Looking for a 40 amp MPPT solar charge controller

4 panels wouldn't replace 30+Ah a day even in winter?

jrnymn7 wrote:
So, clearly I'm still confused regarding series vs. parallel and shading. I thought the bypass diodes were what made series better than parallel with regards to partial obstructions/shading. I'll have go back over some of the recent threads where the issue was discussed.

It depends on the shade.
No set up is superior in all conditions.

So, clearly I'm still confused regarding series vs. parallel and shading. I thought the bypass diodes were what made series better than parallel with regards to partial obstructions/shading. I'll have go back over some of the recent threads where the issue was discussed.

Wiring will be heavy (6ga), regardless, seeing as I've already bought everything to go 12v parallel pwm, with 50' of portability.

Regarding the roof mount, the panels, tilt legs, and wiring connections will all be accessible by simply leaning a ladder against the rig, so no problem there. The tilt 'n' twirl design and build is right up my alley, so I do not anticipate any problems there.

In summer, a single panel, flat mounted, will likely be plenty. In late spring and early fall, two panels, either flat or pointed, should do. But once the temperatures drop, two panels pointed will fall short of my needs; and even 4 panels flat would still fall short, so I see no benefit in adding more panels. And either way I will have to keep the snow and ice off them.

I would like to compare a standard pwm to a pwm with buck and mppt (because let's face it, they're all pwm controllers) for myself. And yes, I want to maximize the few hours available in winter, including those elusive shoulder hours. And I also want to have a back-up controller on hand, just in case.

As for price, no, I do not plan on spending $300+ for mppt, more like $200. And I hope to go Lithium in the future, so something like the Tracer 3215bn would fit the bill in either situation... adjustable voltage for charging flooded, and programmable timing and adjustable voltage for charging Li.

Hi Salvo,

There is no question tilting helps. But many find it unnecessary, too. There is no way I'm getting on my roof at -30 F or C to tilt.

I take it you've never been to Quartzsite. A majority of the snowbirds could be tilting. I tilt all the time in winter. No problem. It's easy.

pianotuna wrote:


Most folks don't bother to tilt

Hi jrnymn,

As voltage rises efficiency of the controller drops. If there is a long run from the panels to the controller some money can be saved by going to series, but there will be losses in the controller. One figure is 98% with nominal 12 volt panels, and 96% with double the voltage. I do not know how low the percentage may drop.

Series may not do well in shade. It depends on the bypass diodes. In my own case there are diodes between each cell. If the entire panel has only one diode then it would not take much shade to "knock out" the entire panel.

On a rainy day you may get 1/6 not 1/2 of the possible harvest. I get output of 3 amps in rain vs 17 amps in perfect solar conditions.

In leafy shade I get 7 amps at solar noon.

I chose series/parallel and mppt because of:

1. a #10 prewire from the factory
2. MPPT was cheaper than buying another panel (at the time $5.50 per watt).
3. MPPT overall manages to extract a bit more energy during the shoulder hours
4. the latitude where I RV has longer shoulder hours

Today it is a different ball game with sophisticated PWM controllers and ultra cheap panels. I would have maxed out my roof and gone pwm.

Most folks don't bother to tilt much less twirl panels. One study suggests that after seven times people just no longer make the effort. Panels are cheap. Get an extra panel or two ($), and do a flat fixed install. OR bite the bullet and get electric tilt motors installed. ($$$$)

jrnymn7 wrote:
Correct me if I'm wrong; if I go MPPT, which ever way I wire is irrelevant, seeing as both will result in the same power output in watts (your favorite subject). Considering temps, rainy weather, etc., it seems if I go series I would have 35v x 8a for 280w, and if I go parallel I would have 17.5v x 16a for 280w. And on a rainy day, when amperage would suffer greatly, at say half, I would have 35v x 4a, or 17.5v x 8a, for 140w, either way.

The only other thing would maybe be the issue of shading or partial obstructions; which if I understand correctly, would indicate series wiring would be best?

jrnymn7 wrote:

BFL13 wrote:
Since the voltages are adjustable in "user", between trips you can pick the same voltage for absorb and float. Then the timing doesn't matter.

Smk is always asking about that time in absorb! :)

The "default" charging profile is the standard EP Solar one I had a couple years ago in the LandStar with that two hour fixed absorb time. The RN series has that too. This new BN series brings the "user" feature plus an extra 50v from 100Voc limit to 150Voc limit.

Trolling eBay.ca, I found the 40a, 4215BN with the MT50 remote and cable for $285 (Can) free shipping.

Don't know the price for a BN 20a, but a 20a RN with remote was $165 free shipping. A 20a Eco-Worthy is still about $100 but has 42Voc limit vs the 100Voc in the RN.

