May have to shut off my MX-60 on sunny winter days

waynefromnscanada

Two PV arrays, one feeding MX-60, other feeding TS-MPPT-60, both feeding same battery bank. All worked well during warmer weather. Now however with battery temp dropping to +5C, the voltage is likewise creeping up, as it should. Problem is however, something that's not exactly new, but far more common now that I have additional PV. The Morningstar inverters kick out on overvoltage @ 15.5. The MX-60 often takes it's frigging time doing sweeps, during which, it pays no attention to battery voltage, allowing it to surge until the sweep is finished. (not a problem until batteries are full, or almost full) This kicks out the Morningstar inverters.
Maybe I should design a circuit that connects a heater or some such load whenever the voltage reaches 15.49?
It's +3C here now, and the problem happened several times in an hour. What the heck will happen when the temp falls to minus 20?
Shut down the MX half an hour ago and it hasn't happened since.
Pain in the butt. I know there are inverters that handle higher voltages, but I LOVE those TS-300 units!

Cariboocoot

Re: May have to shut off my MX-60 on sunny winter days

But Wayne, this doesn't happen because as long as the batteries are connected Voltage can't go higher than they are! (Joke made from an idiot reference in another thread.)

This sweep sequence time is when the MX gets in trouble for other reasons as well. Is the Voltage being brought up that high on charge due to cold temp compensation, or is this only happening on sweep when the controller lets the Voltage go all over?

In either case you need to see how high the surge is. It may be possible to simply "lose half a Volt" with a diode to the inverters. Otherwise your idea of constructing a Voltage clamp might help (although it will possibly cause the MX to pick a wrong MPPT).

Related: they were always going to do something about clamping the input of PV on these, but it never came about. Curiously MidNite has hyper Voc function, though.

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

Cariboocoot wrote: »

But Wayne, this doesn't happen because as long as the batteries are connected Voltage can't go higher than they are! (Joke made from an idiot reference in another thread.)

This sweep sequence time is when the MX gets in trouble for other reasons as well. Is the Voltage being brought up that high on charge due to cold temp compensation, or is this only happening on sweep when the controller lets the Voltage go all over?

In either case you need to see how high the surge is. It may be possible to simply "lose half a Volt" with a diode to the inverters. Otherwise your idea of constructing a Voltage clamp might help (although it will possibly cause the MX to pick a wrong MPPT).

Related: they were always going to do something about clamping the input of PV on these, but it never came about. Curiously MidNite has hyper Voc function, though.

Haha Thanks "Coot" for your thoughts. Yes, as the batteries get colder, their "normal" voltage creeps ever closer to 15, so it doesn't take much to lift the voltage to that critical point. Other than that slow sweep during which the voltage is not regulated, I love the MX. I suppose the worst that can happen is the inverters and thus critical loads will shut down till the day is over and the sun has set, but it's a real pain in the a$$. Hate the thoughts of swapping out the MX for another TS. They each have their advantages, just too bad the MX has this glitch in it's design.

westbranch

Re: May have to shut off my MX-60 on sunny winter days

Wayne, can you heat the area the batteries are in? just enough to limit the voltage spike?

NorthGuy

Re: May have to shut off my MX-60 on sunny winter days

15.5V is not even a regular equalization voltage. Equalizing at these temperatures could make the voltage go to 16.7V. Perhaps it is possible to adjust the cut-off point to a higher voltage?

The other possibility is to lower the absorb setting on the charge controller. But I guess it'll be eaither too low for cold batteries or too high for the inverter.

It is strange that it is doing sweeps when batteries are almost full. Doesn't make sense.

Cariboocoot

Re: May have to shut off my MX-60 on sunny winter days

NorthGuy wrote: »

15.5V is not even a regular equalization voltage. Equalizing at these temperatures could make the voltage go to 16.7V. Perhaps it is possible to adjust the cut-off point to a higher voltage?

The other possibility is to lower the absorb setting on the charge controller. But I guess it'll be eaither too low for cold batteries or too high for the inverter.

It is strange that it is doing sweeps when batteries are almost full. Doesn't make sense.

Equalization Voltage is dependent upon the particular batteries used. Not all batteries demand high charging Voltage like Trojans or (worse) Surrettes.

