Classic 150 voltage readings

[firerescue712]

I have had the Classic for about 6 months.  All firmware updates are current.  I use 4/0 cables between the batteries and the buss bar.  I use 4 ga from the Classic to the buss bar and to the pvs.  The voltages have been slightly off since commissioning.  If the lower voltages are calibrated, the upper voltages are off.  The same if the higher voltages are calibrated.  I have checked the battery and pv voltages with 2 different multimeters and comparing these results with the readings on the two Rogue cc's., which show the same voltages.  It is not a major issue.  I just have the higher voltages calibrated correctly.  Once calibrated, it holds the voltages precise.  Is there any setting that will allow calibration and saving of both voltage settings?  I LOVE the Classic, with plans for another with "Follow Me" utilized.

[SolarVet]

I had to Set the Voltage Adjustment potentiometer inside on the circuit board. I set mine during the night. Disconnected the panels only. And set it using a Fluke meter... Connected to the battery bank.

I hope that helps Jess.....

[firerescue712]

If I knew what a potentiometer was, I am sure I could do it.  My level of expertise is limited on electronic equipment, including circuit boards.  Can you reset it so the Classic will show the correct voltages at the upper and lower limits?  I would hate to ruin the Classic attempting circuit board corrections.

[Westbranch]

FR there is another thread that tells how, search for potentiometer user boB.
hth

[firerescue712]

Thank you,  I'll go lookin'.

[Westbranch]

found it had to use 'adjust'.  I think this is what  you are after..

http://midnitesolar.com/smf_forum/index.php?topic=1055.msg7752#msg7752

[TomW]

FR there is another thread that tells how, search for potentiometer user boB.
hth

branch;

Wasn't that for tweaking the amp offset?

Concept is the same but a different potentiometer.

FR712;

Frankly, I would not advise the uninitiated to tweak any potentiometers on the Classic.

I used to make money when users "tweaked" their color control pots on their old time CRT televisions.

The wrong tweak in the Classic might cook your batteries or something so I would recommend checking very closely for some other source of the offset before changing any hardware settings on the Classic. Everything from loose connections to current in the circuit can throw off a reading. Or simply measuring at different locations will show variations.

Just a voice of caution before you dive in. Not to be a Debbie Downer

Good luck with it.

Tom

. 

[firerescue712]

Thank you for your inputs.  I believe I will see if boB chimes in.  It is not serious, just a bother.  Through the Classic keyboard, I have tweaked the absorb voltage so it reflects the correct numbers, but they drift apart from the other readings in float (.01 volt higher) and at rest (12.5 on the Classic vs 12.7 from the other readings).  I'll just wait and see. 

Again, thank you for the information.

[SolarVet]

Hey Jess it me....Dale.....Skype

[firerescue712]

Hi Dale.  Sorry about the HF forum tidbit.  I gotta download Skype.   BRB.

[Halfcrazy]

So the Classic has 2 ways to adjust the voltage offset on the battery. The Tweaks menu is non linear and as you found out will be good on the low end or the high end but not both. boB was going to write up a white paper on using the Tweaks and the Pot as they have to be used together. I tend to use the Pot if the Vbat is off by more than 0.5v at rest but boB assures me there is a way to use both and make the Vbat linear. Sort of like dialing in Capacitance and Inductance on the old HF antenna tuner.

I will send boB a reminder to visit here and take care of this.

Ryan

[boB]

OK, to adjust the gain (the usually blue trimpot on top near the yellow inductor),
first make sure your offset adjustment is set to 0.0 V in the Tweaks menu.

The best way to do this is to use a power supply so that you can take at least
two measurements, one at a very low battery voltage and another at a
high battery voltage.  If you are using your battery, you will have to charge
it up so the voltage is somewhere near Absorb voltage an then run the battery
down so it reads on the low voltage end of your expected range.

At least try to vary the voltage by a few volts for this adjustment if you can't
go to the absolute maximum and minimum extremes.

Using your Fluke meter (or similarly calibrated volt meter), note one of these
extreme voltage settings from the meter probes with good connection across
the Classic battery terminals.

Make and note a similar measurement at the other voltage extreme.

What you want to try and do is to make the meter read "off" by as close
to the same amount at both ends.  For instance, if at Vbattery of 22.0 volts
by reading the Fluke meter the Classic reads 21.7 volts,  and at 28.0 volts
by the Fluke it reads 27.7 volts, it would be "off" by a constant -0.3 volts
(minus 0.3 volts)  That is what you would want to see and now the blue
gain pot (variable resistor) is set properly.

If the reading was off by -0.3 volts at the low end and say, right on (+-0.0V)
at the high reading, you would adjust the blue trimpot until both readings
were "off" by the same amount (compromise) which might be like,
+-0.1 or +-0.2 volts)

Next and last is to go to the Tweaks menu and now adjust the Vbatt
adjustment for a +0.3 volt offset.

The battery voltage meter should read much closer now.

Realize that after even a good adjustment, the voltage display will
only have an accuracy of +- 0.05 volts.

Let us know how this works for you.

boB

[Vern Faulkner]

My machine was 0.2 volts off (low) on reading battery voltage. I simply used the tweaks menu to give me the right voltage - and this is checked with a multimeter (and two different voltage-displaying inverters, I note.)

[boB]

My machine was 0.2 volts off (low) on reading battery voltage. I simply used the tweaks menu to give me the right voltage - and this is checked with a multimeter (and two different voltage-displaying inverters, I note.)

And that is just fine as long as it fixed the voltage reading at more than one battery voltage throughout its state of charges.

0.2 volts is not that far off.   For a 48V battery bank, most inverter/chargers and controllers can be off by +- 0.4 volts.

+- 0.2 volts off for a 24 volt battery bank

I would prefer to be right on if possible.

boB

[jimbo]

Digging up an old thread here.

My classic's voltage reading is accurate throughout the voltage range at night and while there is around 15amps or less going into the batteries, however while charging at 50 amps this figure is out by around 0.5v.  It's not much but instead of my batteries absorbing at 29.4V they are actually at 28.9V (for the first 2 hours).  A couple of hours into the absorb the current drops down to around 20 amps and the voltage difference is now around 0.2V to 0.1V (no big deal there).  I'm about to add a few more panels which will increase the charge and thus increase the voltage discrepancy.

How do people get around this? Do i need to run larger cables to the battery bank?  My previous PWM charge controller used separate battery sense wires which seemed to overcome this problem.

Cheers

James