High amperage chargng of teardrop from tow vehicle

[tdhcsc]

We're in the process of having a custom teardrop made by Minnesota Teardrops http://www.vistabule.com . We've lived and cruised on our sailboat for 10 years with 900 amps of Trojan T-105's and didn't want to sacrifice any of our electrical niceities on the teardrop. The only way to achieve that was to go with a LiFePO4 Lithium Ion battery bank on the teardrop. We purchased 2-100 amp hour LiFePO4 batteries along with all the goodies to satisfy our needs (1,500 watt pure sine inverter, battery monitor system, 40 amp charger, 200 watts of solar panels, etc.). I believe that with my research the trailer electrical system is completely worked out. It may even be the most advanced electrical system of any teardrop in existance (for the time being)

That leads me to the remaining unknown,,,, tow vehicle charging.

We'll be using a Jeep Wrangler as the tow vehicle and wanted to charge the LiFePO4 batteries while driving. It's my understanding that all 'charge while towing' systems are hindered by 12 volt line loss causing meger charge amperage as the voltage needs to be more than the battery it's charging for current flow. Because of this I was thinking of installing a dedicated wiring harness consisting of red & black 4 AWG copper battery cables to a plug at the back of the Jeep wired directly from the battery. The manufacturer of the batteries has told me that it shouldn't be a problem provided that the cables don't get hot. I wouldn't think that would happen with the 50 feet of #4AWG battery cables. I could also step up to #2 AWG instead of the #4 as a kind of 'chicken soup' concept. I'll also be adding a large fuse and battery isolator solenoid to protect the charge battery.

(as a note: The 200 amp hour LiFePO4 lithium Ion battery bank will accept 60 amps (or more) charging with no problem.)

Anyone have any input on using the system I've outlined above?
Any help is greatly appreciated.

Dan

[Shadow Catcher]

I would be guessing this is a question that will be coming up with some regularity as additional battery types become viable.
Charge regulator from Balmar might work http://www.balmar.net/?page_id=15145
From what I am seeing, the batteries are rather bullet proof more than a conventional lead acid.

[tdhcsc]

We had that Balmar regulator on our boat. I believe there's no problem with using the voltage regulator that built into the Jeep alternator. The only problem I may have is in installing large enough cables to handle the length of the 12 volt circuit and the amperage the alternator will output to the batteries. Then again,,, I'm only guessing.

Yeah, it's a big learning curve. The new LiFePO4 batteries are almost a different animal than all other batteries. From what I've discovered there is so much advantage to installing them it's easily worth the additional cost.

Yeah they're stupidly expensive but,,, you can recharge Lithium Ion 3,000 times with only a 10% loss in efficiency. They only loose 2 percent charge a month while storing so you don't need a trickle charger. Lithium Ion doesn't care if you don't charge before putting the trailer to bed, (actually they prefer not to be fully charged when storing). The weight and size is not much more than 1/2 of other batteries. You can charge a 100 amp hour battery in 1 hour. The advantage list goes on and on. Stupidly expensive but if you're using your trailer a lot it ends up being more than worth it,,,,I think. It's the only way we could have a large enough but small/lightweight house bank to fit in such a tiny trailer.

The biggest problem I've run into is that it's such a new technology that hardly anyone can help in putting a system together and you need to spend hours on discovery. Hell,,,, I couldn't even find someone to help me put a system together and had to figure it out from scratch.

Oh yeah,,,, LiFePO4 (the new Lithium ion batteries) doesn't get hot like older Lithium Ion batteries did.

I'm going to use the same cables I'd use for an 8,000 lb winch as the battery's will take everything the alternator has to offer in charging amps if set up correctly. Actually need to go a couple of sizes bigger as a winch is only a 10 foot circuit run but charging the towed trailer is a run of probably 50 feet. A lot of voltage loss if you don't go huge in the cable wiring.

[capnTelescope]

I ass-ume you have a charger for the LiFePO4's that runs on shore power. If so(if not, why not? ), you can use the DC-AC-DC charging method like my setup. DC-AC-DC works by powering an inverter that powers the charger. The inverter is much more tolerant of 12V voltage drop, and a smart charger is more tolerant of line voltage variations, all the while getting proper charging voltage to the trailer battery. The voltage drop issue pretty much goes away.

