Advice wanted:MPPT charge controller

[Wabbit]

I have decided to go the PWN route and pick up the SC-2030 CC and TM-2030 meter. Of course, as soon as I buy it, I will immediately have buyers remorse...lol. Nah. Thanks for all of the input!


Link: Handy Bobs write up on the SC-2030 and TM-2030.
https://handybobsolar.wordpress.com/2015-the-trimetric-2030-perfect/

 

[jonsun]

lol I know that feeling

 

[Sabatical]

I have decided to go the PWN route and pick up the SC-2030 CC and TM-2030 meter. Of course, as soon as I buy it, I will immediately have buyers remorse...lol. Nah. Thanks for all of the input!


Link: Handy Bobs write up on the SC-2030 and TM-2030.
https://handybobsolar.wordpress.com/2015-the-trimetric-2030-perfect/

Great write up by handy bob. My bet is you'll have zero regrets to go along with a very reasonable price and system adjustability.

Sent from my SCH-I435 using Tapatalk

 

[akrvbob]

MPPT is more than worth the extra cost in extra power produced and longevity of battery life. Not buying a quality MPPT is penny wise and dollar foolish in my opinion.

Most importantly, it does it's best work under the worst conditions, winter when the days are short and sun is low in the sky. Just like the amount of solar, you buy your controller for the worst conditions when you need help the most. That's MPPT by far and away.

 

[jonsun]

If the panels dont get to nominal vmp due to low sun then mppt is outputting -5%

as you can see voltage increases with illumination. So when running say 18vmp panels voltage is not nominal until sun is high around 11am-1pm. During that critical time of bulk charge, MPPT cannot possibly work as there is little voltage over 14.4v. Due to it's own power consumption it is then actually robbing current. Depending on the system by the time you do reach nominal vmp, assuming an mppt hasn't slowed the charge too much, you're already beyond the bulk charge phase.

To further compound the problem, an 18vmp panel will only be outputting about 17v at the controllers input.

 

[jonsun]

the best case scenario you might be getting up to 1 extra amp per 100w@18vmp 4-5hrs at peak sun in the winter but only for live use, not charge (as the batteries are in absorption stage).

and of course those 4-5A gained were mostly lost earlier during the bulk stage effectively breaking you even +/- depending on controllers efficiency.

100w / 17vmp = 5.88imp
5.88 x 14.4v = 84.67w
85w / 14.4v = 5.88A - PWM
100w/14.4v = 6.94A mppt - 5.88A pwm = 1.06A - controller inefficiency

sorry but numbers don't lie

 

[jonsun]

....then there's clouds sometimes

 

[jimindenver]

What isn't being explained is when the battery is at 12v, so is the panel on a PWM system. That is the inefficiency of a PWM system and why you only see the true value of the panel once the battery is up to voltage. Then again pray your battery never sees the true working voltage of the panel which is 18v or higher because that means you are frying your battery.

When does the PWM system work against you the most, early on when the batteries voltage is low, limiting what you can get from the panel. A MPPT system uses all of the potential in the panel no matter what the voltage of the battery is. So what you have to determine is what is less efficient, the 3% loss in a MPPT controller or the 30% of the powwer that is being loss because the battery can't accept the true voltage the panel produces.

also misunderstood is the concept that a MPPT controller only does it's thing in Bulk. MPPT is a program that controls how to use the power to bring up the battery as fast as possible. It's there because there isn't a controlling element like the battery voltage. The program isn't what produces the extra power, a buck converter does. Unlike the program, the buck converter is always functioning no matter what mode the controller is in. So even in float the controller can make use of all the panels power not in a charging sense but when you turn something on. That's why my 230 watt panel could hold the battery voltage up while I could turn on as much as 15-17 amps of load even though the panel was rated at under 9 amps.

Last thing is the thought that one PWM system is going to produce more power than another. A PWM controller keeps you from frying your battery by stopping charging at a certain voltage only, the battery is the true control via it's voltage and acceptance rate. Without a controller the voltage would continue to rise to the voltage of the panel, boiling away as it did. Then you would see 18v and see the true value of a 18v panel. It's the only way you will see it with out a MPPT controller and it's buck converter.

