Cheap MPPT Controllers for casual use

[SolarCurious]

Hello,
I don't plan to have an elaborate solar setup.
I have 5 - 100watt panels (max 5.8A)
I have 2 - 130 Ah automotive batteries

I rounded the max output of my panels to 6A each so 6amp x 5 panels = 30Amps max output?
So I will need a 30Amp charge controller?

I will only use solar power during power outages and emergencies.
All I really want to use my solar setup for is ...

1 full size refrigerator
1 6000btu window AC unit (both do not need to run at the same time
1 Charging miscellaneous batteries (approximately 20aH total for all of them)

So, I am wondering if there's any major drawbacks to using a cheap MPPT controller such as this one on ebay for this purpose?

http://www.ebay.com/itm/30A-MPPT-Solar-Panel-Battery-Regulator-Charge-Controller-12V-24V-Auto-Switch-/311127008318?pt=LH_DefaultDomain_0&hash=item48709d643e

Are they dangerous?
Will they work?
Has anyone used one and if so, how long did it last?

And if this is not recommended, how much would I have to spend on a capable charge controller?

[inetdog]

The CC shown at that link is a cheap non-standard brand unit. The maximum input voltage for a 12V battery system of 20V means that it is not really an MPPT controller (or at best does not give you the advantages you would expect from an MPPT controller) but rather a disguised PWM controller or worse.
Save your money.

[Sunking]

Its is Fraud. It is basically a cheap POS made to separate you from your money.

[ILFE]

If people are going to go into this to power appliances, costly appliances that help them sustain a certain level of comfort, why would they even consider taking a shortcut on the hardware used to power such appliances? Ask yourself that question, prior to purchasing your controller.

I say that, because his reminds me of something I read the other day, and something that is on my mind a lot. Please understand, this is not directed at you. But, rather advice for you. I see it all the time. People will spend big bucks on solar modules. Then, they will spend Lord only knows on batteries. Then, when it comes to the most important part of a solar charging system, the controller, they will take shortcuts to buy charge controllers that are substandard.

Don't be like those people. Buy a quality designed and manufactured unit that has an established reputation. A few examples are Rogue, Midnite, or MorningStar. Don't cause unnecessary problems for yourself in the future, prior to getting started building your system.

[jimindenver]

You would not be able to run the five panels in series, but the controller will do it with them paralleled. A true MPPT controller would get you a bit more out of the panels but the cost is 10x more at least. The better controllers do have other features that make them appealing if they are applicable to your situation.

[russ]

but the controller will do it with them paralleled.

So you suggest using a cheap Chines POS unit?

[jimindenver]

Nope, just saying it would function with the panels in parallel, not series. There were many of these when I started designing small systems for RV use three years ago, the Tracer brand did it and that's why I don't trust the brand today even though I have seen the guts of their newer MPPT controllers. I didn't settle on the Eco-worthy controller for myself until i saw a review that opened up the case and did test proving the MPPT function worked.

As far as recommending something, it takes a lot of info to understand a persons needs, conditions, budget, etc. to be able to recommend something for them. Choosing a controller on price alone is a poor choice if you don't understand what the features are and how they apply to your charging needs. The same is true for following the recommendation of someone suggesting the latest and greatest high dollar unit out there. It is a easy recommendation because well gee it's the bestest out there right? The reality is just because it is the latest popular flavor of the month doesn't mean it will automatically fill someones needs.

[russ]

The reality is just because it is the latest popular flavor of the month doesn't mean it will automatically fill someones needs.

The reality ids to know a brand before saying it is OK -

[Wy_White_Wolf]

...I rounded the max output of my panels to 6A each so 6amp x 5 panels = 30Amps max output?
So I will need a 30Amp charge controller?...

Wrong.

Array wattage divided by battery voltage.

500W/12v = 41.7amps

you need a 50 amp charge controller.

WWW

[inetdog]

Wrong.

Array wattage divided by battery voltage.

500W/12v = 41.7amps

you need a 50 amp charge controller.

WWW

The OP was talking about a PWM CC, not MPPT. So Current IN = Current OUT. (I think he has a mistaken idea of the relative cost of a a good MPPT compared to a good PWM, and is hung up on the low price (but high cost!) of a cheap POS CC.

[jimindenver]

The controller is sold under multiple names on ebay. The ones that don't try to list it as a MPPT controller may be less expensive. On one RV forum we call them RJ specials because one nasty fella that just knew everything proclaimed he wasn't going to spend hundreds on a MPPT controller. He didn't listen and neither did a few others when some of us said wait, so we all had a good chuckle but that didn't mean we discounted what the controllers did when used as they were designed to be. Those people found that they were usable as long as they chose the one with the right feature set including adjustable set points, different battery types, temp compensation either ambient or battery, some even have equalization.

Now usually when I see this situation, it is because someone has panels like mine and are trying to get MPPT on the cheap. In this instance the 12v panels means that the OP doesn't HAVE to have MPPT and the controller could be used as a PWM controller even if the fake labeling is a scam. There isn't enough info to determine if using the five panels in parallel would fit the OPs needs or even if a respectable high dollar controller would be better. MPPT may hold an advantage worthy of the cost, especially if there is limited room for panels. If there is room for more panels, the money may be better spent going PWM and more panel, even with a brand name controller. There are way to many variables to do more than discuss components in regards to the system and needs as a whole.

