Does TV charge lithium?

[AZMike]

Maybe I missed it, but I have not found a post on the subject. Will a tow vehicle with just a lead acid battery charge a trailer with a lithium battery while towing? My truck does have the tow package with the high output alternator, but it is my understanding that the "high output" is just the current, not higher voltage.

[Ynot4me2]

I am by far no expert and I'm still learning. In fact I'm as green as they come on this subject. Hopefully the more experience will chime in soon and correct me. Yes your TV will charge but not effectively. Best to get a DC to DC charger for the TV an tt hook up.

[BB&LAB]

The short answer is yes. The long answer is whether lead acid, AGM or lithium batteries the charge to the batteries is minimal because the distance from the alternator with minimal wire size means there is significant voltage drop. So know your batteries will receive a charge while driving but I would not depend on it to provide a full and complete charge.

[bertschb]

... Will a tow vehicle with just a lead acid battery charge a trailer with a lithium battery while towing?

My understanding is most trucks will put out 7-9amps to the RV batteries and it doesn't matter if the RV has lead acid or Lithium.

[AZMike]

My understanding is most trucks will put out 7-9amps to the RV batteries and it doesn't matter if the RV has lead acid or Lithium.

True, but my main concern is that lithium requires a slightly higher voltage to fully charge, and if we are boondocking many nights is a row will my TV be up to the task of keeping the battery "topped off".

[Bookumdanno]

Here is a chart on wire sizes and current.
Automotive Wire Amperage Capacity Chart

Recommended Length and Amperage for Automotive Wire while maintaining a 2% or less voltage drop at 12 volts
Automotive Wire Size 5 Amps 20 Amps
16 Gauge Wire (AWG) 11.5 ft 2.9 ft
14 Gauge Wire (AWG) 18.4 ft 4.6 ft
12 Gauge Wire (AWG) 29.4 ft 7.4 ft
There other problem will be your TV charging system. It only monitors your TV battery, so it will decrease as that battery is charged. It could care less what's at the trailer end. Your best bet would be a DC to DC charger like Ynot4me2 stated above.

[psy1234]

The standard 7 pin connector does not have sufficient amperage to charge lithium batteries. Lithium batteries can take a lot of amps for charging. The best way to charge them with a tow vehicle is with a DC-DC charger as mentioned. That is wired with a bulky wire from your alternator to the DC-DC charger to you batteries. They range in capacities but usually 30-50 amps. A 50 amp DC-DC charger would charge a 200 amp hour lithium battery array from dead to full in 4 hours of driving. The details of wiring it are beyond me - I will have a pro do it.

[Luke611]

So my hopes of the TV fully recharging the trailer batteries are in vain? I guess solar panels will be on the horizon for us.

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[DarthMuffin]

Yes, but in my experience it maxes out at 50-70% state of charge because the lithiums take a higher voltage to charge (14.4ish and the alternator is probably around 13.8). I disconnected our TV charging since we have solar now that charges just as much while driving. There are very nice DC to DC converters to fix just this problem, and you can limit the charge rate with them too.

[deeuubee]

@AZMike - what size battery are we talking about?

I have a large alternator, I get 14.5V at the battery, and I only get 13.1V / 7A at the trailer battery from the 7-pin.
That is below the 13.2 nominal Lithium battery voltage, so it might maintain the current low SOC, I doubt I'm charging much.

Even if you could get 14+V back there, a 100Ah battery at 50% state of charge will take over 7 hours to charge at that rate.
Do you really want to idle your truck that long?

The only realistic options for boondock charging are:
1 - Solar
2 - Small generator with specific 60-80A Lithium charger. Couple of hours and done for a few more days.

If you don't want to run the generator that long... do it an hour a day.