Adding second Battery

[Richard49]

I have gone back to a TT from a MH and desire more DC amperage. I use my TT in the winter traversing from cold to warm climates and back sometimes covering over a thousand miles one way and I prefer to dry camp overnight while on the road as I'm not carrying any water. I'm in need of increasing my amperage to allow me to run my furnace during the night while I'm sleeping so I have a couple of questions I hope ya'll can answer:

1. To keep the same voltage (12v) I'm planning on connecting the batteries in parallel (positive to positive and negative to negative) with ground to one battery and power to the second to insure they draw equally. Is this the right way?

2. How long should I be able to use my furnace on this configuration?

3. Wired as above will the TT charging system read the two batteries as a single battery and charge until both are full and then turn off or do I need to do something else?

4. Does the TT 12v system draw from my TV alternator when it is connected and the engine is running?

Thanks in advance for your advice. Have a great New Year!!!!

[NVGun40]

The simple answer is:
1. Yes -- However, it is highly recommended both batteries are identical.
2. depends on the type and amp hours your batteries are rated for. However, I think it is safe to say you could get two nights (without a charge) easily if you are only running the furnace at night.
3. No you do not need anything else. However, you may want to consider a more robust converter, though it is not necessary.
4. Yes. However, the charge is much slower than when hooked to a generator or shore power. A way to increase the charge would be to get a higher output alternator and have a specific charging circuit wired through your TV to the trailer plug in. Yet, based on what you are saying it sounds like you will be travelling most of the day and parking only at night, so the battery charge should be ample.

I say this without knowing what your TV or trailer or the year of each is. Many trucks built these days with tow packages already have very good alternators and are wired to provide better charging to the trailer. As well, many newer trailers have converters which are very good for the task.

For what it is worth, we almost always boondock. Our trailer has two batteries, both of which I upgraded to high quality Marine Deep Cycle high amp hour batteries. They are not cheap. I have managed 5 days on batteries in below zero (not just below freezing) temps, running the on board furnace at 45 degrees at night only, and supplementing with a Big Buddy (indoor safe) portable heater during the day and in the mornings and evenings. I turn the onbaord furnace off during the day, and NEVER above 45. The fans suck too much power.

[Nukeneck]

Q1 - Yes, the wiring diagram you described is the most efficient for a two 12v system.
Q2 - Depends on how much of your lights, fans etc. you use in the trailer that drain the batteries. This should certainly keep your furnace going overnight as long as the batteries have a full charge.
Q3 - Yes your charging system will read both batteries as a single battery because of the configuration, no you don't need anything else
Q4 - I'm not 100% sure but I believe it does. Your truck will help trickle charge your batteries though

Hope this helps

[Mustang65]

What type TV are you using?

As mentioned the charging capabilities from the TV (most all) are limited by the small diameter wire between the charge controller unit and the TV's outlet at the back of the truck. Add to that the wire that is in the TT's cable that connects to the TV receptacle, which is also a small diameter wire. Both restrict the amount of Amperage that travels from the TV's charging source to the batteries in the TT. Ford also does not consider the 12volt wire to the trailer a charging wire, but one to supply basic 12 Volts to the trailer.

So even if you have a 200 amp alternator in the TV it is not going to help your TT batteries with the current wiring. On earlier TV's that do not have the trailer charging modules (microcontrollers that control current flow), you could wire in a 8AWG cable from the battery to the trailer outlet at the back of the TV, now with the modules it can confuse the main computer and may cause other issues. You could then rewire the TT's cable that connects to the TV with a larger AWG cable also.

If you do not drop your TT's battery voltage below 12.0 volts, and you are driving most of the day, you should be able to put a good charge back into the batteries. I would recommend installing some inexpensive digital voltage/amp displays to give you an idea as to where your batteries charging is. Anything is better than the useless LED's that come standard with the TT.

Don

[Richard49]

Thanks for the info - it helped solidify my thinking.

My TT is the 2016 Jay Flight 33RLDS. My TV is a 2015 Silverado Duramax 4x4 with the upgraded tow package which includes the over sized alternator. I don't even know the TT is there when towing and the mpg is great.

My TT battery is an Interstate Marine/RV HD24-DP 405 CCA 505 MCA and I intend to get the same battery. We have an Interstate dealer here in town so after the weekend I'll be checking with him as i hope to leave around 1/12 for a couple of weeks.

I have a Champion 4500 generator that I usually throw in the back of the truck but don't like using it except when I'm up and around - too many thieves around which is why I want to use my battery pack for night time boondocking.

All we'll be using is the furnace all night and a light or two (LED) before we go to bed and when we get up. I'll probably check it real close the first night as I get up several times a night anyway.

Thanks again for the info and have a great new year!

[Seann45]

Rich why not go with 2 deep cycle golf cart batteries.. they will have more power and longer life just connect pos to neg to get 12 vdc