Over Amperage to Charge Controller - MPPT-60

[inetdog]

Seano,
It is our pleasure to help newcomers to solar, as long as they, like you, are willing to listen to explanations and learn from them!

[Seano]

The point I'm trying to make regarding your controller being an MPPT controller, or not, is when you series wire your roof top panels you should see possibly higher current to your batteries. If your current is cut in half when wired in series you can be sure that you have a bogus MPPT controller.

The difference between the two types of controllers is this; PWM, current in = current out., MPPT, watts in = watts out.

Thank you for that rule which I have emboldened above, and most of all, sorry for being such a frustrating newbie about all this.

I see now that A purpose of rewiring the fixed panels from parallel to series is to test the controller; to determine whether it be MPPT or a pretender. Yes that makes sense, more sense than I was givng it before, because I have already run all the rooftop wiring and terminated all ends, right to the fuse block inside the van. To change from parallel to series now means an awful lot of back-and-forth for the circuit, because all +ve & -ve points are now inside here, not even 300mm from the top right of this browser window.

Before I was thinking that running in series would reduce the resistance in the wiring - higher voltage, lower current. Still that doesn't make much sense if what were 1m, 2m, 3m & 5m cable runs for LHF, LHR, RHF & RHR panels respectivelty is turned into four different 11m runs. On the next project, I'll wire them in series from the beginning. On this project, I can undo the wires from the panel and twitch them together in series to test the response from the controllerl.

As you mentioned that this Powertech MP-3735 'MPPT' controller cab handle up to 65V, I wonder if it would be suicidal to try to wire 4 x 18.1V panels into it in series. It might be best to try the test with just the two panels I currently have up on the roof and not try the two more I am still to collect from the shop next week.

I shall login and write up the results of the change from parallel to series early next week if not before. Right now I am hoping to make the best of the sunshine over the weekend to charge a rather depleted pair of 100AH SLA batteries. Thank you for putting up with me, for your patience, Little Harbor.

[littleharbor]

The difference you're seeing is likely the Vmp. of the roof top panels and the Voc. of the un connected freestanding panel.

The point I'm trying to make regarding your controller being an MPPT controller, or not, is when you series wire your roof top panels you should see possibly higher current to your batteries. If your current is cut in half when wired in series you can be sure that you have a bogus MPPT controller.

The difference between the two types of controllers is this; PWM, current in = current out., MPPT, watts in = watts out.

Leave the freestanding panel out of the equation for now. The spec I saw for your controller for max voltage is 65 volts. That in itself doesn't guarantee an MPPT controller, all it means is that is the max voltage that controller can handle.

[Seano]

Are your panels series wired? If so then you likely have a MPPT controller. If you are parallel maybe not. If parallel then try series wiring them as they should be on an MPPT controller. The thing is when series wired you'll only see current equal or less than a single panel, but at higher voltage coming into your controller. The controller does the step down and current boost. If you have a bogus MPPT controller the current output will stay equal to or less than a single panel, no boost.

Thanks for this new information, mate. I am really quite a novice at this solar business, and am really lucky to have found this forum and some people who know a whole lot more about my situation than I have been able to fathom in the past six or seven weeks.

Well, the User Manual for the MP-3735 states that only a single array maybe connected to the panel, so what I have done has been to hook both the 150W roof-top panels and the Anderson connector for the 120W portable panel into the MP-3735 all in parallel. I figured that it would not be able to tell the difference if wired in parallel because three panels on a cloudy day are no different to one panel on a sunny day.

I cannot really go with series entirely because the portable panel is only hooked in when I am camped somewhere in the shade and am looking to boost the solar with the portable in the sunlight, with around 10m of lead to get out from under the trees. I could run the two rooftop panels in series, but I am not sure of what reason this would be for. Currently I can pop any one of the three fuses for LHF, RHF, or portable, and read the individual amps of what is left, (or the differrence between the two values before and after to calculate the amps of the disconnected panel).

The volts on the portable are most always 20.5VDC and the volts on the roof-top panels are usually 16.5VDC. I have not yet gotten around to testing the roof-top panels in the sun, so they might also manage a higher voltage then, if I think of the panel as the opposite of a battery, and how the battery voltage discharges slowly overnight. On the other hand, I notice that sun or cloud changes the amps quite dramatically, and not so much the volts. The rooftop panels just might prefer 16.5V. I will have to find some data on the web to check their standard. ***

If I was to connect the two roof-top panels in series, but then piggy-back the portable onto the +ve & -ve in parallel, then that might be workable, although I do wonder about the result of a 20V portable hooked in || with a 32-40V fixed roof-top. That should try to equalise the result to somewhere around halfway between the two inputs, with preference to the higher current, which is likely to be the portable when it is connected, by around 3:1. (due to shade over van roof and fixed roof-top panels).

