ojeysky

Hello,
Has anyone using either of those inverters been able to get the data on  emoncms? I already have historical data on my emoncms (when I had MPP GK inverter) and I like to continue to log on the same emoncms which runs on my pi3+. I will appreciate explanation on how to achieve this? Do I use the WiFi logger or do I need to connect a different cable?
Thanks

The Sunsynk inverter can supply power to all three AC ports on the inverter:
1) It can supply excess power (power not required for battery charging and load connection) to the grid port for powering non-essential items on the grid side of the inverter, and/or selling unused power back to the utility.
2) It powers the load port from solar/battery/grid as required
3) The gen port can be configured as 'SmartLoad', in which case the inverter sends power to this port according to configured rules.

Sadly, it's not possible to directly force the charge state (float, bulk, etc).
But you can get it to bulk stage indirectly. As Weber mentioned, changing the float voltage slightly and putting it back if desired should cause the solar charge controller to reset. I'm not clear on whether it will always start in bulk mode soon after; my experience is that it sometimes doesn't. When in absorb stage, the charger will go to zero charge when the battery voltage falls consistently below a point that is 2.0 V (for 24 V models) less than the float voltage for 10 seconds with no exceptions (500 measurements in a row @ 50 Hz). So to be sure, set the float voltage quite high (you might have to set the absorb/bulk/CV setting high first, since often the float voltage setting can't be set higher than the absorb voltage setting). Once at zero charge for about 15 seconds, it should start a ~1 A charge, then ramp up to a normal bulk charge, i.e. it is in bulk stage. At this point, you could put the float and if necessary the absorb voltages back to what you want them to be long term. Probably waiting 60 seconds would suffice.
The above are based on analysis of 48 V firmware, but I believe that the 24 V firmware is similar (but with voltages halved, obviously, including the 2.0 ΔV).

Really old thread... but... 🙂
For resistive loads, like incandescent lamps, kettles and water heaters (aka geysers in SA parlance), running at a lower voltage does lower the power, but it also reduces the light output and/or it takes longer to heat the water. For water heating there would then be no advantage, it would take slightly longer and use the same energy.
Other electronic loads typically have switch mode power supplies and will compensate for the lower voltage by increasing the current draw, so no advantage there either.

This is not mere theory. Coulomb and I do this with every new battery (set of cells). The typical 55 W headlight bulb draws about 4 A at 13.8 V, so you might expect it would only draw a quarter of the current at a quarter of the voltage, so about 1 A at 3.4 V. But in fact it will draw about 2 A at 3.4 A. This is because the filament has a much lower resistance when it is only glowing a dull red compared to when it is white hot.
A fan will behave in the opposite way. i.e. it will draw much less than a quarter of the current at a quarter of the voltage. I doubt that the fan will draw enough current from a single cell to be useful in balancing the cells in a reasonable time. But it can't hurt to try it.
If you only do this manual balancing after you stop charging, then the cell you connect the load to, and in fact all the cells, will drop below 3.4 V almost immediately, so you will only have a very short time of balancing. You would have to repeat this many many times.

One way is to use one or more car headlight bulbs with alligator-clip leads, and a multimeter. With the battery on charge, and close to full charge, clip the bulb(s) on to the cell(s) with the highest voltage(s), provided that voltage is greater than 3.4 V (for LFP cells), to burn off some charge and let the other cells catch up. You can leave the bulb on a cell until its voltage drops below that of the lowest voltage cell.
You can also work in the other direction. If you have an adjustable-voltage current-limited power supply (a lab power supply) you can set it to 3.6 V, and when the whole battery is being charged and some cells are over 3.4 V, connect it to the lowest voltage cell until it goes above the voltage of the highest voltage cell.
If there happens to be two to four high cells next to each other, you can clip one bulb across the lot to burn off charge faster.
You should put each bulb in a porcelain cup or mug to stop it blinding you and melting things. This is a @Coulomb innovation. 😀
Likewise if you have a number of low cells next to each other, you can adjust the lab power supply to (n × 3.4 V) + 0.2 V. But this is more dangerous. You must monitor the individual cells often to ensure none goes over 3.6 V.
3.4 V is an absolute minimum for balancing. The higher you go, the more accurate the balancing will be, but you shouldn't let any cell go over 3.6 V.
I note that connecting LFP cells in parallel will not balance them unless you charge them to more than 3.4 V while they are connected in parallel.

This is similar to the MPP 3024GK, it works with 250w X6 at 30v each. It didn't work when I used 4 panels.

I intend to do exactly this but @weber suggests that paralleling old Lifepo4 batteries with a new one will kill the batteries.
 Have you done this before and what was your experience?

The best hypothesis I can come up with is that the battery was sitting on the shelf for a while before it got to you. And in that time the cells got out of balance by maybe 2%, so that when the battery voltage gets to 27.6 V you have 7 cells averaging 3.41 V each and one cell at 3.73 V. The BMS would have switched on the bypass resistor for that cell when it passed about 3.5 V, but it can only bypass maybe 1 A, and you're charging at maybe 30 A, which is why it got up to 3.73 V. And then to save that one cell, the BMS open-circuits the whole battery using a solid-state relay so the charge current goes to zero. That's what I think is happening when the voltage suddenly jumps up to the absorb voltage setting of 28.4 V.
After a few minutes of disconnection, the bypass resistor pulls the voltage of that cell below maybe 3.6 V and the BMS reconnects the battery, and the cycle repeats. As it's doing this, the high cell is coming more into balance. But if it was 2% ahead of the others, that's 4 Ah for a 200 Ah battery. And if the bypass is only 1 A, then it will take 4 hours to balance that out. So it may continue these crazy oscillations for several (sunny) days, but if I'm right, they will eventually reduce and finally cease.
If you want to speed the process up a little, and be a little kinder to the battery, you could wait until the problem starts occurring each day, then set the max charge current [02] down to its minimum of 10 A, and then set it back to 30 A or 40 A each evening. But you don't need to do that. You can just let it go as it is now.
Please let us know how it is going in say a week's time.

It's only on cloudy days that it might matter. You can wait and see if you get premature float on cloudy days, and if so, drop setting 02 to 30 A.

Those should be fine, for an 8S LiFePO₄ of any capacity.