Morningstar MPPT 60 Battery Sense

svNorthStar

I've been looking through threads on this problem and it seems like it's been around and there hasn't been a solution. I've been waiting for 2 full days for a response from M* tech support. No joy, so thought I'd come back here. My setup is the above controller, 2 Kyocera 245 watt panels in parallel recently installed and still testing on my boat. I should also mention I have the RM2 remote meter.

We have a boat full on new Lifeline AGMS we are feeding. The problem I'm seeing is that battery sense function of the controller is not reading properly. Looking at the particulars on the RM2, the system is reading about .4 volts higher than actual battery voltage on the battery sense. This obviously causes the controller to go in absorbtion too soon and is limiting power being restored to the batteries. I have checked at the battery sense terminals in the unit many times, with a Fluke DVM and another DVM as well and it consistently reads about .4 volts lower than what the RM2 says. I'm set on battery setting 4 and should go into absorbtion at 14.2, at our temp, and the normal display shows 14.2 ABSORB. Scrolling down battery sense is 14.2 V and "valid". But checking the sense terminals it is 13.8 and the battery posts are 13.8V.

As I said, I've seen this on several threads, but has anyone ever gotten it resolved? I saw one thread where the user was just told by M* to disconnect it. That makes a lot of sense.

I would appreciate any suggestion/insights anyone might have on how to rectify this problem.

NorthGuy

Re: Morningstar MPPT 60 Battery Sense

I don't know anything about Morningstar, but I thought that if it's always 0.4V higher, you could adjust all your charging setpoints 0.4V higher than they are, and it'd be charging correctly.

inetdog

Re: Morningstar MPPT 60 Battery Sense

svNorthStar wrote: »

We have a boat full on new Lifeline AGMS we are feeding. The problem I'm seeing is that battery sense function of the controller is not reading properly. Looking at the particulars on the RM2, the system is reading about .4 volts higher than actual battery voltage on the battery sense.

If the unit is reading .4 volts higher than the actual battery voltage, is it possible that there is a fault in the temperature sensor? Many CCs with temperature compensation will display not the actual voltage, but what charging condition that voltage would correspond to at standard temperature. If the temp sensor is reading low, the voltage will read low too. If the temp sensor is reading high, the voltage displayed will be higher than the real voltage. I guess that the theory is that compensating the displayed battery voltage in that way allows the user to more closely associate the voltage reading with SOC even when the battery temp is far from 25C.
In fact, it does not make a big difference whether the battery voltage measurement is corrected or the set point voltages are corrected.
A .4 volt discrepancy in the voltage reading on a 12 volt battery would correspond to an approximately 15C error in temperature.
Check whether the voltages agree if you disable temperature compensation, and then look into replacing the temperature sensor if the battery temp is really close to 25C.

svNorthStar

Re: Morningstar MPPT 60 Battery Sense

Northguy, that was going to be the next step, if I couldn't get it to register correctly. I haven't yet setup the ability to go into the software and change all the various parameters. It is tracking temp correctly. I checked the batteries and heat sink with laser therm and they are all displaying correctly in the RM2. The only parameter that seems off is the battery sense reading .4 volts high, which in turn makes the controller start backing the charging current down much sooner than it should.

Inetdog, it appears as I said above to be correctly tracking temp and displaying the same temps I get on the heatsink and the batteries. Battery temps here are running about 85 F and that is what the RM2 is reflecting. It seems to have lowered the ABSORB voltage by the correct amount given the temp. It is just thinking the battery is at a higher state of charge than it really is and starts backing it down sooner than it should. As mentioned above, I can just set the charging voltages .4 higher I guess. My only concern would be if the unit starts to work correctly then we could cook the AGM's.

Thanks for the thoughts. I was hoping some of the folks who had posted older threads about having this problem had gotten some resolution from M*. As I mentioned, I haven't gotten the software working to do anything more than what I can do with the dip switch. In MSVIEW, I think that's the name, is it possible to "calibrate" the battery sense reading? Maybe put in some correction factor? Can I do all that the software allows through the ethernet interface, or do I have to make up the serial cable?