I would likely achieve a voltage increase from 16V to 32V for the fixed roof-top panels alone, in changing from parallel to series. When the portable panel is connected in parallel though, the difference would likely be something like 18V in parallel to maybe 24V in series, parked in the shade, and 28V when parked in the sun, (which is not when the portable would nornally be used anyway).

The main advantage I can see in connecting in series where possible (on the rooftop fixed panels), is that the current is reduced by series connection, and the voltage increased, so that the length of the cables will cause less impedance, therby increasing the wattage delivered to the controller. I will definitely connect the two rear panels in series now that you have assured me that it is okay to run a high voltage such as 60-80VDC into the MPPT controller.
Thanks again, Little Harbor.



*** Open Circuit Voltage 22.4V - Short Circuit Current 8.66A - Voltage at Power Max 18.1V
I take it that 18.1V is what I could expect from the fixed panels in the sunshine, or 36.2V in series together.

[littleharbor]

Are your panels series wired? If so then you likely have a MPPT controller. If you are parallel maybe not. If parallel then try series wiring them as they should be on an MPPT controller. The thing is when series wired you'll only see current equal or less than a single panel, but at higher voltage coming into your controller. The controller does the step down and current boost. If you have a bogus MPPT controller the current output will stay equal to or less than a single panel, no boost.

[Seano]

https://www.youtube.com/watch?v=-VP1LCp_qfI

Thanks Littleharbor. It was mine you referred to as I suspected.

I'm sad to see that the company I've trusted for the past ten months with the vital electrics of my life here have been labelled as crooks like that by Adam. How much cred' to give to that youtube video and its sequel is an important question. Whether Adam is motivated by a good reason to share honest information with the public or whether he is motivated by spite against JayCar is another related question. One would have to know Adam a lot better to know Adam's motives a little better.

I don't understand why he has adjusted his float voltage up from 13.7 default to 14.1 and can only assume that he's lucky to have the money for LiFePO4 batteries, while us peasants are floundering around with our plain old SLAs and we don't mind 13.7 float voltage. That might explain why the MP-3735 is stuck on Float at the time of the video. If the settings on the Victron controller were explained, and if there was some illustration of the panel arrrangement and lighting at the time of the voltage reading ... it's a hard one to judge either way, but I'm very sad and unhappy now anyway. I am so sad I am sitting here with my diesel running on a cloudy day, puffing dirty black smoke up into the sky and hoping that the wind will blow it all over JayCar which is SSW of here around 20km, and I don't really give a damn if everyone between here and there gets smogged out by my diesel as collateral damage.

I just spent all my money on dud solar equipment and so what reason could there possibly be for me not to adopt the F.T.W attitude?.

PS: Okay, Deep Breath. Hissy-fit Complete.

Seriously, I'm getting 14A out of twin 150W panels in clear, sunny skies at 33*S latitude before 11am a couple of weeks before the equinox and that's enough to keep me running with amps to spare.

Currently, right at this very moment in time, I've got the portable 120W (60W x 2) foldup panel out front on a dull, cloudy day in the rain with no shadow definition to be seen beneath the trees and my little (overpriced underpowered) MPPT MP-3735 is still dragging in 1.9A which is about half enough to keep the food cooler and the laptop alive (without movies of course). When I get the other two panels installed at the back of the van, I'll have 300W fixed roof-top solar plus the 120W portable, and the controller I've got does seem to be able to operate in various conditions, rain or shine.

It could be worse, could be worse indeed, and Adam can't work out how to calculate his own watts when he is given the amps and volts, I'll stop being so sad and make the best of whatever I've got.

[littleharbor]

Could you post the link to the video please? I am still uncertain whether you're referring to my controller ot the MPPT-60 that the OP inquires about.

https://www.youtube.com/watch?v=-VP1LCp_qfI

[Seano]

After looking up your controller I think you may have a bogus MPPT controller. I don't give Youtube videos much value but I did look at the side by side test video for this controller and a known true MPPT controller and it seems to verify my suspicions.

Could you post the link to the video please? I am still uncertain whether you're referring to my controller ot the MPPT-60 that the OP inquires about.

[littleharbor]

After looking up your controller I think you may have a bogus MPPT controller. I don't give Youtube videos much value but I did look at the side by side test video for this controller and a known true MPPT controller and it seems to verify my suspicions.

[inetdog]

You are very welcome. Keep coming back!

