Re: Johnson 112 SPL running at 17 volts
Hey schematic, happy new yr back at you. Bear with me here, been about 15 yrs since my EE courses, and they didnt cover batteries and coils. What Ive learned additionally I learned thru necessity building peak chargers to charge nicads. But something doesnt still seem right to me. No offense intended to you, Ive read alot of your posts and appreciate what you contribute to this forum. If Im way offbase Im sure youll let me know. <br /><br />What I proposed above was really aimed at limiting voltage to a device from the battery, not from the coil. Once I think about it, I dont think it would do anything to the voltage at the battery terminals. I think it would increase the voltage on the coil side of the diode. <br /><br />To go back to first principles, a current is caused to flow in the stator when the flywheel magnet passes by the coil. The energy used up from the motor is related to the charge created plus eddy current losses which are dissipated as heat from the coil. As long as the coil is present, the same charge per revolution will be created (work or power). The current that flows as the coil discharges and the voltage developed depends on what the rest of the circuit is. Because what you suggest above is still a complete circuit, the same work will be done, and the same power lost from the motor, regardless of whether or not you rectify any or all of the current. All the work done that doesnt end up as charge in the battery is dissipated from the system as heat. Now you could switch the circuit open, in which case it would not draw power from the motor, or generate any heat, but it would not generate any charging current either.<br /><br />I think if you really wanted to half rectify the AC from the stator you need another diode in the ground side. Your diagram doesnt show the neg. (grounded) terminal from the diode bridge. But even if you did this, the same work is being put into the system by the motor, seems to me what would happen is that the coil would only be able to discharge 1/2 as often. Remembering that our power created is constant, if we reduce the time the curent flows, then the current must increase during the time it does flow. To put a higher current rate into the battery will create a higher peak voltage at the terminals, even though the RMS value you measure would be same. The higher voltage and current peaks would be in the direction of shorter stator life, not longer.<br /><br />By my own observations, my motor only makes 17 at full throttle, which motors are not designed to be run at for very long (10% of the time or something like that I recall reading). Since I run mostly at 80% for long durations, the problem is somewhat less severe, but still were talking only about 1-1.5 hrs at a time max.(for me personally), before stopping to fish, or trolling at low rpms that generate lower current flow and terminal voltage. No doubt its not good for the batteries, but I havent had any real problems. I normally replace batteries about every 2 yrs. My problems are usually from letting them go dead when not used for several months due to one reason or another. <br /><br />OK, let me have it.
