Source: http://forums.aeva.asn.au/viewtopic.php?p=60392&amp
Timestamp: 2019-04-19 12:35:02+00:00

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250ma - about 12w x 12hrs, 144whrs overnight. better than 600whrs I guess.
12w sounds like a lot for a charge controller in sleep mode.
250ma is what I see with no solar, no mains and the switch on the bottom off but note the fans are running at very low speed so this may be a third of the power.
The batteries are only 4 x 12v 7ah and old so I need to leave the mains on.
I see a surge quickly reducing to 0.5 mA, and slowly reducing after that. After about a minute or so, it was down to 0.33 mA.
You mentioned fans running; with the mains, solar off, and inverter switch off, my understanding is that this is impossible. Perhaps this was with mains on; I believe that the presence of mains will run the processor. It's not convenient for me to test this just now.
Assuming it goes down to 0.3 mA eventually, 15 mW is a lot better than 12.5 W or 600 W.
My measurements were on a 2015 model, in case that matters. I was using a 50 V power supply, not a battery.
Last edited by coulomb on Thu, 14 Jan 2016, 07:12, edited 1 time in total.
Thanks Coulomb, That sounds much better.
I have my PIP connected to my house bank at the moment though only switch it on for EV charging dutys. I have a spare 1500w of PV and racking sitting in the shed doing nothing so thought I my as well hook it up and have the PIP contribute some solar charging when it's not being used.
If solar charging works with the inverter off and little idle load then that's great.
With mains off (plug out of power point) , switch on the bottom off and batteries connected the unit is communicating so the cpu is up and running I also have the back light on with the panel so a bit more there.
The unit says its in standby mode this is the old style with heat sink on top.
paulvk wrote: With mains off (plug out of power point) , switch on the bottom off and batteries connected the unit is communicating so the cpu is up and running I also have the back light on with the panel so a bit more there.
Huh. The 2015 model doesn't switch the LCD or backlight on at all when in this mode (battery but no mains or solar). I thought the 2013 model was the same (don't have it any more), but I can't be sure.
Maybe it depends on the standby setting 31 was SbE. I changed it to Sbd, and when the LCD eventially went off (took ~~ 45 seconds), there was a faint click and the current on the power supply went to zero (won't read less than 1 mA). So in this model at least, setting 31 doesn't seem to affect this behaviour.
So Kurt: this may not apply to yours. If you turn your PV and mains breakers off, and the inverter switch off, does yours light up the LCD or not?
Edit: Paulvk: when you say communicating, do you mean talking to WatchPower? I had nothing connected to the serial port.
Last edited by coulomb on Thu, 14 Jan 2016, 07:02, edited 1 time in total.
"So Kurt: this may not apply to yours. If you turn your PV and mains breakers off, and the inverter switch off, does yours light up the LCD or not? "
Though I was just talking about having PV input and just the inverter switched off with PIP connected to battery.
I was under the impression that once the sun went down the charge controller would just shut down due to lack of solar input and then come to life again when it had enough PV input to wake it up the next day.
How much energy it consumes from the battery (if any) overnight I haven't measured though I will tomorrow.
Last edited by offgridQLD on Thu, 14 Jan 2016, 07:14, edited 1 time in total.
Software ver 52.30 as shipped Australian agent Giant power.
Note between 3 of us we have 8 units.
Last edited by paulvk on Thu, 14 Jan 2016, 07:18, edited 1 time in total.
Not sure if this is relevant to the current conversation but I found the resolution of currents reported by the PIPS was give or take an amp. So at low idle powers something like 2A reported could be anywhere between 1A & 3A, most likely 3A since they tend to underead. Had to fudge a lot to get decent results at low powers, understand now why Jdp (nice job btw) used the Victron instead.
solamahn wrote: Good. I will continue to turn all my fans upside down pre installation. I have some msd and mst coming next week.
It probably sounds stupid but has anybody tried a standard PIP mounted up side down then the fans would be blowing up. Yes I know.... but worth a comparison to see if it cools beter.
72x82W gridtied CMS2000 2kw north,2Kw East,2Kw west.
weber wrote: Your suggestion that I use 9 strings of 2 instead of 6 strings of 3 with the PIP-4048MS is a valid one, and one I'm still considering.
So what happens above 115 VDC? Does it still PWM, but not track the maximum power point perfectly? If so, how imperfectly?
I decided to try to find out by looking at the binary code. Unfortunately, it's in HCS08 assembler (not that they write it in assembler, of course, but that's what I see). That means I don't get symbols, except for a few from the shared communications, such as the QGS command (SCC to DSP) and (GS command (DSP to SCC). So it's hard going.
