Do I need DC-DC charger if I add Lithium batteries?

[Bob K4TAX]

Originally Posted by phrench

I do love a manual. Really. I’m that guy. which is also why I’m on forums trying to learn more before I am out on the road. There is nothing in the very short Specs section and the chapter on towing says get your dealer to install a hitch and follow your local laws. That’s about it. I appreciate the education that I am getting here. Thanks to everyone that has contributed. I still don’t feel 100% confident making a decision yet. I don’t like trial and error with a brand new vehicle. I guess my concerns are primarily around damage to the vehicle. If I drop in a 200ah-300ah battery will it damage my tv? Will it charge while driving? The vehicle damage is the bigger issue. I understand (I think) that the tv wiring will likely limit the charging of the lifepo batteries and protect the alternator. My electrical knowledge is meagre, but doesn’t that heat up the wire? That doesn’t seem like a good outcome to me. And if I add a dc-dc does that necessitate a heavier gauge wire directly to the battery which can now potentially damage my alternator? Do I need a dc-dc setup that can balance charging my lifepo’s with protecting the alternator and acting as an isolator when the vehicle is off? Will the electronics of the vehicle already be able to do this? I can sacrifice some charging for safeguarding the vehicle.

The fuse in the 12V line, located in the fuse box under the hood, should protect the wire to the 7 pin trailer connector from any overcurrent issues. That's what fuses do. In most cases, the wire size used from the fuse box to the 7 pin trailer connector should be a larger gauge wire. This is to have less voltage drop known as reduced IR loss and thus better charging of the trailer batteries. Some manufacturers use #12 gauge {which is too small} while others use #10 gauge. #12 is the more common installation. It is less expensive.

If your vehicle is equipped with the factory tow option, this provides a means whereby the alternator output is increased when the tow mode is active. This will provide a higher buss voltage and thus more voltage to overcome the IR loss in the wire. This gets more charging current to the trailer.

I can check my vehicle battery voltage, at the vehicle battery, with the trailer connected and the vehicle at idle. {My vehicle has a volt meter on the dash.} I also have the means to monitor the battery voltage in the trailer. The difference between the two readings is the voltage drop of the components in the 12V DC line. Those would be the fuse, the wire, the 7 pin connector male and female contacts, and any connections inside the trailer.

One way to improve the system is to make sure the terminals on the 7 pin connectors are clean and tight and the plug is firmly seated. It sure won't hurt to plug it in and unplug it several times to wipe the contacts.

[nvs4602]

I just installed a 280ah lifepo4 in our motorhome along with a Renogy 40amp DC-DC charger.

The Renogy 20 and 40amp DC-DC charger actually have 2 possible charge settings. Full charge or half charge current. There is a pin on the front that when 12v is connected, it will half the current output. So even if you think all you need to start out is 20amps buy the 40amp and enable this feature. Then you can easily increase charge capacity later.



I bench tested my setup before installing it. I have a 12v 30amp power supply that I connected to my Renogy 40amp DC-DC charger, with it set to output 20amp. I have a amp meter connected to the power supply so while charging the battery at 20amps it was pulling 22amps from the power supply. So yes the draw on the alternator will be higher than the supplied current to the battery. The DC-DC converter has to step up the voltage from the alternator to 14.6 volts to charge the lifepo4 battery to full capacity.

I agree with the others on running a separate charge line to your DC-DC charger. It will perform better and you will be happier.

I have not heard anyone talk about your on board converter that charges the house batteries and powers all 12v devices when plugged into shore power. This will also need to be lithium compatible. Otherwise it will not charge your battery completely.

I replaced my converter in about 15 to 20 minutes. So not a big deal.

I bought eight 100watt solar panels from Harbor Freight
https://www.harborfreight.com/100-wa...nel-57325.html

I got these because they have stands on them and are better made and will last longer than the flexible ones. But you'll need a solar charge controller for them.

https://smile.amazon.com/dp/B01MSYGZ...ing=UTF8&psc=1

[Comanchecreek]

Bob K4TAX: Interesting take on "Tow/Haul" mode. I have never heard that keeping the vehicle in "Tow/Haul" mode changes alternator output. That is a new one for me. I'm just wondering where you have seen the information that this actually happens. My understanding of "Tow/Haul" is that it changes the shifting patterns of the transmission to aid in the performance and power band of the engine. Just asking as I've never heard this before. I know the AC compressor has a heavy load cutout, but did not know they do the same with alternator output.

