PD or Iota for my upgrade?

Salvo wrote:
Nice work! Looks like after 3/4 hr the converter starts to be input voltage starved again. Not as much as before, but somewhat.

I don't think that's the case. I tried increasing the voltage from the gen and didn't see any current increase.

Up to 3/4 hr the current plot is smooth. After that current starts to drop and becomes erratic similar to the low ac voltage plot. There may be a stability problem. Does the radio or TV buzz during this time period?

The "erratic" is me playing with the voltage. It's slow changes - no buzz issues. The sample rate is 4000 samples an hour. I was adjusting input AC voltage by adding AC loads, which caused the gen to work harder and voltage to drop, or by turning the voltage adjustment/speed screw on the gen. These gens have a fixed output voltage as a function of RPM. I wanted to figure out the bottom end voltage that would still produce full output. I had to decrease my gen voltage as normally it runs at about 125 VAC. I did that to give more realistic test since most people won't be able to run above 120VAC.

Can you summarize your test setup?

Sure.

1. AC & DC cable length and size.

The mod tests were all done from the gen. Roughly ten feet of #10 from gen to the dedicated circuit breaker for the PD9280 at the panel and another 10' of #10 from panel to the PD9280 dedicated receptacle. The gen usually runs at 125VAC under normal load and drops to 118 VAC under max load, but for the test it was set down.

With the non mod tests, shore power at the house is 119 VAC typical, and Ive got a 100' #10 extension plugged into the house 20
Amp socket which has another 50', probably #12 to the service entrance.

DC cables are 1/0 about 3' long. I captured both voltage at the converter and at the battery, but they were always the same except when stepping up the next tenth, and then the difference was only for a short while.

2. Detail the 3 mods referencing the patent schematic.

You lucked out with the older Onan gen.

Mod 1: 14.8 V Boost target. There's a 32.4K 1% resistor connected to pin 5 of the microcontroller. This pin goes low in Boost mode. I added about 55K of parallel resistance to it to decrease that resistance. (I actually added a 33K in series with a 50K trimpot to adjust it.)
This isn't in the main patent. The microcontroller is at the lower left of the board near the pendant connector - I'll post photos if anyone wants them.

Mod 2. Decrease output of current sensing circuit. There are 5 resistors R21A-R21E in parallel. See Fig 2B of the 7728002 patent. I added enough resistance in parallel to reduce the resistance by 25%. PD breaks a resistor to tweak the resistance here - it's cheaper than a pot.

Mod 3 current limit to counteract the effect of Mod 2. See Fig 2A of the '002 patent R15 is a 35.7K resistor on the bottom half of the current limit voltage divider. I added enough resistance in parallel to decrease the current limit to match the change above. I believe I had to add 33K in parallel with R15. I was doing this work late at night, so my notes aren't good.

The choice of the PD was partly influenced by the gen I had. There were pros and cons for PD and Iota. I'd read a report that the PD didn't like to run from gen power, but as I studied that comment, it struck me that it was either an inverter problem or a voltage regulator problem. I had just rebuilt the voltage regulator for my backup Onan and was pretty confident the gen would not be an issue for the PD, or if it was, I would be able to design around it. I really wanted a converter with circuit diagrams so I could modify it, as needed.