DC-DC Converter needed after Lithium upgrade

[LBCOX]

Hope everyone is having a blessed Easter!
2011 3150RL; Preparing to upgrade from FLA to Lithium. I'll need to upgrade my power converter as it is not lithium compatible. I read someone's concern about the charging rate coming from their truck's alternator thru the tow cable; the concern being whether it would damage the LI battery, the power converter, the alternator, etc.
Todd Hensen, lead instructor at NRVTA, recommended installing a DC-DC Converter "somewhere" between the truck and battery (I would assume somewhere in the RV battery compartment.
Has anyone had any battery or charging issues, post upgrade/conversion process? Would you agree installing the dc-dc converter is necessary? If so, where would i buy one, where should it be installed?
I thought I was read to pull the plug on all the necessary hardware, but came across this last bit of info.
Thx for your help!

[PNW Fireguy]

If you are charging LiFePH04 using TV alternator you do want a dc to dc converter to prevent damaging your alternator. Several manufacturers provide them. Only have personal experience with Victron. Does what it’s supposed to do every time.

Victron website has all documentation you can review at your leisure.

[LBCOX]

I have a round 7-pin connector on my truck that I connect my pin box cable to. I haven't owned this RV very long, but I thought I have been charging my FLA while driving down the road this whole time.
So, I would assume that if all I do is upgrade the power converter and put a LIFePo4 in place of the FLA, I would end up charging that battery as well.
Do I install the DC-DC converter on just one post of the battery, or is it like a shunt, across the battery posts?

[PNW Fireguy]

That 7 pin does provide alternator output to charge your FLA battery while driving. The issue is that if you change to LiFePO4 the cell internal resistance is so low that they can accept a lot of charge very fast. This can overload and damage your alternator so the DC to DC charger goes between your alternator and the 5er battery. Sometimes this will require running heavier gauge wire from the engine compartment. Many have installed Anderson connections in the truck beds to allow for secure connection that are easily disconnected. All depends on how much current the charger you select can output.

Take a look at this video for basics surrounding why not to directly charge via vehicle alternator:
https://youtu.be/jgoIocPgOug

[Daryles]

You will not over load your alternator by charging your lithium batteries via your 7 way cable. The tow package has a 30A fuse on that circuit. The most I have measured on the 7 way charging circuit is about 7a.
I installed a Renogy 60A DC-DC charger. I did NOT Disconnect the 7 pin charging wire. I don't always use the DC-DC charger.
A month ago we spent 10 days on Ocracoke Island. We had 3 straight days of rain. No charging from the solar panels. I used the truck and the DC-DC charger twice a day for an hour in the morning and the evening to recharge the batteries on those 3 days. Worked great!!
I think I will get a Honda 2200i companion generator for next time boondocking.

Here's my write up of the install and first time using it.

https://www.montanaowners.com/forums...hlight=charger

[Daryles]

As far as the converter goes, I still have my original converter PD4575K18LS8. It is not Lithium ready, but it does get the batteries to about 90% by manually using the "Charge Wizard" and putting it in boost mode (14.4vdc).
Lithium batteries will last far longer if you stay between 90% and 20%. Toyota figured that out with the Prius a long time ago. We had one for 12 years, never had a battery problem.

[Doug Brown]

I also installed lithium batteries on my 2007 Montana a few years ago. I had to change the progressive converter. I didn’t want to go through the expense of a DC to DC charger. I installed a soft start on my air conditioner. I welded on a rack for my Honda 2000 generator. When it’s hot and we’re going down the road I start my generator and turn on my air conditioner this also charges up my lithium batteries if they are down save a lot of money on time and expense.

[LBCOX]

Thanks for the all the input. I guess I should have added I have a 2016 Ram 2500 as a TV. The dash shows alternator voltage; although I don't know how accurate it is, the voltage does vary as I'm going down the road. I've never seen it go over 14V though.
As I have an older PD4590K18L (not the LS8 version) power distribution box that as far as I know doesn't have a charge wizard function, I will be upgrading that when I go to new Lithium batteries.
I have a brand new Honda EU2200i that I converted straight away to propane (never touched a drop of gas); terrific conversion BTW! My wife is very sensitive to smells (especially petroleum-based products).
I also have a Point Zero Energy Titan solar generator with ground-based solar panels that I have successfully used to power the RV.
I installed a SoftStart on my AC once I found out the Titan & Honda wouldn't run it. After that, everything runs just fine.
Since I'm on a tight budget, the plan is to allow either shore power, Honda, or Titan (in conjunction with the new Lithium-compatible PDI) to keep the new battery (or 2 batteries when I can afford it) topped off when we are parked, and then allow the alternator to maintain the battery(or batteries) to at least 90% as Daryles suggested when rolling down the road, all the while crossing my fingers that the alternator stays healthy. If it doesn't, I'll know the other half of you were right.