In other words, more info is needed.

[SunEagle]

The controller is sold under multiple names on ebay. The ones that don't try to list it as a MPPT controller may be less expensive. On one RV forum we call them RJ specials because one nasty fella that just knew everything proclaimed he wasn't going to spend hundreds on a MPPT controller. He didn't listen and neither did a few others when some of us said wait, so we all had a good chuckle but that didn't mean we discounted what the controllers did when used as they were designed to be. Those people found that they were usable as long as they chose the one with the right feature set including adjustable set points, different battery types, temp compensation either ambient or battery, some even have equalization.

Now usually when I see this situation, it is because someone has panels like mine and are trying to get MPPT on the cheap. In this instance the 12v panels means that the OP doesn't HAVE to have MPPT and the controller could be used as a PWM controller even if the fake labeling is a scam. There isn't enough info to determine if using the five panels in parallel would fit the OPs needs or even if a respectable high dollar controller would be better. MPPT may hold an advantage worthy of the cost, especially if there is limited room for panels. If there is room for more panels, the money may be better spent going PWM and more panel, even with a brand name controller. There are way to many variables to do more than discuss components in regards to the system and needs as a whole.

In other words, more info is needed.

You are forgetting the cost of fusing those 5 parallel panels and the wire size of carrying the full current of all 5. Going with a high input voltage MPPT type charge not only is more efficient when you have more than 200 watts of panels but it can result in less expense and complication wiring the panels in series then in parallel.

[jimindenver]

I agree. That is why any one component of a system is only part of the equation.

[SolarCurious]

Right now, I have absolutely no need for the solar power equipment I have. I bought it over time, for emergency and hobby use only.
Right now, the panels are stored away. I never plan to have more than 10 - 100watt panels.
I also realize that this controller will not work with 10 panels.

Fwiw, I also have a Xantrex sw2000 Inverter.

I do know the controller works with one panel because I connected it one day and charged one of the batteries.
But I did not connect all 5 panels.

My budget is focused on things I consider more important at this time. I do not consider solar a priority.
Solar power is near the bottom of the list, however, if (during a power outage of a few days to a few weeks) it would allow me to power
a fridge, small room AC unit (6000btu) and charge a few batteries, then it would be great and worth my time.

So, while I may eventually invest in a better controller, at this time, it would only be if absolutely necessary.

I am not very concerned with optimal efficiency or best results. Just results that will run the appliances mentioned for the time frame mentioned.

Does anyone know if these controllers are inherently dangerous? (safety risk)
If my panels are rated at 5.75Amps MAX.....how do I get 41.7 Amps from 5 panels? I thought that if anything, I would net less amps not more.

Thank you all for the replies.
Jim, you specifically seem to have a very good understanding of my goals and limitations.
Your replies seem to consider all angles.
Thanks.

[SunEagle]

Right now, I have absolutely no need for the solar power equipment I have. I bought it over time, for emergency and hobby use only.
Right now, the panels are stored away. I never plan to have more than 10 - 100watt panels.
I also realize that this controller will not work with 10 panels.

Fwiw, I also have a Xantrex sw2000 Inverter.

I do know the controller works with one panel because I connected it one day and charged one of the batteries.
But I did not connect all 5 panels.

My budget is focused on things I consider more important at this time. I do not consider solar a priority.
Solar power is near the bottom of the list, however, if (during a power outage of a few days to a few weeks) it would allow me to power
a fridge, small room AC unit (6000btu) and charge a few batteries, then it would be great and worth my time.

So, while I may eventually invest in a better controller, at this time, it would only be if absolutely necessary.

I am not very concerned with optimal efficiency or best results. Just results that will run the appliances mentioned for the time frame mentioned.

Does anyone know if these controllers are inherently dangerous? (safety risk)
If my panels are rated at 5.75Amps MAX.....how do I get 41.7 Amps from 5 panels? I thought that if anything, I would net less amps not more.

Thank you all for the replies.
Jim, you specifically seem to have a very good understanding of my goals and limitations.
Your replies seem to consider all angles.
Thanks.

While I do not have first hand experience with one of those charge controllers I wouldn't say it was unsafe just not efficient.

With an MPPT charge controller the formula is Watts in = Watts out. So if you have 500 watts charging a 12volt battery the amount of amps the CC can produce = 500w / 12v = 41.7amps. A PWM type charger is Amps in = Amps out so those 500 watts will only get you about 30amps at best. Having more charging amps with an MPPT type charger will allow you to maintain a larger battery system and is more efficient then a PWM cc.

Back to your decision to have an battery powered emergency backup system. The issue is that even if you do not use those batteries much they still reduce in life. You have to keep them charged and need to at least cycle them every once and a while. Just letting them sit around does not make them happy. It will be more work just to baby sit your investment to they work when you need them.

Next thing to consider is the amount of battery (and the cost) needed to run that fridge and AC unit. Those type of appliances are big watt hour users which will require a pretty big battery bank. Now you have this very expensive solar panel/battery system that is not used much but still needs to be check, charged and maintained with the main reason to be used during a power outage.

If you do not have many power outages then using a standby generator will be much less expensive to have as your backup power source then a very large battery system.

To me it is an easy decision to use a generator as my emergency power supply then to have a bunch of solar panels stored away and a battery system that needs to be baby sat so it will work when I need it.