Deka Intimidator Batteries?

Chris Bryant wrote:
OK- please bear with me, I am trying to understand why that is not balanced, when every battery sees the identical lead resistance, with the identical number of connections- each battery has two extra links in addition to the main feed.
To me balanced simply means each battery will share equally in charging and load current, and the way I did it I believe fulfills that requirement. If it doesn't, why not?

Chris,

I understand you're confusion, as achieving "proper balancing" is very subtle ... but important if one wants to set up their RV battery bank for absolute longest service life.

Proper balancing has two elements: 1) Identical total cable loop length for each battery and the system load and (here's the subtle part) ... 2) identical cable lengths BETWEEN the positive and negative posts of every battery in the bank and it's neighboring battery(ies).

Requirement 2) is because the momentary intrinsic voltage differences between batteries (due to age differences and/or slight construction differences and/or slight chemistry differences) will cause small local current flow between a higher voltage battery and it's lower voltage neighbor as the two settle into a balance between them while supplying total current to a system's load or being charged. For continuing balance over time and at all times during charging or discharging into a load these small currents must flow through identical length cabling between the batteries regardless of whether the batteries that are settling into a balance between each other are side by side or are further apart in the battery bank.

The way you have your three(?) 12 volt batteries connected means that balancing currents (due to differing intrinsic voltages) between batteries one and two, or two and three, would cause different stress on the higher intrinsic voltage battery than between batteries one and three if they were trying to balance each other - all of this happening while being charged or discharged.

Well .... I said that it was very subtle, but I was wrong .... it's ultra subtle.

This article shows diagrams - and tries to explain but doesn't do the best job of it - why there's only two ways to interconnect a bank of 12 volt batteries to attain perfect balance so that they current-share identically under all conditions of charging or discharging over the life of the battery bank. Notice that the article gives actual data to prove the importance of perfect balance:

http://www.smartgauge.co.uk/batt_con.html