PD or Iota for my upgrade?

BFL13 wrote:
My Trimetric rounds up. So meter says 13.45 and Tri says 13.5

I have the PowerMax 100 amper and 4-6s at 458AH rated. It takes about 2 hours and ten minutes to do a 50-90 at 70F roughly when I set the absorption voltage to 14.6 so it stays there instead of dropping to 13.6 like the OEM PM does. You don't want the PM4-100, you would want the new version coming out with the adjustable voltage--whenever Randy starts selling them! ( Not a clue on that)

Salvo made a point about low charging rate and the PD. If you moved your 45 up by the batteries too in order to get that low R, then the 45 and the 60 would each still be at low rates to do that constant amps even though at 100 amps you would be really at a higher charging rate. The 45 doesn't need to be where it is now to act as your converter. You might need to make a (vented) cover for it though where the guts are exposed.

You can use my ugly graph to see how your times would improve going from 60 to 100. As you see it is diminishing returns going higher in amps. At some point is it not worth it for the time saved.

Using the ugly graph, note that if the amps are the same but the bank doubles in size, then the times double. But if you double the amps, that does not halve the times. You can find the time for a 110a on 440 by using the 55a time on 220. do 490/440 times that time.

Using the ugly graph times between the 35's and the 55's on 220, you get the same times with 70 and 110 on 440. You get a WAG improved time there for 60 vs 100 on 490 if you adjust for 490 vs 440. You can play with the numbers and see what you get.

I just completed an experiment charging with both the PD60 and PD45 in parallel. The PD45 isn't by any means an optimum setup with about 20' of #4 wire for the hot side and the chassis for the ground. As expected the initial 100A started to taper soon,and by the end of two hours there really isn't any benefit from the 45A in parallel given the wiring. It did offer an improvement. It went from 50-83% SOC in 2hrs. instead of 3hrs to 84% with just the 60A, but it still took another hour to get to 90%. So while I shaved 1 hour off the 50-85% or so, it only shaved 1/2 hour off the 50-90. Not unexpected once it gets to 14.3 or so on the output it's voltage not current limited. It does look like the boondocker with 14.6V could save 20-30 minutes from your results. I'm 490AH vs. your 460, And I suspect if I moved the PD45A to the pass through I'd see an improvement as well, but that's another project that given how I want to be able to control chargers would mean adding another 120V circuit to the pass through, not sure it's worth it. And if I was starting from scratch the new boondocker would be the way to go. Don't think the gain in time is worth the $$$ now. In the summer I suspect between not using the furnace and my suplimental solar I will be able to go 4-6 days, which is about the longest we dry camp anyway.