra batteries. Nothing is really free we just don't always realize the hidden costs. Can you get by and make the system work with just a set of cables, yes you can. Is it the best most cost efficient way? That strictly depends on who is paying the bills! Lol!!! All the above is strictly my opinion and only that.

 

[bullfrog]

Just so you know how crazy all this can get I understand some motorhome manufactures are using the vehicle alternator with an external regulator with adjustable 3 stage charging to charge the house batteries and a DC to DC charger powered by the house batteries to charge the starting battery! Talk about initial costs but I guess again in the long run it must work cause manufacturers are doing it! Lol!!!

 

[Scott3569]

Ok awesome.. So would a 20A DC-DC charger work? I Don't care if this turns into a big discussion.. we all have different opinions.. And I need  a damn good opinion.. I want to do it right.. but what I can't do.. is continue to spend money where I do not need to..

Do I need the DC-DC charger or not?

If so, will a 20 amp do the job?

 

[bullfrog]

The point is you can use you vehicle's alternator to charge your house batteries. For years people have simply ran a positive and a negative cable from the starter battery to the house battery or if you use bus bars to them. They simply connect the positive cable after they start the vehicle and disconnect it before they park for the night. Super cheap initial cost as it just requires a set of good jumper cables. Problem was eventually some forgot to disconnect the cable when they parked for the night and drained both the house battery but also the starter battery. For a while people that did this carried a charged jumper pack just in case they did it again. They then went to using isolator switches or continuous duty solenoids so they didn't have to remember to hookup or take off the cables as it was controlled electrically by the ignition switch. Lately DC to DC chargers are being used as they limit the amount of charge protecting your vehicles charging system from over heating and wear. Yes a twenty amp DC to DC charger should work fine as long as you can fully charge you house battery each day using solar as well. All of these methods work it is just a matter of debate and your finances what will work best for you.

 

[highdesertranger]

Yeah if you are running lead acid batteries just use a contentious duty solenoid. I have been doing it that way since the 70's. Cheap and simple. I wouldn't rely on it as my sole charging source though. Highdesertranger