N AZ wind and solar has a great page explaining this in better terms than I did. That said I stand by what I said in that you shouldn't upgrade until you have a reason to. The fanciest PWM controller may give you more control but not a ounce more power. A MPPT controller will not give you more for the money that a extra panel will. I am not suggesting either, just trying to let you have the info so that you can make a descent decision.

 

[Wabbit]

The 30% is pretty hotly contested. In perfect conditions, sure, but when does that happen. For me, the winter charging is important. I see myself inside abit more and using more power. Using more power with less power being put back in sounds like a great way to come up short in the power dept. The closest I have gotten to seeing some real world applications is in the PDF below.

View attachment MPPTvsPWM-ParallelvsSeries.pdf

If a person can afford it, use both. Use a battery switcher to choose which one to use depending on conditions. That keeps it simple...?

 

[SternWake]

Why not start arguing which MPPT's buck converter does the voltage conversion most efficiently?

When i installed a Bluesky sb2512i (MPPT) back in 2007, my 130 watt panel cost 735$. Ouch.

Some online forums indicated MPPT was a total waste for such a small system,and I was an idiot and should return everything and go PWM and buy more solar wattage. Beware of opinions shouted loudly. The owner of them is likely still trying to convince themselves.

Get whatever controller allows one to set absorption and float voltages and absorption thresholds as to duration or amperage. A battery temperature sensor can make a bigger difference in battery longevity than MPPT or PWM when there are temperature extremes to deal with.

Employ Any and all charging sources whenever possible to keep batteries at as high a state of charge as possible, ect.... Thicker copper from alternator to house bank could prove a much wiser investment than MPPT over PWM. Or a better plug in charger.

or conserve just a little bit more to make up for inefficiency, or clouds, or Locusts blocking the sun.

 

[jimindenver]

SW

You know me better than that. I ran the side by side test with matching panels on the least expensive functional MPPT controller, The Eco-Worthy MPPT 20a and one of the most respected, the Morningstar 60a MPPT only to find there wasn't a difference in output, hence efficiency. Temp compensation is indeed important if you are dealing with long term extreme temperatures and can't make the adjustments yourself. That said dealing with the conditions at high altitude in the Rockies where there are swings from the mid 20's to the 80's daily didn't cause the thermal mass of the bank to change enough that TC would have been a benefit. Or as our mutual friend Mex said, I can change the set points a handful of times a year and accomplish the same thing.

There are examples of people running side by side testing between PWM and MPPT both here and on the other forum. PWM was never able to mach either the total daily or even peak haul of MPPT although BFL was able to get close showing the reduction in out put of high voltage panels in high temperatures. Here Bob D accused me of trying to confuse and befuddle him just for trying to explain the differences, well untill he put half of his system on MPPT. Guess which the other half was switched to.

There is balance everywhere. A single panel on MPPT still will not improve output as much as a second panel will on PWM. Upgrade when you have a reason to and then to what benefits you the most for the money.

 

[vtwinkicker]

I've been using the Bogart SC2030 and TM2030 combo with temperature compensation for almost 2 years on my current rig with 300w flat mounted solar. I run a Dometic 65qt dual fridge/freezer 24/7. The freezer is set at 13 degrees and the fridge is in the mid 30s. I don't turn it off at night or adjust the temperature. I also have all the other typical loads. LED lights, computer phone and camera charging, AA battery charging, 300w pure sine inverter for the computer charging.  The solar feeds two 6v batteries so about a 220AH bank. I don't have a generator and do not plug into shore power ever as I strictly boondock.

I typically wake up to about 92% charge still in the batteries. The lowest I've seen is low 80% when camping under tree cover for a few days.

The controller/monitor combo has 9 different preset charging profiles that correspond to the recommendations of the specific battery manufacturer. You can also adjust these settings manually for total control of the charging profile.

The monitor tells you everything that is going on with the system as well as 5 days of charging history.

