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Old 11-08-2006, 18:28   #1
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mppt Regulators

now i have been doing a bit of research on these as i am building a boat and obviously wish to get the maximum valus out of everything that i buy now these regulators appear to work by taking the max voltage of your solar array doing a dc-dc conversion to get your charging voltage and improve your charging amperage as a result, now my question is when i look at the powercurve of my solar panels these produce 5.5a from 1v to 17vand then the a starts to drop , now my question is under what circumstances do my panels produce less than 17v and when they do are they still producing 5.5amps, this interests me because say its early morning and my panels are only putting out 5v but this is at 5.5a then my 4 panels in series are actually giving me 20v at 5.5 amps which should be enough for the regulator to function and give me a good charge for my battery
now i am an electrical novice and am just struggling to gain some understanding of how all these things work so any input is appreciated
sean
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Old 11-08-2006, 22:37   #2
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Aloha Northern,

Can't answer your question but welcome aboard anyway. I'm certain there will be a response from those techno folks here soon. I just hook up wires and hope things work. Have a solar panel and some batteries and a little gizmo in between. Works fine. Never a problem and keeps the batteries up.
Did you check in with meet and greet thread?

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Old 11-08-2006, 23:10   #3
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Solar panels tend to be constant voltage devices. The amperage tends to fluctuate significantly. Your panels voltage will vary significantly if there is shade on them, temperature variation (the lower then temp, the higher the output), light intensity and age of the panels. Now, by constant voltage, it means you solar panels will try to put out a certain voltage, regardless of whether the load can accept it or not. For instance most 12 volt batteries tend only be able to accept 15 volts for short periods of time before there internal resistance causes significant damage due to heat. They are much happier accepting something closert to 13.6 or so volts at increased amperage. So, if you have solar panels that are putting out 16 volts, your regulator will tend to want to cut that down to the acceptance level of the battery. So your 17 volts at 5.5 amps which would normally give you a 93.5 watt rating drops to 13.5 volts at 5.5 amps 72.25 watts. What an MPPT (Maximum Power Point Tracking) controller will do for you is gove upi 6.8 or so amps at the same 13.5 volts. It does this over the entire voltage range.

A better question is when will the produce 17 volts as opposed to when they will not. Pretty much they have to be directly facing the sun, in relatively cool weather with no clouds, or shade on them. You will see reduced output with a halyard casting shade on your panels, when a cloud goes by, when it is very dusty or crusted with salt.

You hit on the right installation approach, connect them in series to increase the voltage. If you have an MPPT, it will bring that voltage back inline with the load (12 or 24 volt systems, normally). The only thing you have to be aware of is, that most MPPT's have a limit to how much voltage they can handle. Typically arround 100 volts or so. With 4 17volt panels, this will not be an issue, 5 would be. If it is cold and bright enough, you will almost assuridly go above 100 volts, at which point the MPPT would shut down. This would give you no usable output.
In your scenario, you'd probably see something closer to 8 amps at 13.5 volts in the early hours. You'd see significantly more amps as solar noon approached.

HTH

Keith
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Old 12-08-2006, 01:13   #4
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thanks for the answer to the first part of the question maybe i need to rephrase the other part im wondering i guess how panels work, im wondering on those days when you get a nice mast stripe down your panel this obviously affects the output of the panel and my understanding is that with most pwm controllers when this happens it can affect the voltage of that panel to the extent that the regulator doesnt see enough charge from that panel to use it for the batteries now im wondering if with an mppt regulator and all my panels in series whether this panel will then still be contributing a lesser voltage ie 5-10v which the mppt regulator will still use ie where with the 4 panels on a nice sunny day putting out 68v this might drop to say 59v with one panels voltage halved because of shade etc
sean
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Old 12-08-2006, 07:46   #5
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The MPPT's have varying efficiencies. As I understand it, the lower voltages excentuate the loss. If your input voltage is less than your output voltage your output amperage drops RAPIDLY. With a normal regulator, when your voltage drops below your load level you will not see anything from your panels. Indeed, if you don't have blocking diodes, your batteries will see your panels as a load and try to send current to them. If you put your panels in seiries this doesen't become an issue. If you have an MPPT it is never an issue.

What I have done is use 24 volt panels and an MPPT controler. This works very well! The higher voltage means I don't have as much resitive losses. The 24 volt panels are marginally cheaper per watt and I don't have as many issues with mounting and connections. 3 panels at 24 volts works very nicely.

Keith
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Old 13-08-2006, 01:15   #6
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i think you have anwered my question i want my cake and to be able to eat it here
"if you don't have blocking diodes, your batteries will see your panels as a load and try to send current to them. If you put your panels in seiries this doesen't become an issue. If you have an MPPT it is never an issue. "

im looking at getting either the solar boost 50 or the outback mx 60, not sure yet on which is best
sean
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Old 13-08-2006, 01:16   #7
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i think you have anwered my question i want my cake and to be able to eat it here
"if you don't have blocking diodes, your batteries will see your panels as a load and try to send current to them. If you put your panels in seiries this doesen't become an issue. If you have an MPPT it is never an issue. "

im looking at getting either the solar boost 50 or the outback mx 60, not sure yet on which is best
sean
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Old 13-08-2006, 17:12   #8
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I got the OUtboack MX60. It is reputed to be the most efficient out there. I love it! I love it better if the remote monitoring panel didn't cost so much.
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Old 20-08-2006, 22:39   #9
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what size solar arrays are people out there cruising with, i would like to get an idea of a possible average mine is looking at being 360w but im not sure if this is enough
sean
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Old 21-08-2006, 06:22   #10
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Rv Power Product MPPT

