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Discussion Starter · #1 ·
Colorado 2022 question.
I just change the battery in my towing trailer to lithium ion, I have solar system on my trailer
I wonder if my battery is full or allmost full on the trailer, the hook up 7 pin will over charge the battery if I drive few hours every day? If yes I will be more then happy for solution.
Thank you
 

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2018 Kinetic Blue Ex-Cab ZR2 V6
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The 7pin pushes the exact same voltage spec as the alternator. Lithium batteries REQUIRE a VERY specific charging voltage that varies with percentage of charge (charging profile). You NEED to add a DC-DC Charger that has the charging profile for lithium batteries.

So basically, no. Your lithium will never properly charge if you just hooked it up to the 7pin.
 

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Discussion Starter · #3 ·
The 7pin pushes the exact same voltage spec as the alternator. Lithium batteries REQUIRE a VERY specific charging voltage that varies with percentage of charge (charging profile). You NEED to add a DC-DC Charger that has the charging profile for lithium batteries.

So basically, no. Your lithium will never properly charge if you just hooked it up to the 7pin.
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Colorado 2022 question.
I just change the battery in my towing trailer to lithium ion, I have solar system on my trailer
I wonder if my battery is full or allmost full on the trailer, the hook up 7 pin will over charge the battery if I drive few hours every day? If yes I will be more then happy for solution.
Thank you
Lithiums require very specific charging profiles to capitalize on their chemistry, as hooooogan mentioned.

You'll need a DC to DC converter, which should live with your LiFePo4 battery in the trailer. Lots to choose from. RedARC and Renogy seem to be the most popular ones. Renogy 40A currently on sale for black friday


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I bypassed the battery charging through the 7 way on my camper for similar reasons. My 7 way just powers the running/brake lights.

My solar keeps everything charged.
 

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Lithiums require very specific charging profiles to capitalize on their chemistry, as hooooogan mentioned.

You'll need a DC to DC converter, which should live with your LiFePo4 battery in the trailer. Lots to choose from. RedARC and Renogy seem to be the most popular ones. Renogy 40A currently on sale for black friday


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IIRC, the trailer hot is rated for 30amps. I would opt for the 20amp DC-DC, not the 40amp, so you don't need to run larger wire.
 

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IIRC, the trailer hot is rated for 30amps. I would opt for the 20amp DC-DC, not the 40amp, so you don't need to run larger wire.
Could be even less depending on what it's fused for. I do recall a thread based on this recently with providing power from it...

But based on the wiring mm2 that seems about right. Unfortunately 20A not on sale... 6mm2 = somewhere between 9 and 10AWG. The chart is for stranded and solid core can handle more.

500W draw of the 40A unit at the 14.6V charging from our alternators is only 35A. You know me... I'd run some 4AWG along the frame with an anderson plug on the end and call it a day.
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Could be even less depending on what it's fused for. I do recall a thread based on this recently with providing power from it...

But based on the wiring mm2 that seems about right. Unfortunately 20A not on sale... 6mm2 = somewhere between 9 and 10AWG. The chart is for stranded and solid core can handle more.

500W draw of the 40A unit at the 14.6V charging from our alternators is only 35A. You know me... I'd run some 4AWG along the frame with an anderson plug on the end and call it a day.
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There have definitely been several threads on this in the past and I'm pretty sure it's always came down to: run a lower-ish amperage DC-DC or run new wire so you can use a higher amp DC-DC.

FWIW, the 20amp is the same price as when I bought one, 4+ years ago.

OP, one thing to look out for is heat. Those DC-DC chargers do NOT like heat. I went through the Renogy and Victron DC-DC chargers before settling on the pricey RedArc BCDC1225D that can handle significantly more heat. During the brutal Vegas summers, the inside of my camper can reach 160+° F, which renders the others useless. I had to learn this the hard way.
 

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Discussion Starter · #12 ·
I bypassed the battery charging through the 7 way on my camper for similar reasons. My 7 way just powers the running/brake lights.

My solar keeps everything charged.
Hi
Can you let me know "what pin" out of the 7 is the one that charge the battery? I think that is better to disconnect that pin. I have inverter to my solar system but the way how it's wired, the car charge the battery by pass it.
Thank you.
 

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Hi
Can you let me know "what pin" out of the 7 is the one that charge the battery? I think that is better to disconnect that pin. I have inverter to my solar system but the way how it's wired, the car charge the battery by pass it.
Thank you.
Look at ARCowboy's middle picture in post #10. It's #4. Note the key notch at the top of the picture for guidance. As the picture states it's as if you opened the flip cap and were looking into the receptacle.
 

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My camper may be different than yours but I just spliced in a “heavy duty” in-line fuse where the camper plug ties into a junction box.

I then just pulled the fuse so power never gets to the battery. It gives me the option to put a fuse back in just in case I have to get power to the battery.

I’ll be the first to admit that my set up is ******* but it’s worked for a decade without any issues.
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Colorado 2022 question.
I just change the battery in my towing trailer to lithium ion, I have solar system on my trailer
I wonder if my battery is full or allmost full on the trailer, the hook up 7 pin will over charge the battery if I drive few hours every day? If yes I will be more then happy for solution.
Thank you
Many people have just plugged into the 7 pin and had no problems. Others report the battery will not fully charge because the charge voltage is too low. Your lithium battery should have (check your product manual) a built in battery management system, aka BMS, that will prevent overcharging. My LiFePo4 battery product manual says the LiFePo4 battery has a very simple charging process and mode: Charge/Bulk/Boost voltage14.4/14.6. Absorption voltage 14.4/14.6. The built in BMS manages charge control so you can't over charge the battery. Interesting that my 2018 Colorado charges at 14.6 volts when in tow/haul mode.

I just installed solar panels and LiFePo4 batteries in my travel trailer but have not had a chance to travel yet so I've been asking the same questions. I just plugged it into my truck (batteries are at 75% charge) and it will charge at about 7.5 amps at the battery. You may need a DC-DC charger if you can't get the battery to charge fast enough or fully charge. I would Just drive it as is and see. Why spend money on something you may not need.
 

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Discussion Starter · #19 ·
Many people have just plugged into the 7 pin and had no problems. Others report the battery will not fully charge because the charge voltage is too low. Your lithium battery should have (check your product manual) a built in battery management system, aka BMS, that will prevent overcharging. My LiFePo4 battery product manual says the LiFePo4 battery has a very simple charging process and mode: Charge/Bulk/Boost voltage14.4/14.6. Absorption voltage 14.4/14.6. The built in BMS manages charge control so you can't over charge the battery. Interesting that my 2018 Colorado charges at 14.6 volts when in tow/haul mode.

I just installed solar panels and LiFePo4 batteries in my travel trailer but have not had a chance to travel yet so I've been asking the same questions. I just plugged it into my truck (batteries are at 75% charge) and it will charge at about 7.5 amps at the battery. You may need a DC-DC charger if you can't get the battery to charge fast enough or fully charge. I would Just drive it as is and see. Why spend money on something you may not need.
Thank you for detailed answer 👍
 
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