Charge Controller Recommendations for 200 watt Dokio

[Confetti]

I got the 200 watt flexible panel set from Dokio, as a temporary solar until I can get a proper solar installation on my roof.

My question is: what inexpensive charge controller can I order for the Dokio from Amazon? Reviewers have said the charge controller that comes with the Dokio suitcase set is really junk.

Please don't judge me for getting the Dokio, lol. I already have a Renogy 100 watt suitcase which works great, but it's just not adequate to run my fridge (need at least 200 watts). And a 200 watts Renogy suitcase would be way too heavy for me to haul around.

Thanks!
- Lisa

 

[tx2sturgis]

What do they mean by 'junk'? It might work...give it a try. Or maybe it will kill your battery in a week...we don't know yet. 

As far as a replacement:

Do you want a decent controller that will handle both the Dokio 200 watt and the 100 watt that you have? Or just a simple controller for the new portable set, and you will buy something better later on?

Do you want a controller you can mount inside the RV or van, or one that you can attach to the portable panels with a battery nearby? Or will you be mounting this permanently in the RV, and adding more panels on the roof later?

Some detail here will help us provide a better answer.

 

[Confetti]

Thanks for your reply. I think the attached Dokio controller is thought to be low quality and inadequate. Especially for 200 watts.

I want a decent simple (yet cheap) controller for the new Dokio set. Since it's temporary, the controller doesn't have to be mounted anywhere (just propped up somewhere near the battery). 
Soon I'll be getting someone to install a super dooper (separate) system on the roof. Still looking for an installer in Arizona.

The Renogy suitcase has its own controller. It's great for charging my laptop, phone and lights. But the 100 watt Renogy can't power my 12volt fridge.

Thanks for your help!

- Lisa

 

[Wabbit]

What price range are you looking at? PWM or MPPT? On Amazon you can get a 20a PWM for $15-20. Is that what you're looking for?

 

[Confetti]

Yes, something under $40. I figure only a PWM will be cheap enough. I need to power my Whynter fridge freezer.
What brand PWM do you recommend? Later on, can I connect it to my 600 watt Power TechOn inverter?

Attached is photo of charge controller it came with.

Thanks!
- Lisa

 

[Trebor English]

I just looked at the Amazon picture of the Dokio 200.  The controller looks just like my controller.  

I understand why people call it junk.  It doesn't include a $200 monitor / coulomb counter system or state of charge display.  This controller does not do temperature compensation.  It doesn't give 30 or 40 amps output with only 10 amps input.  It doesn't fix batteries that have been ruined.  It does not make cloudy days sunny.  

I like my charge controller because it does do 2 things.  It keeps the battery from discharging at night.  It limits the battery voltage according to the set point when the sun is shining.    

With relatively long not very fat wires there will be voltage drop.  The voltage at the controller needs to be set to get the voltage you want at the battery.  As the controller goes on and off the voltage changes.  Remember that the goal is to charge the battery.  If you want a stable pretty display then you need a display driven by software that averages.  

There are several web pages and several threads here regarding controllers that turn on the green led and stop charging prematurely.  The controller determines that it is time to stop the absorption voltage.  It is generally accepted that charging is approximately complete when the absorption voltage is held and the charge current drops to 1 amp per 100 amp hour battery capacity.  Without a current sensor at the battery it isn't possible to determine how much current is going to the fridge and how much is going to the battery.  This controller holds the programmed voltage until the sun goes down.  Lacking a state of charge monitoring system the alternative to leaving the absorption voltage on is to turn it off.  Some controllers turn off when the battery gets up to a set level.  Some hold the level for a fixed time.  Some hold the set level for a time period that is a function of how long it took to get to that level.  There may be other algorithms.  Really you want the charge controller to measure the specific gravity of the electrolyte but that is very expensive.  

There is one more thing thay is bad about this controller.  The 2 square inches of documentation are an awkward translation to English.  The constant voltage charging level, what I call absorption, what Renogy call boost, is named "float" which is a word some people use to mean something different.  

I like my controller.  It is charging my battery.  It does everything I expect it to do.  My $80 battery has not been ruined.

 

[Confetti]

Thank you Trebor. 
So you're saying that even though the Dokio charge controller isn't the greatest, it is adequate for my current fridge application? 
Should I get 1, or 2 batteries to run my fridge?

Currently I'm testing the Dokio without a battery (as is advertised). I'm charging my old cell phone with the built-in USB. Seems to be working okay. Obviously, I'll be using batteries to run my fridge.

Lisa

 

[Trebor English]

Should I get 1, or 2 batteries to run my fridge?

Short answer, one series pair of golf cart batteries, the cheapest ones you can find.  

I am an old dog so LiFePo batteries are a new trick.  I probably can be taught but I'm not there.  AGM batteries are almost as expensive and almost as touchy.  I'm not a fan of them either.  

So my opinion is that the best way is to go with flooded lead acid batteries.  You can actually test the state of charge with a $10 hydrometer.  A series pair of golf cart batteries will give enough amp hours to keep an efficient fridge going through a couple of cloudy drizzly days.  Golf cart batteries are sold in substantial volume.  That makes them cheaper.  Golf cart batteries actually do have thicker plates and can deliver many deep cycles.

Another way to look at it is tuition.  The amount you pay for "learning batteries" is like tuition.  If you ruin the first set of batteries within a year you need to buy a second set of learning batteries.  

Batteries Plus Bulbs and Sam's club both carry low price golf cart batteries.  Trojan batteries are excellent but I don't recommend buying anything but the cheapest for learning batteries.  

