native pepper wrote:

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oldtrack123 wrote:

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HI native pepper


Sorry ,but your post is a little confusing ,are you talking about SOLAR PANELS & REGULATORS ,OR CHARGERS???
Both PWM & MMPT regs are full on until the battery reaches fully charged
BOTH then switch to a form of PWM to maintain the battery in that state or allow a soak period![depending on design]

In simple terms, they remove the charge current  read the battery voltage , turn on again  & repeat to maintain the battery at the set voltage
PeterQ

-- Edited by oldtrack123 on Sunday 2nd of February 2014 06:38:19 PM

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 Learn how to read.

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 HI

I know how to read , BUT you seem to not understand what the differences are between chargers & regulators , BUT , you did say you are not up with ELECTRICS!!

So I suppose THAT is a good excuse !!

Incorrect terminolgy can lead to a lot of confusion especialy for those who do not understand the significance

PeterQ

While you fella's are on solar, I would like to know if I need another battery or another 150w panel or both.

I am running out of power on a cloudy day and need the generator occasionally. I would like to be able to survive without the generator.

I have 2/ 120w batterys and a 200w panel (shade tolerant). I like to free camp when I can and stay in one place for a week at a time or more.

Murray J wrote:

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While you fella's are on solar, I would like to know if I need another battery or another 150w panel or both.

I am running out of power on a cloudy day and need the generator occasionally. I would like to be able to survive without the generator.

I have 2/ 120w batterys and a 200w panel (shade tolerant). I like to free camp when I can and stay in one place for a week at a time or more.

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 Possibly both... You don't say what your daily power requirements are so it's not easy to give a definitive answer.

You don't say if your existing 200w panel is fixed or portable, but it is possibly inputting somewhere around 60Ah per day at present, maybe a bit more if portable and diligently realigned during the day and kept shade free.

That's about enough to run a small Waeco fridge.

You say the panel is shade tolerant, be aware that this does not mean that they will operate in full shade, it means they will operate with a bit of shading over some of the panel, but that will still be at the expense of performance.

Amorphous panels are generally more shade tolerant than either mono or poly ones, but it would be a pretty large panel if it was a 200w amorphous,

Retailers often claim shade tolerance for their mono or poly panels because they have a couple or three bypass diodes fitted, but, depending on where the shading is on the panel, you will still lose from 33 to 100% of your output if there is any shading on the panel.

Are your batteries starting off fully charged? 

Putting in another battery without the ability to charge it is like opening another bank account with no extra funds to deposit. All you are doing is postponing the inevitable.

The extra battery alone would be fine if you are only spending a few days off grid and the combined capacity is sufficient to carry you through until you can recharge off the mains.

An extra solar panel alone will help to keep the existing batteries in a better state of charge, but that still may not be enough for long term satisfaction.

oldbobsbus wrote:

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Peter

My question was....

How do I fully charge a battery off a solar setup when they are constantly in use 24/7..

They are AGM's and I have no real way of testing them remembering I am on the road and dont tow a complete workshop with me..

The minute the sun goes down even on a good day they batteries start to discharge..

Surely there is some happy medium where close enough is good enough..

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HI Bob

ONLY ONE way for them  to be FULLY charged regularly 

THAT is to have sufficient CHARGING capacity to FULLY supply your DAYLIGHT loads  Plus sufficient to FULLY replace what was used when the solar could not supply those loads,[insuffieient solar input & overnight usage].PLUS from 20%<  of used capacity[INefficiency losses ]

THAT can be done with AMPLE solar input OR other means of charging

MY own system did just that ,on a regular basis

IN fact, On many occassions ,while driving ,MY system actually topped up the CRANK batterries, AFTER the Alternator had shut down

IT was a motor home wth direct charging of the house batterries

HOW does one KNOW if they have been fully charged?

IF you have a GOOD  solar REGULATOR it will show when it goes into FLOAT mode

THAT is a reasonably good indication if the REGULATOR is wired right so that it READS the BATTERY voltage

SOME have a voltage sense lead for THAT very purpose

Other should be as close as possible to the battery & use HEAVY connection cables to mimimize errors in the voltage reading

The lower the Voltage DIfference between the REGULATOR & the battery the better, but it should not exceed 0.25V MAX

GOOD multi Stage battery chargers do the same ,PROVIDED they have sufficient capacity

MORE difficult with JUST an alternator[ALthough some under some circumstances can get VERY near

f  Vrtually IMPOSSIBLE with engine computer controlled REGULATOR ,Which cuts back the applied voltage before the battery is fully charged

THAT IS when the DC <DC chargers are necessary!!

