Using Alternators to Charge House Batteries: Not sure where to start (a pun there)

[deminimis]

So, me gots a truck with dual batts and dual alts (max output 440amps). Camper has (or will have once I install them) 4 batts for 420 amp hours. Camper has solar, inverter (once it arrives) and if things get real bad, a propane genny (which I hate and would love to never use again). We spend a lot of time up skiing, which often equals low sun or snow on the panels. When driving, or if house batts are too low and I don't want to run the loud genny to charge them when solar unavailable, it would be nice to harness (there I go again) some of available alternator juice for the house batts (I know the alts produce the most juice at somewhere between 20-80% and drop off considerably outside those approx parameters). I recently came across an enclosed aftermarket regulator (or whatever it's called) that would allow the alts to send juice to other batts, but not locating it right now and it was quite pricey. As a side note, I wouldn't mind having house batts available to start the rig in an emergency (like we had on a former RV). Anyway, I'm sure it's been covered before, but does anyone have a simple (and reasonably priced) solution to this? Long jumper cables is not the answer I'm looking for. Thanks.

 

[goodtimes]

Your truck has dual batteries & dual alternators - how are they wired up? Is it all one system, or is the second battery isolated from the first?

On the assumption that the existing batteries & alternators are all a single system, then simply treat the existing truck charging system as you would any other starting system (you just have twice as much battery & twice as much alternator - but doing the same job in the same fashion), and treat house batteries like a typical axillary battery (which it is - just 4 x as big).

Separate the two systems (truck & house) with what ever isolator/combiner you prefer, and call it a day.

 

[Darwin]

Sterling makes a 120 amp dc to dc charger you could probably use.

Now what would be cool is if you could figure out how to have your truck start automatically and run for a set period of time, say an hour, once your batteries got down to 50%. They do this on some Class B's.

 

[deminimis]

Thank you. Sterling was the company I couldn't remember!!

 

[deminimis]

Holy smokes. That Sterling charger is well over $600. I could snag a couple more panels at that price. Okay, this was a bad idea. I'll just carry two sets of jumper cables in case things go bad.

 

[4x4junkie]

Separate the two systems (truck & house) with what ever isolator/combiner you prefer, and call it a day.

This is what I would do also. Easiest, least hassle.
Use a heavy-duty Anderson PowerPole connector to make the connection from the truck to the house batts in your camper (this way you can easily unplug it should you remove the camper).

Have a read here:
http://www.expeditionportal.com/for...ke-a-cheap-isolated-dual-battery-setup-for-50


FWIW, those camper batteries won't get much charge current if you try to charge them through jumper cables, you need to have at least 1/0 AWG (2/0 preferred) cables with good solid connections if you want to be able to pass the full current of your alternator(s) to the camper batts (voltage drop is the big killer of current when it comes to charging batteries located any distance away from your alternator).

 

[unseenone]

Sounds like you picked your direction. For what it's worth, if you've spent as much as you already have, you might consider this battery solution. It will live well with your solar, house batteries and alternators and won't require any fiddling. The kit I'm linking to comes with all the wiring and bits, you could save quite a bit by just doing the controller and adding your own wiring. There is a diagram on the page to give you the idea. Pricing as stated is $AUD560 for the Complete Kit Controller by itself is $275AUD and worth it in my opinion.

 

[deminimis]

Thanks all.

 

[DiploStrat]

Been Done

Assuming that you have a recent American truck running at between 14v and 15v, the simplest solution would be some form of intelligent relay system, I like Blue Sea ACR's, and some heavy gauge wiring (about 100mm2). Unless you are planning to use lithium batteries, this will allow you to harvest the full out put of the trucks's alternators and use your camper batteries to jump the truck. I run a similar system to yours, but with only 250A of alternator and 600Ah of batteries. I do not have or need a genset. You can read about what I am doing on my website. System has worked well to for two years.

You could use a Serling B2B unit, but then you would be reducing you alternator output to only about 100A. The Sterling B2B will not cause the batteries to take a charge any faster than they will normally and, as it is based on diode isolation, will not allow you to use your solar charger or generator to charge your truck batteries. (At least not without some extra wiring.)