Besides which, the set points are not the issue; it is a Voltage independent of charging which occurs only when the MX60 does its MPP sweep.

The operation of the charge controller is quite normal.

NorthGuy

Re: May have to shut off my MX-60 on sunny winter days

I think it'll be hard to charge at 15V while inverter cuts off at 15.5V. So, I thought of a circuit to fix that.

Everything on the left (except D1 and D2) is just a voltage regulated relay with hysteresis. It is normally closed, and all the current to the inverter goes through the relay. As voltage increases above 14V (or whatever is the best setpoint), the relay opens. Once it's open, current to the inverter will go through diodes D1 and D2 and cause a voltage drop of about 1.5V. There will be heat dissipsating through D1 and D2, and heatsinks will be needed, but this shouldn't be a problem because this only happens when batteries are absorbing, so you won't waste any energy.

You can buy a pre-made voltage regulated relay, or you can build the circuit and make it more energy efficient. I didn't put the values and the parts because I didn't do calculations, but I will if you decide to build the thing.

Theory of operation is very easy. Resistor R1 and Zener diode Z1 create a voltage reference. Resistors R2 and R3 form a voltage divider for battery voltage. The comparator IC1 compares the voltage from the R2/R3 diviider to the R1/Z1 reference and if it is higher, the output of the IC1 goes high. which turns on transistor Q1, which activates the relay. When the relay is activated, the contacts close and now the current to the inverter goes through diodes D1 and D2. R4 maintains hysteresis, which will prevent the relay from switching back and forth frequently during the transition periods. R6 is big (1MOhm or so), optional and may be needed to provide current path from the comparator input to the ground. D3 simply protects Q1 from reverse currents when the relay is switching off.

Cariboocoot

Re: May have to shut off my MX-60 on sunny winter days

Or buy a Voltage controlled switch to operate the ON/OFF of the inverter.

Or put a diode capable of handling the inverter's maximum current in-line to knock half a volt out (could be difficult to find for larger inverters, but they usually have wider Voltage latitude anyway).

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

Thanks for all the thoughts, appreciate every one!
Westbranch: I wish the batteries were in a warm location, unfortunately, without major, major changes, that's not going to happen. The whole solar system, controllers, batteries, and inverters are all in an unheated outside shed 100 feet from the house.

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Northguy: Problem is, when the MX-60 does it's regular sweep every few minutes, it totally ignores the battery voltage. It's only aim is to find the MPP, after which it returns to monitoring battery voltage. MX-60's are also notoriously slow completing their sweep, thus giving nearly full batteries plenty of time to raise their voltage to a temporary excessively high voltage. Unfortunately this is their normal way of operation. It USUALLY doesn't cause a lot of problems, but "usually" is not never.

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Cariboocoot hits the nail on the head re this problem.

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Northguy! : THANKS MAN! I love your idea! And I can easily build that circuit and can figure out the values! That's awesome man! Have to say though, I'm rather embarrassed I hadn't thought of it myself. Hahahaha
I'll use two relays, one for each of the two TS-300 inverters.
Getting intelligent, no BS answers is why I love this forum! Awesome people live here.

niel

Re: May have to shut off my MX-60 on sunny winter days

seems to me if the problem is the temp compensation then disable the temp compensation so it follows a normal track in winter. you could then even manually change the charge voltages up a tad to help compensate for some of the lower temps and it'll still have the charge voltage down far enough so as to not press the inverter into overvoltage.

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

niel wrote: »

seems to me if the problem is the temp compensation then disable the temp compensation so it follows a normal track in winter. you could then even manually change the charge voltages up a tad to help compensate for some of the lower temps and it'll still have the charge voltage down far enough so as to not press the inverter into overvoltage.

