house battery with no connection to alternator

[hitek79]

It seems like all the discussion here are about connecting house batteries to the Alt. Is it a bad idea to just hook up the house batteries to solar and completely cut out all the extra steps involved with the Alt connection?

Beyond that question, what parts do I need other that panels, wiring, batteries, and an inverter? Thanks!

 

[unseenone]

You will need a charge controller. You can do it that way if you want to, but there is no harm in connecting it, so you can take a charge when driving. You can use a simple device like this, I've got a couple on the shelf I ordered. http://www.sidewinder.com.au/page79.html It will not put a charge to the starter battery when the engine is not running, which means your solar would charge your house battery, but not the engine battery.

It would be a worthwhile exercise to determine what you want to run, and how much you will draw to ensure the solar is adequate to keep the battery charged up. That being said, avoiding the use of an inverter by using DC devices is going to be the most efficient.

Correct wire sizing will also avoid voltage drop (loss) in your setup as well. I like Morningstar stuff, it's American made and also very well respected for small solar charge controllers.

You've sure got some awesome pictures on your web site there. An amazing bit of work.

 

[Joe917]

I must add , nice work ,fantastic pics.
As for running house batteries off solar alone, no problem IF your solar is enough to fully charge the house batteries. I am not a fan of connecting battery banks dumbly. The alternator is set up to recharge a starting battery quickly after a start not to recharge deep cycle house batteries. It will do it, eventually, but will take a long time. A far better system is to use an alternator to battery or battery to battery charger. These use the same charging systems a a good solar controller or high end battery charger. So much depends on the size of the system and how you use it. It does seem a waste to not use every available charging source.

 

[DiploStrat]

Couple of Comments

-- What makes up a good solar kit? If you do not know, you could do worse than to look here: http://www.amsolar.com/home/amr/page_19

-- Alternator will charge slowly. Not necessarily. A modern truck with a 200+ amp alternator running at 14 volts can easily deliver a sustained charge rate of over 150 amps. My 2013 Chevrolet does it all the time.(An A2B or B2B is probably NOT necessary if your truck already runs at over 14 volts.)

-- Alternators are a great source of boost charge, that is, the high current charge needed to get the batteries to 90% charge.

-- Why cross connect? Among other reasons, to allow your solar kit to maintain your starter batteries.

Bottom line, why would you want to deny yourself the benefits of either alternator or solar charge; use both.

 

[hitek79]

Thanks for the compliments. Hopefully this new rig allows me to take a lot more great pictures!

I'll look in to seeing what my current alternator situation is and go from there.

 

[kpredator]

you got some cool images on your site.
use your alternator, hundreds of thousands south africans,austrailians cant be wrong!!!
keep shootin and good luck
kp

 

[FJR Colorado]

It seems like all the discussion here are about connecting house batteries to the Alt. Is it a bad idea to just hook up the house batteries to solar and completely cut out all the extra steps involved with the Alt connection?

Beyond that question, what parts do I need other that panels, wiring, batteries, and an inverter? Thanks!

Yes. This can be done.

See my build thread:
http://www.expeditionportal.com/forum/threads/127252-2006-1st-Gen-Tundra-Doublecab-Build

While I can see the virtue of having an alternator connection, I like the concept of a self-sustaining discrete solar system.

I also like the idea of having a second battery in the vehicle that will typically be fully-charged and able to replace the main car battery in a pinch.

 

[DiploStrat]

FJR, with 100w of panel dedicated to such a small battery, you REALLY ought to look at a connection back to the starter battery. Not because you need the engine alternator to charge your camper battery, but rather to use all of that solar power to keep your starter battery happy.

 

[Joe917]

I don't see a need to connect the solar to the starter battery if the starter battery has only starting and running loads on it unless the vehicle sits for long periods unused (weeks). I do understand not wanting to waste excess solar.

Charging batteries in parallel does work (DiploStrat has personal experience with that system in his own vehicle). It is not the optimal system though.

