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  1. dehv

    Dry transformer to oil cooled conversion?

    So dry type transformers seem to generally be oversized for the application due to the reduced cooling ability. So in theory how much of a gain would there be taking a small dry type, putting in oil? Would the saturation point be the limit rather than the temperature alone? Would it not do...
  2. dehv

    Aluminum DCEG on aluminum ground mount array

    So. When bonding an aluminum PV rack, wouldnt Al wire be preferable to copper in that there would be less dissimilar metals in contact? Codes seem to say #6 copper, which seems silly on an aluminum rack. Are most rack lugs stainless, or an aluminum alloy that prevents corrosion, or should...
  3. dehv

    AC coupling off grid

    How do delete this post goshhhdarrrn
  4. dehv

    AC coupling off grid

    "Generally, inverters that comply with IEEE 1547 and UL 1741 will be acceptable for interconnection." This pdf is from 2019, but it's a good start.
  5. dehv

    AC coupling off grid

    With a single sunny island you will need a transformer to work with most (240v) micro inverters. Ideally get one with a split phase secondary built in (low freq).
  6. dehv

    AC coupling off grid

    But to get permitted in the future, or get grid hookup, would require rapid shutdown, dc arc fault and more headaches. Not to mention one cloud and the entire string of series panels go down, and a single point of failure in your string, vs a single micro inverter failure.
  7. dehv

    Too good to be true? AliExpress 8pcs 3.2v 280ah lifepo4 for $432 in 8 days?

    I specifically asked them NOT to ship with DHL, always a gongshow here. "Come pickup your package 75kms away", ya nah send it back.
  8. dehv

    Too good to be true? AliExpress 8pcs 3.2v 280ah lifepo4 for $432 in 8 days?

    Firefox keeps deleting my draft when I swap screens or attach a file. Anyway for the 3rd time, aliE tracking didnt work but i found the shipping co and track24 giving this, hopefully its not a spoof site to support the scam.
  9. dehv

    Too good to be true? AliExpress 8pcs 3.2v 280ah lifepo4 for $432 in 8 days?

    Looks like b grade 280ah cells are just over $100 us unshipped. These are only 100ah for almost 1/3 the price... I will report with future news if/when they arrive.
  10. dehv

    Too good to be true? AliExpress 8pcs 3.2v 280ah lifepo4 for $432 in 8 days?

    I wonder if i'm going to get burnt, ordered 24 of these $35cad ea shipped to Canada, supposedly NOS. This video says he saw similar but used cells seen for sale in thailand for $23us on "lazada"... Feedback looks ok-ish... they are supposed to take a looooong time to get here via boat, but...
  11. dehv

    Correct size MPPT charge controller and How I determine correct gauge wiring?

    Beware of CCA copper coated aluminum wire if shopping online.
  12. dehv

    Max input voltage/amperage for MPPT charge controller

    Also if you have more than one string of panels, say two roof sides, it would be good to have a second controller for a separate mppt channel per roof side. This would add redundancy as well as longer life running each unit cooler.
  13. dehv

    Newbie building a portable generator

    If you will be doing construction You want low frequency inverter to start hard loads like air Compressors and power tools. Get a little inverter type generator to backup the solar, and make sure your solar is at least a cheap real mppt, ie a powmr/makeskyblue controller or better.
  14. dehv

    Problems using gas generator to charge battery

    Those lithiums will take as much amps as possible. Also most chargers have 0.7 power factor so you have to derate accordingly. So 3300 generator (running not starting watts) x 0.7 , 2310 ÷56v = 41.25 amps So set you cc to limit to somewhere between 30 and 40. Start at 30a dc in settings and...
  15. dehv

    Transformer question / 3 phase wye delta?

    Are they 6048US models? I had a pair of those until my hillbilly lithium sans BMS system burnt down the power shed, but I recall from the manual: Being able to set them up with 3 for 3ph, or two for split 120/240 So if you have 8 why not do 2x 3ph and couple the DC bus of one 3phase trio to...
  16. dehv

    solar panel old and new connection

    Second that vote for 2 controllers, one for old one for new panels.
  17. dehv

    Correct size MPPT charge controller and How I determine correct gauge wiring?

    I have the 4515bn and can confirm abuse testing way more than 40a potential input, the unit will just ramp up to 40a current to battery and stay there. Good for cloudy days to have more panels than 40a.
  18. dehv

    What is the best cheapest mppt charge controller

    The better quality 200-400w Chinese wind turbines usually use a boost circuit for max efficiency in both low and high winds, so a lower mill voltage isn't a problem if you have an appropriate "boost" wind controller rated for your system voltage. On the other hand If the mill is rated at higher...
  19. dehv

    Bypassing inverter in Inverter Gen (220vDC)?

    Caps are all on the potted inverter board. I have a collection of server supplies, interesting I'll have to give that a try, maybe run 4 with outputs in series to bulk up the battery pack. Thanks.
  20. dehv

    Bypassing inverter in Inverter Gen (220vDC)?

    I got a deal on a 3000W honda clone inverter gen with blown inverter. Testing off the HV DC plug going into the inverter board gives 220vDC at idle (ECO on) and 240cDC with ECO mode off. I was thinking of just running off that (the diode bridge output) into a high voltage input charge...
  21. dehv

    Why did my SIX marine batteries (27DC2) die in less than one year?

    Best value for Roll Your Own lithium (cells) right now seem to be the 290 (aka 300/310/320) ah LiFepo4 cells on aliexpress, 8 for just under a grand. Add bms. Regarding the OP's "hybrid/starting" supposedly deep cycle setup; 1. Buy a $10US battery hydrometer. 2. Buy a few jugs of distilled...
  22. dehv

    Switching to LifePo4 advice needed

    because reasons? One cell can cause cascading failure, and a lack of oxygen will extinguish a fire quicker and protect the building it may be enclosed in. OP requested advice, my opinion is this.
  23. dehv

    Controller recommendation.

    I guess it depends if the panels have bypass diodes, which most do.
  24. dehv

    Switching to LifePo4 advice needed

    Speaking from my own negative black smoke military helicopter fly by experience, don't listen to anyone who might say to not worry about a BMS. Also make sure to put in a fireproof air sealed box (think ammo can). Don't use automotive grade chinese circuit breakers (the square flat kind)...
  25. dehv

    Controller recommendation.

    I have used a 40A epever potted model like you linked to, and they are extremely robust - tolerant of over current potential but just limiting to 40A. They'll take up to 150V input i believe, so you could parallel two strings of 3 panels in series, and eat the potential gain getting over 40A in...
  26. dehv

    15 dollar ebay 5A MPPT Solar Charge Controller

    Most of the cheaper MPP boards seem to lack the tracking function, they're either fixed or you select the mpp by adjusting a pot.
  27. dehv

    Powmr MPPT

    Yes, they seem to lack a true EQ mode, just absorb then float on my v113 POWMR. Other cons are the fans do not have any speed control, they are either on or off, and the voltage accuracy is questionable on mine between 0.2 and 0.4v. The one thing advantage in the POWMR over the MSB are the...
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