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weijing3333
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# Posted: 14 Jul 2015 02:33
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Which Solar Charge Controller?
I've ordered a 100w 12v monocrystalline solar panel and am looking at those solar charge controller jobbies.
Does anyone have any thoughts on the best to go for, and whether they have differing efficiency levels, and whether a good LCD display of information is worth the extra outlay? Money is very tight (when wasn't it!) so I'd really appreciate the benefit of your wisdom.
Thank you.
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Steve_S
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# Posted: 14 Jul 2015 09:04
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There are many small inexpensive controllers readily available at reasonable prices. Key Points are to get one with an MPPT controller and not PWM as MPPT is much more efficient overall. It would be prudent to get one that you can add panels to in the future so you can expand as needed when needed.
Here is one such example from Tracer BN 10A 20A 30A 40A EP Solar MPPT Solar Charger Controller Regulator MT50
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MtnDon
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# Posted: 14 Jul 2015 10:28 - Edited by: MtnDon
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IMO, there is little advantage to using an MPPT controller when using the typical 100 watt "12 volt" panel to charge a 12 volt battery in a small PV system. MPPT controllers have a loss of 5 to 10% just because of the way they work. A PWM controller when used with a "12 volt" panel will also have some loss, but that can be less than the MPPT.
The MPPT shines when used with panels in series. MPPT also allows us to use higher voltage and cheaper per watt PV panels with a 12 volt battery. MPPT also has cold weather advantages. But with a simple 1 or 2 parallel PV panel and a small battery system I doubt the advantages will be realized in better or faster charging.
I'd go for a Morningstar PWM or a Midnite Brat because they have an excellent track record. I am wary of some of the low cost controllers on ebay.
You don't need digital displays if money is tight.
I would buy a controller that would permit me to add at least one more panel in parallel though, maybe 2 more. That's determined by the maximum amps output of the panel and the maximum amps input of the controller.
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razmichael
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# Posted: 14 Jul 2015 11:41
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I also see little value in an MPPT controller for the smaller systems, although the price has certainly come well down from when I was building my system. However, be cautious on the cut rate price controllers - stick to a brand name that has a good rep. I cannot speak for a bunch of brands as I only have one but it has served me well for 3 plus years
Morningstar Prostar PS-30 (PWM). I'm running a simple system with two panels in parallel at 330 watts 12Volts (into 2 trojan T105s). Could I run these in series and use a MPPT controller? I could but the cost difference was much bigger way back when and I do not really need any more efficiency as I waste huge amounts of sun every day anyway as the system is a far bit larger than my actual demand (not a bad thing in moderation).
Prostar Line
Shop around and you can get them for around $120 without the display (not something I have really missed).
Alt-E
The 15 amp version is sub $100. The Sunsaver line is even cheaper but less flexibility for growth.
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groingo
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# Posted: 14 Jul 2015 15:15
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Being that you're just getting started, a PWM charge controller can be had for around $15 and will do very well for your hundred watt panel, once you get over 800 watts of power then you will want to consider an MPPT controller, prior to that it is just wasted money.
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Steve961
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# Posted: 14 Jul 2015 20:21
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Quoting: groingo once you get over 800 watts of power then you will want to consider an MPPT controller, prior to that it is just wasted money.
This is not always the case. Let's consider a small system with just 200 watts of solar. High voltage grid tie panels are readily available for just $1/watt. 12 volt panels suitable for a basic PWM controller will be close to double that. On a 200 watt system that will be a savings of $150-$200. The difference between the 15 amp Morningstar ProStar PWM and 15 amp SunSaver MPPT charge controllers is only $135 - more than enough savings to pay for the MPPT upgrade.
To sweeten the pot even more, let's look at the potential savings from reduced wire size. Due to my cabin layout, my solar panel had to be located about 50 feet from the charge controller and battery. With a high voltage 200 watt panel and MPPT controller, I was able to keep my voltage loss to 2% with 10 AWG wire. With 12V panels and PWM, I would have had to use 4 AWG wire to get near that level of efficiency. The cost savings for me with the smaller wire was easily more than $50.
So, in some cases, it doesn't take a very large solar system to justify going with an MPPT controller.
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MtnDon
Member
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# Posted: 14 Jul 2015 20:42 - Edited by: MtnDon
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The point that the decision here hinges on is mentioned in the OP. He already has a 100 watt, so-called 12 volt panel. No real advantage to MPPT with that, or even with two or three of those panels, unless there are special circumstances.
OTOH if the panels are higher voltage, aka grid tie panels, then MPPT is not only a good idea but a virtual necessity. The killer there though can be the freight costs as the larger panels usually need a freight truck shipment, unless the buyer can pick up locally. The 100 watt size can be shipped cheaper via UPS / FedEx.
And yes PV to point of use distance is yet another variable that can make a decision to go MPPT more sensible. It was a factor with our system (325 feet).
