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  1. efficientPV

    Mixed solar panel angles and/or shading in series strings or parallel?

    Multiple charge controllers work well for bulk charging. I've actually found multiple charge controllers work like crap together if they can't communicate together.
  2. efficientPV

    Mixed solar panel angles and/or shading in series strings or parallel?

    It would be better if each string saw the same amount of sun ant any time to have at least one strong string. Usually about 3/4 of my 2S6P panels are shaded at any one time and I do quite well with that arrangement. It does produce power in ambient light conditions.
  3. efficientPV

    Heater Pad with MPPT, how to make it work?

    We are talking small wattages here. Depending on array voltages, you could just connect a small switching power supply to the array DC voltage to power the control and heater.
  4. efficientPV

    Freezer to Fridge Conversion: Good performance or shitty Freezer Selection

    I would not recommend that temperature control because it does not have a time delay to prevent hot starts. Any control should have a five minute delay. The timed output seems nice, but I suspect that is for total time. I have a timer in my control which turns off the inverter after 20...
  5. efficientPV

    Freezer to Fridge Conversion: Good performance or shitty Freezer Selection

    47.4F <---> 39.3F where? I find most of the newer fridges are highly stratified with cooling coils near the bottom. To make it useful at all I run mine at 34F. Even then I use a computer fan attached to one of the upper baskets. I only run in the day never discharging the battery more than...
  6. efficientPV

    ($750) Tesla Model S 18650 Battery Module

    Have any cells been clipped, the fuse wire cut?
  7. efficientPV

    I may need closely matched Marine batteries. I can only get around 12 hours powering a refrigerator.

    Keep in mind that the inverter just sitting there will consume power. I saw one video and in his refrigerator setup the inverter running at idle consumed 1/3 of the power of the entire system.
  8. efficientPV

    I may need closely matched Marine batteries. I can only get around 12 hours powering a refrigerator.

    It sounds like the real problem is you do not have enough solar or whatever source for power. When the batteries are driven down to 11.5V you are killing them. Refrigerators really need a complex control to avoid problems. Nobody makes these controls. The fallback is just bigger and bigger...
  9. efficientPV

    Energy Conservation

    I drove by a solar farm in the northeast a couple days ago and I swear the panels were set to about 15 degrees when they "should" be in the high 40's. And the direction didn't seem south, though I wouldn't swear to that. That tells me the utility would rather have flatter power all day...
  10. efficientPV

    Panels to heat a 12kw water heater

    In industrial level heating solar thermal is the way to go. I could do PV heating cheaply with a bunch of used panels because I don't use off the shelf products.
  11. efficientPV

    Dumping excess to 120VAC water heater?

    Heating water today is like when solar used relays to charge batteries. MPPT came along and everyone said who needs that technology. I swear MPPT only became popular when they figured out a bunch of panels could be strung together, connected to any battery and they didn't need to know anything...
  12. efficientPV

    battery-desulfator

    If they worked that well, the batteries would last forever on PWM controllers. That said, I restore batteries with my water heater which has high current pulses. I always need an extra battery or two and I get them from town recycling. Usually, batteries ignored over winter. The ones with...
  13. efficientPV

    Diversion loads for freezer possible?

    The arduino NANO is cheap and there is a lot that average people can do with it without really learning programming. Start with their simple boiler plate programs and add in timer functions and voltage readings. $4 isn't a lot to spend on learning something new.
  14. efficientPV

    Any inline 48v water heaters?

    Heating elements will easily fit in pipes. They need to be oriented so a bubble will never form. I think the best deal around would be used stainless hot tub heaters. Several could be linked in parallel or series and nothing wrong with using 240V elements. You should use the highest voltage...
  15. efficientPV

    Diversion loads for freezer possible?

    I use a $4 micro to run mine deciding on temperature, preventing hot starts, minimum run time, battery voltage, auto reset after 20 minutes in case something goes wrong and extended running time. Refrigerators are real battery killers. Timers and logic prevent anything from ever going wrong. I...
  16. efficientPV

    Diversion loads for freezer possible?

    I suppose I do that. chest fridge only operates when battery full. After 5 minutes it checks to see if the battery is still over 13.8V and shuts off if it isn't. And it only operates during the day and stores cold in liquids for night.
  17. efficientPV

    Uneven strings making more power...