SCC = Solar Charge Controller, the part of the PIP inverter that charges the battery from the solar panels. DSP = Digital Signals Processor, the main processor for the PIP inverter.
The code is rather confusing; for example, there is subtraction of two quantities that as far as I can see are never different. So I can't pretend to know all of what is going on. However, the PV voltage (PhotoVoltaic, solar panel input voltage) is one of the shared variables that I am confident is right. So I can see what parts of the code do with the PV voltage.
I see many comparisons with 14500, which is the internal representation for 145.00 V (the SCC deals with hundredths of a volt and amp). When the voltage exceeds this value, I see alarms being set and so on. There are also comparisons with 14000; this is the representation for 140.0 V, where the alarms go off if the voltage stays under this value for a few seconds. All good.
But there is no comparison with 11500, representing the supposed upper end of of the MPPT tracker voltage range. I've done a binary search through the code image to be sure. What I do see are comparisons with 130.0 V. There is a linear ramp from 130 V to 145 V (a range of 15 V), allowing -4 A of maximum charge current per V above 130 V. So at 130 V solar input, the maximum charge current is 60 A; at 135 V, this falls to 40 A (5 V x -4A/V = -20 A), 20 A at 140 V, and zero current at 145 V. There other things that affect the maximum current, for example there is another ramp from 80°C to 90°C. The lower of the two ramps takes effect, so at 85°C (half current) and 140 V (one third current), the larger derating is from voltage, so you get one third current (20 A). At the same temperature and 135 V, the current would be 30 A, since temperature is now more important.
I should point out that all PV currents mentioned are at the battery end, i.e. after the buck converter. The actual PV current will be somewhat lower, due to the "DC transformer" effect of a buck converter.
So what's the 115 V figure about? It's possible that it is buried in there in the form of PWM values sent to the timer registers. But I suspect that 115 V is significant because it's a little under 120 V, the Extra Low Voltage limit. Somehow, they may get to dodge some certification requirement if it's ELV. That's pure speculation on my part.
It seems that operation just above 130 V will be fine, however there will be a reduction of maximum power due to the reduced maximum charge current allowed. But it seems prudent to design any system such that voltages above 130 V will rarely be seen. Again, I point out that this is based solely on references to the PV voltage; there could be other factors that I'm not talking into account.
To me, that makes 3S look more promising. 130 V / 3 = 43.3 V, which is above the MPPT voltage of most 72 cell panels (around 200 W, as mine are). 115 V / 3 = 38.33 V, below the MPPT voltage of at least some of my panels.
With 2S, there is no problem at the upper voltage end, but the problems show up at lower voltages. The MPPT needs a few volts above the battery voltage to operate; I see battery voltage plus 1.0 V and plus 1.5 V in various places. The specifications say 60 V minimum, and there seems no reason to fudge this figure. 60 V for 2S means 30 V per panel; for 3S it means 20 V. Even the poorest usable light would provide 20 V of output per panel, but maybe not 30 V.
So it's still not obvious to me which is best, but at least there are some more clues now. Perhaps those with PIP inverters installed could comment on whether my theory seems to fit their measurements.
Edit May 2018: the arguable consensus seems to be: 72-cell panels should be 2S, 54-cell panels should be 3S. 60-cell panels are usually OK as 3S, but in some cold climates may have to be installed as 2S.
I'm also considering 2S versus 3S.
I'm sorry to tell you that all your theorising is only of academic interest, because some time in 2015 it became illegal to install a PIP-4048MS with a PV array having an open circuit voltage (at the lowest expected temperature) of more than 120 Vdc, in Australia.
This is because the PIP does not do insulation testing of the array, and does not have a cutoff or an alarm to tell you if the array is no longer floating with respect to earth, and is therefore a shock hazard.
That means that strings of three 72-cell PV modules are out of the question. 2S is your only option.
Hey guys, I've only managed to read through about half of this thread but picked up some valuable knowledge.
Anyway I've just installed a PIP and have some questions and possibly a tip or 2.
Q1. What's the difference between AC and DC breakers? Seems to me they are both just a bimetal? I've used one before and it seemed to do it's job.
Q2. Has anyone used the fan 12v pwm as a control output? Seems like you could use it along with the dry contacts to do some tricky stuff without resorting to serial.
Q4. Has anyone used arduino with the serial output for control?
Q5. How easy would it be to modify the display to show input watts and output VA on one screen rather than clicking between screens?
Q6. 3kw is great, but it's not as sunny as aus so we have more overcast / rain than sun. I think adding more panels would be good as long as they are not disconnected before going over the 3kw limit. How could this be done simply?