Makai has been using the Rvpowerproduct now blue sky energy sb50 mppt charger for almost 3 years. We are live aboards and cruised the caribe for the last 3 years. so we used our battery banks heavily and daily. Having said that:

We love the MPPT. Makai has 4 Kyrocea 120 watt panels produce a rate 28 amps @ 17 volts. What we see in both the SBC remote dispaly and the link 2000 monitor is 32-34 amps when the batteries are low starting at around 10:30 in the morning up through about 2-3PM. (the sun is not directly facing the panels and we are still geting excellent output)

2nd and more imporatant is the abiltiy to equalize with the charger controller. Most lead acid batteries makers recommend equalization once a month if the batteries are cycle a lot. Living onbaord they are cycled. Equalization (though anothe topic) makes a huge differnce in total amp output and longevity of the battery bank.

Unlike alt charging the MPPT will use PWM to do the final charge and float. It is near impossible to get a 100% charge running your engines unless you have a multistage controller. Either way it would have to run seeral hours to get a full charge and could be expensive and damaging to the engine.

As noted above next time out I will go with 24 volt panels and have the controller step it down to 12, though we have hade no issues or apparent loss of efficency configure as we are today.

Final note. We just tied up at a marina and we do not use shore power to charge and maintain the batteries. If fact we no longer even have a 120 volt charger onboard, do npt need it!
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Old 03-09-2006, 00:03   #11
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Quote:
Originally Posted by sv_makai
Makai has been using the Rvpowerproduct now blue sky energy sb50 mppt charger for almost 3 years. We are live aboards and cruised the caribe for the last 3 years. so we used our battery banks heavily and daily. Having said that:

We love the MPPT. Makai has 4 Kyrocea 120 watt panels produce a rate 28 amps @ 17 volts. What we see in both the SBC remote dispaly and the link 2000 monitor is 32-34 amps when the batteries are low starting at around 10:30 in the morning up through about 2-3PM. (the sun is not directly facing the panels and we are still geting excellent output)

2nd and more imporatant is the abiltiy to equalize with the charger controller. Most lead acid batteries makers recommend equalization once a month if the batteries are cycle a lot. Living onbaord they are cycled. Equalization (though anothe topic) makes a huge differnce in total amp output and longevity of the battery bank.
I agree with your choice of a charge controller that can also equalize the batteries as this is a process most are not aware of for properly maintaining a battery.

I have just purchased a Kyrocera 130 watt panel and expect I will buy one more. My new Air-X is a bit of a disappointment as I rarely see winds high enough to realize it's potential so I would like to supplement the Air-X with solar panels..... My question to you is do I need the SB50 amp MPPT for two 130 watt panels? Or, should I consider their 30 amp MPPT? My battery bank consists of three Rolls 4-D. ........... Steve
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Old 03-09-2006, 02:26   #12
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in my opinion the 30 amp regulator would be fine
sean
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Old 15-11-2006, 04:21   #13
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i have just purchased 4 90w sun power mono panels at an extremely good price600 per panel the specs are
Minimum Peak Power (Pmin)
Watt
90
Rated Voltage (Vmp)
Volts
17.7
Rated Current (Imp)
Amps
5.1
Open Circuit Voltage (Voc)
Volts
21.2
Short Circuit Current (Isc)
Amps
5.5
Series Fuse Rating

15A
Maximum System Voltage

120V
Temperature Coefficient
(Pmax)
(Voc)
(Isc)

/°C
/°C
/°C

-0.38%
-60.8mV
2.2mA
Module Efficiency

16.5%
PTC Rating

82.3W


now i am thinking of using a solar boost mppt 3024 solar regulator, will this handle the panels or is on the limits of its capability, i want to output to 12v
sean
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Old 20-11-2006, 15:11   #14
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im really trying to get my head around this so i ahve a couple of scenarios are the assumptions correct or not
24Volt system

1/ Panels wired in parallel:
·Voltage remains the same - 12V (don’t confuse this with rated voltage yet)
·Amps will be quadrupled 20.4A (don’t confuse this with short circuit current yet)
·Loss of one panel causes 1/4 the generating power to be lost, plus (if using MPPT) - 40% of the (additional 10%- 30%) MPPT power gains will also be lost.

2/ Panels wired in series:
·Voltage is quadrupled - 48V (don’t confuse this with rated voltage yet)
·Amps will be remain the same as for one panel 5.1A (don’t confuse this with short circuit current yet)
·Loss of one panel causes the whole system to fail – period.

3/ Guessing then from the above data 2 x (2 sets of panels in parallel) wired in series:
·Voltage is doubled – 24V
·Amps will be 10.2A
·Loss of one panel causes ½ the system to fail, plus (if using MPPT) – 23% of the (additional 10%- 30%) MPPT power gains will also be lost.

i cannot seem to get an answer from the sellers of these mppt regulators as to what happens to an array when say for example a panel gets a mast stripe down it, some say the panel will go open circuit and give you voltage but litttle to no amperage therfore affecting the array, others say that because the panel;s are all in series the array will only produce a reduced amperage which will relate to how much of amperage a shaded cell is producing as it will only allow the rest of the array to let that amperage travel across that cell, still others have told me that with mppt the panel will only lose a small amount of voltage and because it is in an array and being mppt regulated that it sill still supply its rated amperage at a reduced voltage which in series the mppt reg will still use
so i am very confused but im sure that there is an expert on here who can clear this up,
sean
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Old 20-11-2006, 19:23   #15
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Don't know if this will help with your system Sean, might just add confusion

Dave


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