 OF course, As soon as you stop charging OR use more than the charging system is putting in the are STARTING to LOSE charge

THat is where that extra <20% of capacity MAY be important

[that EXtra 20Ahrs total 50Ahrs ,compared to only 30Ahrs ]

PeterQ

oldbobsbus wrote:

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I would like to see your perfect system one day Peter..

Now you are gunna tell me that you have sold it and the new owner has changed it so it isn't perfect anymore..

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 HI Bob

Sadly you are right

WE sold it just before XMAS

Due to my wife's serious health problems [I am her full time carer] WE had no more use for it

NO, NO need for changes, The new owner is very happy with both the solar AND THE 3WAY fridge set up. 

PeterQ

oldbobsbus wrote:

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Can someone explain to me when I should expect any batteries to be FULLY charged if they are in service..

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 This may assist in explaining the problem - The 70% debate - how vehicle batteries really charge - click on the link.

The above link is a rather simplified explanation. It does not include the full story, just like some would prefer these threads. Collyn has left out the subject of temperature compensation. Most alternators up to the stage where the engine management system too over the voltage had temperature compensation included in their voltage regulators. As your engine heats up the battery is also heats up. It takes less voltage to charge warm batteries. If you don't reduce the charging voltage you can overcharge them. The temperature compensation reduces the charge voltage of the alternator as it heats up (in the last 30 years the regulator is in the alternator.)

Read this link - it was written by one of the most revered experts on battery theory. In it you will see a typical graph of the temperature compensation built into Bosch regulators. In the page you wil notice also the CHARGING SYSTEM FUNCTIONAL DIAGRAM. in this you will see that the only monitoring the regulator does is to monitor the voltage of the battery. It does not monitor the battery state of charge as many think.

oldbobsbus wrote:  just lost me Peter when you said you had a 3 way fridge...

Weren't you confident in your setup not make it fully electric...

I only have gas for cooking and HWS everything else in the bus is 240v ( the fridge is a 320ltr one from HN) and it runs 24/7 off the solar system..

Mind you I am hoping to one day run into you or Brian so you can point out how I can make my system better..

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-- Edited by oldbobsbus on Monday 3rd of February 2014 08:51:56 PM

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Hi Bob

Perhaps I should have added the Engels which were  run as  FREEZERs

WE use to realy go BUSH for weeks on end

 BUT As I said those days are over

The big trips are to Doctors or hospital ,

Wife[Leila] just had 2weeks in hospital .

PeterQ

-- Edited by oldtrack123 on Monday 3rd of February 2014 09:38:24 PM

Sorry I didn't supply what I we use as I didn't think that was particularly relevant as we use similar power every day unless we travel away touring for the day, plus of course I don't know what we actually use. The thing is when we are camped out free camping most of the time and the sun is shining we have no trouble. I have noticed that after a day or two cloudy and the voltage drops to 12.1 or lower and I have to start the genny, it then takes a fair charge to get the battery's back up to FULL (13.5 plus on the guage) before we start operating safely again as in goes for days in the sun without a problem. If we drop back to 12.4- 12.5 volts on the gauge by night it doesn't take long to pump back up the next day.

I will try and work out our usage but we have 2 computors and spend hours at times using them and they are on the charger from our 1000 watt invert er. We charge out electric tooth brushes and phones, use a few led lights at night but not many. We watch TV at night when we can get Signal. We have a washing machine running off the inverter twice a week(generally run the genny if allowed at the camp, for that). And of course the water pump is 12 volt.

I know we want more storage of power but if I put another battery in will the 200 panel be enough to charge those 3 in a normal sunny day from an overnight of 12.3 maybe. I will obviously charge the 3 batterys fully off AC power for a few days to make sure that they are charged up.

Thank you for your thoughts

MJ

Murray J wrote:

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I know we want more storage of power but if I put another battery in will the 200 panel be enough to charge those 3 in a normal sunny day from an overnight of 12.3 maybe. I will obviously charge the 3 batterys fully off AC power for a few days to make sure that they are charged up.