Q7. Can I use more panels with a separate mppt going straight to the battery? Some mppt have a serial so could they talk to each other somehow?
Q8. Has anyone tried to add a WiFi dongle?
Q9. Has anyone made an android app for monitoring?
Q10. When using the microwave, I get 40A from the battery. Knowing batteries have only a life of 500 cycles or so, this would result in roughly 2 cycles per day including the overnight. That's 250 days. Am I missing something?
I read some of you were considering adding cooling. Surely the added draw would negate the benefit of the cooling? You add draw, which makes the gear work harder, causing more heat, requiring even more cooling. Vicious cycle.
Hopefully you have not overlooked the possibility of a heat wave where the temperature stays high, night and day for weeks? Have you done any viability math on this?
My gear is under the house, cinder block walls so it never goes over 18 deg. No a/c to buy, install, run or maintain. Perhaps you should consider this option. Don't want to dig under the house? Dig beside the house. Worried about water? Don't dig down. Build into the side of a hill or something. Failing all of that, dig a trench maybe 50m, get some 100mm pvc pipe, with a fan at gear end sucking. This will cool the air underground for almost free, forever.
Q11. I would like to control my loads, depending on other loads and input power. As I said, my hot water draws about 1200w. Let's say it's semi overcast and I'm getting 1500w input. Now let's say I want to turn on the kettle. I don't want them both on, it would draw 40A from the battery. So I want to disconnect the hot water while the kettle boils. How hard would this be?
Oh I forgot. I just built a new house behind the old house. Trouble is, the new house is close to trees on east, north and west. In addition, it's a 15 deg pitch roof facing east and west. So I had no north facing roof and a lot of shading issues. The angle issues could be solved with adjustable mounts etc, expensive and an eyesore from the old house (which will be rented out).
The old house however has some roof facing north and zero shading issues. So that's where I put my panels. It also keeps the tenants roof cooler I guess.
It's a rare situation that is probably useless info for most. But if I was off grid inland aussie, I would consider building a structure for panels which hopefully doubles as a garage or something. All things considered, it may actually be easier than dealing with shading, wrong direction issues, expensive mounting kits etc.
I've only managed to read through about half of this thread but picked up some valuable knowledge.
You've done well. It's getting quite long.
3S. In NZ especially, I'd consider changing that to 2S. See below.
Most of us are of the opinion that lead acid is less cost effective than LiFePO4, though you only see the benefits over the long term. I have some LiFePO4 cells from an EV kit that was sold cheap on Ebay. I know these are rare, but perhaps keep your eyes open for opportunities. You possibly very roughly 5 years to find a cheaper LiFePO4 solution, depending on how often you heavy discharge the battery.
Brilliant! I've been thinking about how to make my single 2400 W element draw less power. Maybe I can get it replaced with a dual element.
Note the fireproof gloves They're running much higher voltages, but the same principle applies. It could just take longer at lower voltage. You really don't want a piece of safety equipment (a breaker) to fail when you most need it (turning something off in a hurry), or to overheat and burn your house down. Ratings matter.
I don't think so. It's an interesting idea, but requires opening the box and voiding warranty. (But nearly everything requires that.) To me, serial comms is easier than fiddling with analogue electronics.
Cold panels put out higher voltage than room temperature or hot panels. The rate of voltage rise with fall in temperature is usually readily available from the manufacturer's web site. The PIP will disconnect from PV at 145 V, and reconnect at 140 V. In theory, all that should happen is that you lose out on say 15 minutes of solar input at the start of the day as the panels warm up (not much in terms of kWh), but it worries me that you are relying on the inverter to protect itself from harm that could cause it to blow up. Also, in New Zealand, with 3S panels, this could be happening every winter morning. The SCC should be replaceable without having to buy a new inverter, but it would be a significant nuisance.
The other issue is that the SCC won't produce maximum power, even if available, over 130 V, and we really don't know what it will do between 115 and 130 V. I'm not familiar with 250 W 72 cell panels, but it sounds to me like they might work in the upper voltage range of the PIP's MPPT/SCC.
Perhaps you could observe the PV voltage over a few mornings, then extrapolate to what you would expect on a typical winter day.
I'm sure others have. Weber and I considered Arduinos or similar, but Weber has a prejudice against 8-bit microcontrollers . Plus, we wanted WiFi, and we didn't see any way of getting a TCP/IP stack onto an 8-bit microcontroller. However, I've since seen WiFi dongles that convert to serial over USB, and you can change parameters with an AT command set. (Older readers may remember the Hayes compatible AT commands for 1200/2400/56k phone-line modems, e.g. ATH to hang up. ) So Arduino control with WiFi may be possible now.
