I'm in the process of thinking about our next system & have come up with some ideas about priorities. Longevity and durability are top of the list for me and then budget, although this doesn't need to be a low cost set up, I just don't want to throw money at problems. I'm looking at around, 2000W of panels 24V in series and the Morningstar TriStar TS-60 PWM. Our needs are small, we currently have 460 W of 12V & we ran our genny for charging about 4 or 5 hours last winter. We want to add a fridge/freezer that's rated at .0500 Kwh a day. The weather here is a mix of continental & Mediterranean, hot summers and cold, clear winters, although this is changing. We have the panels on the roof of an outbuilding - a almost flat roof with a rack atttched - & battery etc. inside, so it exposed to temperature changes, although it doesn't see extremes inside there. Because of this I'm thinking about the Morningstar TS , a unit with a reputation for robustness, a working temperature range of -40c to +60 c. So why a PWM unit instead of a MPPT ? Price - the PWM is on offer for €279 & the MPPT is €854 Am i wrong about this ? is it worth spending 3 x as much for small gains ? At the moment we have a %20 DOD on average, in a cycle & plan to size the battery bank for the new system the same. Our backup is usually run when the battery is at %50 discharged.
Trisar TS-60 PWM am I wrong ?
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mikefitz
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What is the system voltage, and what batteries?
Do you mean 24 volt panels in series?
Whatever battery type you have, PWM won't help long service life and could seriously reduce panel yield.
If its a 24 volt system the Victron 150 / 70 MPPT is €460 in Spain.
Yep, that's what I'm thinking, a 24 volt system .
Im interested to hear about reduced battery life. As for panel yield, we're talking about %10 right ?
Batteries , not sure yet but probably FLA, in an unheated outbuilding. Our cabin is surrounded by trees so the current set up is 50M up the hill & we run 220AC down here. The outbuilding site is great, no shading, gets early morning sun, albeit at an oblique angle & the panels are on a rack, better cooling than roof mount.
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mikefitz
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Perhaps not, depends on the specification of the panels, you stated 24 volt panels in series.
seneysolar
24V
With careful design and keeping string voltage /pv input voltage in range of battery volts. They can work great. Back in the day there was much more planning involved when setting up a system. Now people just throw anything at an mppt and it works.
Morningstar does indeed make a quality product.
I tested a Midnite Brat against a Victron 100/30 in my 24v system with no noticeable difference.
Panel Vmp is important, mine were 33v i think which was ideal for a pwm. The farther the spread from Vmp to battery voltage, the greater the inefficiency becomes.
Morningstar does indeed make a quality product.
I tested a Midnite Brat against a Victron 100/30 in my 24v system with no noticeable difference.
Panel Vmp is important, mine were 33v i think which was ideal for a pwm. The farther the spread from Vmp to battery voltage, the greater the inefficiency becomes.
My understanding of MPPT is that in certain scenarios - cold, clear mornings, with the batteries low - in can give significant gains. Im looking at the manual from my solar boost 2000e & it gives the following examples.
Battery 10.9 v 35 F, 38% increase.
Battery 11.8 v 65 F 10% increase
The increase is between PV input current & output charge current. It gives another example with the battery at 13.80 , 45 F , cloudy, giving an 18% gain. The same battery V with the temp at 75F , clear, gives zero gain. To my mind, the first example would be a one off, something to be avoided except in an emergency, the second, Battery V at 11.80 would also be rare, most people avoid more than 50% DOD. an article i read from Victron (I've just skimmed through it at the moment) said that "Clearly, at 25°C a MPPT controller is preferable to a PWM controller"
and;
"Clearly, in our example, both MPPT and PWM controllers do not perform at high cell temperatures.
The solution to improve MPPT controller performance at high cell temperatures is to increase
panel voltage by increasing number of cells in series.
Obviously, this solution is not applicable to PWM controllers: increasing the number of cells in
series will reduce performance at low temperature"
In hot conditions, more than 30 C the MPPT can give gains of 10% according to Victron.
it really needs to be 40c.