I check my water levels 1st of the month and rarely add water 2 months in a row, just top off with a few milliliters as needed. I see charging voltages from low 13s to low 16s. My low battery voltage is usually 12.4 to 12.5 in the morning.

I'm confident I am starting the evening with a well charged bank.

The charge controller is about the size of a pack of cigarettes and barely gets warm telling me all the available power is going to the battery not wasted as heat.

I had the same system on my truck camper with 200w flat on the roof with similar results. I added the extra panel on the van for insurance and because I had the roof space.

These are my real world observations and experience. I am totally happy with these products and feel they work as they should.

I have spoken with Ralph (owner/inventer/engineer) of Bogart Engineering on the phone. He lives in an off grid home and runs his system with these. What does that tell you? They work!

I have also spoken on the phone with Handy Bob. He has tested many controllers, spoken with many people in the industry, installed these systems in peoples rigs and has great reviews from them. Bob is building an off grid home and running his power tools off solar. He does not use a generator. I think he has done the hard work for us and proven what works well.

For a small system like you would put on a van I don't see a reason to use anything else. This is where I put my money and am happy with the returns. Do your own research and spend your money where you think it best serves you.

That's my two cents on the whole solar charging question. 

For those with the bandwidth I have vids on youtube of my setup.

 

[vtwinkicker]

That's my two cents on the whole solar charging question. 

For those with the bandwidth I have vids on youtube of my setup.

I'd also like to add that I am not knocking any system that you use, like, or are thinking of using regardless of brand, PWM or MPPT. I haven't used them or tested them so I can't speak to their performance or comparison.

My previous post was purely to share information gained from my experience on my rig.

YMMV

 

[Canine]

This seems to be an ongoing discussion about controllers.I am the original obstinate sceptic.Disagreed with Bob several times over the years,until I ordered a Blue Sky and an EP Solar 30 amp mppt.The results speak for themselves.All 6 of my controllers are now MPPT.Under a totally cloudy sky at noon yesterday I was getting about 2 amps per panel (100 watt panels) going into my batteries.The 4 EP Solar controllers each were putting out slightly more than the Blue Sky each.Good luck.

 

[jonsun]

You're building a new system. You have 120A daily summer draw, limited roof space, and a budget.

build that as cheap as you can.

 

[anm]

MPPT is more than worth the extra cost in extra power produced and longevity of battery life. Not buying a quality MPPT is penny wise and dollar foolish in my opinion.

Most importantly, it does it's best work under the worst conditions, winter when the days are short and sun is low in the sky. Just like the amount of solar, you buy your controller for the worst conditions when you need help the most. That's MPPT by far and away.

I agree Bob, and something I'd like to point out is that many MPPT charge controllers switch to PWM when that is beneficial.

I've used PWM ccs for a few years on my van. The first time I tried an MPPT cc I noticed a gain in power into the battery. But I didn't like the MPPT cc — not enough bells and whistles — so I went back to my PWM that was completely adjustable (EPsolar VS2024BN). But I have missed that little bit of extra power that the MPPT could wring out of my system, so I have an EP solar MPPT 3215BN and MT50 on order — the 3215BN is ~fully adjustable as well as being MPPT...

 

[Wabbit]

I am thinking of pulling the trigger on that 3215bn + meter combo. @ under $200, seems like you get a lot.

 

[jimindenver]

anm

A MPPT controller doesn't switch to PWM in absorb and float. It switches to allowing the battery to control the acceptance rate. All MPPT controllers do this.

 

[anm]

I am thinking of pulling the trigger on that 3215bn + meter combo. @ under $200, seems like you get a lot.

I installed mine today, an EP Solar Tracer 3215BN MPPT controller and an MT50 remote meter. I bought both on eBay as a package for $169 including shipping — the guy selling it is in San Francisco I think... The 3215BN has all of the user-configurable settings of my old VS2024BN but it's 30A MPPT. If you get the 3215BN you will need the MT50 or something similar to configure it, I think they also have windows software for it.

 

[Wabbit]

@anm- can you configure it so it holds 14.8 for the three hours that people have recommended as a general starting point? Also, first thoughts on it? I'm looking at prob same eBay listing.