Add third 12V battery in parallel to travel trailer?

ScottyP5947 wrote:
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

Good to go. However this is a good time to review your charging system. You need a converter that has a boost voltage at 14.2+ volts to get a decent charge in these batteries without running the generator 12+ hours a day. For example WFCO "3 Stage" is notorious for just doing a 13.6 trickle charge.

Hi,

Welcome to the forums.


Wire the bank in a balanced manner a la method #3 from this link: http://www.smartgauge.co.uk/batt_con.html

ScottyP5947 wrote:
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

KM Rolling wrote:
...the two we have will easily give us 3 days of dry camping without the generator...

I use my batts lightly. 3 days is way beyond what I manage to get. I am jealous of your performance.

Are your two batteries inadequate for a reasonable 24 hours of service? If adequate, why add another new battery? If they are inadequate, consider solar to recharge. At dusk they will be full.

If you're looking to add more available amp hours, what you propose will work fine. Just do a good job on matching the wiring, keep all connections good. I always use dielectric grease.

We lived off the grid for a bit over 3 years, using a generator to charge a bank of batteries.

During that time I added some amp hours by expanding the number of batteries.

The first thing I did when we got our trailer was add another battery to the ONE battery that came with the trailer, doubling my available amp hours. I would not hesitate to add a 3rd battery if I needed it, but the two we have will easily give us 3 days of dry camping without the generator, which is enough for us.

deltabravo wrote:
Mixing new batteries with old batteries is not the best plan.

Sometimes having them connected in parallel isn't the best plan either......although sometimes that is the only practical way.

Mixing new batteries with old batteries is not the best plan.

What problem are you trying to solve ?

I am pretty sure those not true "deep cycle" batteries. A pair of Deka DC27 will give you 180 AHr. A pair of GC2 (Deka/Duracell or Interstate) golf cart batteries will give you 230AHr and will probably last longer (more charge/discharge cycles).

IMHO, stick with the pair you have and start socking away the money for those Lithium batteries.

Match as close as possible and balance the wiring. I have a group of four Gp 27 that range from 2008, 2009, 2012, 2015 and they are all great friends.

If your current batteries are in good shape you should not have any worries. Yes, I would match the specs as close as possible IMO.