Coulomb

As a point of interest, SilverNodashi, what does your manual tell you that U3 display setting is about? They used to be available from the MPP Solar web site, but they seem to have moved. Either they were deleted, or moved somewhere, and no web crawler has come across them as yet. I happen to have 52.30 and 72.40 saved away. and they can be downloaded here: http://forums.aeva.asn.au/forum_posts.asp?TID=4332&PID=59274&title=pip4048ms-inverter#59274 You might be interested in my patched version to fix a different bug: http://forums.aeva.asn.au/forum_posts.asp?TID=4332&PID=59884&title=pip4048ms-inverter#59884 (intro) and http://forums.aeva.asn.au/forum_posts.asp?TID=4332&PID=59908&title=pip4048ms-inverter#59908 (download, lead acid version). People on this forum don't seem to be using LiFePO4 batteries much, it seems. The lead acid patch is untested, so treat with caution, and please report back any results, good or bad. The original 72.40 firmware is int the download, just in case it's bad and you need to revert to factory firmware.

I should note that in firmware version 52.30, which happens to be the one I've examined the most, while the BTA0/1/2 commands are all there, and carefully calculate three mysterious values, and their magnitudes are checked (e.g. the main one should be 1024 +- 500), I can't actually find where they are used. It could be that I just haven't found that part of the code, or it might be that they planned to implement this but never finished it, or they had it implemented at one point, and had to comment it out for whatever reason. It may also be that later versions of the firmware have it implemented. I have found very little difference between 52.30 and 72.40. I'll look at this more closely, but for now, it seems that figuring out how to perform calibration might not be worth too much effort. Edit August 2018: I have since found what 2 of the three "mysterious" values are for; they are a scale and offset for the battery ADC measurement. So the calibration process seems real.

I totally agree. They used to supply the fans drawing the air downwards, instead of blowing upwards. We had a discussion of this on AEVA, starting here: http://forums.aeva.asn.au/forum_posts.asp?TID=4332&PID=54762&title=pip4048ms-inverter#54762 Note that this was an older unit with older firmware. But it seems worth changing the air flow if it's upside down, and possibly replacing the fans with quieter ones. We found that with quieter fans and blowing upwards, the temperature runs at only 35'C or so with a 2 kW load. But we don't run that unit all day; this was a "lab test". This will change in the next few weeks or months, when three of us will be running these inverters full time.

Yes, this appears to be the case. My reading of the firmware indicates that you can use any two voltages in any order (i.e. higher voltage first, or lower voltage first, but a valid BTA1 must come before BTA2). [ Edit: the BTA commands are also sent to the Solar Charge Controller; if it's powered up, it seems to expect the higher voltage first. ] However, they have to be at least 5.0 V apart (both the measurements and the arguments to the BTA1 and BTA2 commands), and the value in the BTA1 and BTA2 commands must not be over 60.0 V, and can't be zero. In addition, the difference between what it measures and what you tell it must not exceed 3.0 V, so you can't "spoof" the battery voltage by more than 3 V (but possibly a little more or less, depending on the natural error). Any violation of these conditions results in the command getting NAK'd instead of ACK'd. It looks to me that the inverter will still be expecting valid BTA1 and BTA2 commands. I don't think you can use really low voltages, say < 40.0 V, since it won't run the inverter. You could run it from mains or PV though. There doesn't seem to be a test for a low value, other than for zero, so that might work. However, best accuracy will be had by using realistic voltages. Yes, it's CCITT, as noted here: http://forums.aeva.asn.au/forum_posts.asp?TID=4332&PID=57733&title=pip4048ms-inverter#57733 I note that this is when I welcomed Chris Hobson to the Australian Electric Vehicle Association forum, and now this is my first post here. Thanks for posting about the calibration procedure. I had noticed the BTA commands some time back (along with perhaps fifty test commands) and wondered what they were about. [ Edit: added comment re 5.0 V difference applying to both measurements and the BTA1/2 arguments. ]