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Power Me

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Everything posted by Power Me

  1. I designed and certified (when SABS was still a functional entity) an intrinsically safe PSU for the coal mines some decades back. If I recall it was a 14V, 400mA design. It started out as a 15V design, but would fail the spark chamber test at 15V vs 14V. (That was a nerve racking test.) One of the requirements for fuses in IS environments is that they had to be a sand filled to quench the arc during fusing.
  2. When did SunSynk come onto the market? I don't recall seeing them when I chose the GoodWe 21 months back.
  3. Cool. As you can see from my plots above, I am essentially off grid too, except I have a prepaid meter connection as backup for those prolonged overcast days and for deep cold winter days when I heat more than my PV can supply.
  4. Note that if the cut off is set at 40% SOC then the inverter will cut off when the battery SOC falls to 39%, the battery can then self discharge (and a little power goes to the GoodWe too) to 38% by the next morning.
  5. I can only assume you must have endured a municipal power loss too? The GoodWe (of which I am no Evangelist) has 2x battery SOC cut off limits. The 1st cut off is for when municipal power is present. The 2nd is for when municipal power is not present. The 2nd automatically gets set to 10% lower than the 1st, when you set the 1st. If you set the 2nd to some other value, you must set it after setting the 1st value.
  6. Hi Hagu13. I have been running Pylon us2000b(x4) + us3000b (x2) for around 20 months now and my battery bank currently reports a 98% state of health (SOH). If this rate of degradation remains linear then after 10 years, theoretically the battery bank should retain 80 to 90% SOH. For the 3 months of winter I drain my battery bank down to 30% state of charge (SOC). I stop at 30% as I cannot fully charge the battery bank from PV the next day if I go any lower. If I had more panel power I would be comfortable taking the battery bank down to 20% daily for the 3 months of winter. During summer the battery bank typically only drops to around 60% SOC by the time the sun rises and then is back at 100% by around 12h00 on a sunny day. Summer plot Winter plot (24% SOC on this day and just missed getting back to 100%) I run the entire house (2x geysers, pool pump, fish pond pump, cooking (no gas), air conditioning units for heating & cooling the home (30000BTU total)) off of the PV and battery storage.
  7. Recovery or Release, that a good thought, thanks for this.
  8. Thanks for this info. What battery state do the parameters with the "R" appended at the end refer to, or when to do they become applicable? For example; High Voltage = 53.9V but high VoltageR = 52.5V I have just had a thought, that perhaps parameters with "R" appended are for reference or are perhaps recommended safe values? (ie non "R" = marketing supplied and "R" appended = engineering proposed limits )
  9. If I owned an EV (and I do want a "Volvo XC40 Recharge" and I do still have my many years old Tesla M3 deposit still in place) I would be charging it at home. I am not sure why there are no DC "fast" (they don't have to be fast, just DC) chargers for home PV owners as they would be so much more efficient, than the process of converting PV array to AC and then AC back to DC battery charging in an EV, and certainly if/when I can afford an EV I would investigate this DC charging possibility. My preliminary investigation revealed that actual data communication would be necessary with the EV rather than the simple pulse based communication used in AC charging. The EV cost problem in SA is that our useless SA Gov always implements the exact opposite of what they should be implementing. A pure EV in SA costs a small fortune as firstly EVs are not subsidised like in 1st world countries, but they in fact occur additional import duties as they don't have an ICE. I think I remember seeing figures like 25% import duty on pure EV vs 18% for an ICE vehicle. Additionally, because an EV has an expensive battery inside which makes the vehicle itself expensive, this pricing pushes an EV above the luxury vehicle threshold and so an EV then incurs an additional luxury vehicle tax. Such is the insanity on this continent.
  10. That is my thinking too. Wanting to eliminate the accumulated effect of mini charge discharge cycles on the battery by rather varying the geyser load. And to leave spare capacity in the inverter for a human in the home to randomly switch on a load such as a kettle and not trip the inverter that will be running off grid
  11. That's exactly the kind of error I was concerned might be thrown up by the inverter. Haha Do you perhaps know if the Axpert inverters use iron core magnetics in their inverter topology? I generally can. I use "Home Assistant" for my home automation and currently use SonOff devices to make sure I don't run either of 2 geysers or pool pump or bore hole pump at the same time. I also use inverter aircons and fridges so no large power spike from those items. See attached typical load profile for a 24 hour period. One can clearly see the blocks of geyser consumption which I want to smooth out. I have heard rumors that GoodWe are working on a FW upgrade that will cater for inverter paralleling in the future, but that means nothing until they actually do release a working update... I have in the passed run the oven off grid during substation/cable fault extend power outages, but to make life easy I would probably automate connecting to grid for an hour during cooking in the evening, to allow for the odd short duration where the microwave runs while a pot on the stove boils and a chicken roasts in the oven.
  12. Feeling emboldened by your comments, Youda, I have just performed a quick basic test. I grabbed a 2.2kW fined oil heater and stuck a 24A 400V diode in series with it. Disconnected my inverter from the grid and ran the load without any complaints (odd sounds) or odd "DC offset" errors from the inverter. I have no doubt an old school inverter with internal large magnet transformers will not like this kind of a load, but the modern high frequency switching inverters like the GoodWe don't seem to have any issue. This kind of set up would provide a very simple and low cost 3 step (0%, 50%, 100%) of load control.
