Opinions on Renogy 20 Amp MPPT?

[Tussah]

Trying to figure out what sort of electrical system I need is really making my brain hurt.  I appreciate and admire the experts who have a true passion for power systems and battery management and want to share this passion and expertise with the rest of us, but it has really been a strain for me to translate all this into something simple and doable.  In squirrel speak, here's what I'm getting out of all of this:

1)  Make sure you have lots of input power (solar, etc)  the more, the better
2)  Buy real big batteries
3)  Never let them drain down to 50%,   the less you use them the better
4)  Keep charging them.  
5)  Expensive controllers have more features than cheaper ones. 
6)  Buy monitors, but don't believe them when they say the battery is full.  
7)  Keep charging the batteries
8)  Buy lots of equipment to measure the state of the battery.  
     (haven't figure out how to use the equipment or what you're supposed to do with this information)
9)  Keep charging the batteries. Maybe at some point they'll get to 100% full, and this will be good for their lifespan.


At the moment, I'm thinking of getting 200-300 watts on the rooftop solar panels, 150-200 Ah of batteries, plus supplemental charging sources off the alternator and (occasionally) shore power.   All I want to run is a small RV AC/DC compressor fridge, rooftop Maxxair fan, a few LED lights, and charge my phone and chromebook.    I'm planning a road trip, so will be running the vehicle most days.  I'll be traveling all over the country, so who knows what the weather will be, but I'll do my best to stay in areas that are not too cold or too hot.

I really, really want a low maintenance system that doesn't require me to make battery management my new hobby.   I was thinking of buying AGM batteries so I won't have to add water.  Now, I'm wondering if they will be more finicky than plain old golf cart batteries.  

I can see the value of having a monitor that lets me know how drained the batteries are, but if they go down, then all I can do is add more charge, or stop using stuff, right?

Does my plan seem reasonable, from a seat of the pants point of view?  I appreciate any advice, just can't promise to understand anything that gets too technical.

 

[highdesertranger]

Tussah let me see if I can make it a little easier.
1. figure out your daily power usage. yes you have to do a little math, add everything up.
2. choose your battery(s) according to your usage. remember the 50% rule.
3. get enough solar to keep your batter(s) full. 1-2 watts of solar to every amp hour of battery.
there is your three steps as you do each step and have a question ask here, there are a lot of helpful people here. pretty soon you will understand it all and you can help the next person out. highdesertranger

 

[wagoneer]

whoh slow down big guy. your going over the top just get to the peak. 2 x 6 volt golf cart batteries a solar panel large as affordable and realistic
a controller and a 600 inverter. done for about 4-5 hundred bucks, personally I rarely use my inverter because almost everything is 12 volt

 

[BradKW]

Jim, for some reason the first reason that got me to go 24v only gets remembered after I post stuff. With 1k watts solar, there was only one single option for charge controller at 12v, a very expensive Outback that I didn't want anyway...

 

[blars]

Jim, for some reason the first reason that got me to go 24v only gets remembered after I post stuff. With 1k watts solar, there was only one single option for charge controller at 12v, a very expensive Outback that I didn't want anyway...

A pair of Morningstar tristar MPPT-60 controllers would be pleanty, they are designed to be able to hook together.

 

[29chico]

BradKW:

My suggestion is to consider a Morningstar Sunsaver MPPT 15 amp controller.

Link: http://www.solarhome.org/Morningsta...troller.aspx?gclid=COWWlOK7m84CFU-CfgodWP0B4w

Make sure to get the remote temp sensor, not sure if it is always included.  You could even slightly over panel it in the future with another 100w solar panel w/o any negative issues and still use it in 12v mode.  You would then stay at the controller's full 15a output into your battery bank for longer when sunlight is less than optimum.  In other words, when you really need the extra charge.

Custom programmable with the Morningstar MSview software and a PC computer.  Just be sure to get the recommended Tripp Lite USB to serial adapter and update the drivers before use.  You will need the Morningstar serial cable as well if you need to custom program.  The Sunsaver MPPT has dip switch settings for several lead acid battery types so you may not have to program it.

