Energy Matters Forums

[davidg]

It's also interesting to watch it try and hover around 0Amps at the shunt when in float and loads come on while the classic ramps up its output to cover loads but not charge the battery any more.

Interesting way for the shunt to linked in. Normally it's linked in so it shows what is being sent from the charge controller only without taking into account any inverter load (only shows charge current) the PS1 should be able to show it's own consumption or have I missing something or not read it right

[offgridQLD]

Yes the PS1 has its own internal shunt that all the PV is sent through and it knows whats going in and out and the total and net . The issue is its not much use to the classic charge controller as it doesn't communicate that info with the classic charge controller it only uses it for its own purposes.

The wiz bang JR unit (funny name) is made by midnite solar and is a accessory for there classic charge controller range. Its a electronic divice that bolts to the side of a 500A 50mv shunt. It's used to to comunicate with the classic charge controller and inform it what the live inverter loads are on battery so it can trigger (end amps to trigger the end of the absorb stage) at the correct value taking battery/inverter load into consideration. (in the past you just had to guess what your end amp value was by using say 1-2% of your battery's AH capacity say 8amps for a 800AH battery and adding any inverter loads to it say 3amps for a total of 11A. So as soon as absorb input reached 11A and held for more than 30 second it would trigger float. The issue was what happend if you have a range of inverter/battery loads as the typical off grid system dose, what do you set the end amps value to ? The wizbangs shunt tells the classic what the loads are so there is no hit and miss guessing or getting upset with your wife to stop turning the tap on and off every 20 seconds and let the thing trigger float.


The internal shunt in the PS1 is only a 100A shunt. The PS1 has a input for a 2nd external shunt so considering I will have well over 100A of PV potential soon (more like 160A with the additional PV) I have the option to connect the ps1 to the (wiz bang) 500A shunt so they can both share it and not even use the internal 100A shunt.

So the midnite classic range with the wizbang is getting smarter and measures everything now including what is coming out of the battery. To be honest I don't even know if I need to connect the PS1 to the 500A shunt as I don't really use the PS1's logging or data . Though I will say the ps1's shunt agreed spot on with the wizbang shunt amps ..

Kurt

[offgridQLD]

Due to a output calibration issue I have new taken my first classic charge controller offline. I have swapped it out with my new classic that was purchased for the additional PV.

The problem with the old classic has been there from the beginning. I performs fine 100% reliable but its output readings have been off from the get go. Around 25% optimistic. I picked up on this in the first week but against my better judgement assumed it was my gear that was out. Anyhow I now have conclusive results to show its out of whack. Midnite gave me instructions on how to tweak the tiny gain pot but unfortunately it looks like the gain pot is not even functioning. They were very good about the issue and said give it back to us and we will sort it out. I'm not to worried about having a issue. Its how the company's handle it that speaks volumes to me.

So this discovery puts a few things into perspective. The first is that my lead acid battery's are a good 25% more efficient that the numbers I was recording . The bad news is my PV is 25% less efficient than I was recording Though some of the output numbers I was getting were just silly way over the rated output of the system. T

he new classic is spot on with its calibration, matches the selectronic shunt, My clamp meter and the midnite wizbang shunt , they all agree. Good to have some reliable data to work with now.

So now I need to reevaluate my system all over again. It will be interesting to see how many KWH is needed to cover a days DC kwh consumption. What the idle/float output is with just base loads and so on.

kurt

[franks]

Borrowed a calibrated digital multimeter from my work, with setting calibration of the classic, the classic is 10mV within calibrated multimeter reading.
if your within 0.5% overall thats good enough for most users.

[offgridQLD]

Franks,
The voltage readings were fine. It was the amp reading that we're way out of whack. For example it might be showing 50amps output but when you measured the output (with no loads on the battery) it was only showing 38 amps . So it was way out to much to correct with a trip pot.

The new classic is spot on in both voltage and amps.

Kurt

[Cherokee Solar]

The first is that my lead acid battery's are a good 25% more efficient that the numbers I was recording . The bad news is my PV is 25% less efficient than I was recording Though some of the output numbers I was getting were just silly way over the rated output of the system.

Hi Kurt,

Well done for sussing out the problem. I thought that the efficiency numbers that you were providing were wrong at the time. Good work.

Things go wrong all of the time. It is the response to the problem that is the real test, and they've passed with flying colours.

I had to calibrate all of the shunts here too (again a trim pot) with the setup. They are bi-directional shunts, but I use one tshunt o record amps in and the other shunt to record amps out of the battery. There is not much point in net readings in an off grid system (although some people will be happy with that data). As the shunts were second hand, I have no idea what strange numbers the previous owners were getting, but they weren't accurate!

Well done.

[offgridQLD]

Yes it would have been nice if the trim pot could bring it back into line. Though the trim pot for that shunt didn't seem to be functioning so I think I have a issue with that section of the circuit inside the classic.Never mind its there problem now.

Some times true accuracy isn't needed and just consistency is all that is needed for comparison purpose.For charge controller output I want true readings.

Regarding my output now. Yesterday with the new classic i was seeing peeks at around 10:00am of 3650w. Given it's a 3960w array that seems a bit more realistic. I'm still happy with 92% of rated output.

Kurt

[offgridQLD]

The new classic 150 has been in for about a week now so I have been able to compare the data to the old classics readings. Below is the 24hr log over two days for both old and new classic. The logs are from days when the house was unoccupied so just covering consistent base loads for a fare comparison.

As you can see the new classic is reporting 5.5kwh for the day old the old classic was incorrectly reporting 7.5kwh a day so it was reading 26.5% high!

On top of this installing the WBJR shunt that can trigger float from (end amps setting) But now its taking into account all real time loads on the system when making that end amp calculation . I have noticed roughly 10% reduction in the days output. I noticed this on both the new and old classic. So it was a sign that the old way of setting end amps (take a guess at what the average loads will be on the system at the time and add it from the true end amp setting you want to use. This is a bit hit and miss, I guess it was better than just using a timer but at times when a larger load come on it was slightly over charging the battery vs using the true end amp number. Perhaps when the fridge did a defrost or sump pump came on as even when your not there the loads varrie.

After speaking to the suppler regarding the old classic it's simply a matter of sending it back . They will check the serial numbers match there records and they will post me a replacement. Nice to have local back up.

old classic 7.5kwh a day


New classic 5.5kwh a day, confirmed with shunt and matches selectroics inverters renewables logs perfectly.


Kurt

[jimbo]

So how long is your absorb now while house is unoccupied? Might just be the graph but mine tapers off a little slower than that.

[offgridQLD]

Yes it looks a little different if you zoom in on a few hrs rather than showing 48hrs on the one graph.

I hit absorb, voltage hits 59V at 8:05Am and held flat at 59V until 9:30am the amps have dropped all the way to 14.5A (triggering end amps) and switching to float . 3.6kwh into the battery at that time. Because the graph is only taking a sample every 10 min it doesn't always reflect everything down to the finest detail.

This is today. The sample starts from 5:00Am - 10:00Am , Just showing voltage (pink line) Amps (yellow line) white marks show start of absorb 59v and end of absorb 14.5A.


Kurt.