"Once battery banks are paralleled, the batteries of both banks will be charged according to the same regimen. But different kinds of batteries commonly used for house service and cranking service (deep-cycle battery for the house, a cranking battery for the engine). These batteries accept charges in different ways. When in parallel, one bank will invariably be somewhat overcharged, while the other will be somewhat undercharged, resulting in reduced life expectancy for all the batteries. Inequalities are likely to be especially pronounced when a single large house bank is paralleled with a relatively small cranking battery." (Nigel Calder, Boatowners Mechanical and Electrical Manual)

A better system requires a voltage regulator for each battery bank (or additional alternator to battery charger , or two alternators, or battery to battery charger)

The Sidewinder listed above is a smart parallel-er not really a charge controller.

The better system costs more but you should extend battery life. The size and complexity and budget of your build will determine the system you choose.

 

[unseenone]

Good advice, you are right on the sidewinder. I thought it might be a happy medium to provide a solar charge to the house battery, while ignoring the starter battery. It accomplishes what the OP originally requested, but also allows to charge the house battery when the vehicle is running. The Traxide system is what I'd prefer to accomplish battery linking from the house battery side to also charge / maintain the starter battery. It's also fairly solid state, so there are not the usual problems associated with relays in other systems.

Good advice and comments on the batteries. I do my solar charging with a Traxide connected to the AGM house battery. It does a great job, and also keeps the starter battery topped up. It simply works, without any hassle. Diplostrat sure has a lot of experience, and a nice thread on his build.

 

[hitek79]

I have a lot of space for batteries and solar panels. As of now I've purchased four 6v batteries for a total of 430ah. I'm considering purchasing another pair for 645ah of power since I have plenty of room for them. I have 3 solar panels for 300w of power, but I have room to put another 3 on the roof.

My main reason for asking about using the alternator to charge is because of how I'll be using my rig. Typically I'll head out on a trip for 2-3 days at a time. Once I get someplace though, I'm really doing very little driving. So my batteries will be fully charged already before I even start the bus up. At that point I'm going to be parked, or doing very short drives. I feel like no matter what I need to optimize my solar charging because I can't reliably count on any driving to be charging batteries on a day to day basis.

 

[Joe917]

very basic rule of thumb: one watt of solar for one amp/hr capacity.

 

[unseenone]

What do you have space wise for your panels. Say you had room for 3 250w house panels, or more, you could run a morningstar mppt-45 or 60, and be able to get a good charge during the day. I have an 800Ah bank, and 500 w of 24 volt panels is not quite enough when conditions are not optimal.

 

[DiploStrat]

Yes, but ...

Joe,

Your comments are correct and indeed, I went the the expense of installing a Sterling A2B for just those reasons. I eventually removed it and went with a simpler system for several real world reasons:

-- The first, big reason to remove the Sterling was that it alarmed when faced with the 15.5v that my Chevrolet produced in cold weather with batteries that had been sitting for a long time. The Sterling has a hard shut down at 15.5v.

-- This lead to a long period of panic that I would destroy my AGM batteries should they be paralleled with my starter batteries. After extensive reading of the Smart Gauge site ( http://www.smartgauge.co.uk ) I ended up installing a Magnum Smart Battery Combiner ( http://magnumenergy.com/smart-battery-combiner-me-sbc/ ) as it has a high voltage disconnect.

-- Further experience showed that the Chevrolet only produced the extreme high voltages when running some form of equalization charge, in normal use, the voltage regulator stays at 14.x volts, perfect for AGM batteries. So, were I doing it again, I would use this as it is simpler: http://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

This brings us to an interesting point - almost all starter batteries in newer vehicles appear to be some form of AGM, so the differences in charge regimes are quite small. Previously, I would have suggested a Sterling A2B for older vehicles which run at 13v, but now I wonder if the real problem is not to find a way to raise older vehicles to 14v as there are not that many 13v batteries left on the market. (But that is another discussion.)

So, how does my system work?

