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Carl

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  1. Thanks
    Carl reacted to Greg in Wanted: Goodwe WiFi Module with 5 Pin Connector   
    Email me: [email protected]
  2. Like
    Carl reacted to pilotfish in Solar panels on flat roof: Does the angle of the solar panel really matters ?   
    This has been done before by people much smarter than me;
      Fixed Adj. 2 seasons Adj. 4 seasons 2-axis tracker % of optimum 71.1% 75.2% 75.7% 100% The table above shows that there is hardly any value at all in adjusting panel tilt each season over a fixed tilt array, however there is a very real advantage to a 2axis tracker over fixed array.
    The above numbers don't really tell the whole story - for a fixed array to theoretically match the annual output of a 2axis array you would need to add 40% panel capacity, but the larger fixed array would still give low output in the morning and evening with a huge output in middle day, whereas the 2axis array would give a much smoother output throughout the day.
    This smoother output would deliver significant benefits in real life over the simplistic result of math on a piece of paper showing equal annual output. To have your output pick up quickly in the morning and extend PV output late into the afternoon would have significant benefits in an off grid situation (and most other situations as well).
     
     
  3. Like
    Carl reacted to Abe53 in Nissan Leaf for sale - R165 000 -SOLD   
    Hi Carl, Yes, would like that Leaf for the 20km school run. Will send detail by PM.
    Have excess production on my solar PV to charge with.
    Am in Gauteng but flying down to Cape for the holidays. However, will have to send the leaf by trailer...
     
  4. Like
    Carl got a reaction from PsyCLown in Nissan Leaf for sale - R165 000 -SOLD   
    Current range that it charges to is between 55 - 65 KM. Range is calculated after every recharge and is based on previous trip conditions.
    The battery pack is a standard 24kWh pack and a new pack will give you 180 KM range in summer and around 160 KM in winter. That is for moderate driving.
    Our long term average for over 2 years of driving is 7.5 KM / KWh (That works out at around 40 cents / km charging from the grid in Cape Town)
  5. Like
    Carl reacted to GreenMan in [SALE] Mecer 200Ah Lithium Battery   
    Yes, it will work. I have a 12V 100A LiFePo4 connected to a 720w Mecer inverter. 
    However, the charge switch MUST only be set to 10A and not 20A. If you do that, the inverter will eventually fail. This is well documented in the mybroadband thread. 
    Other small catch is that if you drain the battery enough, then the battery BMS will turn off the battery. When the power comes back the inverter won't turn on as there is no battery voltage and hence cannot start charging the battery. Solution is to use a voltage source that is high enough e.g. 13.8V and connect it momentarily to the inverter battery terminals. This will wake up the BMS and allow the inverter to turn on and charging to commence. 
    For safety I only use a power supply that is isolated e.g. ye olde transformer based psu. 
    Yes the Mecer does charge the battery at below the ideal 14.0V but so far so good and if necessary I will hook up a 14.0V (isolated) PSU 
    to the battery to let the BMS balancer do its thing. 14.2 V is probably even better. 
  6. Thanks
    Carl got a reaction from BritishRacingGreen in Repair of Axpert Inverters : A Journey Started   
    @BritishRacingGreenyou have inspired me to attempt a repair on a faulty Growatt SPF 5000 ES inverter. With MPPT board removed and only battery connected i noticed surface arcing around the Ceramic caps and the DC to DC Bus Side IGBT's located on the bottom of the middle heat sink. There is a fair amount of black dust on the board and some moisture on the fan unit and on the board.  All the IGBT's and Mosfets test ok on the diode test function so hoping that damage is limited or best case no damage. Inverter came up with warning error 62. Please advise what is the best way to clean the board.
  7. Haha
    Carl reacted to BritishRacingGreen in Repair of Axpert Inverters : A Journey Started   
    I have a nasty solar related problem , but an interesting one also. I passed on my old MKS3 (only 2 years old though) to my son-in-law , he added a Pylon UP5000 and used it as a backup system for a couple of months. Last week we added 4x555W panels to the mix (one string supply (170-180V  working voltage) .
    I encountered a nasty failure mode in that the  PV will supply high loads or charge flat battery without any problems . When the PV demand is in the order of 1kw and higher , no problem. But when the load is only like 300watts and the battery is full, then the system becomes unstable . The battery voltage rise slightly , and of course affects a large charge current from the MPPT . when that happens , the PV drops again , and everything repeats at about 3 second interval. Add a large load , hairdryer at 1.5kw , everything is stable again. or add a flat battery , everything is stable again. weird. What worries me is that sometimes the AC output also fluctuates somewhat.
    The MKS3 MPPT was just working fine when I decommissioned it at my own site.
    So here is my theory . I think the MPPT regulation is faulty . I have seen it on the DC bus voltage curve on the HomeAssistant log. So when there is no load on the MPPT , the DC bus shoots up .  But when there is load , the regulation improves for the wrong reason , dampening the rise in DC bus voltage. Could be a faulty MPPT current sensor , I am taking wild guesses. 
    There are suggestions it may be a panel related issue , but I have my doubts . When a panel is weak , or we have dry joints in the PV cables , we would experience just about the opposite  behavior as described above .
    Fortunately , courtesy of our dear friend   @Steve87 ,  I have an MKS4 which I am going to test tomorrow at son-in-law site , in order to make sure in what subsystem of the installation the fault lies , panels or inverter .
    So I will keep posted on my findings . One thing I have learned , is that my PV  commissioning procedure must be revisited in order to ensure that  PV operates adequately at various load conditions.
    The interesting thing is that no error is offered , I think the poor regulation  is still within the DSP's windows of forgiveness , otherwise it would have raised a DC voltage too high error or so.
    I hope its hardware  related and not require firmware upgrade . I am sh#t scared of firmware upgrade , so far I had no need to touch that , it makes me wake up at 3 in the morning , eyes wide open. Then I realize we have a mentor in @Coulomb , nightmare is over and I fall asleep again. 
     