[Seano]

There are a large number of suspiciously low priced Chinese-made CCs which are marketed as MPPT but are really PWM that has been modified for poorer performance to give the illusion that it is MPPT. One of those will surely fry with too large an array.

Thank you for your reply to my inaugural post, InetDog. Your expertise is appreciated, because while I don't think that the reputable Australia-wide JayCar company would take such cheap shots at customers, there is that kind of shonky business that you mention above. I would assume that by the look, feel, smell & taste of this new controller, as well as the quality of the box & packaging, and the 99% good grammar of the English in the User Manual, and also the reputation of the retailer, (who sell PWM controllers as well, for around 20% of what this MPPT just cost me), that it most likely is what it claims to be.

However, I think I might take it carefully with this next stage of the project anyway, considering your warning on MPPT quality from Shenzhen and such places. I will conclude below.

And the rated power usually assumes that the panel temperature does not exceed 25C, unlikely on top of a vehicle in full sun. So you really need to look at what the array is actually producing, not its nominal power, in figuring out what you can use to drive your CC.

Interesting, because there is a temperature sensor which I have plugged into its port under the controller but am yet to hook into a spot near the batteries, and the User Manual tells me that the MPPT controller can adjust the output current to suit the temperature of the battery. How this relates to the temperature of the panels on the roof is another question, but as you mentioned, the little dual (inside/outside) thermometer I have in front of the desk here in the back of the van (behind the seats) told me that it was 43*C up on the roof-rack at one stage yesterday afternoon, when it was only 37*C in here.

I have some time to consider carefully, but based on your advice, I am inclined to take the Plan C which just eventuated when I was writing the last post. I will purchase the two additiional panels first, with the MC4 connectors already wired into the middle of the roof-rack and then through into the van to a fuse-block, but there are no blade-fuses plugged in yet.

I'll test one extra panel under a tree in the shade first, by plugging its 20A fuse in, then keep a hand on top of the MPPT controller box to sense heat, and keep the nose on guard for brown smells, and watch the LCD screen for E3 error, which indicated 'Module current too high' and give it half an hour. If that doesn't burn my house down, I'll disconnect the fuse, drive out to a place in the sun, and repeat the procedure with the third 150W panel, using the fuse to start the test again.

I reckon that such a methodology would probably allow me to monitor any unhealthy symptons in the MPPT controller, would you agree?

There seems like quite a good education to be gained here at this forum, so I will keep monitoring this thread and also read some more of the information. Thank you once again, sir.

[inetdog]

Hello forum. I have been thinking of doing something like this with the roof-top panels on my Ford Transit Van.

I currently have two(2) x 150W panels spanning the front half of the roof, feeding into a 360W 30A 12V MPPT controller which was only finally connected and set running last Thursday morning, February 28th. Plan A is to save the money to purchase another pair of the same 150W panels to fit to the rear of the van and connect these to a second 360W MPPT controller. I was told by the fellow at the shop that hooking 600W total power into the single 360W MPPT controller will fritz the controller, but it makes me wonder.

You see, last Friday when I took the first and only drive out of the shady spot under the trees by the river where my Transit Van and I are parked now, and stopped at the electronics shop where I have been buying all these solar goodies, I took a reading of the incoming current to the MPPT and even at 11am on a clear, sunny day at 33*S on March 1st, the two 150W panels were only managing 14A or less combined, and 300W / 12V = 25A. I figured that the 150W rating applies to high noon in Singapore at the equinox on a cloudless day, (which is unlikely to occur in Singapore at the equinox anyway).

Suppose I head north to Darwin, which is 12.5*S latitude, and my panels are almost perpendicular to the Sun. I doubt that even thenm these two 150W panels will exceed 20A mainly due to the light gauge cabling and my sloppy connector terminations. So say I was to scrimp in that second MPPT controller and connect the second pair of 150W panels to the single 360W controller, totalling 600W input theoretically, but more likely feeding not more than 40A into a 30A MPPT controller.

That is what I hope to achieve, not just to save some money and hurry this project on by a couple of weeks, but mainly so that I can achieve more consistency when the Winter comes and the sky is cloudy. Having four panels up top to do the work of two seems like a kind gesture to my solar assemblage. The concern is that on a sunny day, would a current input of 40A wreck a 30A MPPT controller, or would it have the brains to moderate the input and continue to output 30A.

It is a Powertech MPPT controller sold by JayCar in Australia. 360W, 30A, 12V and looks like a fairly good quality Chinese product. Should I attempt to wire in a third panel with the current two, and take the van for a drive in the sun and see how the current is flowing? Then, if three panels in the sun are making less than 30A, I could perhaps hool in the fourth panel for the drive home and see if it works.