The PIP's SCC isn't aware of the total power of your panels. If you put say 4 kW nominal at its input, I don't see how this would cause any problems. As with any other MPPT, it should just truncate the power to 3 kW.
I believe that this can be made to work, and I intend to try it, but have not yet done so. I don't believe that they need to talk to each other. You may need to carefully consider the voltage settings. The PIP's SCC/MPPT charger wants to see the battery current drop to a certain value before it will drop out of bulk/absorb into float. But with the other charger supplying charge current, it could exit bulk prematurely, leaving the other charger to do all the work. That might not make good use of available solar energy. But I think that if the other MPPT stops charging a few volts before the PIP decides it's at the CV voltage, then the PIP (assuming it has the majority of the panels) should be able to finish the absorb phase on its own.
Weber and I intend to use a Beagle Bone Black for this. We're busy on other things right now.
Q10. When using the microwave, I get 40A from the battery. Knowing batteries have only a life of 500 cycles or so, this would result in roughly 2 cycles per day including the overnight. That's 250 days.
I assume you're not using the microwave for very long. Let's say it's 1800 W and you use it for 15 minutes total per day. That's 1.8 kW for 0.25 hours, or 0.45 kWh. It's not a huge energy hog, just a moderate power hog. Your fridge on the other hand may use a mere 100 W (0.1 kW), but run for 50% of every day (perhaps less in New Zealand). That's an average of 0.05 kW x 24 = 1.2 kWh. 40 A is only 40/800 = 0.05C. That's a very gentle load for your AGMs, and should not stress them or decrease their life significantly.
Any cooling that's worth installing cools a lot more than it adds in heat. Suppose a fan draws 10 W. So the electronics powering the fan has to work 10 W harder. If it's 90% efficient, that's an extra one watt of heat it has to output. 10 W of fan could remove the heat from hundreds of watts of losses, including that extra watt, or thousands of watts of output power.
Northland wrote: Q11. I would like to control my loads, depending on other loads and input power. As I said, my hot water draws about 1200w. Let's say it's semi overcast and I'm getting 1500w input. Now let's say I want to turn on the kettle. I don't want them both on, it would draw 40A from the battery. So I want to disconnect the hot water while the kettle boils. How hard would this be?
It's probably not too hard for say an Arduino to continually ask (over the serial port) what the DC discharge current is. Maybe if you're using WatchPower, it could just be across the traffic, and pick out what it needs. What it needs is probably field w (PPPPP) of the QPIGS command; see the protocol manual. If the load is over a certain amount and you haven't switched recently, you could turn off your non-essential loads (pool pump, hot water booster, and so on). It would not catch every peak, but it's quite OK to have the battery supply 40 A or 100 A [ Edit: in your case, that's 100/800 = 0.125C ] for ten seconds or so. Keeping the peak current as low as possible (spreading the non essential loads over the times of lower demand) will probably help with battery longevity and may help get the most use out of your solar panels (have more of your loads supplied directly from solar, instead of coming out of the battery and back in again later, with significant round-trip losses for lead acid).
Last edited by coulomb on Wed, 20 Jan 2016, 05:50, edited 1 time in total.
Coulomb's excellent reply arrived while I was preparing this. But I decided to post it in its entirety anyway.
Northland wrote: Q1. What's the difference between AC and DC breakers? Seems to me they are both just a bimetal? I've used one before and it seemed to do it's job.
They are very different, and neither is just a bimetal strip. They both have both bimetal (thermal) and magnetic trips. Magnetic gives fast operation on extreme overcurrents. The difference is in the arc quenching when the contacts open. AC is a piece of cake as it goes through zero 100 times a second. DC arc are much harder to break. Air can be quite a good conductor once you get it started. And DC just keeps on giving.
A standard 250 Vac rated breaker is only good for 48 volts DC. But even then, you need to see an actual DC rating from the manufacturer. Some rate them for 63 Vdc. But don't forget, this is the maximum open circuit voltage.
(b) they will contain permanent magnets to blow the arc into a large circle, in which case you must be very careful about wiring them for the correct current direction (polarised), otherwise the magnets will hold the arc near the contacts and make it _worse_ than if you'd used an AC breaker.
Polarised DC breakers have been outlawed in PV systems in AU and NZ because the polarity markings are too confusing and too many sparkies were getting it wrong. Incidentally, (quiz question) what should you do if you turn such a breaker off and hear it continuously arcing or smoke is coming out?
