Newbie reinvents the wheel, again!

System · March 2008

Us newbie's are always trying to reinvent the wheel, I know this as a old timer on another active forum.

So in keeping with tradition, and your amusement, here is my reinvention!

I boondock mostly. As much as 4 months.

While driving, the Tow Vehicles 60 amp Alt, with #6 charging wire terminates at the standard 7 pin trailer plug.

I have a 2000w Honda

I have a large tow vehicle (1 ton, diesel 15' box truck) it tows a rather spoiled 28 foot Airstream travel trailer.

Spoiled, in the fact that I cannot add any additional weight above its (2) 27 series batteries to its delicate tongue. (really)

As such, and being I have so much roof realestate and weight capacity in the tow vehicle, I thought the following.

(3) 130 W panels mounted flat on my tow vehicle.
(4) 6v batteries mounted in my tow vehicle.

A Morning Star SunSaverDuo controller.

When driving, the controller would charge the 6V battery bank in the T.V., and the Alt would charge the (2) 12V trailer batteries.

When stationary for more than an overnight, I would simply plug a cable from the 6v T.V. battery bank to an external plug that would connect to the 12V buss inside the trailer.

When stationary, the second separate charge line from the SunSaverDuo controller would also run to the 12V trailer batteries in order to charge them also.

Am I missing something really big here?

Is there a problem with both outputs of the controller ending up in the same place?

Why leave the (2) 12V batteries in the trailer?
There are times when the truck will be detached and away from the trailer.
Why (2) 12V batteries in the trailer?
6V batteries will not fit without major modifications to the (spoiled) trailer.

What sage solar wisdom can the experts bestow on this humble tenderfoot?

Thank you,
Michael

mike95490 · March 2008

Re: Newbie reinvents the wheel, again!

You should not switch banks of batteries into parallel (trailer batteries and tow vehicle aux batteries) What will happen is one bank will charge up to 12.84V, and the other to 12.77V. While it does not seem like much of a difference, after a while (couple of months of this) the lower voltage battery bank will "ruin" the higher voltage bank, to the lowest common denominator, and one bank will die. It's iffy enough switching batteries from the same production batch, and from between Mfg's, it will work OK for a while, then fade away.

Also, Vehicle Alternators are generally set to 13.8V, and deep cycle batteries need about 14.8V to fully charge. The alternator will be OK for bulk charging, but not for the final top off.

Get a good 3 or 4 stage charger to run off the 120V generator, run the gennie for an hour in the AM, make coffee, toast, and quick charge the batteries, and let the solar top them off the rest of the day. Best use of fuel.

System2 · March 2008

Re: Newbie reinvents the wheel, again!

mike90045 wrote: »

You should not switch banks of batteries into parallel (trailer batteries and tow vehicle aux batteries) What will happen is one bank will charge up to 12.84V, and the other to 12.77V. While it does not seem like much of a difference, after a while (couple of months of this) the lower voltage battery bank will "ruin" the higher voltage bank, to the lowest common denominator, and one bank will die. It's iffy enough switching batteries from the same production batch, and from between Mfg's, it will work OK for a while, then fade away.

Also, Vehicle Alternators are generally set to 13.8V, and deep cycle batteries need about 14.8V to fully charge. The alternator will be OK for bulk charging, but not for the final top off.

Get a good 3 or 4 stage charger to run off the 120V generator, run the gennie for an hour in the AM, make coffee, toast, and quick charge the batteries, and let the solar top them off the rest of the day. Best use of fuel.

Thank you Mike,
Let me see if I understand you correctly.

If I top up my TV batteries with the gennie THAN it would be OK (I know it will never really be OK) to parallel the banks?

If that's the case, could I use the second charging leg of the SunDuo controller from the TV, to top off the battery bank on in the trailer, than parallel the banks.

What ya think?

Thank you.

Michael

nigtomdaw · March 2008

Re: Newbie reinvents the wheel, again!

Im trying to help picture what your box truck would be like trying so to keep things simple. Rear tail gate ? or swing hoist ?

1.If we could keep the batteries all one type either 4 x 12v or 8 x 6v + same make model, best practice ?. Long Life
2.Remove batteries from beloved trailer to Box Van (everyone feels and look better for shedding a few Pounds. You say beloved is at its max so a plus here !

Then things would be ideal, charging from TV whilst motoring and no need to transfer from TV to Trailer unless there are those infrequent times when you are separated from your trailer when the trailer is occupied and your TV is being driven elsewhere.

So it you could design and make up a Sturdy battery enclosure (Steel) which could easily be sled off or hoisted down from the back of the TV near to the hitched Trailer .The only connection to be removed would be the Alternator charging source from TV via an Anderson Plug. if the PVs were then insalled on the now lighter Trailer. Obviously this may sound complicated but if your box van TV had a tailgate or a swing hoist it could be done quite easily, Just the fabrication of the BB enclosure robust enough to be wheeled or hoisted off.