-- Each set of batteries is connected to its dedicated charge source. That is, the starter batteries to the truck system and the camper batteries to a properly sized Blue Sky solar controller. (And a Magnum charger/inverter for shore power.)

-- The Smart Battery Combiner combines the batteries (not the charge sources) whenever it detects a sustained voltage above 13.2v and below 14.5v at either end. The SBC opens the solenoid when the voltage at either battery drops below 12.7v.

-- Cable between the two banks is some 20 feet long and introduces a voltage drop of under 0.5v. Connecting battery to battery reduces any stress that might be caused by connecting the "wrong" charger to a battery.

Given normal driving patterns of rarely more than six hours a day, this means that the engine alternators contribute only to the boost/bulk charge of the camper batteries and the final absorb/accept charge is accomplished only through the solar kit.

Does it work? I won't really know for about five years, but based on trips the last winter and a 60 day expedition to Overland EXPO it works very well.

-- Many RV/camper/expedition vehicles spend a lot time parked. It is very handy to have the solar kit handle trickle charge duties as well as providing the current needed to support the heater, etc. This is really nice in cold weather.

-- While the engine alternators are great for producing massive amounts of current during the bulk stage, I typically shut off the engine between three and five P.M. While the current output of the solar kit is lower in the afternoon, the acceptance stage requires little current, just voltage and time. Indeed, the Lifeline rep (I use Lifeline AGM batteries) stressed to me that the greatest single danger was not charging AGM batteries long enough.

The design criteria of my truck were three days of dry camping without any sunlight or engine start, producing 150 Ah per day. Full disclosure, I haven't yet had three days of rain to test long term discharge.

As with all of these things, YMMV. I can report what has worked for me on my truck, but only you can decide if it would apply to your vehicle.

Offered in the hope that this information is, clear, correct, and useful.

 

[wrcsixeight]

Solar is great to have, but if it is to be the primary charging source, then, in my opinion, one needs a more significant solar wattage to amp hour capacity.

Batter manufacturers recommend minimum bul charge rates, and these ueually assume you are plugging in a charger which will meet these minimum bulk rates instantly.

Solar, of course, ramps up slowly and does not meet these minimum bulk currents when the battery wants them the most.

The Alternator can be a very effective bulk charger, if cabled sufficiently and depending on what the vehicle's voltage regulator allows.

I always find my batteries respond best to a morning alternator blast, well in excess of the minimum recommended bulk charge, and then letting the solar take over for the rest of the day.

Since I cannot add more solar to my roof without incredible efforts, and I was having issues with 200 watts not being enough for 230 amp hours of battery, I deliberately lowered my overall battery capacity so that my Solar could at least come close to the 13 amp 10% bulk recommended rate from US battery.

As I rarely use more than 60 amp hours overnight, this still is less than a 50% discharge. That extra 100 amp hours of capacity I used to carry was never needed, and my group 31 battery now, seems to be holding its own against my nightly consumption and my majority solar recharge, but I love feeding it alternator amps in the morning, and the voltages it holds the next discharge cycle are always higher than if solar alone was the recharging source.

While my voltage regulator decides at some point all too soon that 13.7v is plenty, it usually allows 14.9v for long enough that the amps taper from 65 to about 25 before 13.7v comes along and asks only single digit amperages from the alternator despite the battery(s) being capable of taking much more current at higher voltages.

For the price of cabling and a Blue seas ACR, the alternator bulk charging your battery bank even for a short duration, could well extend the life of your battery bank and possible more than make up for their additional initial cost.

Battery charging is all about taking advantage of all available charging sources to keep the batteries at the highest state of charge possible. I personally would not remove one of the biggest bulk chargers available. Thirsty batteries should be allowed to be quenched, in my opinion. Low and slow might be fine and dandy when one has a week to recharge, but when the next discharge cycle begins before sundown that day, then more is better.

I'm gonna go dip my Hydrometer now, and see how my group 31 is fairing under my recharge regimen.