The datasheet for your panels will give an open circuit voltage at 25 °C and a temperature coefficient for the same. So you can calculate at what low temperature your 3 series panels will exceed the PIP's 145 V maximum rating.
But from what Coulomb describes above, (by reading disassembly with no symbols! <I prostrate myself in his direction>) it sounds like the PIP's SCC may protect itself. When I asked MPP Solar, they said it would not protect itself.
Only coulomb could answer that. My preference would be to have the up button cycle through the possible variables on the left side of the screen, and the down button cycle the right side, independently, and perhaps add another variable or two to each side.
You don't need to do anything special. The SCC will automatically limit the current to what it can handle.
Yes. No problem. They don't need to talk to each other. They will effectively communicate via the battery voltage.
The problem with 2S is it will only be in the mppt range near full output (I'm assuming voltage drops) and won't be getting the mppt when it actually needs it.
another way would be using phase control (like a dimmer). Thinking about this now, it would actually be better than having 1.2kw on/off cycles. There are ones made for home automation which work off digital, so you ideally could pump any surplus capacity at any given minute into the element. Thus no draw on the battery ever. It would also allow me to pump 3kw in if it had been overcast all day and at 4pm turned to sun.
....but requires opening the box and voiding warranty. (But nearly everything requires that.) To me, serial comms is easier than fiddling with analogue electronics.
warranty for anything out of Asia is almost useless. The cost to return goods by DHL is 10x NZ to China as China to NZ. I would be better off buying any required parts, it's also much faster. I've never used serial before but was pretty good with mIRC scripting back in the day, so I have a vague grasp of programming.
righto. That's open circuit. So why not just close the circuit? A resistor or capacitor to draw the voltage down, then drop it out of the circuit once the SCC kicks in? Now where can we find a big fat resistor rated for 120v and thousands of watts? 2 birds - one stone eh? Did I hear a contactor engage when the SCC kicked in? if so it's just a case of parallel relays using NC contact to send early voltage to the hw element. But will that mess with the SCC voltage sensor?
I'm not familiar with 250 W 72 cell panels, but it sounds to me like they might work in the upper voltage range of the PIP's MPPT/SCC.
37.9v is Voc. 3x 37.9 = 113.7. But not frosty. Actually I got it wrong, they are 60 cell. Will try to find out the frosty voltage.
I find their selection of pairs of data values frustrating.
If you put say 4 kW nominal at its input, I don't see how this would cause any problems. As with any other MPPT, it should just truncate the power to 3 kW.
that easy? When I wanted to buy panels, there was nobody local selling. So it's expensive freight or a 2hr each way trip to horrid Auckland. I knew I needed 12 panels, and found someone selling panels by the pallet (30). It was $55 cheaper per panel. So I figured I would advertise to see if there was a taker for the rest. Within an hour I'd sold one. So I bought the pallet and got free freight thrown in. But no interest after that one sold, so I have 17 panels in storage. I could add as many as I want. But no more north roof so east it is.
40 A is only 40/800 = 0.05C. That's a very gentle load for your AGMs, and should not stress them or decrease their life significantly.
I wrote my battery capacity wrong, it's 2 banks of 200ah, ie 400 total. And that's when I get around to moving and connecting the 2nd set, lol.
They don't need to talk to each other. They will effectively communicate via the battery voltage.
HI Northland this maybe an option.
Northland wrote: righto. That's open circuit. So why not just close the circuit? A resistor or capacitor to draw the voltage down, then drop it out of the circuit once the SCC kicks in? Now where can we find a big fat resistor rated for 120v and thousands of watts? 2 birds - one stone eh?
I don't think you could get that to work practically. There is almost no power in the panels in the early morning, in fact, just enough to blow up your SCC, in accordance with Murphy's law. So you'd need something else to actually heat your water. I don't think you want a relay switching either AC or panels to the element; I can't think how you'd make that vaguely safe.
Besides, if the early morning panels put out over 145 V, even a 24 ohm (2400 W) element will attempt to draw over 6 amps (around 900 W), which the panels won't be able to supply at that time of day, so the voltage will collapse. It may well collapse too low for the PIP to use at all. You also have the problem of chasing your own tail; with the load on the voltage is too low, with the load off the voltage is too high, so the relay chatters until its contacts burn up. Plus, it would have to be a DC rated relay or contactor, which aren't very cheap.
Yes probably creates more problems than it solves. OK well what about a zener with reverse bias?
Northland wrote: Yes probably creates more problems than it solves. OK well what about a zener with reverse bias?
I really don't think you have to worry, since they are 60 cell PV modules. But if you want to tell me their make and model number I'll do the calculation for you.

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