BFL,

Do to parking at work etc., I've had to re-think my set-up, and I now plan to do a roof top install, c/w tilt and twirl (and a custom vinyl cover to keep the snow and ice off when necessary), and probably MPPT. But I'm still not sure whether to go series or parallel (yes I know I would be better off with 24v panels now, but smaller, lightweight portable may still be in the not so far off future).

Correct me if I'm wrong; if I go MPPT, which ever way I wire is irrelevant, seeing as both will result in the same power output in watts (your favorite subject). Considering temps, rainy weather, etc., it seems if I go series I would have 35v x 8a for 280w, and if I go parallel I would have 17.5v x 16a for 280w. And on a rainy day, when amperage would suffer greatly, at say half, I would have 35v x 4a, or 17.5v x 8a, for 140w, either way.

The only other thing would maybe be the issue of shading or partial obstructions; which if I understand correctly, would indicate series wiring would be best?

It is all situational, so you are on your own there! :) Where the camping situation wrt shading keeps changing at each location and it is for all year with roof mounted panels you have to do a giant compromise, which means being wrong all the time :)

I would look into arranging some kind of wiring scheme that can be switched back and forth easily at combiner point between parallel and series with also switching between controller types if you have one or more of each type.

If you have the 12vs in parallel I would just use the PWM. If using 24v array (12s in series or just big panels) you must use MPPT on a 12v battery. But you can also have a 24v battery and use the PWM if it is 12/24. You can get the 12v from the 24v battery bank separately.

With 12v panels you need fatter wire from panel to controller than with 24v panels which have half the amps on that path. From controller to 12v batts the wiring is the same with PWM and MPPT because your amps are back up to 12v level. If you have 24v batt the wiring can stay thin at half the amps. Then you need the fatter wire for the 12v part after that unless it is a short run of course.

I have no clue about shading since there are so many variations on how much by what on what. I have figured for camping in the open "up here", if I had two 12s, I would go MPPT in series in the cold half of the year and PWM in the warm half. I would not get MPPT for the cold half on 12v in parallel but if I already had the controller then I would use it. I sure wouldn't fork over $300 for one for that, when I already have a perfectly good Solar30.

I only have the MPPT because I got a 230w panel and I only got that instead of two 12s because it was almost half the price for the 230w. I could also get the Eco-W for its low price where in that one case at the time, MPPT over PWM controller cost was bearable.

If you have two 12s, the question is whether you want the Tracer for little benefit in AH over the Solar30 or because you want to mess with MPPT as a hobby for entertainment. It is cheaper than golf or fishing! :)

Partial shading would indicate parallel wiring would be best.

On the newer Tracer. It looks more promising that their last series which someone here had used and found it functional. The biggest complaint seemed to be the remote wasn't all that accurate. That's better than when I started and Tracer MPPT controllers were all fakes.

BFL13 wrote:
Since the voltages are adjustable in "user", between trips you can pick the same voltage for absorb and float. Then the timing doesn't matter.

Smk is always asking about that time in absorb! :)

The "default" charging profile is the standard EP Solar one I had a couple years ago in the LandStar with that two hour fixed absorb time. The RN series has that too. This new BN series brings the "user" feature plus an extra 50v from 100Voc limit to 150Voc limit.

Trolling eBay.ca, I found the 40a, 4215BN with the MT50 remote and cable for $285 (Can) free shipping.

Don't know the price for a BN 20a, but a 20a RN with remote was $165 free shipping. A 20a Eco-Worthy is still about $100 but has 42Voc limit vs the 100Voc in the RN.

BFL,

Do to parking at work etc., I've had to re-think my set-up, and I now plan to do a roof top install, c/w tilt and twirl (and a custom vinyl cover to keep the snow and ice off when necessary), and probably MPPT. But I'm still not sure whether to go series or parallel (yes I know I would be better off with 24v panels now, but smaller, lightweight portable may still be in the not so far off future).

Correct me if I'm wrong; if I go MPPT, which ever way I wire is irrelevant, seeing as both will result in the same power output in watts (your favorite subject). Considering temps, rainy weather, etc., it seems if I go series I would have 35v x 8a for 280w, and if I go parallel I would have 17.5v x 16a for 280w. And on a rainy day, when amperage would suffer greatly, at say half, I would have 35v x 4a, or 17.5v x 8a, for 140w, either way.

The only other thing would maybe be the issue of shading or partial obstructions; which if I understand correctly, would indicate series wiring would be best?

What I do not like is the rated Load Current max of 20 amp. Also Max PV input power. I have 1000 w, this spec states = 24 V system and not 12.