Capacity Testing and 20 HR Rating

Did an 86a charge yesterday, from ~79%soc, -93Ah's. Everything lined up as I had hoped. Within a few minutes, Amps tapered very near the -86Ah mark (within one or two Ah's), and at 90% soc, Tri said 43a tapering at -43Ah's. The Tri is still topping out a little high, though, so I'm gonna try lowering P10 from 85% to 84%, and raising Vabs from 14.4 to 14.45v. That oughta git'er done.

Will do. Gonna do a pwm run, then try out the tracer.

Let us know how the solar works out for you.

BFL,

Is that 72% according to the trimetric? I know your P10 is off a bit. Just changing P10 on mine, from 90% to 86% eff, made a huge difference in when amps appeared to taper... 89% soc vs low 80's, at a little under 14.4v.

72% is 128Ah's missing, whereas -103Ah's would be 77.5%, so a slight tweak of P10 would likely line things up... not that you need to concern yourself with that, but it is interesting to see how P10 plays a role. The manual points out that the 94% eff default setting is likely too high, and that 80-90% is more likely the case. Looks like I'm right in the middle of that, doing 70-99% cycles.

I've been wondering if the vector style profile is playing a big part in the numbers I'm seeing? Would the standard cc/cv profile give similar results??? And I don't really know how the pm3 is going to behave after being modified... I'm guessing the same as the pm4b? Does your 100 amper have a vector style profile, with volts rising throughout the entire charge? ( And I don't remember if that one was the one you modded?)

(btw, trying out my first solar run, today.)

With Vabs set at 14.6v, tapering starts when SOC is 72% using 103a on my 458AH bank (22% charging rate) with my PowerMax 100 amper.

With Vectors, which are programmed to begin tapering at 13.9v, 103a worth of them on the same bank has tapering start at 68% SOC, but of course they catch up with the PowerMax in the end by having their voltage continue to rise during Absorption while the PM does CV at that 14.6

Did another 70~99%, down to 3.7a @ 14.4v. Charger dropped into float at the 8 1/2 hour mark. At a P10 setting of 86%, charge ended at 101% and +5Ah's... So, very close... will try an 85% eff setting next. Amps tapered quite early though; in the low 80's % soc range (about -70Ah), so gonna try raising Vabs a little.

Just to clarify my intentions, I'm curious to see if there is a pair of settings that will record amps as tapering at a point where charging amps = missing A'hs, regardless of charge rate. So, if I can get the Tri to zero out just before float is engaged, and at a Vabs setting that has 45 amps beginning to taper at 89%/-45Ah's, then I will switch to the 75a charger to see if 75 amps begin to taper in the 82%/-75Ah range, at the same Vabs setting.

Well, I'm getting closer with the Tri's eff. factor. Did a 70-99?% last night, down to 4.9a @ 14.39v. Just before going into 13.9v float around the 9hr mark, SOC was at 105%, at a little over +18Ah's. Gonna try dropping it to 86%, then do a similar cycle. Didn't catch when amps tapered, exactly, but I caught it shortly after, and it was in that 89% range.

Of course, I'll no sooner get this thing dialed in, and then going solar will mess it all up! :) But it should be interesting to see what eff factor works well with various dod's.

Mex,

I did buy a couple of cheap digital thermometers off eBay. You mentioned once about simply taping the probe to the side of a battery case, creating a sort of cocoon. Which do you think would be more accurate, the case or a post, or is it pretty much a wash?

Place a thermocouple on a snip of SilPad and fiberglass resin it to a negative battery post. A millivolt meter with pot is all you need to make this a wonderful temp sensing tool. There is so much lead mass reaching down into the electrolyte that the TC sensing will be quite responsive.

Mex,

I'm realizing more and more, Temperature is a huge factor in all this, and yet it is one of the most ignored factors, it seems. It may be interesting to have some sort of Temp sensing probe, right down inside a cell, to see what happens at different levels during charging.

But I'll be happy to just find a depth of cycle that plays well with whatever (P10) eff% setting I choose; if only to get a better hold on what % soc amps start to taper. Actually, I did notice amps began to taper right in that 89% soc (-45Ah) range I was shooting for, when at my 14.4Vabs setting. But that was according to the Trimetric, which was clearly off by (?)% points.

And I noticed something the other evening, which I had seen before. Just before amps taper, voltage rises a bit, and then drops back down once amps do begin to taper. It's like a little voltage spike, just before amps are about to taper. It's kinda like the rise in amps I often see, just before going into float.

It may be worth mentioning, the modded pm4b does not go into constant voltage mode, but rather raises volts throughout the entire charge. So, for example, at my 14.4 "Vabs" setting, voltage rose to 14.3v, then dropped to 14.25v, right after amps began to taper, and then continued rising from there.