Sorry my mistake, i meant in parallel, that's what i put into the string calculator.Given what has been said about keeping the battery & Vmp close series is maybe not a good idea?
I've seen 3 different versions of this controller on sale, one with MC4 connectors but without display, not essential with Bluetooth, for sale at €385 or bare bones version, no display, no Bluetooth - is that essential - at €325. Some serious food for thought here, the bombproof nature of the Morningstar is a plus for me, as is the Victron "tax" and lots of versions of the same unit, off-putting. Back to the sting calculator for the moment, im going to try 2 stings of panels in series & see what it says.
Battery 10.9 v 35 F, 38% increase.
Battery 11.8 v 65 F 10% increase
The increase is between PV input current & output charge current. It gives another example with the battery at 13.80 , 45 F , cloudy, giving an 18% gain. The same battery V with the temp at 75F , clear, gives zero gain. To my mind, the first example would be a one off, something to be avoided except in an emergency, the second, Battery V at 11.80 would also be rare, most people avoid more than 50% DOD. an article i read from Victron (I've just skimmed through it at the moment) said that "Clearly, at 25°C a MPPT controller is preferable to a PWM controller"
and;
"Clearly, in our example, both MPPT and PWM controllers do not perform at high cell temperatures.
The solution to improve MPPT controller performance at high cell temperatures is to increase
panel voltage by increasing number of cells in series.
Obviously, this solution is not applicable to PWM controllers: increasing the number of cells in
series will reduce performance at low temperature"
In hot conditions, more than 30 C the MPPT can give gains of 10% according to Victron.
I'm looking at some Tensite , half cell PERC mono, 550W with Vmp of 14.95. Ive used the Morningstar string calculator & 4 550W 24V panels in parallel is fine, although I'm going to redo it as I put the max summer temps at 30c,
it really needs to be 40c.
Sorry my mistake, i meant in parallel, that's what i put into the string calculator.Given what has been said about keeping the battery & Vmp close series is maybe not a good idea?
Now you've got me thinking
I've seen 3 different versions of this controller on sale, one with MC4 connectors but without display, not essential with Bluetooth, for sale at €385 or bare bones version, no display, no Bluetooth - is that essential - at €325. Some serious food for thought here, the bombproof nature of the Morningstar is a plus for me, as is the Victron "tax" and lots of versions of the same unit, off-putting. Back to the sting calculator for the moment, im going to try 2 stings of panels in series & see what it says.
seneysolar
24V
550W panel with Vmp of 14.95v ???My understanding of MPPT is that in certain scenarios - cold, clear mornings, with the batteries low - in can give significant gains. Im looking at the manual from my solar boost 2000e & it gives the following examples.
Battery 10.9 v 35 F, 38% increase.
Battery 11.8 v 65 F 10% increase
The increase is between PV input current & output charge current. It gives another example with the battery at 13.80 , 45 F , cloudy, giving an 18% gain. The same battery V with the temp at 75F , clear, gives zero gain. To my mind, the first example would be a one off, something to be avoided except in an emergency, the second, Battery V at 11.80 would also be rare, most people avoid more than 50% DOD. an article i read from Victron (I've just skimmed through it at the moment) said that "Clearly, at 25°C a MPPT controller is preferable to a PWM controller"
and;
"Clearly, in our example, both MPPT and PWM controllers do not perform at high cell temperatures.
The solution to improve MPPT controller performance at high cell temperatures is to increase
panel voltage by increasing number of cells in series.
Obviously, this solution is not applicable to PWM controllers: increasing the number of cells in
series will reduce performance at low temperature"
In hot conditions, more than 30 C the MPPT can give gains of 10% according to Victron.
I'm looking at some Tensite , half cell PERC mono, 550W with Vmp of 14.95. Ive used the Morningstar string calculator & 4 550W 24V panels in parallel is fine, although I'm going to redo it as I put the max summer temps at 30c,
it really needs to be 40c.