(Quote):Bob K4TAX: With our present tow vehicle with its factory tow package, when the TOW MODE is engaged, the alternator output is maintained at a higher output level. The typical buss voltage is 14.6 volts. Otherwise, in the normal mode, the alternator output is reduced to improve fuel efficiency. In some vehicles when the accelerator is rapidly or fully depressed, as in a passing condition, the alternator is effectively shut off to allow more engine power to be available for the passing situation.

[Comanchecreek]

After posting the comment above I Googled it, and sure enough sone vehicles do in fact alter the alternator output on "Tow mode". Not sure on all tow vehicles, but at least on some. You learn something new every day. That's why I like reading these pages.

[Bob K4TAX]

In all instances where I recommend or quote some artifact, it is due to my own
research and not "what someone said". Frankly, I've never met a person named "someone". The vehicle owner's manual, about a 1" thick book in our case, is a very good reference. It contains this information on alternator output in tow mode.

As to my references on Tire Pressure, again my research found on the tire manufacturers' website or on sites such as eTrailer contains good reliable information. The tire pressure placard on the trailer pertains to the original type and configuration of the tires. If one has upgraded tires, the information likely does not apply. The recommended TP is then found molded on the sidewall of the tire.

There is a LOT of incorrect information posted by "others" on the internet. Just because it is found on the internet is certainly no indication it is anywhere near correct.

I try to research and determine the accuracy of any information I post. Not trying to belittle others and their information, but I find a lot of non-supported statements.

Just sayin'.......your mileage may vary.

[phrench]

Originally Posted by Bob K4TAX

There is a LOT of incorrect information posted by "others" on the internet. Just because it is found on the internet is certainly no indication it is anywhere near correct.

I have to disagree with you. As a high school teacher I can tell you that almost every student in the building assures me that the first answer that comes up on google is the best, most correct answer

I am finding it a little overwhelming how many forum "rabbit holes" I have fallen in to....just because my new trailer came with a 12V fridge:
- series vs parallel solar connections for shaded campsites
- mppt vs pwm charge controllers for a small solar array
- solar panel bypass diodes
- need for dc-dc charger to protect tv
- lifepo batteries
- backup generators vs solar only
Add to that the Andersen vs Equalizer hitch debate for a small trailer like mine and my poor brain is overloaded. When the overload switch trips, it defaults to just wanting a beer.
I appreciate all of the advice and time given by every contributor. It makes me wish that I had enough expertise to be of use to somebody else. I still haven't decided to add a dc-dc charger or just let my car's brains take care of things. The challenge now is to pull myself away from the forums for a while and make some actual decisions before my first trip. It looks like a budget of at least $2500-$3000 (for my specific needs) after purchasing a new trailer. It's just harder to spend it when you weren't expecting it. Thanks for the education!

[TitanMike]

Originally Posted by phrench

The challenge now is to pull myself away from the forums for a while and make some actual decisions before my first trip.

I've always waited until AFTER the first trip to make decisions on additions or modifications.

For the first trip I have used my trailer as I took delivery of it adding only supplies and personal items necessary for eating, sleeping, etc.

This way I learned what I actually needed rather than PERCEIVED needs.

[phrench]

Originally Posted by TitanMike

I've always waited until AFTER the first trip to make decisions on additions or modifications.

For the first trip I have used my trailer as I took delivery of it adding only supplies and personal items necessary for eating, sleeping, etc.

This way I learned what I actually needed rather than PERCEIVED needs.

I appreciate that. It's good advice. In my case I have owned trailers on and off for the past 25 years. I have a very good idea of my needs. I know that I will get a wdh. I know that I can't boondock successfully with the crappy FLA battery that the dealer gave me. I know that the single 190w solar panel with pwm controller won't allow me to run my 12V fridge while boondocking for a week. I don't want to use trial and error for some things; to find out if the lithium battery will damage my wife's brand new SUV, for example. I am hoping to do the work right, and do it once. There is just a whole lot to learn on the solar/electrical side and a lot of good answers that sometimes contradict each other. Each question seems to lead to 2 more problems (and 2 more expenses). Throw in my general distrust of dealerships (from experience), and the fact that I primarily boondock in remote areas, and you can see why I want to have enough understanding to be able to troubleshoot and repair if need be. I will get there, I just need to vent my frustration periodically. Thanks again everybody for your contributions.

