New Boondocker converter test
So I connect it to a pair of 6 volts and measure immediately a whole bunch of amps heading toward my batteries. 64 or so. Is a 60 amp unit. I panicked cause I didn't want to overcharge but my god did...
Forum Discussion
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?
It fries if it is already warmed up when hit by big in-rush. So no hot restarts please. Also clamp to battery first then start up or else it will start no load, let the thermistor warm up, then you clamp on and bam it gets a big demand with in-rush on the warm thermistor.
The in-rush is 120v and the thermistor is supposed to slow that down which it can while it is cold but not after it warms up. This protects the ? ISTR bridge rectifier ? which gets warm and it is placed right up against the heat sink. Going from memory here--last winter's long thermistor thread has all this spread over forty pages.
There is some sort of relationship between DC output voltage and amps and the 120v inrush on start-up but I am unclear on that (to say the least) A PowerMax guy mentioned in passing that by setting my 100 amper at 15.5 and starting it from there makes for an extra big inrush at the thermistor-max stress.
The higher the converter's DC amp rating, the "bigger" its in-rush thermistor is, which is another bit of evidence.
So that is why I thought perhaps Randy has limited his to 15.5v DC instead of the original PMBC 16.5v spec so they don't have a lot of returns due to blown thermistors. Totally just guessing, I haven't asked anybody.