Thanks again for all the guidance.

svNorthStar

Re: Morningstar MPPT 60 Battery Sense

An additional bit of interesting info. I just checked the voltages while in "night" mode. Basically, everything shutdown. The battery sense and actual battery voltages are 12.74 V. The 12V out terminals, battery posts and battery sense in the RM2 all agree while the unit sleeping. I thought when I checked it earlier that the spread between the actual battery voltage and the battery sense voltage got wider as the unit loaded up during the peak of the day. I guess I'll have to check this at various times and see the discrepancy at different levels of output. This actually concerns me a little bit more because it may not be as simple as just faking the unit out by setting higher charge settings to make up the difference between measured and reality.

Any thoughts?

inetdog

Re: Morningstar MPPT 60 Battery Sense

svNorthStar wrote: »

An additional bit of interesting info. I just checked the voltages while in "night" mode. Basically, everything shutdown. The battery sense and actual battery voltages are 12.74 V. The 12V out terminals, battery posts and battery sense in the RM2 all agree while the unit sleeping. I thought when I checked it earlier that the spread between the actual battery voltage and the battery sense voltage got wider as the unit loaded up during the peak of the day. I guess I'll have to check this at various times and see the discrepancy at different levels of output. This actually concerns me a little bit more because it may not be as simple as just faking the unit out by setting higher charge settings to make up the difference between measured and reality.

Any thoughts?

The only other thing that comes to mind is something that you have probably looked at already, namely to attachment of the voltage sense wires.
If the voltage you measure with an independent meter is anywhere in the neighborhood of .4 volts higher at the inverter end of the inverter-to-battery cables (including the negative cable of course) then the unit may for some reason be using the internally attached sense voltage instead of the remote sense wires. Or else one of the wires is attached at a point where there is a voltage drop caused by the charging current somewhere between the voltage sense line and the battery post. I assume that you are measuring your reference voltage post-to-post or flag-to-flag rather than on any sort of screw or connector part. Where and how have you attached the two sense wires? If my hypothesis is correct, the other thing you should see is that once the CC gets into Absorb and the current drops (which it won't because the battery is still in a Bulk-appropriate SOC) then the difference should decrease. If it ever gets to Float, the offset should go away almost completely. The nite mode has no current going to the battery, so no voltage drop there either.

mike95490

Re: Morningstar MPPT 60 Battery Sense

NorthGuy wrote: »

I don't know anything about Morningstar, but I thought that if it's always 0.4V higher, you could adjust all your charging setpoints 0.4V higher than they are, and it'd be charging correctly.

That's what I was going to suggest, if you are sure you have a good reference meter. And what about the battery temperature sensor, using one ?

Cariboocoot

Re: Morningstar MPPT 60 Battery Sense

Just out of curiosity, got RTS? It will change the Voltage reading for the battery but not the set points and cause the reading to differ from any independent meter.

Otherwise it is perfectly normal to see differences in Voltage readings between different meters on the same battery under loaded conditions. The fact they all agree when the system is not loaded shows it is working.

Also try and remember none of the controller's read that accurately, even with the sense wires.

Bottom line: does it work? Yes? Don't worry about it.

Muskoka

Re: Morningstar MPPT 60 Battery Sense

Here's some numbers from my Morningstar MPPT 60 for reference. The battery terminal voltage on my "high end" meter measures 15.09v.

Attachment not found.

Glen

Cariboocoot

Re: Morningstar MPPT 60 Battery Sense

You are using your meter at the battery to get the 15.09 Volt reading? That differs from the sense wire reading by 0.02 Volts. No reason to expect anything to be more accurate than that. Likewise the difference between that and the battery terminal Voltage is 0.05. We're talking 0.3% here. And since the reading is 15+ it must be under charge.

I do not see anything to be worried about.

Muskoka

Re: Morningstar MPPT 60 Battery Sense

Yes, measured at the battery. I have no problem with these numbers, quite happy. Only posted for the original poster too see.

Where I have issues is from controller to controller. They are never the same, and can be close to a full .1 volts apart, even with temp compensation on both. I just play with the voltage settings in the software for each to get what I want. They're balanced pretty well now, the one always gets to float about 10-15 minutes before the other, no big deal.