     
     
     
  8. Like
    Carl reacted to Steve87 in Hoppecke Battery lithium cell salvage   
    This rebuild has been a major success. After about 10 cycles I am happy to report that the Hoppecke has been fully restored to produce & store energy again. 
    The function of top or bottom balancing cannot be stressed enough. 
     
     


  9. Like
    Carl reacted to BritishRacingGreen in Axpert Inverter: Error 52   
    Yes, its a very unforgiving failure,  because the neatral is also grounded, the full bridge converter now gets shorted, and mostly leads to the full bridge IGBTs getting destroyed. 
  10. Like
    Carl reacted to BritishRacingGreen in Repair of Axpert Inverters : A Journey Started   
    Chapter 5 : Beginning of the End 
    I am definitely not out of the woods yet , not sure yet if the fan controls and relay switching logic , control board and display will work , but I decided last night to introduce the control board and display. I have no way of verifying the operation of the control board , other than to make sure that there i no bad resistance between rail supply inputs etc.
    So I inserted the control board and realized early that one can actually misalign when docking it to the main board , which I reckon could cause havoc , and undo all our hard work. I wired up the bare minimum , including the display .
    Switch on , and after the usual startup timer timed out , it gave me Warning 01 , fortunately that is fan locked , so i plugged in the 3 fans . The machine then started up  without any further warning or error . obviously the battery icon flashing as well because I have not connected battery or grid to the power chain.
    I was satisfied with the progress and decided to  add battery power  in the early morning , which will be an indicator whether all my hard work was worth the while.
    No PV  modules added as that is the very last thing i will do in the final analysis . PV1 metrics does show up on the display though , but that is hogwash. I have seen it before on other machines as well when pv mppt module removed .
    Today I decided to take the big step to add current limited DC power  to the battery port and bring up the power chain. A bit nervous though .I have two 30V variable supplies I cascaded to set to aggregate of 51V.
    Here is me pre-charging the MAX battery input with suitable resistor.
     

    and here is me going firing  51V DC , attacking the MAX full-on , no more 'Mr Nice Guy' :

     
    The MAX submitted  immediately , produced about 380V on the BUS , opened its front porch with a beautiful sine wave 228VAC .  I also checked the IGBT gate drives and saw the magic in action . One half bridge had a continuously changing PWM to produce sine , wheras the other part of the half-bridge was constant at 50% duty cycle @50HZ.

    Have I won the war ? not yet , but many battles yes , still has lots of work lying ahead . So the journey continues ....
     
