Add third 12V battery in parallel to travel trailer?

[ScottyP5947]

Hi all -
I am looking to add a third battery to my TT. It has 2 12V Deka deep cycle/marine batts that are just under 1.5 years old. Will I run into any issues with adding a third 12V batt? Should I try to match specs with my current batteries? After adding, I plan to use them until they are junk and replace with Lithium ion - hopefully 3 or 4 years from now.

Thanks for your input!
Scott

[pianotuna]

Scott P,

Make sure you balance the wiring for the batteries. I would go with the biggest meanest cable I could for all the wiring between jars and inverter.

[ScottyP5947]

Hello all - me again. Just wanted to update on this. I have a third battery, made a plywood (3/4") extension shelf so I can fit all three batteries in between the trailer tongue rails. I tried to run my microwave off of the 1500 watt inverter that I had and it barely runs it, plus the inverter goes into alarm while it's running.
For now, I will just enjoy the extra time between needing to run the gen with the bigger battery bank and run the gen when I need to make popcorn in the microwave. I am also adding a third 100W solar panel.

As for the wiring for the battery bank in parallel, I want to do it with the largest gauge wire that is reasonable. From my research I have found that 4/0 is the biggest that's normally used, I already own a hydraulic lug crimper so should I just go for the big 4/0 and be done with it? Or is the 4/0 complete overkill for interconnecting the batteries? What would you recommend?
I am attempting to future-proof myself, because I know I will be adding a beefy inverter in the future. I will connect to the TT 12V system using 2 gauge wire (I have some left over from another project), no need for it to be crazy big when the TT uses 6 gauge. Of course, the inverter will be wired with 4/0 when the time comes.

Thanks for the advice!
Scott P

[SoundGuy]

Ozlander wrote:
To run the microwave, make sure you get a True Sine Wave inverter (TSW).

Never have heard that term - most manufacturers would advertise it as a PSW (Pure Sine Wave) inverter.

[Ozlander]

To run the microwave, make sure you get a True Sine Wave inverter (TSW).

[pianotuna]

scotty can you resize the width of the photo--it makes reading text none too pleasant. Just set the width to 375.

I would jump to a 2k inverter rather than 1500. Inverters are mostly posted in VA and that is a bit misleading as to actual capacity.

My microwave draws 1591 watts, there is surge to deal with on top of that.

[Sam_Spade]

ScottyP5947 wrote:
as well as plan to add a 1500w inverter so I can make popcorn in the microwave without firing up the gen.

Now you are getting close to a justification for more battery capacity.

BUT....a 1500W inverter will require a bit more than 100 amps, continuous 12 V input, if you get anywhere near its top capacity.
That will require close attention to the 12 V input wiring....and ventilation of the inverter.

SO....I don't understand the aversion to running the generator.
Do you ever stay in a place the prohibits generator use ??
If not, I personally think you are killing an ant with a shotgun here.
When you want to make popcorn, run the gen and leave it on for at least an hour. That is an hour that you won't have to run it later to replenish the batteries.

[ScottyP5947]

Yeah I don't understand that comment, I didn't even see his earlier one be claimed to have made. Maybe with a different name? An extra battery will add more AH, that is a given.
And yes, I completely agree with the statements about adding more solar being a good idea AND about my camping style. I haven't had any issues making my current setup work for us as a family. I just added a 32" TV and a small inverter too run it, as well as plan to add a 1500w inverter so I can make popcorn in the microwave without firing up the gen. I think I'd still make it with what I have but I'm just looking for more breathing room energy wise. I have 100% LED now, I replaced my only incandescent light, the porch light, with an LED. That should help a little. I plan to increase solar as I can, up to 4 panels total. I keep thinking I want to mount one or two up top but then I'll be camping in the shade and will be wasted. With my 200w of panels, I've already been in situations where they make more electricity than I need - in the desert of course.
I still think I'm adding a third battery and maybe a third panel depending on how the first camping trip of the year goes. Hopefully with no gen usage!
My coach has this up front - I'm guessing it's for DC connections to things like my powered stabilizers, right?? Do they sell a DC distribution block with breakers that I can use to clean this up? I don't like the live bus bar on the top. Obviously not the end of the world, but while I'm in there.... 🙂
Thanks
Scott

[pianotuna]

Blazing,

More storage just means longer between complete recharges. 200 watts is only going to do that with the RV in storage. Double to 400 watts and the bank may generate 2 kwh per day, plus run the RV once the bank is filled.

Blazing Zippers wrote:
Sam Spade, Wouldn't adding another battery add the amount of available power? If you had one battery at , say, 100--and added another battery at, say, 100---wouldn't that add up to about 200? Now add another battery at, say 100--wouldn't that add up to 300 total?
Not saying this is something I would actually do, but I have explored the possibility of a third 12 volt battery in my battery bank.
Just questioning....

[Sam_Spade]

Blazing Zippers wrote:
Sam Spade, Wouldn't adding another battery add the amount of available power? If you had one battery at , say, 100--and added another battery at, say, 100---wouldn't that add up to about 200? Now add another battery at, say 100--wouldn't that add up to 300 total?
Not saying this is something I would actually do, but I have explored the possibility of a third 12 volt battery in my battery bank.
Just questioning....

Yes. But if your normal situation does not run the existing batteries down overnight......or between otherwise allowed generator runs.....then all you are doing is adding reserve capacity.

You will not have to recharge as often but it will take longer.

[avoidcrowds]

I agree with pianotuna -more solar.

I am not intending to insult your camping style, as we are all different. But... 😉 , with 2 "deep cycle" batteries and 200 watts of solar, I don't see why you are running low on power, except in the winter. If you have all LED lighting, and are not watching TV all the time, seems like you would be good for days.

I say this, as we have had two trailers with two Group 24 batteries, and 200w of rooftop solar, and could go as long as we wanted. The batteries were topped-off each afternoon, and I could run the furnace in the evening and morning (didn't need it overnight while camping with DW). In the winter when I went pheasant hunting, I was still able to run the furnace when I wanted, as the solar and batteries kept up each day. I have not owned a generator.

You may want to look at your electric usage. Your style may require more power, but I think you would be ahead to add another 100w panel to top-off your batteries each day. If you add another battery, yet you are not fully-charging what you have, you won't gain useable amp-hours; you will just be storing the same amount in 3 batteries, instead of two.

Just my thoughts.

[Blazing_Zippers]

Sam Spade, Wouldn't adding another battery add the amount of available power? If you had one battery at , say, 100--and added another battery at, say, 100---wouldn't that add up to about 200? Now add another battery at, say 100--wouldn't that add up to 300 total?
Not saying this is something I would actually do, but I have explored the possibility of a third 12 volt battery in my battery bank.
Just questioning....

[pianotuna]

Scotty,

Is there room for more solar panels? If so, I'd do that first before adding more battery capacity.

[socal]

Think indoor LED lighting.

David
Off grid deserts of the Southwest

[Sam_Spade]

ScottyP5947 wrote:

I only need to fabricate a battery rack to hold my third battery now.

Did you read my previous post ?

There are very few situations in which adding a 3rd battery makes any sense......and you haven't mentioned any of them.

I think this is a waste of time and money.