Later on, if you decide to go with a 24v system by adding a few more panels and another controller, the Morningstar Sunsaver MPPT can also be used to down convert, with pretty high efficiency, from a 24v battery bank to a 12v 15 amp output so you could still use 12v devices.  That down converted 12v at 15 amps could be used to keep a moderately sized 12v battery charged so that 12v devices with a higher than 15 amps draw could be used for reasonable periods of time. There are other, more arcane, ways to take advantage of the fact that Morinigstar's MPPT controllers are high quality current limiting devices that I will not get into.

Options are good...
 
If you call Arizona Wind and Sun and refer to the price in the above link they will probably beat that already good price by a few bucks.

 

[Spaceman Spiff]

. . . In squirrel speak, here's what I'm getting out of all of this:

1)  Make sure you have lots of input power (solar, etc)  the more, the better
     This is true but within reason.  You don't need 1KW of solar for 200 AH of battery.  1 to 2 watts per AH is sufficient, especially as you plan on alternate sources of charging.

2)  Buy real big batteries
     Don't know what you call 'real big batteries'.  I have two Energizer GC2 (208 AH) that meet my needs.

3)  Never let them drain down to 50%,
     The more they drain down and the longer they are in a drained state the more hard sulfates they create.  50% seems to be a point of significant damage. 
      the less you use them the better
      You bought them to use so use them.  Even if you don't use them they will go dead sometime in the future.
4)  Keep charging them.
     A good controller will charge your batteries appropriately (and you have good sun and it is programmed correctly).

5)  Expensive controllers have more features than cheaper ones.
     Expensive controllers usually have better components, are more rugged, can be programmed, and have more features 

6)  Buy monitors, but don't believe them when they say the battery is full.
     If you give your monitor good information it will give you good information and vice versa.
      
7)  Keep charging the batteries
     see #4
     
8)  Buy lots of equipment to measure the state of the battery.
     I have a Trimetric 2030-RV, a specific gravity 'turkey baster' with temp compensation, clamp on ammeter/multimeter.  That's all you need.

     (haven't figure out how to use the equipment or what you're supposed to do with this information)
     That can be answered when you have specific questions.

9)  Keep charging the batteries. Maybe at some point they'll get to 100% full, and this will be good for their lifespan.
     See #4, #8.  with the Trimetric I know when my batteries are full.  And yes it will be good for your batteries.


At the moment, I'm thinking of getting 200-300 watts on the rooftop solar panels, 150-200 Ah of batteries, plus supplemental charging sources off the alternator and (occasionally) shore power.  All I want to run is a small RV AC/DC compressor fridge, rooftop Maxxair fan, a few LED lights, and charge my phone and chromebook.
I have 200 watts of solar and 208 AH of battery.  With this I run a 1.8 cu. ft. compressor frig, MaxxFan, LED lights, iPhone, MacBook, InReach SE, WeBoost 4G-M, and miscellaneous other fans.  I rarely get below 80% in the AM; usually back to 100% by noon.  I have vehicle charging wired but not hooked up; haven't needed it.

I really, really want a low maintenance system that doesn't require me to make battery management my new hobby.
I check SG on my batteries about once a month and before trips and reset the Trimetric if needed (it hasn't yet).  Equalize once a year.  Thats it.

I was thinking of buying AGM batteries so I won't have to add water.  Now, I'm wondering if they will be more finicky than plain old golf cart batteries.
They are.  And they are more expensive.  And it is harder to determine when the battery is full. 

I can see the value of having a monitor that lets me know how drained the batteries are, but if they go down, then all I can do is add more charge, or stop using stuff, right?  Yup.  And without a monitor you don't know when your batteries are below 50% and you need to 'do something'.

Does my plan seem reasonable, from a seat of the pants point of view?  I appreciate any advice, just can't promise to understand anything that gets too technical.
Use big wire.  I have 4 AWG from panels to controller to batteries.  Overkill for 200 W but I had planned on adding 200 W if needed (I don't think I will).

HDR gave good advice.  Start with your needs and work backwards.