So I guess all this proves there is seldom a simple one word or even one sentence correct method. 
Crap! The OP member ID looked wonky after I paid attention to it. Member details indicate location is China with a link to a website that sells PV. Website ownership comes up as being in China. Anyone want to bet this is an SEO spammer?
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groingo
Member
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# Posted: 15 Jul 2015 09:51
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Best advice, do your homework, read up on the differences between PWM and MPPT and be very aware of fake MPPT controllers, there are a lot that say they are but are in fact PWM.
Bottom line, a little education can save you plenty and a good solar system is not rocket science, just keep it simple.
I have a small Renogy 400 watt system that meets all power needs (after some PWM controller fine tuning) and in fact spring through summer I am running between 80 to 90% power surplus and this winter it will also meet all needs on its own without need for generator backup.
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offgridjunkie
Member
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# Posted: 15 Jul 2015 13:48
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Quoting: groingo Best advice, do your homework, read up on the differences between PWM and MPPT and be very aware of fake MPPT controllers, there are a lot that say they are but are in fact PWM.
Good advice. Charge Controllers advertised as MPPT that cost less than $200 are most likely only PWMs. This one URL works well for small systems and is very reliable. Best if you are going to use full 200 Watts at 12 volt or step up to 400 watts in 24 volt.
I have been using the Tracer 40 AMP URLfor a year now. know some people who have had issues with it, but so far I have been lucky. I am going step up to the morning start TS-MPPT-45 when the tracer dies.
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creeky
Member
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# Posted: 15 Jul 2015 15:35
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those new bn class tracers look good too. and i'm really happy to see the Victron's in N.A. now.
offgridjunkie: a Victron MPPT 15 amp controller for 120 on amazon. Kind of a no brainer. Victron is one of the most respected names in solar. don't get me wrong. love my tristars. but the comparable tristar is 240.
And while wei is a one poster with a link to a chinese solar site that may or may not actually sell equipment. welcome wei.
plus this is a great issue 
for me MPPT is always about off season. yes any controller gives you good performance if you match battery voltage to panel voltage and you use it during the summer only for a holiday cabin when the sun shines and the days are long. and you never ever decide you want more power.
but when the days get short or the weather gets cloudy. math time.
batteries. 10 a.m. 12.4v.
PWM: 12.4 x 7 amps = 87 watts
MPPT: 14.5 x 7 amps = 101 watts.
you get 3 miserable hours of sunshine. okay it's only an extra 20%. minimum. but don't forget: better performance under cloud. morning/evening; more flexibility in the future for running higher voltage arrays (adding panels / decreasing line loss).
pwm is for teensy weensy systems used on rare occasions. sure if you go up to your cottage on weekends for 24 weeks of the year your pwm will charge up your matched batteries to array while you're away.
or you're Groingo. My personal most appreciated solar user. He's like the zen master of solar power in that he has his life with the barest minimum, most thoughtful of electrical use.
but if you're living with kids and need every spare watt. or you're me and trying to see what you can do with solar. i'm not sure pwm has a place.
mppt rules.
(ps. remember both pwm/mppt controllers use pwm to charge the batteries. mppt adds dc to dc conversion to allow more of the actual solar panel power to get to your batteries / loads.)
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offgridjunkie
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# Posted: 18 Jul 2015 21:52
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Creeky- So those Victrons are pretty reliable? Have you used them? I agree $120 is better than $240 -
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creeky
Member
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# Posted: 19 Jul 2015 08:32
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offgridjunkie. as I understand it.
victrons are one of the oldest and most venerated names in solar. The boating community uses them extensively. And they are big in europe and australia.
they come up in the various forums again and again as one of the top choices for solar. plus they have some pretty good products. they've got combi chargers and a neat all in one system that has transfer switch, ac box, inverter, charger. all you do is plug in the panels and the batteries. ideal for small off grid.
check out the specs on the new chargers / inverters. pretty impressive. and the prices, for the quality, are very reasonable.
and european manufacture. the highest level of testing/quality assurance etc we're likely to see.
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offgridjunkie
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# Posted: 19 Jul 2015 13:53
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Creeky, I can not believe I have not seen that EasySolar module. That is a very slick set up for us small off griders. I need to spend more time on the boating sites.
When I do the full Electric upgrade to my cabin, this will diffinitly be on the list.
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creeky
Member
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# Posted: 19 Jul 2015 18:27
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Quoting: offgridjunkie a very slick set up for us small off griders.
I know. after all these years of feeling that no progress is being made on the install side. here's something that really makes a difference. especially for those who are not technically adept.
And they have lithium profiles for their controllers already. so. plug in your lifepo4 battery. plug in your panel array/arrays. yer done for the next decade. next issue.
Anyone who is troubled by the arcane mumbo jumbo of building a solar system ... go see this thing. coughgary0cough
and like I said. they seem to have a sterling reputation.
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