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  1. ajw22

    Adding a 16S battery to a 14S battery

    This is a topic that seems to come up every few months, usually combining 36V and 48V batteries. It's doable, but a really bad idea. Doing some math, in order to keep all cells between 3.40V ~ 4.10V, you'd be cycling between.... 54.4V and 57.4V total voltage. The 14S cell voltage would be 3.89V...
  2. ajw22

    Aggregate loss of PV wiring losses

    Ah, that translation is wrong. You need to know the overall voltage to turn that voltage loss of 0.7823V into a percentage loss. Eg1. if the panel voltage were 20V, then the percentage loss would be 0.7823V / 20V * 100% = 3.91% Eg2. if the panel voltage were 150V, then the the percentage loss...
  3. ajw22

    Aggregate loss of PV wiring losses

    One important issue being overlooked: Those are peak losses, when the solar panel is putting out peak current. In reality, current will be lower most of the time (due to weather, seasonal/daytime angle of sun, etc), so the loss% will also be lower most of the time. Another related thing that may...
  4. ajw22

    Charging a big 72v battery with a small 72v battery

    14s will be better in most aspects. The boost converter should run more efficiently, lower losses due to 1/2 current load on the cells, wires, and BMS.
  5. ajw22

    Charging a big 72v battery with a small 72v battery

    Interesting, those roll up "panels" are amorphous (aka thin film) technology... I thought they had gone extinct. The big disadvantage with those is the bad conversion efficiency of 6.67% (when new!), vs the ~20% of crystalline tech (incl foldable/flexible panels). Since amorphous degrade much...
  6. ajw22

    Charging a big 72v battery with a small 72v battery

    This is available now, and should work pretty much right out of the box: https://www.aliexpress.com/item/1005001865313174.html It's a boost converter, so the aux battery will need to have lower voltage, perhaps 14s / 58.8Vmax? Setting the output voltage to 72V should start the assist before the...
  7. ajw22

    connecting solar panels

    Also, the model or spec sheet of your PV panels. Key issue is whether the "~40v" is Vmp (Voltage for max power) or Voc. If Vmp, the total Voc could potentially go above 150V and damage the charge controller. Especially if you live in a cold climate, as PV panels produce ~0.3% more voltage for...
  8. ajw22

    buying second hand pv, what to look out for?

    Just a quick 101 on the basic construction of a solar cell/panel. Hope it helps. Below is a closeup of one solar cell. Voc (Voltage Open Circuit, ie no load connected) is generally around 0.6Volt, affected somewhat by temperature, a little by light intensity, but definitely not size. Current...
  9. ajw22

    DIY Backup Power Supply Build

    Had to look up what exactly 1G was - it's analog tech from the dinosaur age!! Quite possible that no modern Pocket Wifi is backwards compatible to that. Yes, still needs a mobile signal, of course. The advantage is that you can duct tape it to a window, or even put it on a 10m tall pole on the...
  10. ajw22

    eSmart-3 Controller

    Best to set the target (ie 14.5V) in the charger, and the BMS limit slightly higher and avoid tripping. Having the BMS trip should really be the last resort, as chargers often do not like operating without a battery (ie. can be damaged). Again, make sure to check the actual voltage. I have 4...
  11. ajw22

    DIY Backup Power Supply Build

    Very very nice! For a portable solution, the AC/Solar toggle switch sticking out will get bent or broken sooner or later. A different switch, or perhaps 3D print a recess? The exhaust fan is located quite low, so heat from the inverter will likely accumulate in the upper part of the box. If it...
  12. ajw22

    eSmart-3 Controller

    Have a look at the graph on page 8/9 in the manual, available here: https://www.solartex.co/tienda/wp-content/uploads/2019/04/eSmart3-User-manual.pdf The terminology mess is likely due to the charger being designed mainly for lead acid batteries, but also with support for other kinds of...
  13. ajw22

    Home PowerDrive V2 - Germany ** 39+ kWh ** Big Power ++

    Have you considered tilting the panels by slightly raising one side of each panel? Raising just 1cm on a 1m wide panel creates a 1% slope - a typical amount for a drainage pipe. I imagine that'll reduce dirt accumulation significantly, except for the lips on the very edge of the panels.
  14. ajw22

    Bus bar thickness?

    It totally depends on how many Amps the bus bar has to conduct, ie the power of the charger/load, ie. the charge/discharge rate. Eg. If you charge it with only a 10W PV panel, and powering a 10W LED lamp, then the current would be approx 10W/24V = 0.4Amps. For that, anything that could be called...
  15. ajw22

    DC MCB Not Working?

    That probably means it has both the "thermal" bimetallic heat switch, and the [electro-]"magnetic" switch. That's pretty much the standard with these kinds of breakers.
  16. ajw22

    DC MCB Not Working?

    In principle yes, but there is quite a large leeway to prevent nuisance tripping. Below is a link to some extensive explanations, but to make it short, have a look at the graph below of a typical breaker. Most breakers have 2 tripping mechanisms: 1. A bimetallic switch (light blue in the...
  17. ajw22

    Using Diodes???

    Unfortunately no. You have to look it up in the ForwardVoltage-vs-Current graph in the datasheet. At 60A, it's around 1.2V, much higher than the typical 0.2V~0.4V of a schottky diode, so not particularly well suited for your use case. Even if you were to use 2 of them in parallel (so 30A...
  18. ajw22

    Using Diodes???

    Like AGM, and flooded lead acid, each requiring different charge voltages? Or LiIon / LiFePO4? Are you planning to use something like an Arduino to automate the switching? Details would help to find better options, or rule out others. In any case, the circuit looks fine, but be careful when...
  19. ajw22

    Re-wire a house to use 24v LEDs ?

    100%. Adding a "light blub extension" helps to move the electronics away from the pocket of hot air, but then the bulb sticks out and some people don't like that... makes the room a lot brighter though, allowing to switch to a lower wattage LED that produces less heat in the first place. The...
  20. ajw22

    TP4056 current overhead?

    EDIT: I didn't look closely at the picture - I assumed you're using 5 modules. If 3 modules are really taking 5.26A, then expect release of magic smoke sooner rather than later. Also, not sure, but combining the outputs of multiple TP4056 modules may not be the best idea. I would not be...
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