Power Me

Bump

Goodluck. Keeps us updated.

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.

When did SunSynk come onto the market? I don't recall seeing them when I chose the GoodWe 21 months back.😒

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.😉

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.

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.

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.

Recovery or Release, that a good thought, thanks for this.

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 😉 )

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.

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

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.

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.

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).