Problem is the Mx-60 doesn't give a hoot and pays no attention to where the battery voltage may or may not go while it's doing a sweep. If the batteries are nearly full and there's bright sun, and even more so if there's also cloud edge effect happening with that bright sun, (like there was yesterday) the MX can and does pour big amps into the batteries (regardless of battery voltage) while slowly sweeping through the MPP. This then can drive up the voltage. Once the sweep is completed, the MX starts monitoring battery voltage again and gets things back under control, but by then, depending on how high the voltage went during sweep, the inverter may have kicked out. If the MX was capable of doing a really fast sweep like the Morningstar does (less than half a second against the 30 or more seconds the MX often takes) there would be no problem. I love the MX-60, but sometimes like a slow driver on the Trans Canada Highway, it can drive me up the wall with it's long, drawn out, slow sweeps. Hahahaha

NorthGuy

Re: May have to shut off my MX-60 on sunny winter days

waynefromnscanada wrote: »

Northguy! : THANKS MAN! I love your idea! And I can easily build that circuit and can figure out the values! That's awesome man! Have to say though, I'm rather embarrassed I hadn't thought of it myself.

You're very welcome.

30 seconds for a sweep is really a long time. My XW does sweeps really quickly, you cannot really notice. Perhaps, MX dosn't have a shunt on the PV side, so it has to measure on the battery side and needs long time to wait until the battery side stabilizes. In this case, in order to do measurements, it has to push the full current into a battery. Otherwise it's nothing to measure.

What I don't understand is why it is doing sweeps when the battery is full, and controller produces only a fraction of what it could. Sweeps are needed to find the best production point, but if you only use 10% of what's available, who cares.

I guess what is happening is this: A cloud comes and shades the panels. The battery voltage drops down. The controller sees that there's not enough energy and decides to do a sweep, but then the sun comes out, and you also get a cloud's edge effect, and it puts the full current into batteries for several seconds until the sweep is over. If this is correct then there should be no problem when there's no clouds.

Cariboocoot

Re: May have to shut off my MX-60 on sunny winter days

MX60 does periodic sweeps to find maximum power point regardless of what is happening in terms of panel input or charge stage. That's just how it was done back when it was designed and it was the hottest thing going then. The new FM and Classics adjust continuously so this issue does not arise.

Vic

Re: May have to shut off my MX-60 on sunny winter days

As Marc stated, the MX-60 was a huge leap forward. But my two MXes are 9 years old. The design of this box is approaching 15 years of age about now +/--.

The longest interval between Sweeps is 15 minutes., and as Wayne mentioned, the battery voltage is a don't care during these sweeps, as the MX is needs a place for the max current to go, and the battery is it, so the battery voltage just rises when the MX is in a voltage regulating mode.

The SureSine is a very nice inverter, and most users love them, BUT, seems to me that its High input V limit is simply too low (as is the case with many 12 V inverters).

I have not ever played with any of the MPPT functions in the MX, as have not ever needed them, but seems that you can choose an operating point that might eliminate Sweeps.

On the systems using MXes here, a sweep takes about one minute. Part of this LONG Sweep time is due to the relatively high Vin of 106 volts for a 48 V battery bank. The MX is very studious in its sweeps, but they are still great boxes, especially considering their vintage, and are quite efficient, AND they will even trigger an Aux function showing that the CC is in Float and generating power. Some more stunted CCs produced today still lack this function.

Opinions, Good Luck, wayne

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

Thanks again all.

niel

Re: May have to shut off my MX-60 on sunny winter days

wow i wasn't aware the power was allowed to flow through it unregulated during sweeps. that's bad. may be time for another controller down the road and either sell the mx or keep it as a spare cc.

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

niel wrote: »

wow i wasn't aware the power was allowed to flow through it unregulated during sweeps. that's bad. may be time for another controller down the road and either sell the mx or keep it as a spare cc.

Been thinking the same thing re a new controller down the road - - - but which one - - - ?
I really like many of the MX-60's user adjustable (with no special tools or equipment) features, but also really like the TS-MPPT-60 for it's lack of RFI, it's fan-less cooling and it's extremely quick sweeps. With all the adjustments available on the MX-60 I was able to tailor it's characteristics so it would work very well with the TS-MPPT-60, no arguments or fights between the two while in operation.
Should I be keeping my eye open for a good price on another TS, or should I be looking at something else? The TS and the MX are the only two I have any experience with.
By the way, re the MX's lack of regulation during sweeps, on special days of very clean air, bright sun and scattered edge effect clouds, I've seen the MX pumping out over 70 amps during sweeps, with no regard to battery voltage. Furthermore, before I disabled the auto restart feature, it would sometimes do a restart shortly after a sweep where it had temporarily driven up the battery voltage, and if the battery voltage had not had a chance to settled back to normal by the time the restart finished, the MX would see that short lived but high battery voltage, and go to sleep (stating "Battery Full") without finishing the Absorb phase. This controller definitely has a few strange quirks. Haha

