Converter In-Rush Thermistors etc, UPDATE -4
UPDATE on 17 Nov, Update 2 on 22 Nov, Update 3 on 16 Jan 14, Update 4 on 19 Oct 14. --------------- In a recent thread there was mention of how you can wreck your gizmo (in my case a converter) ...
Forum Discussion
No new thermistors in yet, but I decided to get a start with some bench testing on the old one:
As you can see it has only about half its thermistor still there. I plugged in the converter and put the meter on DC output. It was running up and down the scale, which told me (previous trouble I fixed) that a wire had broken away from the big coil between the two black capacitors and the thermistor, so I fixed that again, this time properly (I think!)
So now the DC output voltage was steady at 13.66 and stayed there for a few minutes ok. The thermistor was not even warm to the touch.
I tried using the voltage pot (this converter has its internal) and it worked ok so it would stay at whatever I set it to such as 14.65v
Still running so I unplugged it and waited a few minutes and plugged it in, no problem (of course there was no DC load for all this)
Now the big test. Got the trailer unplugged from shore power, and plugged shore cord into the inverter, ran kettle 85a to make the full batteries look thirsty, ran up the Honda 3000 and extension cord from that to trailer front, all same as when camping.
So with converter voltage set at 13.6, not clamped to batteries, plugged in to Honda on eco. Was a tiny blip indicating the Honda saw that load and then settled again.
Turned off inverter so no big load just full batteries, clamped on the converter to batts, Trimetric showed it was charging ok at a few amps then turned on inverter -85a load and Honda revved up with the load, no smoke from the converter!, Trimetric showing + 9a so converter is doing +94a approx.
Left it running for a few minutes, no problems, unclamped from batts, unplugged from Honda, wait four minutes, plug in converter, clamp on batteries, no smoke while Honda revs up again.
Changed voltage setting on converter to 14.78, wait another four minutes start it---oops was a tiny red spot on the side of the thermistor and a puff of smoke, but the red spot went out immediately and no more smoke. All ran ok for a while after that no problem.
Did it all three more times no more red spots though just that once. Each time I waited four minutes, turned on the converter first then attached clamps to batteries. No problem.
Last run decided to go for broke and leave the inverter on with -93a load showing on Trimetric, left the converter clamped on, I did wait the four minutes, plugged in the converter. This meant the converter was hit with a big load on start-up.
No red spot, no smoke, Honda revved up, Trimetric showed +9a instead of -93a, so converter doing 102a and battery voltage was 14.6 on Trimetric by then. Left it all on for a few minutes, nothing changed. Shut it all down.
So it seems I have a working 100amper again, but with only half its thermistor!!!! Of course it might not last hours and hours of recharging, can't say. Didn't seem to overheat--fan came on once in a while to cool it down as normal. Beats me!
I tried the newer converter bench test no load, but no joy. It has a steady DC 2.98v output, that's it. Voltage from the top of each big black capacitor to the chassis ground is about 60v each, with about 120v at the input wire. Remains of thermistor not getting red or doing anything.
So the next trick when I get them is to install a new thermistor in the newer converter and see if that will make it go.
I am inclined to use the old one as is with half a thermistor until it blows (if it does) and then replace that thermistor with a new, whole one. It is working now, so IMO, leave it be!
It all makes the thermistor specification choices we have been discussing a little strange, when this one works ok all wrecked as seen in the photo, even after it got that red spot. I guess the trick is to get a red spot that goes out right away like that did, and not shoot flames. :)
As you can see it has only about half its thermistor still there. I plugged in the converter and put the meter on DC output. It was running up and down the scale, which told me (previous trouble I fixed) that a wire had broken away from the big coil between the two black capacitors and the thermistor, so I fixed that again, this time properly (I think!)
So now the DC output voltage was steady at 13.66 and stayed there for a few minutes ok. The thermistor was not even warm to the touch.
I tried using the voltage pot (this converter has its internal) and it worked ok so it would stay at whatever I set it to such as 14.65v
Still running so I unplugged it and waited a few minutes and plugged it in, no problem (of course there was no DC load for all this)
Now the big test. Got the trailer unplugged from shore power, and plugged shore cord into the inverter, ran kettle 85a to make the full batteries look thirsty, ran up the Honda 3000 and extension cord from that to trailer front, all same as when camping.
So with converter voltage set at 13.6, not clamped to batteries, plugged in to Honda on eco. Was a tiny blip indicating the Honda saw that load and then settled again.
Turned off inverter so no big load just full batteries, clamped on the converter to batts, Trimetric showed it was charging ok at a few amps then turned on inverter -85a load and Honda revved up with the load, no smoke from the converter!, Trimetric showing + 9a so converter is doing +94a approx.
Left it running for a few minutes, no problems, unclamped from batts, unplugged from Honda, wait four minutes, plug in converter, clamp on batteries, no smoke while Honda revs up again.
Changed voltage setting on converter to 14.78, wait another four minutes start it---oops was a tiny red spot on the side of the thermistor and a puff of smoke, but the red spot went out immediately and no more smoke. All ran ok for a while after that no problem.
Did it all three more times no more red spots though just that once. Each time I waited four minutes, turned on the converter first then attached clamps to batteries. No problem.
Last run decided to go for broke and leave the inverter on with -93a load showing on Trimetric, left the converter clamped on, I did wait the four minutes, plugged in the converter. This meant the converter was hit with a big load on start-up.
No red spot, no smoke, Honda revved up, Trimetric showed +9a instead of -93a, so converter doing 102a and battery voltage was 14.6 on Trimetric by then. Left it all on for a few minutes, nothing changed. Shut it all down.
So it seems I have a working 100amper again, but with only half its thermistor!!!! Of course it might not last hours and hours of recharging, can't say. Didn't seem to overheat--fan came on once in a while to cool it down as normal. Beats me!
I tried the newer converter bench test no load, but no joy. It has a steady DC 2.98v output, that's it. Voltage from the top of each big black capacitor to the chassis ground is about 60v each, with about 120v at the input wire. Remains of thermistor not getting red or doing anything.
So the next trick when I get them is to install a new thermistor in the newer converter and see if that will make it go.
I am inclined to use the old one as is with half a thermistor until it blows (if it does) and then replace that thermistor with a new, whole one. It is working now, so IMO, leave it be!
It all makes the thermistor specification choices we have been discussing a little strange, when this one works ok all wrecked as seen in the photo, even after it got that red spot. I guess the trick is to get a red spot that goes out right away like that did, and not shoot flames. :)