[Bob K4TAX]

I've always said "new" only guarantees new, not necessarily good. In my world of electronics, we have the term "infant mortality". That says anything new is likely to fail on the first day, the first week, the first month, or the first year. The point being, the further in time one gets away from day one, the likely it is to work on day two, or three, or four, etc. Expect things to not work and expect things to break. That is why companies provide a warranty with anything new. Again in my world of manufacturing electronics, I could give expected failure rates based on 1000 units as such.

I hope you have great luck with a new trailer. A bit of advice. Make a dummy run or short camping trip to a local state park for a couple of days. It is much easier to deal with issues 20 miles from home as opposed to dealing with an issue 200 miles from the nearest service facility.

As to the students researching on Google and finding the correct answer, well maybe or maybe not. One needs to review several sites to confirm consistency in data results as well as verify the source of the data.

As one who attained an MSEE degree followed by a graduate degree in Physics, I have to admit I find it necessary to do research to find many answers to issues today. In other words, "I am not the brightest bulb in the box". At age 79 much of my education is comprised largely of old technology. I have to work and study to keep up.

If one believes that computers and technology will resolve their issues, then they don't understand computers and technology, nor do they understand their issues.

[Gllo1954]

I have a 2019 Forest River Leprechaun 260D with a Ford E-450 chassis. I dropped in a 200 AH Expert Power Lithium battery. Now I'm reading I need a DC to DC charger. How do I find out the alternator specifications? The owners manual doesn't list it.

[Flat_twin]

What model travel trailer will you be towing with your Hyundai Palisade? You mention 5000 lb towing capacity but no other weight specs. I realize your main question had to do with alternator output vs lithium RV batteries but being a Hyundai owner (though not towing with it) and an RVer I am curious. Thanks!

[Half Ton Heavy]

Originally Posted by Gllo1954

I have a 2019 Forest River Leprechaun 260D with a Ford E-450 chassis. I dropped in a 200 AH Expert Power Lithium battery. Now I'm reading I need a DC to DC charger. How do I find out the alternator specifications? The owners manual doesn't list it.

It’s pretty likely you have an alternator greater than 200 amps. Take car/ truck alternators and use 50% of the value for true continuous output rating. You may be able to find out by looking up at rockauto or something. If the truck has factory heated seats, diesel, or onboard inverter, these all usually point to the bigger alternator option also.

[Bob K4TAX]

Originally Posted by Gllo1954

I have a 2019 Forest River Leprechaun 260D with a Ford E-450 chassis. I dropped in a 200 AH Expert Power Lithium battery. Now I'm reading I need a DC to DC charger. How do I find out the alternator specifications? The owners manual doesn't list it.

Depending on it being an 8 or 10 cylinder engine, Autozone list the replacement alternators as: 130 amp, 150 amp, or 225 amp depending on the brand of the alternator.

[Half Ton Heavy]

Originally Posted by Bob K4TAX

Depending on it being an 8 or 10 cylinder engine, Autozone list the replacement alternators as: 130 amp, 150 amp, or 225 amp depending on the brand of the alternator.

Again, it will depend on the options. Heated seats and onboard inverter gets the big one.

[phrench]

Originally Posted by Flat_twin

What model travel trailer will you be towing with your Hyundai Palisade? You mention 5000 lb towing capacity but no other weight specs. I realize your main question had to do with alternator output vs lithium RV batteries but being a Hyundai owner (though not towing with it) and an RVer I am curious. Thanks!

GeoPro 15tb. Nowhere near 5000 lbs, I don’t ever like to get too near the limit. Dry weight is around 2700# and hitch about 375#. I am picking up my Palisade Calligraphy on Tuesday.

I made a decision today and ordered a Renogy 30a dc-dc charger with mppt for towing and my 200w portable solar panels. After consideration of no dc-dc charger, and buying separate mppt solar charger and dc-dc, I decided on the combined unit. The deciding factor was having the “solar system blueprint” for this setup explained by Will Prowse and easily accessible online.

[distracto]

Originally Posted by phrench

I made a decision today and ordered a Renogy 30a dc-dc charger with mppt for towing and my 200w portable solar panels. After consideration of no dc-dc charger, and buying separate mppt solar charger and dc-dc, I decided on the combined unit. The deciding factor was having the “solar system blueprint” for this setup explained by Will Prowse and easily accessible online.

Congratulations on your decision, looking forward to hearing how everything turns out. Happy camping!