Sun Dog

Re: May have to shut off my MX-60 on sunny winter days

Wayne, could you clear out your PMs

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

Sun Dog wrote: »

Wayne, could you clear out your PMs

OOPS! Sorry. Seems like birthdays, the messages slowly added up when I wasn't paying attention, and suddenly I was old and the inbox full!
Hahaha

Cariboocoot

Re: May have to shut off my MX-60 on sunny winter days

Wayne; both the Outback FM series and the MidNite Classic series eliminate the most annoying faults of the old MX. No surprise why, since the same guys are responsible for all three designs. They just keep getting better at what they do.

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

Cariboocoot wrote: »

Wayne; both the Outback FM series and the MidNite Classic series eliminate the most annoying faults of the old MX. No surprise why, since the same guys are responsible for all three designs. They just keep getting better at what they do.

Thanks for that "Coot", appreciate it. Tossing the idea of a "better" controller around in my mind and have been wondering about one of the ones you mentioned - - or another Morningstar. I'll try to put up with the problem for a while (this winter?) but it's mostly overcast today and already once I know of, the sun partly showed it's nose through a wee opening, and POOF1 Off went the Morningstar inverter for a moment. Things have settled back to 15 volts and all is OK - - for now. I can see myself getting ticked off and ordering something when the temps turn really cold. That or wade through the snow to shut off the MX when the sun is shining. lol

westbranch

Re: May have to shut off my MX-60 on sunny winter days

Wayne have you read up on the classic Lite CC's? lower cost than the Cl 150 but all the guts.

niel

Re: May have to shut off my MX-60 on sunny winter days

any of the 3 would probably do, but the outback fm series was not of those at midnight and was basically the mx modified. boB and robin had left outback prior to the fm series.

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

Thanks a lot Niel for that info. Greatly appreciated.

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

westbranch wrote: »

Wayne have you read up on the classic Lite CC's? lower cost than the Cl 150 but all the guts.

Thanks Westbranch. I will be checking on it. Appreciate your message.

vtmaps

Re: May have to shut off my MX-60 on sunny winter days

westbranch wrote: »

Wayne have you read up on the classic Lite CC's? lower cost than the Cl 150 but all the guts.

NOT all the guts... no arc fault detection in the lite. --vtMaps

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

vtmaps wrote: »

NOT all the guts... no arc fault detection in the lite. --vtMaps

Good to know, as at this time I don't want to go the arc fault route, and I didn't realize the "Lite" doesn't have it.
thanks!

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

By the way, bright sun and scattered cloud edge happening today. The old MX was causing so much trouble that I had to go out and shut it down, leaving just the Morningstar on the other array to take care of business. Guess that's it, time to replace the dear old MX-60
Wish the import duties weren't so frigging high, otherwise our host would be getting the business. Past experience has shown me it's cheaper to buy locally. Local for me is a 4 hour drive. haha
Now it's product decision time. Time to start researching again because at the moment I'm torn.

Sun Dog

Re: May have to shut off my MX-60 on sunny winter days

Sorry to hear that. I've never bought a charge controller out of the US but I do buy a lot of other things and duties aren't normally a problem anymore. Shipping, on the other hand, can be very expensive. Stay away from UPS and most the of the other courier companies and see if the retailer will go with US Post. Good luck.

waynefromnscanada

Re: May have to shut off my MX-60 on sunny winter days

Sun Dog wrote: »

Sorry to hear that. I've never bought a charge controller out of the US but I do buy a lot of other things and duties aren't normally a problem anymore. Shipping, on the other hand, can be very expensive. Stay away from UPS and most the of the other courier companies and see if the retailer will go with US Post. Good luck.

Yes, I've been warned about UPS, and experienced their high charges as well. Sucks!

NorthGuy

Re: May have to shut off my MX-60 on sunny winter days

waynefromnscanada wrote: »

Yes, I've been warned about UPS, and experienced their high charges as well. Sucks!

They cought me once, but since then I never use them again. I wonder if $50 that they stole from me was worth losing me for life - thousands of dollars I could've paid them for shipping.