RV Voltages too high while charging
I have a problem and have been wrapping my head around this for a few days. I have four 100w Solar panels, and a Morningstar RJ-45 programmable charge controller wired to batteries. I have Four In...
Forum Discussion
Grizzzman,
Thank you, but I'm quite familiar with the terminology regarding c.c. and c.v.. In fact, I much prefer to think in those terms, rather than bulk and abs. But what is missing in those recommendations is the fact that true c.c. chargers are hard to come by. What these folks are calling "constant current" is actually the result of "current limiting". If it wasn't for a factory preset c.l., during "bulk" stage, the current would not remain constant. It would go as high as the bank would accept, and then taper; (provided the charger didn't go up in smoke, first). Same goes for constant voltage. It is actually the result of the charger's voltage limit (i.e; Vabs set-point). And yes, I'm guilty of calling bulk stage 'cc', and abs stage 'cv', but technically I'm wrong, doing so. I do it if I think it will help someone understand what's going on during the various charge stages.
I have a gophert cps 1620 that is an adjustable variable (i.e; cv cc) power supply, and can be manually operated in either cv or cc. I use it for individually EQ'ing my 6v batteries. But even then, it cannot hold both voltage and current steady... likely due to thermal issues, nor can it operate in both modes simultaneously. So all this talk about cc and cv is nice, but not really technically correct, nor practical, when dealing with so-called "smart" chargers. You simply cannot hold both current and voltage steady on an ever changing load like a battery. The best you can do is limit them.
Moreover, not all chargers follow the same profile. My pm4b, like the vector portables, actually has tapering current and rising voltage during the abs stage... which results in the highest voltage occurring at the very end of the charge cycle... just like so called "3 stage" charging. In other words, my Vabs set-point is not reached until the very end. And in my experience, raising voltage above my Vabs set-point, at the end of the cycle, actually results in lower, uneven ocv's among my four 6's.
I do not float my bank, and therefore I essentially do "2 stage" charging. A third "finishing" stage is simply a higher voltage charge at very near full. If a charger was so equipped, it would hold the bank at a preset current limit (there's that term again), just like when in float mode.
But as I have said many times, one must familiarize oneself with their own batteries. Recommendations and suggestions are just that. If I believed folks when they told me 12.6v IS a full battery, I'd be chronically undercharging by bank to only 85%, and if I believed folks when they told me 15.3v is required to fully charge my bank, I'd be chronically over-charging... something I'm quite familiar with, seeing as my Peak 40a portable "smart" charger loves overcharging my bank.
Establish a baseline for SG's and resting OCV's, while the bank is out of service. Then, while in service, try to maintain those baselines as best you can. That's it! If your bank responds well to 15.3Vabs, then go for it. If it does not, then find out what does work well. And if you do not cycle your bank hard (i.e; deep) on a daily basis, there should be no need for daily "finish" charging nor frequent EQ'ing.
Thank you, but I'm quite familiar with the terminology regarding c.c. and c.v.. In fact, I much prefer to think in those terms, rather than bulk and abs. But what is missing in those recommendations is the fact that true c.c. chargers are hard to come by. What these folks are calling "constant current" is actually the result of "current limiting". If it wasn't for a factory preset c.l., during "bulk" stage, the current would not remain constant. It would go as high as the bank would accept, and then taper; (provided the charger didn't go up in smoke, first). Same goes for constant voltage. It is actually the result of the charger's voltage limit (i.e; Vabs set-point). And yes, I'm guilty of calling bulk stage 'cc', and abs stage 'cv', but technically I'm wrong, doing so. I do it if I think it will help someone understand what's going on during the various charge stages.
I have a gophert cps 1620 that is an adjustable variable (i.e; cv cc) power supply, and can be manually operated in either cv or cc. I use it for individually EQ'ing my 6v batteries. But even then, it cannot hold both voltage and current steady... likely due to thermal issues, nor can it operate in both modes simultaneously. So all this talk about cc and cv is nice, but not really technically correct, nor practical, when dealing with so-called "smart" chargers. You simply cannot hold both current and voltage steady on an ever changing load like a battery. The best you can do is limit them.
Moreover, not all chargers follow the same profile. My pm4b, like the vector portables, actually has tapering current and rising voltage during the abs stage... which results in the highest voltage occurring at the very end of the charge cycle... just like so called "3 stage" charging. In other words, my Vabs set-point is not reached until the very end. And in my experience, raising voltage above my Vabs set-point, at the end of the cycle, actually results in lower, uneven ocv's among my four 6's.
I do not float my bank, and therefore I essentially do "2 stage" charging. A third "finishing" stage is simply a higher voltage charge at very near full. If a charger was so equipped, it would hold the bank at a preset current limit (there's that term again), just like when in float mode.
But as I have said many times, one must familiarize oneself with their own batteries. Recommendations and suggestions are just that. If I believed folks when they told me 12.6v IS a full battery, I'd be chronically undercharging by bank to only 85%, and if I believed folks when they told me 15.3v is required to fully charge my bank, I'd be chronically over-charging... something I'm quite familiar with, seeing as my Peak 40a portable "smart" charger loves overcharging my bank.
Establish a baseline for SG's and resting OCV's, while the bank is out of service. Then, while in service, try to maintain those baselines as best you can. That's it! If your bank responds well to 15.3Vabs, then go for it. If it does not, then find out what does work well. And if you do not cycle your bank hard (i.e; deep) on a daily basis, there should be no need for daily "finish" charging nor frequent EQ'ing.
