I have one of my controllers outside the house in a weatherproof box. Needed to charge some 12V batteries inside, so I ran one of my regular panel extension cords (10AWG - 25') from the controller to the battery (the panel is next to the controller). Was 5 ft short so grabbed a short one off the rack and let it rip. A bit later I see that the amps are kinda low but the batteries are not likely close to fully-charged. Turns out the controller was in float mode. That was odd. Checked the voltage drop between the controller and the battery: over 0.5V. Turns out the short extension cord that I used was only 18 AWG, I didn't check earlier cuz I was in a hurry. OK, not good. Replaced it with a 10 AWG but there is still 0.3V drop with about 3.5A.
Short story: the poor controller was a bit confused, I think. It saw 14.4V and went from bulk to absorption even though the battery was only at something like 13.8V, nowhere close to 14.4 . So basically, what happens is that the voltage drop leads to it switching to absorption mode too early. Now, in principle that should not necessarily affect the final charge (except see below), but it will at least make it longer because it switched to absorption too early and so shortchanged the battery in amps. So if you're in a hurry to charge, that's not the best. But it should still charge at least some at that point. But...
Now, why it went to float with the battery not fully charged, I think (need to check the manual) that was because the duration set for the absorption phase in the menu (1hr) was exceeded. Not surprising since it went to absorption too early and the battery was still not fully charged. But going to float in turn would not give me the full charge for a while if at all, then. So not good, that is a more serious problem than just a somewhat longer charging time, both in the short term but also, if it is true indeed that a battery benefit from full-charging at 14.4, and in reality it never gets there because of the issue above, well, that is not good in the long term either. Basically, all of this would defeat having a good charging scheme. All cuz of a pesky voltage drop.
(Interestingly, I'm still getting 1.5A in Float mode (13.6V) rather than the expected 100mA or so, so that in turn may help a bit.)
(Predictable) Conclusions: don't use skinny wires and put the controller close to whatever battery you are charging if in a hurry to charge or if you want a truly fully-charged battery and want to keep it healthy. (Or increase the absorption phase duration.) Of course, I knew that, but still messed up cuz I warnt thinkin' .
Short story: the poor controller was a bit confused, I think. It saw 14.4V and went from bulk to absorption even though the battery was only at something like 13.8V, nowhere close to 14.4 . So basically, what happens is that the voltage drop leads to it switching to absorption mode too early. Now, in principle that should not necessarily affect the final charge (except see below), but it will at least make it longer because it switched to absorption too early and so shortchanged the battery in amps. So if you're in a hurry to charge, that's not the best. But it should still charge at least some at that point. But...
Now, why it went to float with the battery not fully charged, I think (need to check the manual) that was because the duration set for the absorption phase in the menu (1hr) was exceeded. Not surprising since it went to absorption too early and the battery was still not fully charged. But going to float in turn would not give me the full charge for a while if at all, then. So not good, that is a more serious problem than just a somewhat longer charging time, both in the short term but also, if it is true indeed that a battery benefit from full-charging at 14.4, and in reality it never gets there because of the issue above, well, that is not good in the long term either. Basically, all of this would defeat having a good charging scheme. All cuz of a pesky voltage drop.
(Interestingly, I'm still getting 1.5A in Float mode (13.6V) rather than the expected 100mA or so, so that in turn may help a bit.)
(Predictable) Conclusions: don't use skinny wires and put the controller close to whatever battery you are charging if in a hurry to charge or if you want a truly fully-charged battery and want to keep it healthy. (Or increase the absorption phase duration.) Of course, I knew that, but still messed up cuz I warnt thinkin' .