The required maintenance is monthly watering with distilled water.  With the charge controller at the end of a long wire I recommend setting the voltage higher and checking the water use weekly until you see how it is actually working.  Ten minutes, in my opinion, is reasonable to get good battery life.  The result of water use is that small amounts of hydrogen are produced.  Leaving a window open will let it go.

 

[tx2sturgis]

By the way, if those panels are 12v output only, (probably closer to 16-19v) then an MPPT controller won't give you any tangible benefit at all.

As I said, (and Trebor confirms), give that simple PWM controller a try...run it for a week or two...

Look at the battery water levels a couple of times, make sure the battery voltage in the morning just before sunlight, after an all night run with the fridge, is not getting too low after a few days. If the water levels drop, replenish with distilled water.

If the voltage in the morning before sunlight is above about 12.3 I'd say it's gonna be ok. If you see it below 12.0, then let's talk again.

Of course, if you have a week of cloudy weather and/or rain, then all bets are off....you better eat all the food that will spoil!

 

[highdesertranger]

I am curious what refrigerator do you have that 100 watts of solar is not enough. I run 2 Engels off of two 100Ah marine batteries and two 280 watt panels. I have plenty of power even on multiple cloudy days. maybe you have other problems. highdesertranger

 

[Confetti]

Thank you Trebor and tx2sturgis for the battery advice. That's just what I needed to know.

hidesertranger, I have a Whynter 62 qt fridge freezer. In Bob's video comparing 12 volt fridges, he mentioned that you need at least 200 watts of solar to run it. So, I put 200 watts on the roof of my van, and the fridge runs just fine. But now I'm changing rigs and sort of starting over.
But I'm keeping my Whynter fridge!

By the way, the Dokio flexible panels worked fine charging my phone using only the on-board USB (no battery). I'll let you know how it does after I hook up to batteries.

 

[frater secessus]

My question is: what inexpensive charge controller can I order for the Dokio from Amazon? Reviewers have said the charge controller that comes with the Dokio suitcase set is really junk.

The controller is a simple on/off controller* but it will work.  If Trebor hadn't already chimed in I would have PM'ed him and asked for his input here.

Since you basically get to pick one setpoint I'll mention some considerations for picking that setpoint:

• battery manufacturers recommendations for Absorption (usually in the 14s) and Float (usually in the 13s)
• on/off (and PWM) controllers make more power with higher setpoints
• this "higher setpoints" issue is even more important with mono panels
• Sternwake has observed that people who cycle their banks daily may be better off by effectively only Absorbing, by setting Vfloat to Vabsorb.

Putting all that together my approach would be to set the controller to charge to the battery manufacturer's recommendation for Absorption, or perhaps a couple 1/10's lower.

* sometimes called shunt but that isn't really correct


Bonus rant

My rules for reading reviews includes discounting the opinions of reviewers who:

• use emotional or hyperbolic words like junk or nothing but problems
• cannot write in standard english in at least a junior high level:  run-on sentences, misused punctuation, bizarre capitalization
• include racist, sexist, xenophobic, or political swipes in the review

 

[DLTooley]

My food storage consists of a 45 quart 12v run as a freezer and a 55 quart cooler used for above zero cooling I maintain ice by rotating half gallon juice bottles.

I chose to upgrade my controller before my panels or battery and run the freezer during daylight hours only using little battery. I have 150 watts of panel and that is enough to run the freezer on cloudy days success with 100 watts has been reported by a few folks, but it isn’t easy

Understanding exactly how much power you are getting and using under different conditions is crucial. The $120 Victron does this well and also maximizes your power. I’d recommend returning the flexible panels and getting a basic set of batteries as above and a power measuring controller.

You may also be able to use your existing controller with your current panels or with a second 100 watttraditional. There are other ways of measuring power also.

Electricity and battery chemistry is complex. The best way to learn is to get accurate measurements and use theory, and this board, to interpret. As in life there are few absolutes.

 

[Trebor English]

Putting all that together my approach would be to set the controller to charge to the battery manufacturer's recommendation for Absorption, or perhaps a couple 1/10's lower.

After that measure the voltage at the battery.  Due to the long wire between the controller and the battery while charging current flows the voltage at the battery will be lower.  Adjust the controller to get the battery voltage you want at the battery.  This adjusting has to be done with a full battery or an almost full battery.  With a discharged battery the controller is always on, full solar panel current flows, the voltage is set by the battery, not the controller.   

This applies for any controller that isn't real close to the battery.  If the controller doesn't allow setting the voltage like the cheap PWM then it must be close to the battery.  Exception, some controllers have another pair af wires to remotely sense the voltage atthe battery.  That's the best.

 

[frater secessus]

Excellent input as always, Trebor. I'm starting to actively look for your contributions to threads.

 

[DLTooley]

I’ve just read the Dokio description. This is a new brand to me.

The previous generation of flexible panel were failure prone. At least some of those problems have been addressed. Heat from surface mounting is unavoidable.

I think the Chinese are using off brands as a form of market test

Suaoki is becoming an established brand and their products on easily accessible specs are driving the value market. I just purchased my first of their products.

The price on the Dokios was much better than expected. Let us know how they hold up.

 

[frater secessus]

I've been thinking about current-generation flexible panels, too.  I've split my reply off to a new thread to avoid sidetracking OP's thread.

 

[coronan]

The d rings keep pulling off of the dokio panels. Anyone have a retrofit / repair???