boB,
My older Classic #879 has battery voltage reading problems, it was good until a few months ago when I needed to use tweaks -.1 and over time to -.5
Its now never giving an accurate battery voltage reading
When resting it reads too low by as much as .6v and when making power it reads too high by as much as a volt.
This means I have to use tweaks every day to stop it going into absorb at too low voltage. I notice it works the absorb/float based on its displayed batt V.
I have also followed the procedure of adjusting the gain pot on the pcb but its been at the minimum setting since I bought the Classic. Adjusting the pot just increases the displayed batt V.
I notice a proper thru soldered 2k7 1/8watt 2% resistor R100 just below the pot. On my other classics this a much smaller SMD resistor. Is this related to the gain pot and acting as some offset for it??
It looks easy enough to replace or to parallel another resistor on top.
Can you say if this would help and what final value resistor may be useful? 2k, 2k2 or above 2k7 ?
dgd
I'll let boB answer the part about the resistor, but I am wondering how heavily was this Classic used? I have already put through 15MWH on mine since 2011, and it shows no signs of fading or any issues.
Quote from: laszlo on July 23, 2014, 12:36:28 AM
I'll let boB answer the part about the resistor, but I am wondering how heavily was this Classic used? I have already put through 15MWH on mine since 2011, and it shows no signs of fading or any issues.
Its done under 1MWH, 886kwh to be exact but its on a 24v battery system and I bought it mid 2012 when it was already old shelf stock. :(
boB provided instructions on gain adjustment in 2012 so i was able to calibrate it within 0.1volt. but this year its lost all accuracy. Resting its 0.8v too low and it reached absorb at 29.2v when real voltage is 27.9 at 1200watts+
I need to readjust tweaks every day when resting and at high(ish) power.
dgd
Hi !
are you sure you do not have any contact resistants in your cabling ?
I would measure voltage between bat positive and Classic bat positive at high amps. Maybe something is corroded
or not tightened.
Geri
Good suggestion :)
When all else fails check the obvious - so I looked at all the cables and was able to get a bit more torque on a few of them. Then I noticed the little pot for adjusting the voltage gain was in a different position from where I had last left it so after closer inspection I could see it was loose and made me doubt the contacts in it were good.
So I gave it a good pressing and it seemed to click into place somehow.
Now just waiting until a good sunny day to see if there is any change or if the pot is now completely munted.
Have ordered a replacement 150 anyway.
dgd
Quote from: dgd on July 25, 2014, 04:48:27 AM
Good suggestion :)
When all else fails check the obvious - so I looked at all the cables and was able to get a bit more torque on a few of them. Then I noticed the little pot for adjusting the voltage gain was in a different position from where I had last left it so after closer inspection I could see it was loose and made me doubt the contacts in it were good.
So I gave it a good pressing and it seemed to click into place somehow.
Now just waiting until a good sunny day to see if there is any change or if the pot is now completely munted.
Have ordered a replacement 150 anyway.
dgd
What color and size is the trim-pot ? We changed from a thru-hole to SMT version a while back.
The old thru-hole was either blue or gray I think.
Also, next time you try adjusting the voltage gain, start off with the Vbatt offset up around +0.3 to +0.4 volts
first, before adjusting the gain.
boB
This problem is fixed :)
Absolutely superb service from Midnite to resolve this, a field replaced top circuit board did the job and my Classic 150 is now perfectly tracking the battery voltage.
I always knew that I had bought the best controller available and this level of support proves I made the right decision..
THANKYOU Midnite
dgd
Excellent DGD ! Glad it is working well now.
Thank you for the kudos ! Much appreciated !
:)
boB