Can anyone enlighten me with some personal experience on the foolishness of this Plan B?

A true MPPT charge controller is able to limit the amount of power it takes from the array to control the output current to the batteries. But some manufacturers still specify not to exceed some multiple of the input power required to produce the rated output. That multiple may be as low as 1.5, or go to 2 or more. Other manufacturers simply do not put a limit on allowed array power, but the extra power capability will simply be wasted.

A PWM CC, on the other hand, tries to regulate the average output current by switching the panel circuit on and off at a high frequency. During the time the switch is on the current may be limited only by array power and may exceed the maximum instantaneous current of the control elements if the array is too large.

There are a large number of suspiciously low priced Chinese-made CCs which are marketed as MPPT but are really PWM that has been modified for poorer performance to give the illusion that it is MPPT. One of those will surely fry with too large an array.

In your case the situation is complicated by your panel arrangement. Other than at the equator at noon, a horizontal panel will produce far less than the rated output, even under full clear skies.
And the rated power usually assumes that the panel temperature does not exceed 25C, unlikely on top of a vehicle in full sun. So you really need to look at what the array is actually producing, not its nominal power, in figuring out what you can use to drive your CC.

[Mike90250]

NO. Your batteries are partially charged, and they are not drawing full current. Want to test this ?

Get a opaque dark tarp, use your batteries all night, cover the panels with the tarp (or switch them off, leaving the controller still powered by the battery) Wait till noon and power the panels up and feed the charge controller, you will see full power for a couple minutes.

[Seano]

Hello forum. I have been thinking of doing something like this with the roof-top panels on my Ford Transit Van.

I currently have two(2) x 150W panels spanning the front half of the roof, feeding into a 360W 30A 12V MPPT controller which was only finally connected and set running last Thursday morning, February 28th. Plan A is to save the money to purchase another pair of the same 150W panels to fit to the rear of the van and connect these to a second 360W MPPT controller. I was told by the fellow at the shop that hooking 600W total power into the single 360W MPPT controller will fritz the controller, but it makes me wonder.

You see, last Friday when I took the first and only drive out of the shady spot under the trees by the river where my Transit Van and I are parked now, and stopped at the electronics shop where I have been buying all these solar goodies, I took a reading of the incoming current to the MPPT and even at 11am on a clear, sunny day at 33*S on March 1st, the two 150W panels were only managing 14A or less combined, and 300W / 12V = 25A. I figured that the 150W rating applies to high noon in Singapore at the equinox on a cloudless day, (which is unlikely to occur in Singapore at the equinox anyway).

Suppose I head north to Darwin, which is 12.5*S latitude, and my panels are almost perpendicular to the Sun. I doubt that even thenm these two 150W panels will exceed 20A mainly due to the light gauge cabling and my sloppy connector terminations. So say I was to scrimp in that second MPPT controller and connect the second pair of 150W panels to the single 360W controller, totalling 600W input theoretically, but more likely feeding not more than 40A into a 30A MPPT controller.

That is what I hope to achieve, not just to save some money and hurry this project on by a couple of weeks, but mainly so that I can achieve more consistency when the Winter comes and the sky is cloudy. Having four panels up top to do the work of two seems like a kind gesture to my solar assemblage. The concern is that on a sunny day, would a current input of 40A wreck a 30A MPPT controller, or would it have the brains to moderate the input and continue to output 30A.

It is a Powertech MPPT controller sold by JayCar in Australia. 360W, 30A, 12V and looks like a fairly good quality Chinese product. Should I attempt to wire in a third panel with the current two, and take the van for a drive in the sun and see how the current is flowing? Then, if three panels in the sun are making less than 30A, I could perhaps hool in the fourth panel for the drive home and see if it works.

Can anyone enlighten me with some personal experience on the foolishness of this Plan B?

[Mike90250]

Thank you!........It's a Morningstar MPPT-60 .......Good to know I can hook up enough panels to where at times under high sun, it will put out more than the 60 Amps it's rated for.....

No, it will always limit to 60 amps max. I would be careful about oversizing the array to too high of voltage, no more than 3x your battery voltage. Morningstar may have some info on their web site where they cover the danger limits.

Most of the time it probably won't go over that......but when it does, I imagine I'd be wasting power from the panels........power that is over the 60 Amp rating.

Fwiw, I've got a DIY 24 volt system, and right now I've got 7 panels hooked up......that have 67 cells each.....

I'll take current measurements in the summer time when they're putting out max......and if I'm generating way too much, I'll switch some panels to another controller.....

Thanks again!
z