Do I need to protect the vehicle alternator if doing a drop in lithium replacement?

[Ynot4me2]

Quick question I hope.
I'm doing a lithium drop in replacement to my LA as a first phase.
I've been seing some info on the web that my truck alternator might take a hit trying to charge the lithium while traveling.
Do I need to disable pin 4 in order to save the alternator or is this not necessary?

[MoonShadow_1911]

Quick question I hope.
I'm doing a lithium drop in replacement to my LA as a first phase.
I've been seing some info on the web that my truck alternator might take a hit trying to charge the lithium while traveling.
Do I need to disable pin 4 in order to save the alternator or is this not necessary?

It's not necessary. On 99% of modern trucks, batteries (no matter what kind) will only pull what the alternator gives them.

[xrated]

Quick question I hope.
I'm doing a lithium drop in replacement to my LA as a first phase.
I've been seing some info on the web that my truck alternator might take a hit trying to charge the lithium while traveling.
Do I need to disable pin 4 in order to save the alternator or is this not necessary?

A couple of things. LFP batteries will allow a lot more charge current (amps) to be drawn into them while charging than FLA and AGM, so there's that. But, most charging circuits on the 7 pin, like you have pictured, has fairly small gauge wire and is protected with a fuse in the truck fuse box. Between the smallish gauge wiring and the inline fuse for that circuit, not a whole lot of charging is being done. Of course, the alternator output size of your particular truck will also come into play, but not as much as the things I just mentioned.

Lots of folks that want to efficiently charge an LFP battery in the their camper, while driving/towing the trailer will install a DC to DC converter on the truck and feed it with a separate wire, and basically not use the built in charging/aux. circuit from pin #4 . And again, depending on the size of the alternator on YOUR truck, you can choose different size DC/DC converters. 30A seems to be a pretty popular size and in most cases, will not be enough to damage the truck alternator...but you really need to figure out the size of the one you have in the truck first, and you can then make a more informed decision. Just don't expect much charging with the stock charging circuit.....it's more like a trickle charging than a decent charger that will actually bring the battery up to full charge.

Edited to add........If you aren't concerned about or wanting to charge the battery as you drive, you can certainly disconnet that wire inside the front compartment of the trailer that comes from Pin #4, so that it has zero affect on the battery, and does not charge or attempt to charge the battery. I would do the disconnecting in the trailer end of it, so that the #4 pin is still working correctly on the truck, just in case you have another trailer or tow a different trailer that has electric brakes and an onboard breakaway battery.

[xrated]

It's not necessary. On 99% of modern trucks, batteries (no matter what kind) will only pull what the alternator gives them.

The problem with that statement ^^^ is that LFP batteries, depending on how much battery capacity it is, can pull EVERYTHING that the alternator can produce, and burn the alternator up. The alternator will try and supply the load.....and the LFP battery will take a lot of that, again, depending on the size of the battery, the integrity of the wiring, and connections.

[traveldawg]

Steph,
Check out this video on charging from an alternator. Around the 12:30 mark he explains some things about a direct connection to the alternator. After I saw it I was pretty much convinced to install a DC to DC charger between my truck and camper.

An alternative you can just not charge the battery at all when traveling. I only found this out after installing my DC-DC charger. I don't travel long enough on anyone day to appreciably discharge my 200ah battery when going from one camp ground to another. So mostly I leave the DC-DC charger off and let my battery get exercised; the RV converter brings the battery back up to a full SOC once I get connected (which is about 99% of our 'camping'.

An advantage of the DC-DC charger is that it keeps the charge voltage constant; generally at a voltage you set that is spaced by your battery manufacturer. I suppose there are other advantages too, but I kind of rationalized my purchase using that logic.

So - can you charge directly from the truck - yes. But do you want to really do it that way.

[Ynot4me2]

Thanks you 2 @xrated @MoonShadow_1911.
I should of specified that I'm not looking at efficiently charging the lithium but more looking at not ruining my alternator. However I wouldn't mind a little charge.
I will eventually go with a DC to DC unit but not for now.

[JKellerJr]

Quick question I hope.
I'm doing a lithium drop in replacement to my LA as a first phase.
I've been seing some info on the web that my truck alternator might take a hit trying to charge the lithium while traveling.
Do I need to disable pin 4 in order to save the alternator or is this not necessary?

Unless you change the stock wiring on the truck you do not need to do anything. It will not hurt the trucks alternator. The issues you see floating around the internet are caused by bypassing the trucks 7 pin and connecting directly to the alternator.

I get around 7 amps to the trailers batteries while towing. Almost enough to keep up with the residential fridge draw.

[huntindog]

Quick question I hope.
I'm doing a lithium drop in replacement to my LA as a first phase.
I've been seing some info on the web that my truck alternator might take a hit trying to charge the lithium while traveling.
Do I need to disable pin 4 in order to save the alternator or is this not necessary?

I like you (probably) have read many conflicting reports on this.
Since I always boondock in remote locations, an aternator failure could be a major problem. So I elected to pull the fuse disabling that fuction. With my sizable battery bank, and 1860 watts of solar, this has been working for me. I even run the gas fridge on electric when under tow.I am not sure if this thinking works for you though.

[Ynot4me2]

Steph,
Check out this video on charging from an alternator. Around the 12:30 mark he explains some things about a direct connection to the alternator. After I saw it I was pretty much convinced to install a DC to DC charger between my truck and camper.

An alternative you can just not charge the battery at all when traveling. I only found this out after installing my DC-DC charger. I don't travel long enough on anyone day to appreciably discharge my 200ah battery when going from one camp ground to another. So mostly I leave the DC-DC charger off and let my battery get exercised; the RV converter brings the battery back up to a full SOC once I get connected (which is about 99% of our 'camping'.

An advantage of the DC-DC charger is that it keeps the charge voltage constant; generally at a voltage you set that is spaced by your battery manufacturer. I suppose there are other advantages too, but I kind of rationalized my purchase using that logic.

So - can you charge directly from the truck - yes. But do you want to really do it that way.

I know I will eventually be installing a DC to DC unit. It is the safest and most efficient way of charging from a TV. There's just a few other things that I have to do first like replacing the convertor/charger to lithium compatible and the unit that I currently have is the all in one. So the entire breaker/fuse panel has to be replaced.
In the meantime I was hoping to stay as is with a little charge coming from the alternator but not at the expense of it failing.

[Ynot4me2]

Well now, since I dont have solar yet (phase 4 of my project), I'm leaning towards accelerating installing the DC to DC unit. We will sometimes boondock or use HH/BW for a day or 2 while on our trips. I could disable the charging from our TV but then I would have to rely on our geny if we run out or to low (not likely to really happen with 305ah with no invertor use).
Larry, can you re-post that link. The video was only 2min on the one you posted originally.