New User - Having a little trouble understanding the Classic 150...

[boB]

WELL. I guess we will just have to see about that !

Will check it out here, too in the next day or two.

Turns out that I am actually working on some Classic software things.

boB

[SunTim]

I'd suspect that battery voltage carries some noise, spikes, etc, that result from battery BMS actions. I'm rigging up an analog isolated amp which should allow me to get a closer look. I'm a little paranoid about putting scope on a floating circuit.

I agree, the classic is likely doing its job and acting on voltages that don't necessarily show up in digital sampling for displays or data logging.

In any case, I should have some data in the next few days.

Thanks, Tim

[FNG]

One thing I have noticed with Classics is they can be in a state 0.4 or even 0.5 volts lower than target. If memory serves the classic MUST hit target on its instantaneous battery voltage NOT averaged voltage then it is allowed to fall 0.4 volts and stay in that state.

Now back int he day with only lead acid that worked as the absorb timer played out the current dropped and the voltage rose to target allowing a nice full charge. But with Lithium its such a small voltage window this can be temperamental. It seems to be the harder it is pushing to get to target the more it drops below target.

I wonder if Larry can log instantaneous voltage instead of averaged?

I know this is one of the things boB is currently working on, he is diving deep into the classic now to make a few code updates, Mostly to better support lithium. For example we will be able to ignore temperature compensation now but still use the BTS to do cold stop charge on Lithiums

[SunTim]

Interesting stuff.

I put a scope on battery voltage during Bulk MPPT phase. Voltage does in fact jump around in the neighborhood of 1 V P-P. The dither of noise tends to look pretty random with a rough frequency 2 - 4 cycles per second. Its really hard to characterize the noise since its too fast for a meter to report accurately and too random for the scope to trigger on. The one thing that's pretty visible is the magnitude of about 1 volt. Also noticed that a few times a minute the voltage will drop about .5 to .75 volt then return very quickly. Maybe this is an MPPT artifact?

During Float, battery voltage is pretty quiet, as expected.

One thing I want to study a little closer is whether using WBjr current limit feature contributes to noise. I would suspect that a current regulator function such as this would definitely add a little cyclical noise.

All this seems to correspond to Absorb starting about .5 V early.

I hope this info is helpful, You guys do a commendable job of 'continuous improvement' on your product.

Related question...
I had planned to use an Analog Devices isolated (1500 volt) dc amp from my stash to scope the voltage from the battery. I tested the amp in the house, it worked fine. It never worked again once I connected to battery. This is the third time I have destroyed some sort of isolation device when I connect it to the battery. Seems to be the initial hookup that is the killer, static charge?
I have a Midnite MNSPD-115 across the PV at the combiner and a MNSPD-300AC across the inverter AC output. I have nothing across the battery buss. At first glance that would not seem necessary, but if the CC and the inverter are both transformer isolated devices, I wonder if my battery circuit is still susceptible to static?
BTW, I lugged the old line voltage isolating transformer to the barn to achieve an isolated scope measurement.

Thanks, Tim

[ClassicCrazy]

One thing I have noticed with Classics is they can be in a state 0.4 or even 0.5 volts lower than target. If memory serves the classic MUST hit target on its instantaneous battery voltage NOT averaged voltage then it is allowed to fall 0.4 volts and stay in that state.

Now back int he day with only lead acid that worked as the absorb timer played out the current dropped and the voltage rose to target allowing a nice full charge. But with Lithium its such a small voltage window this can be temperamental. It seems to be the harder it is pushing to get to target the more it drops below target.

I wonder if Larry can log instantaneous voltage instead of averaged?

I know this is one of the things boB is currently working on, he is diving deep into the classic now to make a few code updates, Mostly to better support lithium. For example we will be able to ignore temperature compensation now but still use the BTS to do cold stop charge on Lithiums

Ryan - is there a way to log that on the MNGP ?
If it is a modbus number that isn't in the program code I use , I would have to redo some of the magic monitoring things to make it work and not sure i can do that.
But yes today I again noticed that the Absorb was lower than the setpoint.
I increased the setpoint from 55.2 to 56 when it was already in absorb  and you can see the resulting voltage increase in the attached screenshot.
I am not sure how much more absorb time was left when I changed it .

Larry

[SunTim]

Follow up...
I disabled the WBjr current limit by raising the value over 100A.
The voltage dither reduced significantly.
Put CL back to 30A and the wiggle returned.
The current controller probably need to be a little more sluggish to avoid hunting.
Hope this helps.

Thanks, Tim

[boB]

Follow up...
I disabled the WBjr current limit by raising the value over 100A.
The voltage dither reduced significantly.
Put CL back to 30A and the wiggle returned.
The current controller probably need to be a little more sluggish to avoid hunting.
Hope this helps.

Thanks, Tim

Yes ! 

I believe that the default WB Jr current limit is set to some insanely high limit to do just what you are saying.

boB