Golden Jubilee
Posts: 5211
Joined: Thu Nov 29, 2012 9:28 pm
Location: Lyman, IA
Re: '55 R-122 rehab
VWJake wrote:I blew out and pressure tested the heater core on Saturday. 13lbs for over 30min. I'll call that good. I re assembled the heater and installed it in the truck. I had to rework the old crusty shut off valve, but now I've got a good one. im running a 6v tap from my battery bank to run my gauges. That power feed runs through a relay. It took me a minute, but I was able to scrounge up a relay with double 87 contacts.]
You can likely "get away" with a center tap for very small loads like gauges with little or no ill effects, but the same DOES NOT hold true for higher loads like heater fans.
For the sake of argument, lets say the heater fan draws 5 amps @ 7.2 volts. You are charging you battery cells in series, with 12 volt (nominal, 13.8-14.2 actual) but loading the "lower" 3 cells with an additional 5 amp load. This means the "upper" 3 cells must pass 5 addional amps to replace the load on the other 3 cells, they will over charge and over heat, while the loaded cells will not fully charge. The long and short of it is you will have short battery life and risk body damage from acid expelling from overheated cells.
It is possible to make an alternator charging system that has duel (or more) outputs that are in lock-step with eachother. Delco made such an alternator for use in 24 volt start, 12 volt run trucks. The same idea can be used to make a 6 and 12 volt unit.
Best would be a 12 volt heater motor, it load the system correctly, next best would be a high amp dc to dc convertor, which places the 6 volt load across the 12 volt system. lastly and a very distant 3rd is a resistor which will not allow for varying amp draw (like motors have) to reduce the current to the motor.