Thank you for your thoughts

MJ

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 If your 3 x 120Ah batteries are down to 12.3v, then that's around 65% State of charge (Soc).

That means that you have to replace about 150Ah to get back to full charge.

A 200 watt panel, will at best, give you around 80Ah on a cool, clear, sunny day.

Once your  batteries get to around 80% Soc (12.5v) the charge rate will reduce, which means that putting that last 20% in will take longer than the previous lot, so some of the available energy from the panels will be lost.

This will leave your batteries at about 85% Soc, 12.55v (300Ah) at the end of the first day, 70% Soc, 12.4v (250Ah) at the end of the second day, 60% Soc, 12.25v (190Ah) at the end of the third day, etc.

So increasing your battery capacity without the solar ability to get a good bulk recharge into it in the early part of the day is simply prolonging the inevitable.

If using the generator to assist the solar, then it is best to do this later in the day after the solar has dropped off.

Murray J wrote:

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Hi Peter

Where do I look for the WATT rating on our appliances?

We would camp for a week or weeks if we liked where we are at the time. We are full timers on the road, this 24ft. Kingdom Van is our home.

I have found the Tassie sun at the moment has more kick in it than the Qld sun back in September. I that because of the high UV?

We have a fixed 200 watt panel on top of the van.

Thanks MJ

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HI

THere should be a rating on a label showing Voltage ,AMPs  Frequency, [Hertzs  50] & Watts 

If the Watts are not given then the Volts & Amps can be used

Volts x Amps =WATTS

PeterQ

Thanks Brian that is easy for me to comprehend very well put.

Cheers MJ

Murray wrote:

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Hi Brian and Murray j from Murray b Iooking at your formula am I safe to assume 2x 200 watt fixed panels will keep up with 3x120 ahr batterys given plenty of sun also running thru a 30amp reg. We also have 2x120 watt fixed panels running into 2x105ahr agm batterys, 20 amp reg.The original system was the 2x200 panels and 105agm batterys and this would only last 2 days. Bush camping a week at a time diesel htr wont start on second morning, to much draw 8 amps to heat the probe. we run cpap 4amp,vitrofrego compressor fridge, sat tv etc and led lighting. I was going to spread the discharge loads between the 2 separate systems. Any thoughts would be great.Also what is a life po battery? any ideas. Also on batterys any brand recommendations as I can purchase 120 ah supercharge deepcycle at195 incl gst retail 280 but only 1 yr garrantee and there is so many choices

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Without knowing what the actual daily load is on the 3 x 120Ah batteries it's not possible to say whether the 2 x 200w solar will keep them in a good Soc.

You could expect an average daily input from the panels of between 100 and 120Ah, maybe a bit more in good insolation, and less when it's not so good. Poor weather conditions could see the input fall considerably.

If you were to draw no more out of the batteries than the solar can put in daily, then you will be OK.

Not sure which battery/solar combinations are running what in your description, maybe you could make that a bit clearer.

A LiFePo4 battery is a type of Lithium based battery which is rapidly gaining a strong following in the RV fraternity due to its light weight and high power capabilities as compared to lead acid types. 

I'm pretty sure that Supercharge battery will be a flooded type, so be a bit careful of mixing it with AGMs as the charge parameters are different.

Plendo wrote:

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I stated earlier:

"The only caution I would give is that your solar panels need to be connected differently depending which one you go with. With the PWM they would be connected in parallel (all the +s connected together, and all the negatives connected together), if you go MPPT you would connect in series (+ to -, then + to -)." 

And as Brian picked up this is a little over simplified.

Yes you can use serial and parallel configured panels with either type of controller, the difference between the two is the voltage requirement for them to operate. When a PWM controller is managing the voltage it supplies to a battery it basically throws away the extra voltage, thus it makes sense to configure your panels to supply a voltage just slightly above the maximum voltage you need to charge your battery. Remembering of course  to allow for the reduction in voltage as the cells in the panel heat up.

MPPT operates differently, it uses an inverter to convert the incoming voltage to AC, then rectifies it to an optimal charging voltage, thus the extra voltage is effectivly converted to current. Thus with MPPT you can reduce the impact of line loss by pushing up your voltage by placing your panels in longer serial strings, this does of course introduce the potential for higher loss when a single panel is shaded.

