Replacing current 30A with MPPT controller - make sense?

[obiwancanoli]

Some of you have followed other posts of mine re: solar, and satellite, so hope this additional inquiry elicits similarly helpful info...

If I knew then what I suspect now, I'd have had the Dealer install an MPPT controller instead of then apparently standard 30A controller, despite my limited research and knowledge. Nevertheless, it would seem updrading to the MPPT would be a more efficient use of the additional panels I recently added.

I don't plan to add further panels, though if I do, it will be limited to a 4th 160W, 8.7A panel. Seems like I have enough to accomplish my likely dry camping goals. And yet, I want to make the best use of my charging system, in order to squeeze out the most amps in the shortest time, at minimal loss, and maximum efficiency.

Prices seem to be all over the map, and unfamiliar as I am, don't know what brands, features, or price ranges I should be considering, nor if it would, in fact, be worth the cost.

Thanks for your input!

[BFL13]

The best prices locally are about $1/watt for 24s and $2/watt for 12s in panels. But` PWM vs MPPT controllers is not such a big deal anymore as it was for PWMs that have adjustable voltages.

The big factor is still roof real estate for your particular rig. Some have big wide open spaces, and others have things sticking up all over so open spaces are smaller. You need big open spaces for 24s.

You can beat that if you cover some of those things that stick up with panels that are mounted on higher "legs", but it is all "situational" for what is possible for each case.

[pianotuna]

jaycocreek wrote:
In a test I saw,a $15 PWM controller got 2 watts less than the Victron $$$ MPPT,in fact,all the different PWM controllers were only 2 watts lower than the various MPPT controllers..

So,I guess it depends on if those 2 watts are worth the huge step in price..Myself,I am trying to justify the MPPT controller price over the much cheaper PWM, for my upcoming solar instal.

Repeat the test with the battery at 50% state of charge, and the panels configured to have 2X the voltage going into the MPPT controller.

Then check what time the first charging happens with PWM vs MPPT, and what time charging stops in the evening.

When a battery approaches full charge the MPPT will move into pwm mode.

That said, if there is LOTS of room on the roof, an excellent system based on PWM will be less expensive and give good results.

On the other side, if you want every erg of power from the panels and there is no room left for more panels, then go MPPT.

When I got my system in 2005 the panels were $5.50 per watt and that was a tremendous bargain. So going to series/parallel and using MPPT was the best bang for the buck.

[BFL13]

"..Having said that, one controller is better that two competing controllers."

Controllers don't compete. Same as any multiple chargers. You just have to set their voltages to the same set-points to get them to add their amps all the way up.

If one drops out first because of a lower voltage setting, it may not matter at all. It can be that by then in the afternoon, the battery bank will only accept the number of amps the remaining charger can do by itself. BTDT.

I don't see hardly any diff between PWM and MPPT in real life in our situations for amps to the battery. Only thing is that you must have MPPT to do any drop- down from panel voltage to battery voltage because an MPPT controller has a buck converter in it and a PWM does not.

Big thing is to have adjustable voltages for both absorb and float in either PWM or MPPT--that is what counts.

[3_tons]

Either way, you’ll gain some with MPPT, more so in series, but at more of a loss too in shady conditions - a compromise combination of series-parallel could help at mitigate shading losses, but since you’re going with LiFePo4’s, understand that unlike the high chemical soup resistance associated with wet cells, Li charge receptivity is uber high (i.e low internal resistance), along with a uber high amp charge rate, which means far quicker recovery times, including a greater ability to exploit ‘off-peak’ harvest hours (and those critical winter hours), enhancing even a less than optimum harvest - I see this is as a huge benefit with Li ...Having said that, one controller is better that two competing controllers...

3 tons

[jaycocreek]

In a test I saw,a $15 PWM controller got 2 watts less than the Victron $$$ MPPT,in fact,all the different PWM controllers were only 2 watts lower than the various MPPT controllers..

So,I guess it depends on if those 2 watts are worth the huge step in price..Myself,I am trying to justify the MPPT controller price over the much cheaper PWM, for my upcoming solar instal.

[obiwancanoli]

Almot wrote:

obiwancanoli wrote:
If each panel has the capacity to provide 8.7 amps of charge, I've read that without the MPPT controller, I could lose up to 30% of those amps in the process, and thus, it would seem to take longer for the batteries to recharge, or to maintain their charge. In times of limited sunlight, it seemed wise to make the best use of the tools available, and it appeared such a controller would improve the charging process.

Q 1. I doubt you are losing anywhere near 30% with PWM and your present panels, unless wires are really thin - both before and after controller. Need more details on wiring.