Glen

Cariboocoot

Re: Morningstar MPPT 60 Battery Sense

Voltage discrepancies between controllers on a single system are standard, even with the same make/model controller. Even with OB's connected via HUB. You can mess around forever trying to get them to agree. Even so, the difference is usually a nominal <1% so it doesn't hurt anything.

If you're wondering why the differences exist, keep in mind every component that goes into making a charge controller will have specification tolerances. They could be as much as +/- 10%. As such it is possible to have two of the same where on one every individual piece causes the whole circuit to lean towards the minus by 10% and another that leans towards the plus by 10% making a total potential difference of 20% on two identical units.

Considering that, variations of less than 1% are pretty good.

Muskoka

Re: Morningstar MPPT 60 Battery Sense

Ya, you could really beat yourself up trying to get things exact, it's never going to happen. It takes a while, but you do get to understand your system the more time you have to stand there and watch what is going on. They each have their own "personality" if you like, and once you figure out how they like to operate (voltage / temperature), you can set them up accordingly. Can't wait until I throw the 3rd one into the mix, it's always interesting. My friend wants a system that "looks after itself" and I keep telling him it doesn't exist. There's no "set-it" and "forget-it", especially with off-grid solar. I suppose you could, if you don't mind replacing batteries every couple years.

Glen

inetdog

Re: Morningstar MPPT 60 Battery Sense

Cariboocoot wrote: »

You are using your meter at the battery to get the 15.09 Volt reading? That differs from the sense wire reading by 0.02 Volts. No reason to expect anything to be more accurate than that. Likewise the difference between that and the battery terminal Voltage is 0.05. We're talking 0.3% here. And since the reading is 15+ it must be under charge.

I do not see anything to be worried about.

Those were Muskoka's numbers for comparison. The OP with the .4 volt issue is svNorthStar. :-)

Cariboocoot

Re: Morningstar MPPT 60 Battery Sense

inetdog wrote: »

Those were Muskoka's numbers for comparison. The OP with the .4 volt issue is svNorthStar. :-)

Oh yes. So there we're talking 3% variation instead of 0.3%.
If we were talking 10% variation we would be looking for problems.
People do get obsessed over tiny numbers. :roll:

inetdog

Re: Morningstar MPPT 60 Battery Sense

Cariboocoot wrote: »

Oh yes. So there we're talking 3% variation instead of 0.3%.
If we were talking 10% variation we would be looking for problems.
People do get obsessed over tiny numbers. :roll:

Batteries seem to care too. I think that a difference of .4 volts on a 12 volt battery is really pretty big when it comes to charging voltages. If we were just talking about meter inaccuracies I would agree with you 100%. But the CC seems to be reading a different voltage from the same battery (as compared to an external meter as a reference) depending on the charging current. That is just not supposed to happen when you are using sense wires.

Cariboocoot

Re: Morningstar MPPT 60 Battery Sense

Just read back and checked: the OP says the Voltage readings agree when in "night mode", i.e. no current flowing. Since this is when we'd expect them to agree it doesn't look like there's really any problem other than current-affected readings.

That brings us to two things: wire sizing and current at the reading time (disregarding the fact the RTS will skew the actual Voltage reading according to battery temperature against the fixed settings).

So then you have to look at how the Voltage discrepancy changes through the charge cycle. A large difference during Bulk is not significant. Beginning of Absorb the current should be lower and so should the Voltage difference. By the end of Absorb/start of Float they should be very nearly the same. If not, suspect the wire size on the controller's charge output and the amount of current flowing at that time: it may not really be finished with Absorb so the current may be too high. Loads pulling current will change this, especially if they are wired in less-than-ideal manner (as in connected to the controller or nearer it than the battery).

The ultimate test of whether or not the SG is reaching full charge state is why flooded cells are recommended to start with; any kind of electronic "gauge" is subject to numerous errors.

svNorthStar

Re: Morningstar MPPT 60 Battery Sense

Ok guys, I'll try to hit the points of the various threads. Yes, I have the temp sensor hooked up and it works fine. The RM2 displays both the heatsink temp and the battery temp accurately. It seems to work just fine and basically agrees with my battery sensor on my inverter/charger and handheld laser therm.

