Blue Sea 7611 or 7622?

[DiploStrat]

… At a 50% DoD, I will need to replace 150A.

Actually more like 160-1756Ah. FWIW, I use about 125Ah overnight, running a large Nova Cool refrigerator, heat, and cooking dinner and breakfast all electrically. You are unlikely to use as much as I do if you use propane or diesel for your stove. Between solar and alternator, I can generally recover 130Ah in about three hours of driving.

My solar system will on paper input 23A/hr x ~5 hrs. I'm considering an alternator source for times when I need electricity in cloudy weather or night. Plus, it seems wasteful to be driving with a full starting battery and the alternator has Amps to spare.

So you have about 400w of panels? You can expect about 5A per hour per 100w. More in strong sun.

I know the alternator will never get me past absorption at 13.5. I'm counting on the solar to finish getting me to float. I'm just thinking when my house bank is discharged 150A, the alternator (assuming I've broken camp and am travelling) will replinish the bank quicker.

Put a voltmeter on your Jeep right after you start the engine. I would expect that you should see over 14v. If so, you should be fine with a relay based system. If you really only see 13.5v, then you may want to look at some of the options that I posted.

I have metering equipment in the house system thatets me see its state of charge and % of recharge. So, I'm thinking if i monitor that well while driving, I might get by without a 7728. I own a Perko 1-2-both-off switch. I guess the risk wo the automatic isolator is running the alternator too jard for too long.

Given my 160A OE alternator and the size of my house bank, and 12' between the isolator' location and the house Pos buss bar, what size cable do I need for the Pos run?

You can play with this calculator:http://www.calculator.net/voltage-d...ce=12&distanceunit=feet&amperes=160&x=53&y=12

Assuming a full output of 160A (you won't get it) and a charging voltage of 14v, over 12 feet, you will see a maximum initial voltage drop of about 0.5v with a 1 AWG. By the time the charge drops to a more normal 50A, you will see a drop of only 0.2v and it will only get lower with time.

There is not much chance that you are going to work your alternator too hard; with a modern vehicle it has all manner of protection. One of the great advantages of an intelligent relay is that you don't have to remember to turn the switch and it allows your solar or shore charger to keep your starter battery happy - most useful when your vehicle is sitting idle between trips.

 

[JCTex]

Diplostrat, thanks a lot. It is tremendously helpful to find an "expert" with about the same system and needs.

I think you answered, but to be sure: if the bank is low at wake up, and if I going to be driving, an intelligent solenoid like the Blue Sea WILL help me refill the bank faster than relying just on solar, Yes? I know the alternator won't help beyond 13.5V; and I know my Lifelines will be screaming for 14.4-14.8 to get out of bulk. So, I guess I'm wondering if the alternator will do any good at all until the State of Charge gets to low-absorb at 13.5. My Lifelines want to float at 13.2-13.4. That's almost the alternator's max.

If I go with the 7728, what sized breaker should I put between the Blue Sea under the hood and my house bank's Pos buss bar (12')? IOW, given my numbers, what's the most current that might flow through that cable? I don't think it's the alternator amps because those are being strained thru the starting battery. I don't know the maximum discharge rate of my Deka AGM. With the large #1 AWG, should I go with a 60A breaker ILO a 50A? Or another number? If I can pin down that piece of information, I think I'll be ready to order and install.

I can do #1. I want to keep the voltage loss at 2% or less, if I can.

You are right about the panels. I have 4-100W Renogy flex series mounted atop my Front Runner rack. I need all this power for my overlanding, partly due to a couple of medical machines, both of which are Amp hogs, plus the refer, fan, electronics, etc. I want to cook with my induction burner if I end up with enough surplus.

 

[DiploStrat]

Various

As noted, with a dual battery circuit you want to fuse at each battery at a value that protects the cable. Remember, a dual battery circuit is live at both ends; you don't want an arc welder running under your truck. I use Blue Sea terminal fuses as they are easy to install and you can't get any closer to the batteries.

Are you really sure that your alternator does not go above 13.5v? I find this a bit hard to believe. If your voltage really is only 13.5v, then you might see of one of these would work: http://www.mechman.com/voltage-control-modules/ If not, you may be in the market for a CTEK or Sterling Battery to Battery charger. If all else fails, a good intelligent relay will allow your solar charger to top up your starter battery, assuming that your solar controller is properly set for the Lifelines. (Otherwise, your DEKA isn't going to be happy with only 13.5v.) While most people don't need it, the CTEK D250S/SmartPass combo is excellent as, unlike the Sterling products, it allows you to feed solar and shore power back to your starter battery.

In any case, the speed at which a lead acid battery charges depends on two things (at least):

-- The voltage differential between the battery and the charge source. If you run your camper battery down to 50% SOC, it will be at about 12v. A 13.5v charge source will make quite a difference. Obviously, 14.5v would be even better.

-- The amps available from the charger. Lifeline specifies a charger source of up to 5C, that is, 5x the capacity of the battery bank. In your case, the full 160A of your alternator is well below that number.

Bottom line, even limited to 13.5v, you will get a much faster charge from your alternator than you will from your solar controller. (Although 400w will give you a nice 20A through a good controller.)

Shameless plug: I have all manner of material that you can download from my website, all with extensive references. As I present this stuff at Overland EXPO, I welcome feedback and corrections.