Double battery bank question

[mhjackson123-ESC]

I currently have surveyor 202RBLE with a pair of newish 6V AGM batteries (200+ Ah) in the tongue box. I am thinking of getting a 230 or 280 Ah Lithium and putting it under the bed and using that battery to power an inverter (using the inverter prep by the water heater). (thinking GoPower SW1500-TS).
The current factory solar system is hooked up so that it charges the pair of 6V batteries when the master battery switch is off - even with the winter cover on! I also have a GoPower solar panel and controller from another trailer that I could add to this trailer.
I am wondering if it makes sense to essentially have two separate 12v systems (The lithium one could be charged when on shore power or by the second solar system if I install it, the existing system would be left essentially untouched).
I could also put in a 1-2-both-off switch which could allow me to share the systems... (charge the lithium from the main converter?) Would that make sense or am I better off to keep the systems separate?
I hope this all makes sense... By adding a separate system, I don't have to make a hole to reach the battery box and can leave the existing wiring as is...

 

[pgandw]

With 2 different battery types, you cannot safely put them in parallel. Huge fire starting currents will flow as batteries equalize voltage. Been there, done that, saw the pretty blue flame burning hydrogen makes.

 

[tomkatb]

Buy two or more lithium batteries and put them under the bed. Sell the AGM batteries and put a locking toolbox there.

No ab switches or complex switching stuff.

Inverters are BIG battery users. Modern rv’s use a ton of power. Rewire once.

KISS

More smaller batteries are for sale today. Two .200 ah batteries might fit on the front. But, lock them up!

 

[Aussieguy]

what do you want to power from the INverter

TV and Cpaps can use 12v to 24v converters
coffee made on the stove is just as nice as a Kurig'
I get along quite well on just 12v

If I was you.. keep the 6v you got until they do NOT provide the power you need
the 6v will work if you need some small Inverter usage
Add 600w or more of solar to the roof IF you intend to be offgrid for days at a time
if you only want to use the trailer once in a blue moon for longer trips ... you can get by with a generator
and maybe improve the 7pin charging by adding a dc-dc + wiring

or if you want the benefits of Lifepo4 .... if you got receipts for the 6v try and and sell them?

would NOT try and add 2 x 12v systems

what style of camping ...
weekends ... maybe a week but on shorepower ............. just add a good solar string
OFTEN boondock a week or more at a time with no hookup ......... Lifepo4 + solar works in many areas of the lower 48

 

[mhjackson123-ESC]

Thanks for all the suggestions. Gives me something to think about. My current system gives me around 110 Ah of usable energy (215Ah AGMs drained to 50%) which is definitely enough for a long weekend of boondocking in the trees with an occasional boost from a generator. The 400W of solar definitely helps though not always the greatest in BC! Replacing the 2 6V with a single 12V 230 or 280Ah LiFePO4 would effectively double or triple the available energy since I understand one can almost completely drain an LiFePO4. Is there much benefit to going to a single large battery over two or 3 smaller ones (eg 3x 100Ah)?

 

[Aussieguy]

if you go 2 batteries if one dies you can still use the other

if you got a heavy load 2 x batteries may be able to supply the load better than a single one
make sure you look at the DISCHARGE amps of the battery , make sure it suits your loads

ex: you want to use a inverter
max load you want to use is .......... 2000w = 166 amps@12v
1 x 100ah battery with 100amp BMS won't power the load
whereas 2 x above battery will do 200amps in parrallel

 

[dave neiser]

I also have the 202rble and looking at Lithium batteries. Installing under the bed or in the front crossover storage would require getting the battery cables from the exterior to the interior of the trailer. Not looking forward to removing the under-belly insulation to do this. Is there another entrance that I'm missing ?

 

[Aussieguy]

my trailer only had cloth underbelly at the very front plastic underbelly started about 2 feet further back
allows for easy access to junction box 7pin , disconnect switch and breakers

took 5 minutes to locate a place to drill a couple of holes
drilled separate holes just big enough for one cable 11/16"
removed the original cables from the wiring harness , so had just the 2 cables to tend with

whole job of relocating batteries took about 2 hours
included putting tongue jack and 7 pin wiring back together with zip ties
looks like it came from factory

 

[mhjackson123-ESC]

I also have the 202rble and looking at Lithium batteries. Installing under the bed or in the front crossover storage would require getting the battery cables from the exterior to the interior of the trailer. Not looking forward to removing the under-belly insulation to do this. Is there another entrance that I'm missing ?

That is why I have been hesitant to start... I am going to have to take a closer look.
Aussieguy suggests that it is not as hard as it looks

 

[mhjackson123-ESC]

my trailer only had cloth underbelly at the very front plastic underbelly started about 2 feet further back
allows for easy access to junction box 7pin , disconnect switch and breakers

took 5 minutes to locate a place to drill a couple of holes
drilled separate holes just big enough for one cable 11/16"
removed the original cables from the wiring harness , so had just the 2 cables to tend with

whole job of relocating batteries took about 2 hours
included putting tongue jack and 7 pin wiring back together with zip ties
looks like it came from factory

Where did you relocate the batteries? Under the bed or in the pass thru?

 

[Aussieguy]

underbed............... on my model it is the same thing

most travel trailers have combined underbed / pass through
5th wheels and motorhomes can have a true pass through