PD or Iota for my upgrade?
I'm thinking about a converter and battery upgrade. The batteries will be wet cell lead acid 6 volt Possible T-105s or the 230AH, EGC2 from Sam's club. I'll probably go for four. (Does nayone have...
Forum Discussion
This will be a short post as I'm pressed for time.
It was stupid of me to test power output from the PD9280 when I knew full well I was starving it for power by trying to run it off 105-106 VAC.
1) The first test I posted showed what I thought was pretty good performance, but it did show current decay from 80 to 60 amps.
2) I thought the current decay was due to limits in the PD, so I modified those limits, but the test of the modified PD showed nearly identical performance. I suspected, and now am certain, that the current decay had nothing to do with the PD design. It was due to the fact I was starving it of AC input power, so naturally, when I tried to get more power out, the current dropped.
3) The PD like all other switching converters (except those specifically designed for unity power factor) draws power only at the top of the AC voltage wave form. By feeding it with only 105-106 volts, there just wasn't enough voltage at the very top of the waveform to supply the input caps and produce the desired output power it was trying to supply. That's why the output current dropped even after I modified it. It was limited by the input voltage, not the PD.
4) Last night I reran the same test described above, except I used my 4.0KW Onan generator which produces about 126 AC volts+. The modified PD 9280 held 80 amps rock solid all the way from 12.4 volts to 14.7 volts! Then it began to drop rapidly as the voltage reached the new target of 14.8 volts. That's exactly what should have happened. I screwed up the data capture - I was watching it, but not capturing it - and didn't realize it until it had reached 14.6 volts, but the capture still shows steady 80 amps from 14.6 volts to 14.7 volts, followed by the drop. I'll try to post it some time. but can't now.
5) This is consistent with the report by others that an unmodified PD 9260 produced 60 amps steady at 14.3+ volts. I thought that report was not consistent with my results. I now think it was just better testing than I was doing - it was supplied with enough AC voltage.
6) So the question is what would I have seen if I'd originally tested the PD9280 properly. I'll probably remove my mods to the slope of the current decay, but keep the 14.8 limit and test - but it will have to wait for my vacation.
The good news for me is that my gen produces plenty of power/voltage to rapid charge my batteries via the PD 9280 exactly according to the profile I've selected. When I'm plugged in to shore, the current droops a bit, but I don't really care if I get 80A or 60A when I'm plugged in all day. I only want maximum rate when running the gen.
I'm very very happy with this answer. The bottom line is that so far I see no sign of any deficiency in the PD design. I'll get a solid 80 amps up to my new 14.8 target voltage, and I can manually adjust the target voltage with the potentiometer I installed per the outside temp. I can add a remote battery voltage sensor easily, if I want to, and modifying the voltage automatically with a temp sensor should also be easy now that I know the circuit so well.
I hope all have a great holiday weekend. Mine will be filled with smiles after these results. :)
It was stupid of me to test power output from the PD9280 when I knew full well I was starving it for power by trying to run it off 105-106 VAC.
1) The first test I posted showed what I thought was pretty good performance, but it did show current decay from 80 to 60 amps.
2) I thought the current decay was due to limits in the PD, so I modified those limits, but the test of the modified PD showed nearly identical performance. I suspected, and now am certain, that the current decay had nothing to do with the PD design. It was due to the fact I was starving it of AC input power, so naturally, when I tried to get more power out, the current dropped.
3) The PD like all other switching converters (except those specifically designed for unity power factor) draws power only at the top of the AC voltage wave form. By feeding it with only 105-106 volts, there just wasn't enough voltage at the very top of the waveform to supply the input caps and produce the desired output power it was trying to supply. That's why the output current dropped even after I modified it. It was limited by the input voltage, not the PD.
4) Last night I reran the same test described above, except I used my 4.0KW Onan generator which produces about 126 AC volts+. The modified PD 9280 held 80 amps rock solid all the way from 12.4 volts to 14.7 volts! Then it began to drop rapidly as the voltage reached the new target of 14.8 volts. That's exactly what should have happened. I screwed up the data capture - I was watching it, but not capturing it - and didn't realize it until it had reached 14.6 volts, but the capture still shows steady 80 amps from 14.6 volts to 14.7 volts, followed by the drop. I'll try to post it some time. but can't now.
5) This is consistent with the report by others that an unmodified PD 9260 produced 60 amps steady at 14.3+ volts. I thought that report was not consistent with my results. I now think it was just better testing than I was doing - it was supplied with enough AC voltage.
6) So the question is what would I have seen if I'd originally tested the PD9280 properly. I'll probably remove my mods to the slope of the current decay, but keep the 14.8 limit and test - but it will have to wait for my vacation.
The good news for me is that my gen produces plenty of power/voltage to rapid charge my batteries via the PD 9280 exactly according to the profile I've selected. When I'm plugged in to shore, the current droops a bit, but I don't really care if I get 80A or 60A when I'm plugged in all day. I only want maximum rate when running the gen.
I'm very very happy with this answer. The bottom line is that so far I see no sign of any deficiency in the PD design. I'll get a solid 80 amps up to my new 14.8 target voltage, and I can manually adjust the target voltage with the potentiometer I installed per the outside temp. I can add a remote battery voltage sensor easily, if I want to, and modifying the voltage automatically with a temp sensor should also be easy now that I know the circuit so well.
I hope all have a great holiday weekend. Mine will be filled with smiles after these results. :)