  11. Like
    Carl reacted to BritishRacingGreen in Repair of Axpert Inverters : A Journey Started   
    Chapter 3 : The AC IGBT Drive Section
     
    Haven't even started on a schematic trace here , hope to add it during next week.  But for me , the show already stops at the very beginning . The 12 SMPS flyback transformer provides an ac signal  which is diode half wave rectified , which in turn drives the primary of TX7 , the IGBT drive transformer. So I thought i will put the diode back because my rail supply is back to 12V again, in the hope that the igbt transformer was just incapable of coping with the faulty high voltage. Solder D20 back on , switched on and smoke came from the transformer . Ai, Ai , Ai. Brand new difficulties and possible cul-de-sac lying ahead. 
    So in retrospect , when the SMPS failed and decided to throw max voltage on the bus , this TX7 transformer actually failed first and clamped the rail. Thats the reason why initially when i removed the hot diode D20 , all hell broke loose as i described in chapter one !!!!
    I hate transformers , probably because I know too little about them.  The worst news is this transformer is Voltronics proprietary , so no ways I can even think about getting a spare . Only alternative is reverse engineering the device , and re-building from scratch. If you see what Coulomb and Weber do on their AUS forum , its clear that these guys fathers have raised them not to be scared. So inspired by them and others , I decided to rebuild this show-stopping sun-of-a-gun , how difficult can it be?.
    Very fortunately , a member by the name of Holmes on Coulombs AUS site has done something similar , so I had a good idea what was lying ahead.
    This time I did not have the luxury to cut the devices legs to desolder, so my solder wick skills was tested again , this time I managed well , but it takes a long time , and you need to be patient.
    I fired up my gas-braai and cooked the transformer in boiling water for about 30 minutes. That softened up the glue sections , so I was able to dissasemble the split core halves. Next I removed the Mylar tape layer and started to unwound the the coils , obviously documenting it carefully . I am going to make proper notes of my rough sketches and publish it here at a later stage.  
    Rewinding these devices is not rocket science , but one must be careful to keep the windings flat , or your next layer will become unmanageable. There is one primary winding , 21 turns of .3mm enamel copper wire , then there is three secondary windings each 35 turns , each winding section is nicely insulated with about two layers of Mylar tape. oh , and of course testing for isolation between windings as well (insulation).
    I was not confident enough to just plonk it back onto the mother board . So I bench tested it , in order to both check  voltage gain in terms of turns ratios as well as polarity of winding in relation to each other . It passed all test surprisingly with flying colours .
    So I soldered it onto the board , switched on , and I got the secondary voltages that the drive section desires . Next post I will post the drive schematics and show the waveforms of the secondary winding in more detail.
     
    EDIT : oh , I forgot , all did not go plain sailing , when I first bench tested the re-winded transformer , the core got hot !. Long story short , there was a nasty air-gap formed by me not putting the split core properly together. So this is a forward mode transformer , it does not store and release energy like a flyback transformer (which is really a multi winding inductor) .  So the air gap caused inductance to lower , huge magnetizing current flow in primary.  So I made sure to mechanically secure the split halves by a healthy layer of Mylar tape.
     
