I bought my TT 10 years ago this month. When I bought it the RV store showed me how to hook up two 12v batteries. he jumpered the batteries together positive to positive and negative to negative. Then he hooked the TT leads to one battery.Today my brother in law says "Your batteries are hooked up wrong." He said the TT leads should be one on each battery. I looked online and most sites say he is right. but there are a few that show it the way I have it. What is the proper way and what are the advantages of doing it that way?

Balanced wiring (what BIL says) is generally accepted around here as the proper way. Whether it makes any difference over time is debatable, but, it costs nothing to do it that way so why not?

Is balanced wiring the way I had it or my brother in law?

I've used pos on one battery and neg on the other with several RV's.

The BIL is right. Buy him a couple of beers, he has saved you at least that much in battery longevity.

Budman1962 wrote:Is balanced wiring the way I had it or my brother in law?I said "What BIL said"

Dual battery hookup | Good Sam Community

2oldman
Explorer II
Aug 06, 2016
Balanced wiring (what BIL says) is generally accepted around here as the proper way. Whether it makes any difference over time is debatable, but, it costs nothing to do it that way so why not?
Budman1962
Explorer
Aug 06, 2016
Is balanced wiring the way I had it or my brother in law?
coolbreeze01
Explorer
Aug 06, 2016
I've used pos on one battery and neg on the other with several RV's.
westend
Explorer
Aug 06, 2016
The BIL is right. Buy him a couple of beers, he has saved you at least that much in battery longevity.
2oldman
Explorer II
Aug 06, 2016
Budman1962 wrote:
Is balanced wiring the way I had it or my brother in law?
I said "What BIL said"
Bumpyroad
Explorer
Aug 06, 2016
I have never hooked my 12 volters that way. I have had no issues. yes, it is probably better however, but my cables wouldn't reach and I am sure I won't spend the $$$ to get longer cables.
bumpy
pianotuna
Nomad III
Aug 06, 2016
This is what is balanced and best for twin twelve volt batteries.

As it often doesn't cost a dime more to do this, I think it is worth the trouble.
RoyB
Explorer II
Aug 06, 2016
This is what the folks here are saying... Each battery in the group will see the same VOLTAGE DROP in the + and - cables being used.

Roy Ken
pianotuna
Nomad III
Aug 06, 2016
RoyB that is not balanced.

If you wish to understand the "why" surf here:

How to wire multiple batteries in a balanced manner.
http://www.smartgauge.co.uk/batt_con.html

RoyB wrote:
This is what the folks here are saying... Each battery in the group will see the same VOLTAGE DROP in the + and - cables being used.

Roy Ken
bobndot
Explorer II
Aug 06, 2016
Budman1962 wrote:
I bought my TT 10 years ago this month. When I bought it the RV store showed me how to hook up two 12v batteries. he jumpered the batteries together positive to positive and negative to negative. Then he hooked the TT leads to one battery.Today my brother in law says "Your batteries are hooked up wrong." He said the TT leads should be one on each battery. I looked online and most sites say he is right. but there are a few that show it the way I have it. What is the proper way and what are the advantages of doing it that way?

Doing it this way causes a voltage drop between the 2 leads from batt A to batt B . The batteries will notice the difference when drawing as well as charging.
By routing one wire from batt A and one wire from batt B to earth, you eliminate that uneven voltage drop. Its slight, but it there and would have an affect on your batteries over time.
Wire it up as your BIL suggested to get the maxx life from both batts.