Parallel Compatibility of Various Firmware Versions
There has been some discussion recently, here and in the South African Power Forum
, about which versions of firmware are able to co-operate with which other versions, when paralleling more than one inverter. The same issues would affect three-phase systems. I assume that all three-phase systems would have sets of three machines bought at the same time, but for very large systems, another set of three might be added later.
When all the machines run the exact same firmware version (e.g. 72.70c with 72.70c, not 72.70b or 72.70), then there is no problem with paralleling. However, this post shows how some different firmware versions can be paralleled successfully.
This post refers exclusively to 48 V machines rated at 5 kVA inverter output (both 4 kW and 5 kW models).
There have been several major version numbers (the number before the dot) in official firmware versions:
- 52.XX: these came with older machines, whose SCCs were limited to 60 A. The maximum AC charging has always been 60 A, so the total charge current (setting 2) was limited to 120 A. Updating to newer firmware on such machines gives you the option of increasing the maximum battery current to 140 A, but it will never achieve this. So such updating is harmless. These older machines were all 4 kW/5 kVA. Note that there is another series of 52.30/40/60/70 for 4 kVA/3200 W models, that are not the same as the 5 kVA/4 kW versions. The higher numbered 52.XX (certainly 52.60) have SCC currents limited to 80 A. Perhaps they were the same source code compiled with different #defines for maximum VA and real power.
- 72.YY, YY < 40: This comes with the 5 kW models (PF1.0) that also have the higher battery voltage limit of 64 V.
- 72.XX, XX ≥ 40, newer (manuactured 2020 or later): this is one of the areas where firmware version numbers overlap. This indicates a 5 kW model (PF1.0) that also has the higher battery voltage limit of 64 V.
- 72.XX, XX ≥ 40, older machines (manufactured 2016 or earlier): this series replaced 52.XX for some old PF0.8 models. 72.40⁰ was still limited to 120 A maximum total charge current, hence 60 A for the SCC. 72.6X and 72.70 have the maximum charge current at 140 A, and allow SCC charging to 80 A if the SCC firmware allows it. 72.70 also allows paralleling to a total of 9 machines, as long as they are all running 72.70.
- 73.XX: This appears to be an update to 72.70. I used to think that this was essentially to control a relay that connects neutral to earth when the inverter is in battery mode, but now I believe that this happens automatically, with no extra logic from the firmware. 73.00 has extra logic for handling CAN packets from older firmware versions, such as 72.40⁰ and 72.60⁰. This allows it to parallel with other inverters with older firmware, up to a maximum of 6 inverters total. It can of course parallel with other inverters running 73.00; if they are all running 73.00 then a total of 9 inverters can be paralleled.
- 74.XX: This comes with the 5 kW models (PF1.0) that have the usual 58.4 V battery voltage limit.
- 75.XX: This comes with the dual/triple SCC models. It has a different protocol for the SCC commands, and a different LCD segment mapping, so it's not compatible with models with single SCCs.
- 76.30 appears to be an updated version of 75.XX, but the compatibility is unknown.
- 71.XX: This comes with the higher voltage (400/450/500 V) MPPT models. NOTE: some 145 V MPPT models also run version 71.20, and it seems very likely that these are not the same firmware. PIP-5048MKs / Axpert Kings seem to run 71.XX with XX ≥ 50.
For what can parallel with what, resulting in fault code 71 (error 71) if they can't, the firmware uses a constant that it expects the other machines to send in a special CAN packet. These are the constants for the firmwares I have examined, which therefore separate the firmware versions into "parallel compatibility groups". There are additional factors related to our patches that further subdivide the groups. Only firmwares on the same line are "parallel compatible".
f = the LF
P version has changed ranges for the Back to utility voltage (setting 12) and the Low cutoff voltage (setting 29)
z = Z
ero is allowed for the Max total charge current (setting 02)
Constant Firmware version(s)
101 72.10, 72.20, BC1_72.20a
102 71.80, 71.86 (MK/King)
103 71.92 (MK/King)
116 52.30, 72.40⁰, Pb_Cv.PCH, 72.60⁰, Pb1_72.60a, Pb1_72.60b, 72.61⁰, 73.00
116f Li_FE.PO4, Li1_72.60a, Li1_72.60b
118 * 72.70, PB1_72.70a, PB1_72.70b, 71.71**, 71.80**, 71.80a**, 74.10 (presumed), 74.40 (doesn't parallel properly with 72.70)
118f LF1_72.70a, LF1_72.70b
118fz LF1_72.70c, LF1_74.40e (doesn't parallel properly with LF1_72.70c)
118z LC1_72.70c, LC1_74.40e (doesn't parallel properly with LC1_72.70c)
130 † 75.31, LC1_75.31a
* Note how 72.70 is in a different parallel compatibility group to the other 72.XX (XX >= 40) versions. So it seems that it is possible to parallel 5 kW (PF1.0) machines that don't have the 64 V option with 4 kW machines (PF0.8), as long as the 4 kW machines are running 72.70. It is known that 72.70 will parallel with 74.10 (see this post
). However, if the new machine is running 74.30 or presumably any later 74.XX version, it doesn't work. See this post
** Firmware versions marked with two asterisks are for the PIP-5048MG / Axpert MKS II (450 V SCC, PF1.0); from the paralleling constant, it looks like it might be possible to parallel machines with 145 V max SCCs with others with 450 V max SCCs. However, this seems unlikely.
† It seems that dual/triple SCC models can't be paralleled with anything else, at least at this stage.
⁰ This indicates a firmware version for older machines (manufactured 2016 or earlier). There is a firmware version number overlap with newer models.
The takeaway lesson seem to be that while exact firmware matching is not essential in some cases, attempting to parallel machines with widely different firmware version numbers is likely to fail. To put it another way, having the same paralleling constant is a necessary but sometimes not sufficient condition for paralleling machines of differing firmware version.
[ Edit: Explain the f and z "modifiers"; added info on the 64V PF1 models. ]
[ Edit: The non-LFP version of 72.70a/b were called PB1_72.70a/b, not LC1_72.70a/b. ]
[ Edit: Added note re 71.71. Added 73.00e. ]
[ Edit May 2020: Added 71.80a, 74.40e. Added note re fault code 71. Added "takeaway lesson" paragraph. ]
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