DryCamper11
Hartford
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Thanks for the comments and suggestions. The generator is a 4KW Onan. I'm going to get a DC current meter or a Trimetric or similar current monitor to check output.
I spent some time reviewing the circuit diagram of the PD from the patents. I was surprised at how closely the patent shows the PD. It's nearly identical to the design being sold, all the way down to resistor values.
The fundamental operation is relatively simple. There are lots of bells and whistles, but ignoring those, the system takes the AC voltage and runs it through a full wave bridge to produce 170VDC unregulated.
It takes that voltage and chops it, sending the chopped voltage through a center tapped transformer to produce lower voltage AC that is sent through another bridge circuit to rectify back to DC and supply the output.
The chopping is controlled by a Unitrode chip that has inputs from the output voltage and the output current. If the current gets too high, it cuts the output. If voltage gets too high, it does the same. It looks like it will be very easy to readjust the output voltage or the maximum output current to values that match the specs for my batteries.
That's why I'm thinking about the large PD9280, even if I decide to go with smaller batteries initially. I can just limit the current to whatever I want.
It sounds like the suggestions here match what I've been reading in the other posts from my research. The Iota may have an advantage for short cables, which I will be using, but I suspect that advantage comes mostly from the higher charging voltage it uses, and I can easily adjust the PD to that higher voltage if i want to. Increasing from 14.4 to 14.8, which is the highest I would go, is less than a 3% increase.
Again, thanks for the comments.
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Wayne Dohnal
Bend, OR.
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Drycamper - I have a PD9160 and WFCO 8955 and have done some extensive testing to compare them. One of the characteristics of the PD converter is that it is highly dependent on the voltage of the AC peaks to produce its full output. On 120 volt shore power mine will slightly exceed 60 amps at 14.4 volts. As the voltage drops below 120, the max current at in boost mode drops with it. By comparison, the WFCO holds its boost mode current quite well. I unfortunately don't have an IOTA to test. This peak voltage characteristic comes into play with the generators. The Onan Microquiet (and I believe most small conventional generators) produce a horrible waveform when hit with the "unfriendly" 0.7 PF load of most converters. The RMS voltage is there but the peaks are way down. As a result, the PD converter's maximum output is reduced. The WFCO converter, by comparison, maintains its full output when run by the Onan generator. A Honda inverter generator maintains its peak voltage correctly when driving the converters, making the full PD output is available. When running from the Onan, I'd guess that the 9280 will probably give you 60 amps in boost mode. With an eu3000i or good shore power, I'd expect the full 80 amps to be available.
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KendallP
Grants Pass, OR
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IMO, the 9280 is not too big for a pair of GC2s and certainly not too big for 4 as the OP has suggested he wishes to go with.
Also, my guess is that the 9280 will probably peak out at 70A with the dirty sine wave of the Onan.
Based on everything you've said, I say get the PD.
Cheers,
Kendall
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smkettner
Southern California
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I doubt you will find much time savings by modifying the PD9280.
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Hybridhunter
At home
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Agreed. Battery bank acceptance rate issues would apply.
And as I learned today, and posted in another thread, running the PD off a synchronous genset really trims it's output. So far, I see it running 60% of rated.
* This post was
edited 06/18/12 07:48pm by Hybridhunter *
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DryCamper11
Hartford
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I've tried to post about 20 times and can't I'm going to try a shorter message.
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DryCamper11
Hartford
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Hybridhunter wrote:Agreed. Battery bank acceptance rate issues would apply.
Help me understand this comment.
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DryCamper11
Hartford
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As you drive the voltage up won't the current increase?
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DryCamper11
Hartford
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Trojan recommends 14.8 VDC daily charging.
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DryCamper11
Hartford
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Won't the charge rate increase when charged at 14.6 vs the default PD 1`4.4 boost rate?
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