Q 2. If limited sunshine affects your charging, you need more panels. Not necessarily a different controller. First you need to check whether your charging is really poor.

My thinking, too... first to get installed is the Victron-712 Voltmeter. I can then more accurately observe the status of current flooded batteries - which, IMO, are due for replacement anyway. A Victron 100 A controller would reveal if additional solar would be needed, and assuming this is so, a controller with greater capacity is necessary to handle the additional 340-600 W panels, 24 V, needed on the roof, taking into account the wiring gauge and distance between all components. Existing panels are 12V.

[obiwancanoli]

pauldub wrote:
Are you panels wired in series or parallel or a combination of the two? What gauge and length is the wire between your panels and controller? Are you willing to rewire the system if that is what is needed to improve the performance?

Panels are currently wired in parallel... my installer tells me that with an anticipated change to an MPPT controller (Victron 100 A), a new Victron voltmeter install (Victron 712), Lithium batteries, and another 300-600 W solar on top (24V), connecting panels in series should be considered...

[time2roll]

If your current controller has a fixed charging profile you could benefit with a full function adjustable MPPT controller. Also you can overdrive your MPPT controller a bit with more panels and the controller will just limit the output to the controller rating.

In parallel you will want to match the voltage specs (Vmp) of the panels as close as possible. In series you want to match the amp rating.

The Morningstar MPPT is excellent and very programmable although it is a bit of a premium price.

[obiwancanoli]

Another thought occurred... my current arrangement is using 3 - 160W panels from Zamp Solar. If I add another panel or two, MUST they also be Zamp Solar panels, or is it no problem using other manufacturers? Of course, this would require a new controller, so might as well replace mine with MPPT, yes?

[obiwancanoli]

red31 wrote:
Keep what ya got.

the combiner box makes it plug and play, may be a weak pt.

Yep, the pic in red31's post is the system I have... tried to post the entire pic from Zamp Solar's website, but unsuccessful. It comes with a 3-port expandable roof cap, which is the pic in red's post, and a 5-stage controller.

Given this, it would seem I don't need to add an MPPT controller.
Thank you all for your input... I'm now less clueless than before 😉

[Almot]

obiwancanoli wrote:
Yes, more than 20A... also noted that full charge is being maintained without having to plug into power... minimum 12.8V+

12.8 is where solar begins charging. Full charge (with running solar) is when it goes into Absorption mode 14.4-14.6V AND stays there for an hour or two, and then Float mode about 13.6V AND stays there for a few hours or more. After charging in daytime, you should wait at least until the morning before taking your multimeter to battery. Measuring right after charging will result in over-stated voltage readings.

obiwancanoli wrote:

Spoke with the panel installer, and he noted that the 1st solar panel that was installed by the dealer included an inlet box which has a 3-tier plug-in (three 2-wire plug-ins), two of which each additional panels are plugged into. ....

He went on to say that while other systems would essentially shut down when the sun goes down, the system he was referring to would go on to continue charging the batteries

Photos, please. Sounds like parallel wiring. If this is something like 3-plug box in the Red31 post, then it's parallel and you don't need MPPT controller.

If I read the manual correctly, this is rather primitive controller. It exits Absorb and goes to Float when charging current drops to 0.5-1.0A, depending on what model you have. With 4*6V it should've been set to 4.5A. It will take a long time to drop to 1A, and as a result it will stay in Absorb for 4 hours on timer, which may or may not be what your system needs. It's better to have adjustable end of Absorb stage - both current value and timer.

[red31]

Keep what ya got.

the combiner box makes it plug and play, may be a weak pt.

[obiwancanoli]

Yes, more than 20A... also noted that full charge is being maintained without having to plug into power... minimum 12.8V+

Spoke with the panel installer, and he noted that the 1st solar panel that was installed by the dealer included an inlet box which has a 3-tier plug-in (three 2-wire plug-ins), two of which each additional panels are plugged into. He also noted that he really didn't prefer this type, suggesting another brand (Go Power) that, while expensive, produced significantly higher voltage - if I understood that right - and included a more expensive and sophisticated control box.

He went on to say that while other systems would essentially shut down when the sun goes down, the system he was referring to would go on to continue charging the batteries, I believe, due to the higher voltage these panels produced.

I think I got that right, but appreciate corrections and observations.

[MEXICOWANDERER]

When doing a decisive workup refer to a 3% volt drop chart then select total wire length to obtain wire cost per foot. Include tax and transportation cost.

[red31]

obiwancanoli wrote:
English, please...

do you see 20A or more charging?