jrnymn7 wrote:
What is it that fries the thermistor, though? Is it the 'current inrush' to the charger? And if so, would a lower start-up voltage reduce the inrush?
Thermistors are simply resistors with a large coefficient of temperature. They either get more, or less, resistive when they get hot. Makes them good for limiting inrush current cause you use a NTC (negative Temperatore Coefficient) unit and when it's cold the high resistance limits the current by causing voltage drop.
When it warms up the resistance goes down and the current can increase.
However there is a formula I^2*R (I Squared R) this is the watts it needs to dissipate (The watts of heat)
If you are trying to control say 40 amps, Well, you are going to make some serious heat
OF course the Thermisistor is often put else where so it controls a far lower current.
I have two converters in this coach, one is the factory PD-9180 with wizard mounted as far from the batteries as possible,, This unit in theory, should never hit max amps due to the 50 feet or so of wire, It will suck over 10 amps though in boost mode.
The other one is a Prosine 2.0 Inverter/Converter.. it connects to the batteries with just a few feet of like 0000 wire (That is bigger than your thumb more than likely) and I have seen it break 100 amps, (as in 104) it is supposed to limit to 100.
Sometimes the "overage" is nothing more than meter inaccuracy, sometimes it's a limiter that needs a touch of trimming.
In any case so long as it's no more than 10% of the converter's rating I would not worry about it.
