Hey Hot Dog Guy. I too have a 1450LMT, and I too have replaced the original power cord with a MotherMoto cell phone unit because of that silly Garmin fail trait. Fortunately for me, mine didn't see an epic fail.
If the power supply in the power cord goes south but not completely out, the common symptom is that the display becomes intermittent or won't light, and the battery charge rate is slowed down or ceases. If it goes a bit too high, the symptoms are somewhat similar or the display goes out altogether. If the voltage goes too high for too long, one of the first things to cook is the temp sensing part of the circuit that protects and regulates the charge rate according to ambient temperature. Either way, there will be subtle changes in the charging cycles as the first symptoms appear, and there may be things it starts to forget to do, like retain your setup choices such as screen brightness, or fail to auto change from day to night screens, and it may not allow you to correct these little annoyances. The test solution for the GPS itself is to power the unit down and let it sit overnight to allow the battery voltage to stabilize, then turn it on and reset your user settings and parameters. If it does OK, then you probably have lucked out. Don't plug the power cord back into it until you have the cord's operation checked out by someone who knows what they're doing or until it is replaced.
Look at at the paperwork that came with the unit and see what the operating temp range is and see if it tells you what the charging temperature range is. Depending on battery chemistry and design, most batteries will not take a full (rapid) rate charge below about 55 degrees or above 85 degrees, and won't charge at all below about 25 degrees or above 95-100 degrees. So think about what temps the electronics in your vehicle see when closed up on a hot summer day or in middle of a February night.
Battery charge rates are dependent on battery voltage vs battery temperature, so if your device is between the safe temp limits, the battery will charge. If the ambient temps are below or above the full rate charge limits, the battery will be charged at a lower or even a trickle or maintenance rate. If the temp is above or below the battery's safe charge parameters, the charging circuit just won't charge the battery at all until the temps come back into the operating limits. Inside the GPS is a temperature sensing circuit with a thermistor or other device that senses ambient temperature. If you know how to get to the service sub menus in the setup pages, you can read what ambient temp the unit is seeing, btw. Anyway, the part of the processor that makes the charging decisions looks at the temp sensor's output and the battery voltage and determines whether or not to charge and at what rate.
The point of all this is that after seeing over or undervoltage for a while or repeatedly, your GPS may continue to work but it may not be consistent in its charging activities or won't charge at all, and the battery will definitely be damaged by overvoltage charging. Let it go too long and epic fail is the result. Since the majority of the electronics today are built with surface mount component technology, the only real option for those not equipped with the proper bench repair equipment and knowledge is returning them to the manufacturer for service or warranty. Either way, they don't really repair them, they just replace the guts.
Just thought y'all might wanna know this info because I experienced all the symptoms I mentioned before looking for the problem.