  12. Like
    Carl got a reaction from Gerrie in Maximum demand metering   
    The maximum demand charge is actually based on the highest average demand (KVA or KW) during a 30 minute window period starting at midnight on the beginning of the month.
    So the billing period is broken down into 30 minute blocks and then you get charged for the block with the highest demand.
    Maximum Demand = kVA = kVAh/T      (Where T = integration period of 30 minutes)
    So from this you can see that the starting current of motors will be an insignificant contributor to your maximum demand charge.
    So the trick is to reduce your energy consumption for any 30 minute block period.
  13. Like
    Carl got a reaction from Richard Mackay in Maximum demand metering   
    The maximum demand charge is actually based on the highest average demand (KVA or KW) during a 30 minute window period starting at midnight on the beginning of the month.
    So the billing period is broken down into 30 minute blocks and then you get charged for the block with the highest demand.
    Maximum Demand = kVA = kVAh/T      (Where T = integration period of 30 minutes)
    So from this you can see that the starting current of motors will be an insignificant contributor to your maximum demand charge.
    So the trick is to reduce your energy consumption for any 30 minute block period.
  14. Like
    Carl got a reaction from viceroy in PV circuit breaker tripping!!   
    Circuit Breakers can typically either have a thermal / magnetic or an electronic trip unit fitted. Some points to consider are:
    1) Electronic trip units are far less affected by ambient temperature.
    2) Thermal magnetic trip units typically have to be derated for ambient temperatures above 40 degrees C. (Eg. at 50 degrees, delta T = 10 degrees, 5% current derating)
    3) Trip units are sometimes interchangeable for AC and DC circuit breakers. As @plonkster pointed out the thermal protection of the trip curves are identical since the bimetal strips are responding  to the RMS value. The instantaneous protection against short circuits are influenced by the "ferromagnetic phenomena" which in tun is affected by the circuit breaker design and the way the poles are connected. ABB have a coefficient called "KM" that the instantatneous trip value for AC has to be multiplied with to obtain the DC values. This coefficient varies between 0.9 - 1.3 
    So coming back to @viceroyproblematic circuit breaker.
    1) I would suspect that the breaker may have a high internal contact resistance which is causing  localised heating near the bimetal strip.   
    2) Other factors such as undersized cabling (@Chris Louw), poor crimp connections, incorrectly tightened etc. will also cause localised heating resulting in a derating of the trip setting.  
  15. Like
    Carl got a reaction from ___ in PV circuit breaker tripping!!   
    Circuit Breakers can typically either have a thermal / magnetic or an electronic trip unit fitted. Some points to consider are:
    1) Electronic trip units are far less affected by ambient temperature.
    2) Thermal magnetic trip units typically have to be derated for ambient temperatures above 40 degrees C. (Eg. at 50 degrees, delta T = 10 degrees, 5% current derating)
    3) Trip units are sometimes interchangeable for AC and DC circuit breakers. As @plonkster pointed out the thermal protection of the trip curves are identical since the bimetal strips are responding  to the RMS value. The instantaneous protection against short circuits are influenced by the "ferromagnetic phenomena" which in tun is affected by the circuit breaker design and the way the poles are connected. ABB have a coefficient called "KM" that the instantatneous trip value for AC has to be multiplied with to obtain the DC values. This coefficient varies between 0.9 - 1.3 
    So coming back to @viceroyproblematic circuit breaker.
    1) I would suspect that the breaker may have a high internal contact resistance which is causing  localised heating near the bimetal strip.   
    2) Other factors such as undersized cabling (@Chris Louw), poor crimp connections, incorrectly tightened etc. will also cause localised heating resulting in a derating of the trip setting.  
  16. Thanks
    Carl got a reaction from Lourens78 in New Installation advice required?   
    Technically this is called "Current Level Discrimination" and is a technique linked to the staging of the Long Time (LT) tripping curves of two serial-connected circuit-breakers. (Quoted from the Schneider Electrical installation guide)
    An interesting point is that overload protection of a cable can be implemented either at the source or at the load side but short circuit protection has to be implimented at the source.
    @plonksteris spot on.
  17. Thanks
    Carl got a reaction from ___ in New Installation advice required?   
    Technically this is called "Current Level Discrimination" and is a technique linked to the staging of the Long Time (LT) tripping curves of two serial-connected circuit-breakers. (Quoted from the Schneider Electrical installation guide)
    An interesting point is that overload protection of a cable can be implemented either at the source or at the load side but short circuit protection has to be implimented at the source.
    @plonksteris spot on.
  18. Like
    Carl got a reaction from Fuenkli in New Installation advice required?   
    Technically this is called "Current Level Discrimination" and is a technique linked to the staging of the Long Time (LT) tripping curves of two serial-connected circuit-breakers. (Quoted from the Schneider Electrical installation guide)
    An interesting point is that overload protection of a cable can be implemented either at the source or at the load side but short circuit protection has to be implimented at the source.
    @plonksteris spot on.
  19. Like
    Carl reacted to phil.g00 in PV Panels Creating A Current On My Roof   
    @Jaco de Jongh, Ah this is something different, still not eddy currents though.
    Eddy currents by their very nature are current flow internal in a metal and are effectively flowing in a short circuit so there is very little voltage. 
    This is induced current, but no real potential build up, think of a lump of metal as being made up of windings of a transformer but each winding being shorted out. Plenty internal current rushing about and plenty heat but no voltage build up to speak of. 
    I think your dealing with the capacitive effect of an electrostatic charge which does have plenty voltage, but normally not much current.
    Like the little shock you get when you touch the door handle from some carpets.
    You have all the components a large plate being the panels and the roof combination, the other plate being the ground, and high frequency MPPT switching.
    The higher the frequency the lower the capacitive reactance (it is inversely proportionate to frequency) so it could probably develop enough current to deliver a nice shock.
    Mmm, interesting.
     