There's a good description of my charging system, complete with photos, starting here in my build thread. There is also exhaustive discussion of the DC>AC>DC charging method starting here in the Charging While Towing topic.

Here's a schematic of the system I'm describing:

With the 110VAC relay, it automatically charges when plugged into shore power (like when at home) or on the road. It looks roundabout, but charges reliably for AGM batteries. I see no reason it wouldn't work with the right charger for your LiFePO4's.

The one drawback I see might be the cost of the charger, vs. what the Balmar costs. You wouldn't need both, just one or the other.

[Dale M.]

Have you given any thought to what the output of Jeeps alternator is.... My early Jeep 2002 only has a 130 amp alternator (I believe)...

Dale

[jonw]

Another thought - to avoid current loss why not relocate the batteries to your tow vehicle when driving during the day, where a much shorter cable run will not have as much power loss?

These batteries are pretty light, right? Might be the simplest solution...

[PaulC]

All you need is a decent DC to DC charger, such as the one CTek produce. I use one and it produces around 98% charge with a day's driving.
Cheers
Paul

[Shadow Catcher]

Stupidly expensive would mean take care of them I do not know I would trust an automotive regulator.
I use 150A Anderson Power Poles with the 6ga jumper cable I have set up to charge the trailer battery from the TV.

[OverTheTopCargoTrailer]

Very nice trailer.
Your link above is spelled wrong and is dead.

http://vistabule.com/

I have 2,000 ah in lithium LifeP04 batteries in my trailer, folks make this issue with lithium batteries 10x more complicated then it really is. You can buy 100 ah for $500.

Let them know how your system works , maybe you will make some more converts.

Cheers

OverTheTopCargoTrailer

Wow, I gotta say the price on this puppy makes a Airstream Bamby look cheap.

http://vistabule.com/pricing/get-the-pricing-worksheet/

[tdhcsc]

WOW! quite some trailer. I'm going to spend some time exploring your site. Yeah, I keep spelling Vistabule wrong by putting an i where the a should be.

For us,,, after selling our 50 foot cruising boat, the price for the Vistablule isn't much for getting back the traveling and exercise we're looking for. At 70 the work involved with distance liveaboard cruising was becoming too much work. Camping in comfort should be a lot easier. Only problem is that we want everything our cruising boat had,, except for the water maker. I don't think that would work.

Vistabule was offering 'Airstream aluminum' when we ordered ours but they no longer do so I believe ours will be the last one with an Airstram aluminum exterior. If a new one is ordered it comes with a silver finish but not the polished Airstream aluminum it did last year.

Hopefully you're right about Lithium Ion being 10 times more complicated than it really is. We decided to go with a packaged battery that includes a battery management system. It just seemed simpler,, but at a cost of $900 for 100 amp hours.

Thanks for all the ideas and suggestions so far. I think that for the moment I'm going to postpone the 'charge from vehicle' idea and just see what our amperage usage is and just how much we'll be dry camping. We're installing a 40 amp 110 volt charger for when we're plugged in and we always have the solar panels or,,,,,, charge by running the Yamaha 2,000 watt portable generator. Fortunately I'll only need to run it for an hour a day for charging.

[OverTheTopCargoTrailer]

Hi tdhcsc

Bellow is worlds best, number 1 seller & cheapest lithium battery.

http://www.electriccarpartscompany.com/100Ah-32V-2C-br-CA100FI-br-CALB-EV-Lithium-LiFePO4-br-UL-Certified-br-Prismatic-Cell-Batteries-br-USA-Stock-br-56L-26W-86H-in-br-142-67-219-mm-br-75-lbs-34-kg-br-For-Quantity-Pricing-and-Specifications-See-Details_p_38.html

$508 for 100 ah Lithium, for the same money I would just buy 400 AH and chuck the BMS......in the GARBAGE.....most fires are from bad BMS systems....
SAME PRICE......

I love this config as if you need more, just add a few more cells, if one should die, $127 gets you a new one.....
get a simple $20 volt meter and watch the show.....13.8 max charge, 13.3 normal resting voltage, 12 or below recharge, 11 below disconnect
America has 10 million lithium battery EXPERTS - ZERO OF THEM own a lithium battery LOL


FOR ME: 100% solar AC is my min requirement, then I can live in a box