Gen 1 is Dc to Dc converter needed with lithium?

215 Views 7 Replies 3 Participants Last post by snydmax, 10 d ago

Trapper

Discussion Starter · 11 d ago

I have installed a lithium 100Ah on my trailer and I have seen online in a few post about this being needed but not really anything backing the reason. I am not counting on my alternator charging the battery, I have solar and will do little boondocking but wanted the extra power for the night or two we do go.
Will this do damage to my alternator in the long run? I would rather put that money towards sumo springs

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snydmax

· #2 · 11 d ago

My trailer is set up with a 50ah lifepo4 and i charge it while driving without a dc-dc setup.

the 12v from the 7-pin connector is run through my solar charge controller which cleans up the power and ensures the lithium battery is happy… it’s nowhere near the 30a charging you can get with dc-dc, but offsets the fridge’s draw and helps to top-up the battery while driving between points.

the clever bit with this setup is a 3-pole “on-off-on” switch that lets me select between solar-none-truck for 12v input.

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Trapper

Discussion Starter · #3 · 11 d ago

snydmax said:
My trailer is set up with a 50ah lifepo4 and i charge it while driving without a dc-dc setup.

the 12v from the 7-pin connector is run through my solar charge controller which cleans up the power and ensures the lithium battery is happy… it’s nowhere near the 30a charging you can get with dc-dc, but offsets the fridge’s draw and helps to top-up the battery while driving between points.

the clever bit with this setup is a 3-pole “on-off-on” switch that lets me select between solar-none-truck for 12v input.

Yeah I don't have that option on my solar charge controller, mine is LA,LI or AGM. I will usually have the battery charged up when leaving. I am just more concerned with the 2012 F150 ecoboost original alternator being strained after boondocking. But maybe the solar will do most of the work and it will be fine.

Also I am not sure the 7 pin goes through the solar charger but trying to get the wiring schematics to see how everything is wired up.

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Trapper

Discussion Starter · #4 · 11 d ago

snydmax said:
My trailer is set up with a 50ah lifepo4 and i charge it while driving without a dc-dc setup.

the 12v from the 7-pin connector is run through my solar charge controller which cleans up the power and ensures the lithium battery is happy… it’s nowhere near the 30a charging you can get with dc-dc, but offsets the fridge’s draw and helps to top-up the battery while driving between points.

the clever bit with this setup is a 3-pole “on-off-on” switch that lets me select between solar-none-truck for 12v input.

Did you run the 7 pin to the solar or did it come from the factory that way? My 7 pin goes to the positive fuse directly to the battery and I am wondering if your solar charge is setup for that or if I can run mine through the the solar charger.

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Trapper

Discussion Starter · #5 · 11 d ago

snydmax said:
My trailer is set up with a 50ah lifepo4 and i charge it while driving without a dc-dc setup.

the 12v from the 7-pin connector is run through my solar charge controller which cleans up the power and ensures the lithium battery is happy… it’s nowhere near the 30a charging you can get with dc-dc, but offsets the fridge’s draw and helps to top-up the battery while driving between points.

the clever bit with this setup is a 3-pole “on-off-on” switch that lets me select between solar-none-truck for 12v input.

Ok I know I keep coming up with more questions but... why a 3 pole switch? Could you not just run the 7 pin into the same input as the solar? It seems to me like it would be like adding another solar panel and the solar charger would adapt. I may be way off as I not know what I am talking about lol

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mass-hole

· #6 · 11 d ago

The charging profile for a litium battery is different than a lead acid, thats why your supposed to use a dc to dc charger. Thats one reason.

but also I believe the output voltage of an alternator is higher that what LiFePO4’s like. They really dont like being above 14.3V and their resting voltage(when disconnected from power) is 13.6 at 100% soc.

I dont charge mine all the way either. I usually let them come up to 90% which is more like 13.4V

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Trapper

Discussion Starter · #7 · 11 d ago

mass-hole said:
The charging profile for a litium battery is different than a lead acid, thats why your supposed to use a dc to dc charger. Thats one reason.

but also I believe the output voltage of an alternator is higher that what LiFePO4’s like. They really dont like being above 14.3V and their resting voltage(when disconnected from power) is 13.6 at 100% soc.

I dont charge mine all the way either. I usually let them come up to 90% which is more like 13.4V

I don't think the alternator will overcharge the lithium or nothing I have read about it at least. I was more worried about the alternator but I guess with a small gauge wire and the distance it should not be a problem. If I wanted to use the alternator to charge the battery I would want a Dc to DC direct charge controller hooked directly to the alternator with the correct wire to pull the amps, but not my concern. I have enough solar for what I use.

But I am intrigued by the idea of it going to the input of the solar to clean up the power going to the battery, or I am just over thinking it.

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snydmax

· #8 · 10 d ago

mass-hole said:
The charging profile for a litium battery is different than a lead acid

This is why its ran through the MPPT solar charge controller… trucks “12v” is converted to what the lithium wants

Trapper said:
Could you not just run the 7 pin into the same input as the solar?

I suppose you could… the original builder of my trailer did it this way. Not sure if the 3-pole is necessary but have no reason to change it. FWIW, ive got a 100w suitcase solar panel which pretty well maxes out my 10a charge controller. It also means i never have both inputs “hot” simultaneously. I like being able to have the switch off when connecting the solar panel to prevent arcing at the plug… once it’s plugged in, flip the switch and your charging. If desired, I can also prevent the trailer from drawing on the trucks system by switching to “off” position

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