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Thank you for the great forum, Safe Driving over the weekend. Sincerely Jason

Richard Mackay

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    DC microgrids

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  1. I'm like a dog with a bone on this subject. It's good to see someone else realizing the advantages of DC minigrids. I haven't come across PoE as a power reticulation system other than powering the Ethernet device it is connected to. The CAT 5/6 wiring must have limitations about how much power it can deliver. There's no DC reticulation equipment that's available because it isn't an established standard.
  2. I knew a colleague who was a senior engineer at Eskom and I witnessed how they monitor the status of the grid: There is an automated SMS that is sent out to all concerned that is generated by all the power stations around the country. The key indicator in this report is the frequency of the generation equipment. As the frequency slips down it triggers the alarm for the management to do something!
  3. It's common knowledge to those who implement load shedding that there's this tidal wave of demand that the grid has to cope with when the power resumes. This doesn't imply there's no savings to be had. There are many users who are clueless about their power consumption. So during load shedding all the unnecessary loads are also disconnected from the grid as well. Then there are the delinquent municipalities (and their equivalent clients) who aren't paying for electricity so one can only imagine what loads they have connected! In my opinion the smart way to manipulate users power usage to a different time (to avoid peaks) is to provide an incentive such as a reduced price for doing that.
  4. With RE systems the power used has to be managed since the power that's available varies and load shedding isn't built into the system! I haven't read much on this topic on this forum. I have seen comments about time scheduling certain loads but I'm sure there's a smarter way to automate this. I was referred to this controller to do this: https://www.morningstarcorp.com/products/relay-driver/
  5. Not a good idea. Heating is a no-no due to the amount of power required. A better idea is to schedule the geyser element to heat the water during the day when you have excess power available from your PV panels. This does require some fancy footwork with how you do this..
  6. Where are you located? This makes a BIG difference to what the best options are...
  7. You will not find heavy current jump start cables in the automotive stores (no names mentioned!) All their offerings come from China.. Look out for the cable and clamps you need and make the jump start cables yourself. A good place to look is welding equipment suppliers.
  8. I presume this inverter isn't for a DIY enthusiast? (He wouldn't be able to move it!)
  9. Post a pic of the batteries you have..
  10. Transformers do have their place. The substations that transmit power to you are all regular 50Hz transformers. They have the edge with being able to handle power. Small laminated core transformers that we used to see have vanished having been replaced by switched mode PSUs. However every now and then you come across a beauty like this one: I salvaged it from a wrecked (having been 'repaired' ) old school battery charger. I'm sure these are destined to become a collectors prized item!
  11. I doubt this. When a 50Hz transformer is used in a power supply (I presume a DC power supply) the bridge rectifier that rectifies the voltage on the secondary winding only produces a voltage pulse every every 10 ms. This is used to charge an electrolytic capacitor which has to be large enough to store the voltage until the next pulse. Switched mode PSUs rectify the mains voltage and this produces a DC rail of 320V approx. This is the supply to the dc-dc converter that reduces this voltage way down to the DC voltage required. As stated this happens at a high frequency so the charge pulses are arriving every x micro seconds. Also due to this speed the voltage regulation is also operating at this speed which allows for better voltage regulation.
  12. There must also be the claim that 'transformerless' is more efficient? (i.e. no losses primary/secondary windings)
  13. Forget about the PCB. Simply cut the original battery case, remove the batteries and replace with new ones. Then tape the battery pack up again.
  14. Take them to: https://www.africanadvice.com/1373348/Scrap_Metal_Merchants/Boksburg/Reclam/
  15. Hi Robert, Where are you located? (This does matter!)
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