Charging Lifepo4 via Chevy 3500 RV Motorhone using a dc2dc charger

Hello my questions pertain to
Charging Lifepo4 via Chevy 3500 RV Motorhone using a dc2dc charger off of the alternator.
●What is the rule to calculate the Max Amp of the DC2DC Charger for LifePo4 batteries
• Is this dependant on size of Battery •What max Amps to charge 100ah vs 260ah?

●Alternator Specs Requirements
What is needed to manage the extra load?

Backstory:
Trying to have alternative to proposed solar for charging battery bank.
If I could get battery bank to charge while driving RV w existing Alternator & additional equipment or replacing w appropriate Alternator, I can then budget next season for solar install.
I cannot afford to purchase both Solar & Batteries in same year.
Thus trying to get Alternator specs Requirements
Looking To Understand additional charge control requirements for LifePo4 when using vehicle & Alternator load.
Thx

Your alternator must be rated to handle the maximum current and the duty cycle needed. Some are smart and will taper their output to protect themselves when they get hot. Many will burn themselves up.

I would personally target a maximum sustained output of 50% rated, i.e., if I determined I need 100A for charging + normal loads, I would want an alternator rated for 200A.

Yes as said above, the limiting factor will most likely be your alternator.

This is what I am going to use on my 2009 2500HD.

KISAE DMT1250 Abso 50A DC-DC Battery Charger

Webpage

I am adding a second alternator to just charge my house battery. I will then have control of the amps and the temperature.

sunshine_eggo said:

I would personally target a maximum sustained output of 50% rated

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I sized my DC to DC charger so as to never exceed 65% of my rated alternator capacity. I have second guessed my self several times thinking I was being too OCD conservative.

Your 50% number makes me feel better.

I would still add a temperature gauge on the alternator as you also need to remember modern cars and trucks use a lot of power with heated everything and lots of electronics running. A $10 gauge is a lot less than a $200 alternator. With that in mind think about a switch to turn off house charging from the cab.

Larry-Cleveland said:

A $10 gauge

Click to expand...

Thank you for your suggestions. Can you provide a link to a guage that you recomend?

Thanks again!

One sensor on the alternator and the second on the battery.

Amazon

Larry-Cleveland said:

One sensor on the alternator and the second on the battery.

Amazon

Click to expand...

Thanks for taking the time to find that link.

I notice that the description says the temp probe wires are 100mm/39.3” long; but 100 mm is only 3.9 inches long. I suspect the actual length is 39” and would need to be extended in my case to mount the monitor in the cab of my vehicle.
Also, the probes are not ring terminals which would pose a mounting problem for me.

Thanks to your original comment, I have been searching the web for a temperature probe with ring connectors and, so far, I have only found probes with short wires that would need to be extended.I think extending the wires would be possible.
I will continue searching to see what is available.

Thanks again.

You can use something like a grounding lug to hold the probe in place. I made my own, but any Bog Box store will have some.