A group 31 with 105AH is likely the Lifeline gpl-31t, the gpl-31xt has 125AH.

Good batteries, but....
AGMs in deep cycle duty really need, more so than their cheaper flooded/wet brethern, a true full charge every 7 deep cycles or more often, AND when drained to the 50% range, need no less than 20 amps charging current per 100Ah of capacity.

If they are never given this much current when deep cycled and if they are cycled often and only recharged to 95%, they will lose capacity quickly, and disappoint greatly, considering their reputation, and price.

Lifeline are pretty much top tier deep cycle AGMS, but no lead acid battery is immune to chronic undercharging and AGMS can be tickled to death with 'trickle' charge currents, in deep cycle applications.


https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/

as for the TV,

I've got a 13.3 inch RCA 12vDC TV for many years now. While not very big I have it on a long double elbow swing arm to position as needed, whether in my chair or lying in bed.

Turned off, but still hooked to 12v, it draws 0.09 amps. This parasitic draw is the TV awaiting the signal from the remote to turn on. I put an inline rocker switch on it to eliminate this draw when not in use.

Rounding this parasitic draw upto 0.1 amps, every 10 hours it draws 1 amp hour from the battery.
So one single 100 amp hour battery would be 50% discharged by this parasitic load in 500 hours.


The TV is rated for 18 watts, which is about 1.5 amps, but it can only draw that much juice when the brightness is turned all the way up, and the volume is too, and it is spinning a DVD.

Generally it draws 0.9 to 1.1 amps, 10 to 14 watts or so. It has Zero issues with 14.4v or 9.7v DC input voltages.

An inverter is generally no more than 85% efficient. If a AC to DC powerbrick is used( and could be inside the TV itself) they too are no more than ~ 87% efficient, so this can be a big waster of battery power.

An inverter can also induce a 60HZ buzz into the speakers, and if watching over the air TV, will knock out some TV stations as it is electrically noisy.
A pure sine wave inverter might eliminate the Buzz, but likely not the TV interference, and they are usually slightly less efficient than Modified square wave inverters.

Ciggy plugs and 12v powerports are extremely poor electrical connections, and more so with time and when they are asked to pass more current. Even the best ones will become problematic, it is just a matter of time.

Best to eliminate them when possible. but do consider they have an internal glass cylinder fuse to protect the wiring from plug to tv itself, which is part of their issue in the long term, all that extra resistance, along with spring loaded connections built as cheaply as possible.

I've no experience with 12vDC TVs that are susceptible to issues with voltages far outside of 12v, as might be seen with a low battery to too long and thin of wiring to the tv from the battery.

There are devices to deliver a stable output voltage. A buck/boost converter can deliver a very steady voltage, and can be upto 94% efficient, but they can induce the electronic noise which can kill TV stations. I use B/B converters to power/speed control 24v fans and at certain speed ranges it will knock out my VHF channels 8 or 10, which are my two strongest stations.

If searching for buck/boost converters, make sure the description says both 'buck/boost' and 'step up and step down converter'. They generally have limits of 5 or 10 amps. I've had no luck with 5 amp versions at well less than half their rated amperage, but no issues with the 10 amp versions.

My RCA TV, several years ago had issues with one of the LEDS on teh bottom going out and causing a V shaped shadow and flickering. I disassembled the TV and applied some Caig DeOxit D5 to the ribbon cable connectors and the issue has not arisen in many years, though it did not go away immediately.

My major issue with the TV, has been the remote. The battery contacts and that internal plastic which supports them got damaged and need reinforcement.

If you can find the figures listed on a TV power brick, know that is the maximum current the brick can handle or the TV can ask for. It is not the current the TV will always consume, only the maximum it can possibly draw.
Actual consumption in use varies depending on brightness of the screen, and volume, and if it has a DVD spinner and is spinning it and using more CPU power.

NO experience with Smart TV's steaming internet video, but my laptop the average consumption goes from 32 watts typing this, to about 55 watts streaming videos at 720p.

So two group 31 house batteries if the TV were the only load will have little issue for X amount of time, but other electrical demands could make or break them.

Also know while an alternator might be able to deliver its rated capacity, it can only do so at 2000+ engine rpm, when cold and when the voltage regulator is asking for voltages in the mid 14 range.
getting even teh best healthiest lead acid batteries from 80% to 100% requires no less than 3.5 hours, assuming mid 14v is held that entire time, which few voltage regulators will allow for fear of overcharging the starter battery.

Far too much of the motoring public act like the alternator is free energy that nearly instantly recharges a battery to full.
Don't be like the general motoring public.

The battery itself decides how much amperage it wants to accept at the electrical pressure( voltage) reaching the battery terminals.

The BEST healthiest AGM batteries still need no less than 6 hours of charging to reach full from 50% and this assumes a high amperage source for that uner 80% range and one which can hold 14.4v+ for the final ~4 hours.

So even a long drive home is highly unlikely to return the battery to a true full charge, and one should employ a plug in charging source which can complete the charge.
Note one will likely have to trick the average smart charger into doing this. Trick it into restarting by loading the battery until voltage drops to below 12.7 then restart charger, over and over.

210 Ah of Lifeline AGM can only be considered truly full when held at 14.4v, amperage tapers to 1.05 amps or less.
Full charge cannot be determined at lesser voltages.

If you want the Lifelines to last, achieving this threshold is required, regularly and becomes more important the deeper the discharge, or the longer since it was last achieved.

Note if it has been a long while since it was achieved, that 6.5 hours minimum from 50% to 100% might double or triple until that threshold is attained, and No garage grade 'smart' charger ever accomplishes it.

The Green light on Smart chargers ONLY means the charger has decided to revert to 'float' voltage. The green light indicates the battery is charged enough to start an engine, not that it is fully charged as its marketer's would have you believe.

The marketers of smart chargers will try and make you believe the smart charger will fellate you afterwards too.