Sorry my mistake, i meant in parallel, that's what i put into the string calculator.Given what has been said about keeping the battery & Vmp close series is maybe not a good idea?
Now you've got me thinking
Something is not right here
mikefitz
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Only consider the Victron Smart version with Bluetooth.
littleharbor2
Solar Wizard
Don't you find the low 30 volt max. VOC on those Solar Boost controllers bothersome? In a 12 volt configuration you can't even series wire two 12 volt panels without overvolting the controller. Almost like a PWM controller.
Sorry my mistake, I'm confusing Vmp , 41.95 in this case with Isc from another panel entirely. This is quite a steep learning curve for me, when i started out i only bothered about W, A & V , im still getting a grip on Vmp , Isc etc.
How important is it really to know the numbers on charging ? The Morningstar comes in a bare bones version & i was considering that. Are we talking more about configuration ?
Our current system, including a Sterling Power 60A charger, a Morningstar SureSine 300 , 2 second hand batteries and some of the panels was sold to us and installed by my closest friend, at a symbolic price, in fact less than the charger was retailing for at the time, when he upgraded his own house system. 15 years ago, the solar boost was cutting edge, its a decent bit of kit for 460W of panels.
seneysolar
24V
A pwm controller is like an on/off switch. It will connect panels to the battery momentarily until target voltage is achieved. The efficiency problem is when it pulls the panels below Vmp. They still work but you just dont get max power out of the panels. The closer Vmp is to battery charge voltage, the better.
MPPT finds that max power voltage, maintains it and converts to battery charge voltage without disconnecting in the process, the result is more efficient charging.
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Yes agreed, but most of what I've read puts the difference at around 10%. Some years ago i researched the gains from MPPT & found that people in the RV & yacht communities were keen because of the limited space for panels they had, orientation and angle restrictions plus times when a generator or shore power was unavailable. The consensus was that real world gains over time were between 6 and 10 %..... Panels are dirt cheap here at the moment, 24V 600W 132 cell class A panels are €115 so oversizing the array isn't a problem. 15 or 20 years ago with the price of panels I think there was a better case for the gains with MPPT, just as trackers were a big thing. The local solar farm has some panels on trackers but those installed in the last few years are fixed.
Now, to be a contrarian, having said all that the Victron unit at €100 more offers a lot more in terms of monitoring, set up and usability than the Mornigstar. However, I think the TS-60 is more robust.
Some of the online string calculators I've used, including Victron are telling me that a 150/60 will do the job with a 25 to 30% margin. What's your view on this ?
mikefitz
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Divide 2000 watts by the expected charge voltage to get the theoretical maximum charge corrent. For most of the charge cycle the battery volts will be in the region of 27.4 volts.
There will be losses and reduced pannel power with temperature, and all Victron MPPT can be over panelled, so a 60 A unit is possible.
Personally I find, when specifying a system, 'leaving something on the table ', leads to greater reliability.
There is a 10% increase is cost for the 60 amp compared to the 70 amp unit, no more than €40, both share the same case with identical dimensions .
There is a lot to be said for that philosophy. Thanks for all the replies everyone, much food for thought but the more I learn, the less I Know
Having learned about CC & string config and calculation I'm now going back to where I should have started, calculating current and future loads and sizing the system from that. I had started out with an idea that oversizing the panel array was a good idea, now I'm thinking start with needs & then see what room there is for oversizing in the budget. I think that a Victron smart is the way to go, the Morningstar is a unit but without any monitoring or connectivity via Bluetooth.
HalfBaked
Ever the student
You can monitor Morningstar via ethernet/wifi. They have a built-in webpage with live monitoring and history. I have the ts-mppt-60.
I was looking at the PWM model that only has hardwired connectivity.
HalfBaked
Ever the student
The mppt is the same, built-in network card. Take a short network cable, connect it to a router and login via Wi-Fi on phone.
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