    I wouldn't do it unless you have blocking diodes on the lower voltage strings. It could create a situation where current backfeeds the shorter strings. Although one panel extra probably wouldn't be enough voltage under load and unloaded it wouldn't matter. Some here may take this concept to the...
  18. efficientPV

    Using excess solar to heat house

    That is E-test for use with Atorch/Hidance AC or DC power meters. It has some features that almost make it useful, but ok for a $13 100A 300V power meter. Sorry, not an app for diversion. A lot of beer talk about what to do with excess solar. Not much at all about how to control it. Even...
  19. efficientPV

    DIY accumulator tank.

    I have a hot water tank in the garage for laundry. It is heated only with excess PV so it can have wild temperature swings. Garage is supplied with water by a garden hose which is turned off between use. Even depressurizing the tank, Pressure builds up to 70psi from water expansion. I used 5...
  20. efficientPV

    What size solar system to run a refrigerator for backup if grid went down?

    Refrigerators are great battery killers. You need more protection than just the 10.5V disconnect the inverter has. That isn't to save the battery, it is to keep the FET from being destroyed. In emergencies you need to change your habits and not just open the door all the time. Big battery...
  21. efficientPV

    Has this been discussed somewhere? Are there inverters that automatically start up when connected to 12V?

    Those measurements were made from a power meter on the 12V going into the inverter. I used a 200A shunt to handle the 120A surge with a $10 50A power meter in parallel. That calibrated to a 8.6 power multiplier. Usage can change that. Don't try putting in new groceries at 4pm or it won't have...
  22. efficientPV

    Using excess solar to heat house

    My math may be wrong, but $18 at grid fuel costs looks like 310KWH excess for the year exported. At grid rates it is less than $50. It doesn't seem like you should invest in more than a space heater to utilize that.
  23. efficientPV

    Using excess solar to heat house

    Everyone likes to spend OPM (other peoples money). Resistive heating is an ultra cheap investment and can have very fast response times to gather moments of power. Here is just a half hour of my diversion in cloudy conditions.
  24. efficientPV

    Has this been discussed somewhere? Are there inverters that automatically start up when connected to 12V?

    7CF chest freezer Only use the camp from June to Oct in northeast # of panels not applicable as more than 70% of them are shaded at any one time, under 800WH a day. I run it down to 33F, in the morning it is 39F. New freezers are highly stratified, use a computer fan to circulate air. Very...
  25. efficientPV

    Why is mppt better than pwm?

    I don't think anyone is going to take an ohm meter to their Midnight or other expensive controller to see if it is real. So, the discussion is about the moderate price stuff. Sure, I'd like to see it on the high side for the things I'd like to do. But I have three different make charge...
  26. efficientPV

    Why is mppt better than pwm?

    For low cost you put a N FET on the low side. I'd agonize for a couple days to save a 1/3 cent resistor.
  27. efficientPV

    Repairing inverters...

    Why pay someone $20/hour to spend an afternoon fixing something ....... I got more than that 40 years ago! If you have to ask how to fix something, you probably can't even if there was a manual available.
  28. efficientPV

    Rheem Solar hot water tanks experience?

    My idiot sister replaced one of these when it started leaking, this tank is the same as they sell for hot water oil furnaces. The room it is in is like a sauna with the oil burner kept hot all summer. She should have replaced it with a HPWH since she runs a dehumidifier year round and air...
  29. efficientPV

    Why is mppt better than pwm?

    Not a good test. Many MPPT if not most use a FET on the low side panel - as the blocking diode.
  30. efficientPV

    Solid state relay for PV disconnect

    The capacitor in this application is not required in this application, but is suggested. Some other viewers might want to copy this for another application where it would be necessary. FET are pretty easy to use. This is a great project that many should adapt for their needs. You should show...
  31. efficientPV

    How to detect surplus PV power?

    Shading screws up everything. Almost by definition you don't have any significant excess power when voltage drops below MPP/
  32. efficientPV

    Solid state relay for PV disconnect

    I forgot to tell you to put a minimum of 4.7uF capacitor across the zener. When switched on, all those FET gates will have a lot of capacitance and drag down the gate voltage for a very small amount of time. The capacitor will supply the current in that time to keep the FET in full conduction...
  33. efficientPV

    CPAP question

    State which machine you have.
  34. efficientPV

    How to detect surplus PV power?

    PV voltage is a good way to tell if there is excess power available, it just won't tell you how much. For loads like resistive heating variable amounts of power can be put into the element until the voltage drops to MPP. This is how I heat water. As mentioned before, A small pilot panel will...
  35. efficientPV

    Inverter with off grid capabilities WITHOUT battery

    I run my washing machine from solar panels with a $20 inverter and no battery. A cloud passes and it will stop. I just press start after it is gone and the machine remembers where it was. No need for expensive technology.
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