Its just a thought even if the operation took 5 minutes each time TV and Trailer were divorced it is an alternative to look at.
Or a pull out cassette type arrangement fabricated underneath Box Van like some RV generators are ?

I just know Im gunner get my butt kicked on this

mike95490 · March 2008

Re: Newbie reinvents the wheel, again!

I like nigtomdaw's idea of a removable battery box. Keeps it simpler. One charge controller.

What loads do you run, are they all 12V or any 120V ? Maybe consider the next step, and run a 24V system, if all your loads are 120V ? Would mean a new inverter, but less DC loss, and series batteries play better then parallel.

System2 · March 2008

Re: Newbie reinvents the wheel, again!

Michael,

Just wondering what your loads are? I have a 31 ft airstream, two group 27 batteries, a blue sky mppt charge controller, 150 watts of solar power, and a honda 1000. The solar panels are stored in the T.V. and placed in the sun keeping the trailer in the shade while booddocking. The honda is all most never run. Perhaps calculating your loads before adding the wieght. Extra weight translates into extra transportation fuel. From another traveler.

System2 · March 2008

Re: Newbie reinvents the wheel, again!

Let me preface this thread with the following statement.

The availability of some used 130W PV's here, has precipitated my crash 3 day learning course on Solar, so please pardon all the stupid assumptions on my part..

Bill thanks for the suggestions. I run a monster lap top, external HD's and 2 wide carriage printers. That alone eats my (2) 27's in a few hours. They are charged by a Intellipower 55a 3 stage converter when on shore power or the Honda 2000. Being a full timer and living and working on the road, I spend a lot of time working in the trailer.

nigtomdaw, now if I stayed out here in Quartzsite, AZ, I could just spread stuff all over the place, BUT…
The roll out battery box would be a problem while I'm in some parking lot, and my TV is off at the show site. Same holds true for leaving panels on the ground in a strange parking lot or side street in downtown Chicago.

Thanks for the alternative ideas, that's exactly why I joined this forum.

Mike, the Morning star is a dual charging controller (SunSaverDuo 25A) and will charge 2 banks. So I would not need 2 controllers. (Any opinion on this controller)?

What say this. Replace the original idea of a 6V battery bank in the TV with 12V G27's matching the ones in the trailer..

We know the T.V. Alt. charge line does a poor job of charging, so let's remove it from the equation.(or should I ?)

Let's say the (2) 12 V trailer bank will be charged by the 2nd leg of the dual controller.
Meanwhile, the 1st leg of the controller will charge the 12V bank in the T.V.

The trailer and TV would always be connected while in motion and most other time, thus charging both banks equally, yes?
(what gauge wire would be needed to connect the TV battery bank to the 12V trailer buss?) at about 10 feet

The times the TV is away, things like the Refer circuits, water pump and exhaust fan's would work just fine off the topped of trailer bank.

I do realize the both banks would never be perfectly equal, but?

Any alternative ideas, questions, comment's.

Thanks heaps!

Michael

nigtomdaw · March 2008

Re: Newbie reinvents the wheel, again!

Buy a magic wand get Niel to bless it with a $500 spell and boB or Bill or Super Ted may be your solution, Then wait for the travelling hoodlum to forklift your power supply away ,shit dont you hate co incidences ...man arn't we unlucky or what. Pray for simpler times.

The lord serves wine and bread :grr
Is the USA that bad that tracking exposed RVs for slide out battery banks is a comercial avenue ...woohoo?:p

System2 · March 2008

Re: Newbie reinvents the wheel, again!

nigtomdaw wrote: »

Buy a magic wand get Niel to bless it with a $500 spell and boB or Bill or Super Ted may be your solution, Then wait for the travelling hoodlum to forklift your power supply away ,shit dont you hate co incidences ...man arn't we unlucky or what. Pray for simpler times.

The lord serves wine and bread :grr
Is the USA that bad that tracking exposed RVs for slide out battery banks is a comercial avenue ...woohoo?:p

How do I get in touch with Niel, and does Wind&Sun sell magic wands anymore?

Michael

BB. · March 2008

Re: Newbie reinvents the wheel, again!

Maybe it is not the problem it once was--but leaving a bunch of batteries "unlocked" was a low-riders dream (personally, I had "difficulties" starting my pickup truck 30 years ago when a probable Low Rider decided he needed my battery for his hydrolics more than I needed it to get home from the night shift...At the time, quite a few lift-gate trucks in the area would stop lifting after an overnight "rest"...

A good alternative for getting better charging out of your alternator is to get a good 3 stage AC charger (like Iota Brand--Xantrex also seems to make some modern battery chargers too that have "power factor corrected" AC inputs--very nice for running on generators and inverters)... And get a good sinewave inverter installed on your truck. Run an 120 VAC line from the inverter back to the charger in your trailer. You will get "good" charging from that setup (Inverter must be sized to mange the load of the charger).