  13. Electronics design is more than a hobby it is my career too. Thanks for confirming your test results. Running completely off grid (incoming breaker in open position) is my end goal too. I am kind of tired of paying for the (1 to 2)kWh/day that leaks back and forth through the pre-paid meter as the GoodWe attempts to achieve 0 export. The pre-paid meter obviously has been configured to meter feed into the grid as if one had fed the power off from the grid and so the only way to achieve true 0 consumption is to sever the connection completely, but obviously cloudy days happen and the connection must be very easily reconnected (even automated).
  14. Thanks for your quick reply, @Youda Very encouraging that you have successfully tested ~2.7kW phase angle switched load on a single 5kW inverter. Can you confirm this single inverter was running off grid at the time of the test and not in hybrid mode (grid assisted)? I personally would have guessed worst case would have been switching the load on mid cycle (peak inrush current) for 50% power delivery. I am running a GoodWe 5048D-ES which practical testing has confirmed is good for 5.4kW with grid present and 4.6kW running off grid. I want my geysers to heat even during load shedding taking place midday and so have to move the geysers to the backup output of the inverter. I must however then give the geyser loads smarts to avoid overloading the backup phase as I can't always be around policing what other loads are being humanly activated in the home. I have tested the geyser and even the oven(4kW) on the backup phase and there is no issue driving the loads with no grid assist, obviously not at the same time. Yip, heat sinking is a must for the SSR or Thyristors. (2V drop at 14A rms = 28W heat dissipation in the SSR) I will go with a custom discrete component design to reduce costs as a phase angle controlled SSR is very costly. In the long run however I might still go and design the DC power circuit running directly off a portion of the PV DC supply, so as to avoid the conversion efficiency losses of the whole PV DC to 220V AC. Why place a 3kW resistive load on the inverter when it could just be supplied smartly from the PV array directly. I am aware of existing products on the market with similar functionality, but in my opinion they are grossly overpriced and I don't think they can share existing PV panels with an inverter.
  15. Hi Youda Thanks for sharing your experience on this forum. I am planning on converting my geyser loads to variable loads too, the amount of power going to heat the water would vary based on current solar radiation, current household load, and battery bank SOC. I have been looking into designing the equivalent of essentially a solid state variac so that I can ramp the AC voltage up and down to control the power going into the element. I figured it would need to be done this way as I expected the inverter would not cope with a heavy phase angle switching load of 3kW on a 4.6kW inverter. I then decided that designing a simple high power buck converter running directly off of the DC PV panel string voltage going into the inverter would be much simpler and lower cost and I was going to pursue this solution until I came across this topic. I wouldn't have to added in the complexity of MPPT into my buck converter either as I was going to rely on the inverter MPPT by using only a portion of what the inverter was taking from the panels, eg 50% Can you confirm that your inverter has no problem driving a geyser element through a phase angle switched SSR to control a varying amount of power going into the element? You have 2 inverters running in parallel for 10kVA and so your heating element is only 24% of you total inverter available power so perhaps this is making the solution viable for you? Can you comment on using phase angle power control of a 3kW load on a 4.6kW inverter that is running off grid? Thanks for your comments
  16. I am running a Goodwe GW5048D-ES with 5.6kWp PV panels and 16.6kWh Pylon battery bank. In the spec sheet for the inverter it documents that; the unit can supply 4.6KVA backup power (6.9KVA for 10s) with grid connected the unit can supply 5.1KVA In practise though, with the grid connected and the inverter running at 53Deg C I have seen the unit happily supplying 5.4KVA for over 30min without drawing on the grid.
  17. Wouldn't be anywhere near as bad as the massive load switching that occurs at the end of a load shedding interval. After 4h of no power to the entire neighborhood with geysers cooled down and fridges and freezers warmed up and then bang on the entire local network at close to maximum load at each individual household. Note that my post regarding a constitutional right to privacy specifically referred to systems that in no way had any connection to a municipal grid and thus in no way infringe on anyone else's rights.
  18. If one has an off grid system, and I am referring to a stand alone system that is isolated from the municipal electrical grid and at no point will have any electrical connection to the municipal electrical grid, I feel it can be defended in a court of law that this situation is one's own private business and no one can force you to register or declare that you have such a system on your private property. Section 14 of the South African constitution gives all citizens the right to privacy, and this as I understand is what was used in the Constitutional court ruling that legalised the growing and consumption of marijuana for personal and private consumption. I see the installation of pv panels (planting marijuana) and using the electricity for one's own private consumption (smoking the marijuana) and synonyms under the right to privacy ruling.
  19. Hi Guys, great forum, I have learned much reading the conversations. I am in the market for a US3000B to link up with my existing 4x US2000B Plus pack. Noticed that @2una was helped out by @Silver. I am in JHB (Roodepoort side) and can come and collect, payment via EFT. I would love to hear if stock is available and pricing? Thanks
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