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JaseZA

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JaseZA last won the day on June 18

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  1. Item: Kodak VMiii 3kw 24V Inverter Age: 18 months Price: R6000 Payment Method Accepted: EFT/Cash Warranty: 6 Months of original warranty left Packaging: In original packaging Condition: Excellent used condition. Still functioning perfectly. Location: Richards Bay but visit Durban occasionally. Reason: Upgraded to 5kw 48V Shipping: Sure - For buyers account Collection: Sure Link: https://www.sustainable.co.za/kodak-vmiii-3kw-24v-solar-off-grid-inverter.html https://www.gumtree.co.za/a-generators-solar-power/richards-bay/kodak-vmiii-3kw-24v-inverter/1009522647220910040456009
  2. Very interesting, thanks for sharing! So 13S at 51V nominal = 3.92V per cell, 54V Max = 4.15V and 42V cutoff = 3.23V. Interesting seeing a chemistry that isn't LFP but NMC!
  3. Correct! In fact it turns out the Mecer 200ah is just 100ah cells in parallel!
  4. Exactly the problem with LiFePO4 - the inverter doesn't do a very good job I'm still deciding - might have another project for it. But will let you know. I have a "Smart BMS" from Ali-express (Sometimes called the 'ANTbms'). With a lot of creative programming I managed to link my rPi over bluetooth to pull the data. Then use Solpiplog to pull data from the inverter over serial and send commands.
  5. Sorry, missed your reply! As far as I know, in-rush current is the initial current the inverter pulls to fill the capacitors. In theory capacitors can fill at incredibly high currents so if there is nothing to slow the rate down, it can damage the inverter. It's why it is always advisable to connect your batteries via a resistor (can be a light blub) the first time to slowly charge the capacitors. Again, 100ah vs 200ah batteries both have very high short circuit currents versus the safe current for the inverter, so I'm not sure it would make a difference.
  6. Looking at electricity like water flow actually works very well. Pressure=Voltage, Flow=Current. Batteries in parallel are like two 100L tanks sitting next to each other, 2m above the ground. The pressure is the same at the tap except you can now allow twice as much water to flow out before it's empty (200L vs 100L). You also have two taps so your flow rate can be twice as high. Batteries in series is like having both 100L tanks at 4m but only having a single pipe! So now your pressure is doubled, you have the same quantity of water (200L) but you're trying to push that through a single tap, so you have reduced flow rate. This analogy isn't perfect though - in theory they're very thin tanks so the pressure doesn't drop very much as you drain them. Hmm, right thinking but there is an actual formula for this: P = Rho x G x H where P=Pressure, Rho=density, G=Acceleration due to Gravity and H=Height. As you can see, there is no mass - this is because pressure isn't changed by how much water, just how high it is above the ground. So Ah (Amp-Hours) is a measure of energy quantity. Basically it's how many amps can be delivered for an hour. 100Ah = 100A for an hour. Adding more batteries increases the total energy. Sorry, this turned into a lesson far more quickly than I imagined! Hopefully it's a little bit helpful. I'm also sure there are much more qualified people here to explain this! Hopefully they'll correct anything I've gotten horribly wrong.
  7. Definitely don't do that - most multimeters are only rated to 10A. If you just connect it across the battery terminals it will short the battery, allowing VERY large currents and popping the multimeter fuse.
  8. I bought a Minleaf 30V/10A PSU from Banggood - working well so far, but as I said, 10A is a bit light sometimes. But it works! And hard to beat the price. Problem is you need to accurately set the voltage to 3.6V - hard to do with an inverter I think. I've got a mix - got some from China, but that was very painful and worked out quite expensive... The rest I got from LithiumBatteriesSA. They had 120ah 2nd life cells at R750 last year which was a good price. That being said I'm busy building a DIY bank using some secondhand pouch cells I got from Mecer 12V 200ah lithiums I've been very happy for the most part with my VMiii, considering what I paid for it. It doesn't have some of the features of the fancier systems but it's been reliable for me. I am in the process of upgrading to the 5kw though - 48V is much nicer with lower currents from the batteries and while we've made 3kw work, my wife is getting a bit irritated now when I tell her to wait for the kettle to finish before she uses the microwave! But it's been over a year and we've been fine. As of last month I have saved R4744 on electricity and been the only people in our complex not worried about load shedding One thing to note - I manage my inverter and BMS through a Raspberrypi which gives me even more control than most CAN connected batteries. Without this you're relying on the inverter to figure out SoC from the battery voltage. There are quite a few threads on this and why it can be problematic. In summary, you generally just lose out on some available battery capacity. There are some BMSes available with CAN communication but you need to make sure they work with Voltronic inverters.
  9. Also, the fans will run if the unit is charging the battery. You might need to look at these settings and see what works for you. I imagine USB, ECO and BYE?
  10. That being said, even if you were to overload it, it would bypass to grid or shut down depending on your settings. But it does use energy the whole time in Line mode doing the conversion. I'm not sure if it will use the battery to power loads when in Bypass if the grid fails.
  11. Remember this is a King unit and operates differently to the MAX/VM/MKS inverters in that it has zero transfer time and does double conversion. This means it must be in bypass and not line mode to purely pass through grid.
  12. Speaking from experience, you definitely need to charge them. Or they must be right near their highest voltage when paralleling them. I bought a bench power supply just for doing this, although even that is a bit low on current. My strategy in the past has been to get them as high as possible (When the most full battery hits 3.6V) while unbalanced with my inverter charger, then connect in parallel and do a final charge with the bench power supply set to 3.6V. This being said, my cells were never hugely out of balance... And a year later they are almost still perfectly balanced.
  13. I would happily leave it at 20A - that's only 0.1C for a 200ah battery. I intend to charge mine at 50A or 0.25C. Most lithium recommendations I've seen are around 0.5C max for continuous and 1C max intermittent. I generally like having the inverter DC low cut off higher than the battery BMS. This way the inverter cuts on it's own terms rather than there being a chance the BMS might cut first. This is unlikely though as there is almost always some voltage drop across the cables from battery to inverter, so the inverter tends to read lower. Raising this value will reduce your total capacity but increase the life of your battery.
  14. Hmmm, I think the best option here would be 2 strings, each with a 265W + 335W + 335W. Your 335W will have their output current reduced to 8.66A though, so probably only give you max 329W. Your Voc total is 129.9V which is in the save range of your inverter. Total current will be 8.66A x 2 = 17.32A which should again be safe.
  15. Thanks for the feedback! I still haven't had a chance to update mine...
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