[nvs4602]

Originally Posted by Gllo1954

I have a 2019 Forest River Leprechaun 260D with a Ford E-450 chassis. I dropped in a 200 AH Expert Power Lithium battery. Now I'm reading I need a DC to DC charger. How do I find out the alternator specifications? The owners manual doesn't list it.

According to your battery manufacturer you can only charge at 50amps max. So a 40amp DC-DC charger would work for you. That is what i put on my e450 with the V10 and no problems so far.

[pgandw]

Originally Posted by phrench

I am picking up my Palisade Calligraphy on Tuesday.

I made a decision today and ordered a Renogy 30a dc-dc charger with mppt for towing and my 200w portable solar panels. After consideration of no dc-dc charger, and buying separate mppt solar charger and dc-dc, I decided on the combined unit.

We bought a 2022 Palisade SEL in late January. Came with the factory tow package - which did NOT include 7 pin wiring or a brake controller. Just a 4 pin setup for boat trailer. I had dealer recommended trailer shop install 7 pin wiring and my Tenkosha Prodigy 2 brake controller so that there would be no warranty questions. Kia Engineering refused to honor warranty on a Kia Carnival because of "unauthorized connection of after-market brake controller to the brake system."

Fact is that ANY electric brake controller taps into the brake light switch, and is not the cause of computer malfunctions. Second fact is that depending on how closely coupled your trailer is, tow vehicle may cause some interference with the rear and quarter view sensor software. The software, if not programmed correctly, does not know how to handle "seeing" a trailer constantly or even intermittently so close to the rear of the vehicle while traveling forward.

In the Kia Carnival's case, towing our A-frame camper caused error overflows on the lane assist computations. When enough errors have accumulated, the computer dumps and the Star Wars array goes wild on the dash (I had learned how computers do this from the early software on the H60 helicopter). One time on the Carnival, the ESC tripped, putting the engine in limp mode momentarily. Learned the hard way to turn lane assist off while towing.

Just my experiences, hope yours are different. We'll be towing the A-frame camper with the Palisade on a trip starting 19 April. Towing boats and utility trailer has been no issue so far. Just a reminder - the manual states no towing for the 1st 1200 miles, engine break-in is 600 miles.

Fred W
2019 Flagstaff T21TBHW A-frame, E2 600/6000 WDH
2022 Hyundai Palisade SEL

[Redtickcpa]

Originally Posted by distracto

I feel your pain... My dealer says he is not ordering any more 12v fridges, too many customers come back complaining. We knew what we were getting ourselves into and had a plan before we ordered it.

We had ordered it with a few things that the dealership wouldn't have ordered as a standard like the radiant barrier pack and the fridge. He didn't have any 257BHS models in the lot, so we put a deposit down and hoped we'd like the layout and such. His manager told him I'd lose my deposit if I didn't like the trailer when it arrived because of the fridge...

It's not a good design idea for boondockers, but cheaper for the manufacturer. Imagine the savings on the cost of the fridge never mind every gas line and connections they don't have to make!

I am in the same boat, with a 12v frig (prior rockwood had a two way), dealer orders only 12v frig, i added two 100 ah Dicovery ion, when boondocking the frig runs and runs, we use two CPAP's so the draw is quite large, added a renogy 200 watt suitcase and that helps but the frig is my concern, it draws 13 amps with the roof and external panels i get 18 in mid day then 8-9 thus loosing ground on the batteries. The go power sales men told me that refrigeration units will soon be 12 volt, they are killing us in my opinion. I have a honda 2000 that i change direct to the batteries by a cable that works better than connecting to the shore power connection.

[wolfnwillow]

All us amateurs wanted was to put in a LifePo4 battery and now our heads are ready to explode. Even if we understood everything many of us and I am guessing the OP only understand part of the EE explanations and probably don't have the ability to install half of it. And talking to a few dealers,,,forget about it! I know nothing and I know twice as much as they do.
Don't get me wrong as I have learned quite a bit with all the knowledge I see on these forums but as I said my head is swimming as one thing always seems to lead to another thing to add.
As happens in many thread including two other on the same topic they get hijacked. But that is how we learn. But the OP's questions don't seem to get answered.
But the original question as is mine and regardless of the benefits of a DC to DC charger, what will happen to our TV and/TT alternator or batteries if we do NOT add one. I am speaking of a basic one 100 Ah battery. No inverter.
I know this is an older thread and I may post it this question again as a new one.