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.
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.....
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.
FR there is another thread that tells how, search for potentiometer user boB.
hth
Thank you, I'll go lookin'.
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
Quote from: Westbranch on February 27, 2013, 08:34:13 PM
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
.
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.
Hey Jess it me....Dale.....Skype
Hi Dale. Sorry about the HF forum tidbit. I gotta download Skype. BRB.
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
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
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.)
Quote from: Vern Faulkner on February 28, 2013, 03:48:09 PM
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
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
Where are you measuring battery voltage and with how good of a meter? Is the voltage measured with your meter at the Classics input terminals different that what it measures at the battery terminals themselves? If lower at the classic - perhaps you do need larger or shorter cable or need to check your connections.
FWIW my Classic's voltage readings are within 0.1 V of what I measure at the batteries with a good meter.
I'm measuring the voltage with a cheap multimeter AND my SunnyBoy inverter under no load and both are identical.
When there is little to no sun the classic, inverter and multimeter all match up, however while there is a fair bit of current going from the classic to the battery the classic is reading 0.5v HIGHER than both the inverter and multimeter.
Well if the Classic is reading higher than the batteries measure at the battery terminals then its hard to blame it on too long or to small a gauge wire to the batteries.
For a check have you measured the voltage at the Classics battery terminals?
Not yet
When current is flowing and you have the 0.5v discrepency get these 3 values and report back:
Battery V as read from the classic display:
Battery V as measured on the Classics terminal block with a meter:
Battery V as measured on the battery terminals with a meter:
Ryan
Ok will do. Just need some sun....weather has been terrible!
Quote from: jimbo on August 02, 2013, 09:48:06 PM
I'm measuring the voltage with a cheap multimeter AND my SunnyBoy inverter under no load and both are identical.
When there is little to no sun the classic, inverter and multimeter all match up, however while there is a fair bit of current going from the classic to the battery the classic is reading 0.5v HIGHER than both the inverter and multimeter.
If you are reading higher voltage on the classic when it is putting out substantial current, then you have a high resistane connection, or you wire is too small. While you are experiencing the volt drop, feel the insulation on the wires, if one is warm, than tighten its connections. If that doesn't work, than upgrade to bigger wire.
I just had the same issue, one of my charge controllers started reading 1v higher than everything else when charging. I felt the wires and the negative wire was warm, it is under a foot long, 6awg and only carrying 25a. It was quite warm, turns out the screw holding the wire in the busbar was loose because the stranded wire crushes. That is a common problem with stranded wire, the finer the strands, the worse it is.
Good catch dbcollen. Somehow I totally missed the part about the Classic's reading being higher only when it is putting out high current. It makes more sense now! I would still measure voltage at the Classics battery terminal to help narrow down the problem. A voltage drop there when at rest would help confirm a problem with wire or connection from battery. If there are other connection points between classic and battery bank (bus bars, etc) checking there as well could help pin it down.
The voltage drop is a function of resistance and current, the more current flowing through a given resistance, the more voltage drop there will be. When the controller is not charging it should still read volts accurately if there is a high resistance connection.
With offset set to 0 and around 35-40 amps going into the battery
Battery V as read from the classic display: 28v
Battery V as measured on the Classics terminal block with a meter: 27.9-28v
Battery V as measured on the battery terminals with a meter: 27.6v
Like the other have said i do think it is a wiring issue. The wire run to the batteries is around 2ft but is not 100% ideal as i have replaced 2 controllers with one and done a bit of 'massaging' with the wires to get them in the terminal block. I will replace them some time this week and see what happens.
2 feet is not a long distance for a wire run to the batteries. The issue is likely the connections. You may want to replace the wire though. If 50 amps is about the max you will be putting out of your Classic 6 AWG would be plenty large enough. Bigger is always and you can get 4 AWG into the Classic terminals with a little finesse (but unnecessary for 50 amps) The connections are really the key.
I see 63 amps when the batteries are low and the sun is shining and hoping to add some panels this week to bring it closer to 90 amps. Might as well use the biggest wiring possible as it is such a short run.
So with wiring up to spec does anyone else see a different voltage at the battery terminals to the terminal block under heavy charge?
What kind of volt meter are you using to verify ?
It might be that the Classic measures voltage a bit
differently than your meter does.
Also, you might also try to connect the meter probes to a piece of exposed
copper going into the terminal block rather than the screw itself.
boB
With a cable that short, can you measure the voltage across the cable? As in from Classic terminal to the battery terminal? Under heavy charge will show any significant drop due to cabling / connections quickly.
Set for a low range this will show any drop from cable losses. And the quality of the meter or calibration differences will not be an issue.
Just an idea.
Tom
I have had the cables upgraded to the battery and there is still a 0.4v difference while charging at anything over 50amps.