On the left you can see a battery pack like mine. The three 12 volt batteries that result by series connecting
each pair are then connected in parallel. By connecting the coach cables to the top battery, the top battery
is connected directly, the 2nd battery is connected through 2 lengths of added cable, and the third battery
through 4 added lengths of cable
Each cable has some resistance, so during discharge, the top battery is suupplying the most current, the 2nd
somewhat less, and the bottom battery even less. The same is true during charging, escept the top battery is
receiving the most charge, etc. The higher the current flow, the greater the imbalance.
On the right, by connecting one coach cable to the top battery and the other to the bottom, every battery is connected
through 2 additional cables. All three batteries theoretically receive exactly the same level of discharge and charge.
They are balanced! Yes it really matters!
I started making the bus bars by heating a length of copper pipe to a cherry red, then quenching it in
water. I found that by using a reducing (low on oxygen) flame and quenching it, the black oxidation that
I had on early trials flaked off into the water, leaving a fairly nice finish. The right picture shows
this finish and the finish after a light polishing with a Schotchbrite pad.
Now that the copper is dead soft, I can flatten it. I ended up using my shop press
for this. I smoothed one face of a couple lengths of angle iron and used these
to give a nice finish on the flattened copper.
For the series connection links, I curved the soft tubing before flattening it to provide a little clearance
around the battery posts. Each battery terminal has both a threaded stud and an automotive type post. I solder
coated all the ends to minimize oxidation of the copper at the terminal areas. I then put on a piece of shrink
sleeving over each one to reduce the potential for shorts.
is what I ended up with. All six batteries are installed and
connected. I managed to find some small vinyl
that fit the studs and nuts, and some plastic chair tips that fit
the automotive terminals. This should pretty well
protect against shorts from accidentally dropped wrenches, etc. The connections to the coach are at the upper right
and the lower left. The items on the upper left and lower right are the temperature sensors for the inverter/charger,
the solar controller, and the 12 volt monitoring system.
My final task of this project was to set all the correct parameters in my inverter/charger and in my 12 volt monitoring
system to correspond with my new battery type and capacity.
am very pleased how this project came out. The $400 it cost me
was about $1000 less than I would have had to spend to replace my
batteries, and I now have about a 33% higher battery capacity. If
any time in the future I desire to go back to the original type
batteries, all I have to do is place a 1 1/2 inch wide spacer like a 2
x 2 in one end
of the battery rack and the batteries will fit perfectly again.
R. S. Mason 11/14/2014