The other factor to consider is of course the input voltage required to start the inverter, this is often programmable, but on teh simpler controllers used in RV it is usually fixed (and not declared). Then of course you have the effect of the different MPPT algorithms (S&H, P&O, etc) and the scan frequency used, all of which have an impact on the configuration of a good well balanced system. In a good clean environment, you may use Scan and hold, with a low scan frequency. On the other hand in a dynamic environment it is likely that P&O with a short frequency would work better.

Now I know that most of the people who read this are scratching their head wondering what I am talking about, this is exactly why my initial statement was simple, and intended purely to make readers aware that the two types of controller work better with different panel configurations.  It was then followed up with advice to talk to someone who knows the game before spending money.

 

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 I had this 12v versus 24v panel debate on another forum some time back .

The other party had 24v panels and a morningstar MPPT controller, he swore blind that it performed better (about 100% better) this way than did his old setup using a Morningstar PWM controller and 12v panels.

His position was that Morningstar literature states that an MPPT controller works better at higher voltages.

My position was that they were referring to charging 24v batteries with 24v panels, not 12v batteries with 24v panels, and that there were higher conversion losses when down converting to a significantly lower battery voltage than the panel voltage    ie 36v down to 12v as opposed to 18v down to 12v.

After much heated debate, he suggested that I contact Morningstar in order to learn a little about the subject. 

I did just that, and posted the return Email from Morningstar's technical department, see below (note the 2nd last sentence).

The question marks in diamonds in the text are hyphens, apparently not recognised by this program

 Hi Brian,

I can only speak to a comparison between our PWM controllers and our MPPT controllers (as other brands may be more/less efficient), but I see only two reasons why your friend may have saw such an increase in charging current:

 #1 His 12V panels were in fact wired for something more than 12V (such as placing the panels in series for higher voltage). In this case, the PWM would be significantly less efficient than the MPPT and you could very well see such a large difference between the two controllers.

 #2 The 7A (PWM) he is referring to was noted when the batteries were close to full charge, while the 16A from the MPPT was noted when the batteries were not near full. When the batteries get close to full, both controllers will limit charging current to prevent overcharge. In order to accurately compare the two controllers, amperage readings must be taken when the batteries are less than full (and both controllers are in the BULK charging stage    delivering all available power).

 To give you an example of #1: An array wired for 24V (whether using 12V panels in series, or 24V panels in parallel) on a PWM controller will be about 50% as efficient as the same array wired for 12V on the PWM controller (both assuming the batteries are 12V). This is because the PWM cannot do a DC/DC conversion of the input voltage. It is not able to make use of the full 24V input, so about half the input power gets lost. An MPPT controller has DC/DC conversion capability, which allows it to make use of the full 24V input to charge 12V batteries.

Now, to compare the two controllers when you have a 12V solar input and a 12V battery output: In this configuration, the MPPT will (on average) harvest about 10-15% more power. However, this is highly dependent upon environmental conditions, particularly temperature. The full benefit of the MPPT will be evident in colder weather (this is where you will get the full 10-15%). In warmer weather, the MPPT benefit is less (but it will not be less efficient than the PWM you will always get a benefit from the MPPT, it is just a matter of how much).

If your friend indeed had his array wired for 12V into the PWM controller, I see no physical way the MPPT could have improved his efficiency by nearly 100%. The only explanation for the readings in this case would be due to #2 above (or outright erroneous current measurements).

 Just dealing with the MPPT, the controller itself will be slightly more efficient if you wire the solar array for 12V input instead of 24V input (12V battery system). This is because less of a conversion needs to be done when the array is at 12V nominal, compared to if it was at 24V nominal. 

It is impossible to say how many additional daily Ah you will get from the MPPT controller, as this is strictly dependent upon environmental conditions. Again, all things being equal, you can expect about 10-15% more power in colder weather.

Regards,

Adam Kehlenbeck

MS Technical Support

www.morningstarcorp.com

I just re read you note, and your friend could well have had a couple of situations:

1. 24V panels into both chargers, charging a 12V battery, the MPPT would be much more efficient as the panels would be mismatched to the PWM.

2. Alternatively if you replace a set of 12V panels with 24V panels you could conceivably be doubling your wattage.

Either situation would explain the significantly higher level of output from the MPPT.