Sig Energy Topic

Author	Message
wiseguy Guru Joined: 21/06/2018 Location: Australia Posts: 1294	Posted: 12:08pm 22 Dec 2025         KeepIS said   Hi Mike, I was wondering about the Battery modules and how they might build a system that was economical, and handle various battery bank voltage/power levels as they were stacked in various power configurations in an installation for a given Inverter & solar controller. If the battery compartments are anything but cold (ambient temperature) then each battery box must have a high voltage generator inside with each output being paralleled as extra banks are added, something you suggested earlier on, unless I misunderstood. Similar to some quality smaller 5/10kw HF inverter on steroids.   I have around 36kW of LiFePO4, the batteries run cold with a 14.6 kW load on the Inverter (no solar), as does the BMS. The balances shunt power around between cells in a bank, so only consume power internally from the battery cells as a result of the cell levelling action, and these can run slightly warm at a few Amps of balance, but that's with some suspect Cells a few years old and the bank close to 90% SOC, with a new system they should hardly be running. Hi Michael, When I spoke about warmth of the battery I should have been more specific as I was referring to the whole battery module, which of course contains the batteries and I am guessing also has some voltage conversion, bi-directional power transfer circuitry, which I reckon causes the heating of the whole module and hence the battery. Given the expected ultra-low impedance of a 270 A/H battery, I would not expect the battery itself to be the cause of any heating it just got hot as it was along for the ride with the other less efficient circuitry. I also suspect the batteries which have apparently a 4kW rating for each 8kWh module are identical for each and every configuration. I suspect the power limiting is just a software value in the inverter that can be preset for the inverter rating, I wonder how different the 6/8/10/12kW units really are? Maybe they do what we did, I created a range of power supplies with various current outputs but 100% identical circuitry and components. The software either allowed 13.6V @10A or @15A and if they paid more money we released an extra 5A. That meant we only had a common design and one type of unit to make and we would only do the final testing and labelling after loading the software required to meet the order. As far as the battery goes, for their various power configurations, the batteries only come in 8kWh increments and a 4kW limit per module. If they are creating ~ 30W of heat for their 4kW rating that means the circuitry run at ~99% efficiency. Maybe I was a bit misleading when I said that they were 10 or 20 degrees above ambient as given their 80kG bulk meant their thermal inertia ensured a slow drift back to ambient? Also the 30W loss was lightly loaded over-night, maybe as the power transfer has the wick turned up during bulk charge or heavy discharge the losses increase to maybe 200W at 4kW in (or out), still around 95%+ efficiency? hence their being quite warm to touch. I hope that addressed your query or maybe I misinterpreted what you were asking? Edited 2025-12-22 22:11 by wiseguy