Solar Controllers--Don't be a Sucker! :(
Just got to say it again, how it is we are sitting here for five months off grid on solar with no problems at all (third season on solar like this), using the non-programmable, non-MPPT, solar control...
Forum Discussion
My biggest reason for wanting programmability or at least configurability is to be able to get specific batteries the charging profile the OEM specs, instead of a generic charging algorithm that does not actually meet OEM requirements. If I had used the LandStar controller out of the box on my AGMs, it would have cooked them in a few years left hooked up full time. Luckily is is a nice platform for some simple hacks.
Secondly programmability is handy for me to be able to data log, experiment and try things with ease. Manual data gathering is getting labor intensive.
Once you get programmability, the incremental cost of MPPT tends to be a lot lower.
Also I think if you long term camp on solar vs just camping a few weeks a year like I do, getting to 98% vs. 95% on a routine basis is a pretty big deal around progressive capacity loss. More so with AGMs though where you would think twice before massively overcharging them weekly or monthly to reverse sulphation from undercharging. That's why I am very interested in being able to trickle charge overnight from a secondary source. I think it's probably much better for the batteries.
I will say though that I feel like at least on my solar units, I am flushing a lot of the FUD out of theoretical gains in MPPT and real world by being able to measure the difference in output between PWM and the power that would be harvested at Vmpp. When I get some time I am going to make some plots throughout the day to approximate PWM yield vs perfect MPPT yield. The question mark will still be how far a given MPPT controller (especially the ones with the simplistic algorithms) is from true single panel MPPT yield. But this will give me an upper bound.
In the end I guess I still believe in the advice as applying in a lot of cases to first get more solar capacity if you want more yield, then consider MPPT after. But if you think you might EVER want MPPT on a group of panels, it's worth matching them for *at least* Vmpp as closely as possible. More mismatch means less system yield vs. PWM for a single controller.
Jim
Secondly programmability is handy for me to be able to data log, experiment and try things with ease. Manual data gathering is getting labor intensive.
Once you get programmability, the incremental cost of MPPT tends to be a lot lower.
Also I think if you long term camp on solar vs just camping a few weeks a year like I do, getting to 98% vs. 95% on a routine basis is a pretty big deal around progressive capacity loss. More so with AGMs though where you would think twice before massively overcharging them weekly or monthly to reverse sulphation from undercharging. That's why I am very interested in being able to trickle charge overnight from a secondary source. I think it's probably much better for the batteries.
I will say though that I feel like at least on my solar units, I am flushing a lot of the FUD out of theoretical gains in MPPT and real world by being able to measure the difference in output between PWM and the power that would be harvested at Vmpp. When I get some time I am going to make some plots throughout the day to approximate PWM yield vs perfect MPPT yield. The question mark will still be how far a given MPPT controller (especially the ones with the simplistic algorithms) is from true single panel MPPT yield. But this will give me an upper bound.
In the end I guess I still believe in the advice as applying in a lot of cases to first get more solar capacity if you want more yield, then consider MPPT after. But if you think you might EVER want MPPT on a group of panels, it's worth matching them for *at least* Vmpp as closely as possible. More mismatch means less system yield vs. PWM for a single controller.
Jim