In any case, the biggest cost is likely to be the wiring. N.B. A Blue Sea ACR is considerably less expensive than either a Sterling B2B or an imported controller: http://www.amazon.com/Blue-Sea-Systems-Automatic-Charging/dp/B001C7CJHC/ref=sr_1_7?ie=UTF8&qid=1448420679&sr=8-7&keywords=blue+sea+ACR

 

[deminimis]

Thanks. Big fan of Blue Sea (use some of their stuff in my boat and just bought one of their sub panels for the camper). Looks like a good solution. Some 4/0 wire an Anderson connector, and I think it would be about perfect. Thanks!

 

[DiploStrat]

You may find it much easier to work with one or two 1/0 or 2/0 cables as opposed to 4/0 cable. Copper is copper.

 

[deminimis]

I like 4/0. Keeps voltage drop to a minimum and I have around a bazillion 4/0 lug ends (okay, about 10 or so).

 

[DiploStrat]

I tend to geek out on this stuff and have assembled a lot of info on my website. There is nothing wrong with 4/0, other than the difficulties of bending, cutting, and terminating. You seem to have the last of these covered.

I find this an indispensable tool: http://www.calculator.net/voltage-d...nce=15&distanceunit=feet&amperes=100&x=38&y=6

The other thing to remember is that assuming a healthy battery bank and a decent solar set up, you may never exceed 15 to 20% discharge. In which case, you will rarely seem a charge rate of much over 100A and that only for an hour or so. Those 400A of alternator are nice, but you are unlikely to ever be able to harvest much over 150A for battery charging. (Instant loads are, of course, another story.)

The dirty secret is that even large battery banks connected to healthy alternators spend most of their time charging at 75A or less. Bummer, but that is simply in the nature of lead acid batteries.

 

[deminimis]

The back story here is my solar was not up to speed (one 110 panel) and batt bank limited to 210 AH. It worked, but we had no 110v unless we fired up that miserable propane generator. I was going to tap into my 77 gals of diesel on board and pick up an Onan 6k Quiet Diesel generator on the cheap ($4k). The problem was trying to fit that beast under my flatbed. Doable, but I would have destroyed a relatively new Protech box to do it ($700-ish, if I recall correctly, plus a 1500 mile round trip to pick up the genny, plus a hell of a lot of cutting and fitting). After a lot of back and forth, I decided to wait until I find the right generator for me (a Powertech 3000 or Onan 3200), if ever, and build up solar, batts, etc, as best I could. A lot of places we hang out at frown at noisy generators and I don't want to be a ******** with our noisy propane generator, so I wanted to come up with something. Right now I've bumped solar to 270, but I'll increase that to 590 in a couple of months (will require I update my controller for that as I'm limited to 30 amps right now). A lot of new stuff is arriving today (except my new batts, it seems), so over the next couple of weeks, I'll be upgrading everything with new ATS's, inverter, sub, and so on. When all said and done, I suspect we'll be in pretty good shape. However, on those long winter nights up at the ski area, there may be a time or two or three where I'd like to introduce more juice in the system for short periods of time while warming up a Hot Pocket or bring the batts up enough so we can finish an episode of The Family Guy, or whatever. Seems tapping the alts for some extra juice (truck is very quiet at idle) instead of the propane generator would be nice (plus, I want that propane for heat). I do like the Blue Sea system you pointed out (think I'll get the one with the additional manual shut off switch) and for under $200 (before wire, etc), it seems like a great, cheap and simple idea. Thank you again for that tip. I have a fair amount of 4/0 arriving today. This stuff flexes pretty good. I'm definitely overkilling it with 4/0 (other than inverter hook up), but I'm dealing with fairly straight runs. I think it will work well for the other, but if not, I could grab some 2/0 or lighter, if need be. Oh, the reason I even started thinking about the separator/combiner was when we had out Sportsmobile, the solar (140) w/ a single 4D, could handle the microwave during daylight just fine. At night, we'd have to fire up the rig to use the microwave (dual alts, but a lot lower total amps than the new Ram). Worked okay when it came to addressing the extra load (fridge ran on 12v, so had to keep the batt up as best we could for that to run all night so my Pacificos woudl be nice and cold). Seems like it would work even better in this situation. Thank you again.

 

[deminimis]

Crap, you're right. The one thing I didn't think about is running 4/0 into the camper (that's not a problem) to the batt banks (which are in the dinette slide). Need to have more flexibility (or a giant loop) for that action. I may need to go with a smaller gauge for the camper part for the ACR wiring. Ah, I'll cross that bridge when I get there.