 -- Spiff

 

[Tussah]

Tussah let me see if I can make it a little easier.
1.  figure out your daily power usage.  yes you have to do a little math,  add everything up.
2.  choose your battery(s) according to your usage.  remember the 50% rule.
3.  get enough solar to keep your batter(s) full.  1-2 watts of solar to every amp hour of battery.
there is your three steps as you do each step and have a question ask here,  there are a lot of helpful people here.  pretty soon you will understand it all and you can help the next person out.  highdesertranger

I'm not afraid of the math a bit.  The issue is that the best that I can do is estimate a range of possible daily power usage.   One sunny day, I may spend the entire day driving.  On this day, power usage will be minimal and charging via both solar and alternator.  Another dark, rainy day, camping in the woods, it may be all power usage and no power charging.    If I buy a fridge that draws 4 amps, how many hours a day will it actually be running?  20% of the time?  Half the time?  For sure, when it's hot, the fan will be running all day and the fridge will be working harder.  When it's cold, not so much.   In Arizona, I'm sure that I'll get maximum benefit from solar, but probably not so much in other parts of the country.  Since I haven't actually hit the road yet, it's all theoretical.   My suspicion is that the range of my power usage will be pretty broad.   I think that the best I can do is rate electrical appliances, guesstimate how many hours I will be using them, work with the constraints of rooftop and battery space, and make an equipment decision that I hope will come close to meeting my needs.  But it definitely feels more like smart guessing than calculating.

I appreciate the advice about measuring equipment needed to monitor things, but have no idea at all exactly how one would use this equipment.   Are they hard wired in?  Clipped to the battery?   Hope to learn more as I go on.

 

[SternWake]

 All I want to run is a small RV AC/DC compressor fridge, rooftop Maxxair fan, a few LED lights, and charge my phone and chromebook.    I'm planning a road trip, so will be running the vehicle most days.  

You can get away with a 100Ah AGM battery and 200 watts of solar.

AGMs basically are lower$ or higher$$, with the higher $$ AGMS having no upper limit on charging amps, and in fact prefer huge charge rates, which is nice when a well wired alternator is involved.

Les$er AGMS generally do not want more than 30 amps per 100AH of capacity, and if allowed to drink all they want from a source like a fast spinning  alternator allowed to seek 14.5v by vehicle voltage regulator, can drink too fast and vent.  this can be mitigated somewhat by thinner cabling between alternator and AGM, but this sacrifices charge performance.

Issues can arise with reduction in alternator life from excessive heat with a hungry higher$$ AGM battery asking for everything the alternator can make.  This can be mitigated by not idling excessively with a drained battery. Highway speeds keep the alternator much cooler.  Hot idling with a depleted battery is when it gets hottest and damage is cumulative.

AGM batteries have different recommended absorption voltages ranging from 14.2 to 15 volts, so one needs to ignore the wide AGM brush that often gets painted across all manufacturers and find the recommendation of their AGM manufacturer.

6v flooded Golf cart batteries are the best bang for the buck and most tolerant of abuse, but you need 2, and your stated needs do not require that much capacity.

Your stated loads are slightly less than mine, and I have only 90AH of capacity total( for both engine and house), and 200 watts of solar.

Plugging in to the grid to hold absorption voltage as long as required and give the battery a break from cycling is a good way to 'reset' the capacity to maximum remaining.

Plug in charging sources is another thread entirely.  I use an adjustable voltage power supply, but this is a manual charger, requiring me to choose voltage and the time it is to be held at this voltage.  Automatic smart chargers are too timid in regards to the time they hold absorption voltage, especially on a hard working deeply cycled battery.

They can be tricked by lowering battery voltage to below 12.6v by the application of loads then restarting charger then turning off loads.  In general, do not trust automatic charging sources when they first flash the green light.  Trick them into restarting and seeking 14.x volts again.

  I bring this up incase one already has an automatic battery charger they plan to bring along.

 

[Spaceman Spiff]

I'm not afraid of the math a bit.  The issue is that the best that I can do is estimate a range of possible daily power usage.   One sunny day, I may spend the entire day driving . . .  I think that the best I can do is rate electrical appliances, guesstimate how many hours I will be using them, work with the constraints of rooftop and battery space, and make an equipment decision that I hope will come close to meeting my needs.  But it definitely feels more like smart guessing than calculating.