And, most likely, charging with a dedicated generator (Honda or RV type) will be more efficient that running the tow vehicle (other than when driving place to place).

Certainly, reducing power use as much as possible (conservation) is the way to go... Using appliances that use propane rather than electricity (fridge, oven, hot water heater, etc.), using the smallest possible computer for the job at hand--laptops tend to be more power efficient than current desktop systems.

I don't remember if you have a Kill-A-Watt (or even if I recommended one to you)... But it really does help.

In the end, you may be better off (cost wise) just using a fuel efficient generator (like the Honda inverter type) during the day when you have the "large" loads, and use the batteries for non-work times when you want the quiet... Discharging and recharging a large bank of batteries with a generator vs just running the loads on well matched (in size) generator (for example, running a Honda eu2000i between 400 and 1,600 watts) vs running a 10 kW unit to run a 40 watt laptop (running the light loads on batteries can be much more efficient that the windage losses in an oversized generator). If you are running heavy loads on batteries--you just add the losses of charging/discharging/AC to DC/DC to AC convertions, etc... And, in the end, you might spend more in fuel to be "quite" during the work day...

-Bill

nigtomdaw · March 2008

Re: Newbie reinvents the wheel, again!

Another alternative maybe to just let your TowVeh battery power a dedicated circuit in your trailer that is only used when your home, like a socket connection for the TV and coffee maker or to a second inverter and plug in what s needed into that. spreading the load As long as you manage its soc you could have your cake and eat it without combining the 2 mismatched battery banks. A 2nd Inverter adds a level of backup as well.

crewzer · March 2008

Re: Newbie reinvents the wheel, again!

Art,

A couple of things to consider. One, as mentioned previously, is that stock automotive alternators and their related wiring systems don’t do a particularly good job of charging RV deep cycle batteries. The typical regulator voltage (~14 V) is too low (14.4 required for Group 27 “RV” hybrid batteries), and the voltage drop in the wiring and connections between the alternator and the battery terminals just exacerbates the problem.

Another problem is that the SunSaver Duo’s fixed absorption voltage setting (14.3 V), while probably OK for hybrid marine/RV batteries, is too low for the golf-cart batteries requirement of ~14.8 V or so. Accordingly, I don’t think the SunSaver is a good idea for your proposed application.

I ran into a variation of these issues when I had my RV. My solution was to use my TV’s alternator to power camper loads (i.e. 12 V fridge) while underway, and to separately use my camper’s PV system to recharge the batteries. The truck’s electrical system and the RV battery terminals were never connected.

The fully charged voltage for the GC battery bank and the RV battery bank will be ~12.7 V, Personally, I wouldn’t have a problem with connecting the two bank to power DC loads. But, the two banks do have different charging requirements, so that’ll have to be addressed.

One possible solution might be to separately charge the two battery banks from two controllers connected to a common PV array. See the following diagram. One controller (a Morningstar TriStar 45?) could be set to ~14.8 V to charge the GC battery bank, and the other (a smaller SunSaver?) could be connected to the RV batteries. It might be worth contacting Morningstar and verifying that this arrangement would indeed work for your proposed application.

See: http://www.morningstarcorp.com/products/FAQ/iso_banks.pdf

Ultimately, a more practical solution would be to buy more marine/RV batteries for the truck battery bank instead of GC batteries. For example, three or four Interstate 12 V SRM-29’s wired in parallel, or a couple of 12 V SRM-4D’s wired in parallel, should provide as much capacity as the four GC batteries. Since their charge voltage requirement would likely be the same as the RV batteries, you could then use the SunSaver Duo as a charger.

A couple more things. One, remember to provide adequate ventilation for the RV batteries stored in your TV while they’re being charged. Two, don’t mount the PV panels directly to the TV’s roof. Leave several inches between the roof and the modules to allow for circulation of air to cool the modules. Three, assuming the modules are mounted flat, you’ll need to go up onto the roof on occasion to clean off the debris that will “pool” on the modules and reduce their power output.

HTH,
Jim / crewzer

System2 · March 2008

Re: Newbie reinvents the wheel, again!

Thank you crewzer, and nigtomdaw for your thoughtful responses.

I've taken both your suggestions to install group 27 batteries as the TV battery bank in order to keep both trailer and TV battery banks about the same.

The SunSaverDuo will charge both battery banks.

The controller will always be connect to the trailer battery banks by tapping into the existing alternator #6 gauge wire to the male TV plug

Does that make sense?

Also, I'm thinking I will need some sort of isolation to prevent power flowing back to the TV voltage regulator. Right now, I always see voltage at the male TV plug?

Question:

Is it OK to have all the following connected at the same time?

1. The alternator connected to the trailer 12V buss. (#6 wire from the regulator) is it OK for the controller to see a 60A alternator?

2. The TV battery bank connected to the 12V buss.

3. The trailer battery bank connected to the 12V buss.

Thanks for your time helping me work this out.

Art

Newbie reinvents the wheel, again!

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