     
  20. Like
    Carl got a reaction from ___ in PV Panels Creating A Current On My Roof   
    Technically its a fault voltage that we come into contact with that will drive a current through us.
    Our impedance is determined by many factors such as the current path through the body, amplitude of the applied voltage, duration of the applied voltage, frequency of the applied voltage, contact surface area, pressure exerted and skin temperature.
    IEC 479-1 Table 1 (for the highest risk 5 % of the population) shows that the total impedance between dry hands varies from 1750 ohms at 50 V rms to 700 ohms at 1000 V rms. The impedance of an arm is very similar to a leg. So the values mentioned also apply for the current path from one hand to one foot. The more typical situation is where the current path is from one hand to both feet and then you can use 75 % of the bove impedance value. 
    So start by measuring the fault / touch voltage. 
  21. Like
    Carl reacted to Elbow in Available solar power prediction   
    Hi,
    I made a NodeRed flow that attempts to predict available solar power.
    It does it using a node calls "Solar Power Forecast Plus" that takes your position, panel alignment etc and predicts the power that should be available.
    I then took a www-request node to request weather info from darksky.net, and attempted to factor in the cloud cover to try to come up with a prediction.
    The resulting info I send into MQTT to EmonCMS so I can chart it and so on.
    My flow looks like so:

    An export of the flow is also attached if anyone wants to play.
    The MQTT message generated looks like so - EmonCMS can import it nicely:

    You can see that right not the ideal available power is 3019W.  Darksky says there is 98% cloud cover, so my estimation gave 1243W achievable.  The formula is a guess, I used:
    actual = ideal * (1 - 0.6*cloudCover); I'm finding that Darksky overstates the amout of cloud - so my estimates are too pessimistic.
    Still - here's how it came out compared to actual yield this morning:

    You can see Darksky saying 98% cloud.  Nevertheless my actual yield was close to the "ideal" figure.
    The actual weather reported at Cape Town Airport is FACT 060900Z 16011KT 130V190 9999 FEW030 21/11 Q1015 NOSIG - ie few clouds at 3000ft.  Looking out the window there seems to be high clouds but its a bright day.
    Did anyone try to do something like this before?
     
     
     
     
     
     
    solar-prediction.flows.json
  22. Like
    Carl reacted to Elbow in I'm all official!   
    Yay.  All official!
    Thank you to @Rautenk, @Mike, @Carl, @Jaco de Jongh, and tons of advice from the ou manne of the forum and lots of others besides.
    What an interesting project - I learned a lot in the process and so far not a single shock!
    On a day when we face Stage 6 shedding I feel like very clever to have  this system in the house!
    Thanks,
    @Elbow / Steve
     
  23. Like
    Carl got a reaction from Jaco De Jongh in Random earth leakage trip   
    That may be one reason but i think it is far more scientific than that.
    The reference curve for potentially lethal currents applicable to the current path from the left hand to both feet obtained from IEC 479-1 Figure 14 is shown below.
    From this graph it is clear that at 30 mA the probability of ventricular fibrillation is 0%.
    Currents > 30mA  can have serious consequences.

     
     
  24. Like
    Carl reacted to ___ in Random earth leakage trip   
    I actually wrote that and noticed after hitting "Save" that it was no longer there. Oh well... how terribly fortuitous that the human body has a nice 30mA gap so we have some room to mess around 😛
     
  25. Like
    Carl got a reaction from ___ in Random earth leakage trip   
    That may be one reason but i think it is far more scientific than that.
    The reference curve for potentially lethal currents applicable to the current path from the left hand to both feet obtained from IEC 479-1 Figure 14 is shown below.
    From this graph it is clear that at 30 mA the probability of ventricular fibrillation is 0%.
    Currents > 30mA  can have serious consequences.

     
     
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