Charge controller recommendations

[TurnThePage]

I have a small solar charging system consisting of two 12v 75w panels wired in series and a failing cheap MPPT charge controller. I may be acquiring another identical panel too. I'm currently leaning toward the Morningstar 15 Amp MPPT model. I looked at that Eco-worthy model that several forum members purchased, but am now a bit gun shy about off brands. I don't think it could handle a third panel in series either. Bluesky doesn't appear to offer anything that fits my system at a reasonable price point. I couldn't tell what Rogue had available.

I also seem to remember that my panels can be configured for 6v operation which may open the door to some of those marginal controllers.

Any thoughts or recommendations?

[time2roll]

PWM is fine but look for multistep programmability and temperature compensation.

[Salvo]

That doesn't sound right. You mentioned Voc = 21V. Connect two panels in series and you get 42V, not 12V.

As mentioned before, your best bet is to connect panels in parallel and use a pwm controller.
http://www.ebay.com/itm/5-30A-Solar-Charge-Controller-Regulator-12V-24V-Battery-Charging-PWM-Solar-P...

BillyW wrote:

As for the 6 volt comment, if they are in series, they should be equal to a 12 volt panel.

[HiTech]

Yes if putting 3 in series at 6v gets you to 18 v nominal and the Voc in series is withing the controller limits that should work fine, as long as the current is within what the controller can do.

MPPT is certainly the most output, the question is always by how much? If cost were no object I would have an MPPT controller rit now, just for the programmability, since many of them seem to have the most ability to customize the set points and duration of each phase of charging.

Jim

[TurnThePage]

I guess what I was trying to say is that despite being measly 75 watt panels, they are feature rich, and perform reasonably well. And the price was right (free).

Commercial grade in this case means they were actually in commercial use before they became available to me. They were part of a backup power system for a remote location that suffered fire damage.

As for the 6 volt comment, if they are in series, they should be equal to a 12 volt panel.

[Almot]

BillyW wrote:
If I choose to not bother with the third panel, I probably won't bother with MPPT again either.

If MPPT gain makes any sense, in this scenario (which I tend to think it doesn't), it's with 2 panels rather than 3. With 3 panels you'll get a lot more output that MPPT gain.

BillyW wrote:
These panels are older, but are commercial grade and perform well in a wide variety of conditions.

Most panels perform well these days, as long as they are not too old. The days of solar cells covered with cheesy plastic and leads delaminating off the panel are long gone. But, if they are old, they perform poorly even if commercial grade - whatever this means. 10 years = roughly 10% drop in efficiency. This is the nature of PV cells.

BillyW wrote:
And don't forget that 6 volt setting. Maybe I should leave them in series and try that.

I think most controllers don't have 6 volt setting. Besides, with 12V system of trailer, charging voltage has to be nominal 12 anyway, unless you split the bank for some temporary reasons.

[TurnThePage]

It's been a long time, but I believe the voc was around 21 volts.

If I choose to not bother with the third panel, I probably won't bother with MPPT again either.

These panels are older, but are commercial grade and perform well in a wide variety of conditions. Low light and shadows have not been a big issue. And don't forget that 6 volt setting. Maybe I should leave them in series and try that.

[full_mosey]

What is the Voc of the 75W panels?

Three in series may exceed the 75Voc limit of the MS MPPT 15.

Three in parallel should work with the MS SS-20 PWM.

HTH;
John

[pianotuna]

Hi fun,

AM solar you definitely pay for what you get.

[fun_in_the_sun1]

Check out this company....Truly are the best around and are there to educate, not sell. I just purchased 200W from them and have been amazing with my million questions. www.amsolar.com

[JiminDenver]

I like my Eco worthy a lot and it makes a affordable MPPT controller to use with the larger 24v panels. That said I'd suggest sticking with PWM and spending the extra money on panel.

[TurnThePage]

A lot of great info! I already have a TM2020, so display is not important. Wired in series has worked out very well until the BZ controller chose to go wacky.

[Salvo]

I would configure the panels in parallel and use a pwm controller. You can get a pretty good 20A pwm controller at ebay for $20. A $300 MPPT controller is way over kill. If you want a display, get a Turnigy Wattmeter for $25. An excellent meter.

[HiTech]

x3 here too. You either cook or under charge the batteries on longer term charge here without temp comp unless you have a method and the inclination to manually adjust the voltages.

Jim

[pianotuna]

x2 on the temperature sensor. Where I live it should not be optional.

[time2roll]

^^^^^ Yes I would opt for the optional battery temp sensor. But I have never felt I needed a display.
Hard to recommend Rogue until we have price and availability.