Estimating is the best you can do right now, along with using how others that are using similar battery draws are running.  There are just too many variables to get definitive answers.  I started out with 200 W and 208 AH because that is all I could afford and I estimated I would be close:

https://vanlivingforum.com/Thread-Energy-Budget   #3

The issues I have with Sternwakes system is he lives in California and probably has sun every day.  He knows his system and his usage very well.  I can get three days with no solar input and still be above 50% with my usage.  I like the margin the extra battery capacity gives me.

What i did to get my numbers for the refrigerator is to get a Kill-A-Watt meter and run it off of 110V during a hot spell and get real numbers for power usage and duty cycle.  Numbers for the other stuff is easily attainable.  The estimating comes in on how much you will be using them.

Here are my questions on Specific Gravity testing from a couple of years ago:

https://vanlivingforum.com/Thread-Testing-Batteries-with-Hydrometer

 -- Spiff

 

[BradKW]

BradKW:

My suggestion is to consider a Morningstar Sunsaver MPPT 15 amp controller.

Link: http://www.solarhome.org/Morningsta...troller.aspx?gclid=COWWlOK7m84CFU-CfgodWP0B4w

Make sure to get the remote temp sensor, not sure if it is always included.  You could even slightly over panel it in the future with another 100w solar panel w/o any negative issues and still use it in 12v mode.  You would then stay at the controller's full 15a output into your battery bank for longer when sunlight is less than optimum.  In other words, when you really need the extra charge.

Custom programmable with the Morningstar MSview software and a PC computer.  Just be sure to get the recommended Tripp Lite USB to serial adapter and update the drivers before use.  You will need the Morningstar serial cable as well if you need to custom program.  The Sunsaver MPPT has dip switch settings for several lead acid battery types so you may not have to program it.

Thanks, I will take a closer look...I did look at those recently, but I had no idea they were as fully featured as all that. Maybe it's just me, but I swear that much of this equipment is poorly described in online stores...it's almost like you need to know a feature exists and then delve into product literature to find it...

 

[akrvbob]

Trying to figure out what sort of electrical system I need is really making my brain hurt.  

At the moment, I'm thinking of getting 200-300 watts on the rooftop solar panels, 150-200 Ah of batteries, plus supplemental charging sources off the alternator and (occasionally) shore power.   

I really, really want a low maintenance system that doesn't require me to make battery management my new hobby.   I was thinking of buying AGM batteries so I won't have to add water.  Now, I'm wondering if they will be more finicky than plain old golf cart batteries.  

Does my plan seem reasonable, from a seat of the pants point of view?  I appreciate any advice, just can't promise to understand anything that gets too technical.

You have an excellent plan! Get the 300 watts and a pair of AGM golf carts, plus charging it off the alternator and you will be fine. Don't worry too much  a monitor, every morning before sunrise check the battery and as long as it's over 12.2 and preferably over 12.4, your batteries will be fine. Bob

 

[SternWake]

The issues I have with Sternwakes system is he lives in California and probably has sun every day.  

 -- Spiff

I read that on my phone sitting on the beach under an umbrella and had  a good chuckle.

The OP said they were likely going to drive daily and utilize the alternator in addition to solar.  With their stated loads and alternator and 200 watts of solar and driving daily, I thought they could easily get away with 100Ah of house battery capacity for the duration of the trip..

I could make use of more solar, certainly, and i have little capacity  buffer, If I do not drive and do not plug in. But if I do plug in or drive, I can get to 80% charged in less than 45 minutes, and my 90Ah AGM battery will not protest a 50% or higher charge rate, long as I  somewhat mind its temperature and the voltage I allow it at that temperature when it can feed on 40 amps( meanwell) or alternator which which has fed this battery 106 amps when depleted when new.

now  at ~400 deep cycles and 33 months of age, depleted to ~50%, it takes about 76 amps to instantly raise battery voltage to 14.46v, but this instant absorption voltage amperage rate,  also varies.

There's no ONE right way to do things.

I'm living on the edge, with no capacity buffer. 
 But I can easily add another battery or two, i just have found I don't need to, currently.

But I have the amp hour counter telling me generally how much electricity I use.

A newb would have a voltmeter and no real Idea what the numbers really mean.