The issue does seem to be current dependent. Although, according to the manual that is exactly what the "battery sense" option is supposed to deal with.

This is a section in the manual entitled Battery Sense, page 39 of mine, that perfectly describes what is going on. The second paragraph is exactly what I'm describing.

Battery Sense
Voltage drops are unavoidable in power cables that carry current, including the TriStar MPPT
battery cables. If Battery Sense wires are not used, the controller must use the voltage reading
at the battery power terminals for regulation. Due to voltage drops in the battery cables, the battery
power connection voltage will be higher than the actual battery bank voltage while charging
the battery.
...
Generally accepted wiring practice is to limit voltage drops between the charger and the battery
to 2%. Even properly sized wiring with 2% drop can result in a 0.29 Volt drop for 14.4V charging
(or 1.15 Volt for a 48 Volt nominal system). Voltage drops will cause some undercharging of
the battery. The controller will begin Absorption or limit equalization at a lower battery voltage
because the controller measures a higher voltage at the controller’s terminals than is the actual
battery voltage. For example, if the controller is programmed to start Absorption at 14.4V, when
the controller “sees” 14.4V at its battery terminals, the true battery voltage would only be 14.1V if
there is a 0.3V drop between the controller and battery.

This is what the battery sense is supposed to avoid. It should just read the battery voltage, irrespective of any current flow on the charging line. There should be zero current flow on the battery sense line. When I check it at the battery sense terminals with a DVM it just displays battery voltage as you'd expect, no matter what the current flow. But, the controller isn't reading the exact same terminal voltage and getting the same answer. The reading it gets fluctuates based upon current flow. At no current, it reads the same. At max current that I've seen so far, it reads .4-.45 volts higher than the actual voltage on the battery sense terminals. Which means as it is coming out of bulk mode the controller starts dialing back the current at 13.8V Battery instead of the 14.2V where it is supposed to go into absorption mode. This greatly reduces the ability of the unit it fully charge the batteries in the days time. It then holds the voltage at 14.2V displayed on the unit, when the battery is actually only at 13.8 V and stays there until the absorption cycle is complete.

We were without line power here all day. Common here in Panama. I spent most of the day trying to find a DB9 connector so I could make a cable to use the software. Wouldn't you think for the price they'd include the cable. Unsuccessful on the cable. So, I have to either keep looking, order and wait or cannibalize a pactor modem cable for the SSB email system.

Since I was gone most of the day and it was overcast, I was unable to monitor the spread here at various levels which I'll do. Anyone have any ideas how I can fix the discrepancy in the battery sense readings the unit is seeing? I thought maybe during the high output time tomorrow I'd try to verify zero current flow on the battery sense line. I am using #16 stranded copper for the sense lines to the battery terminals. They aren't a twisted pair, but wouldn't think they would pick up anything that would cause this. Wish I had my scope from home.

Anyway, as we cruisers say, "cruising is learning to fix your boat in exotic places", this is just another example. On Thursday, I went to Panama City, which from here is an all day affair and went to all 4 "solar paneles" dealers to try to find MC4 connectors for hooking up the system. Each and everyone of them said they just cut cut the connectors off all the panels they install here. No one knows anything about them or where to get them. Oh well, already got that one behind us.

I do think finding the solution here is worth the effort and appreciate all the suggestions. If you have any more please post them.

inetdog

Re: Morningstar MPPT 60 Battery Sense

svNorthStar wrote: »

I do think finding the solution here is worth the effort and appreciate all the suggestions. If you have any more please post them.

I am not intimately familiar with that CC, but my guess would be that either a jumper or a setting needs to be changed to tell the CC to use the sense leads instead of the output terminal value.
If you look at Muskoka's post you will see that among the voltages reported are
Battery Terminal Voltage (at the output leads of the CC)
Battery Sense Voltage (should match your DVM measurement if the sense wires are connected and unbroken)
Battery Voltage (unless there is an incorrect software option or a bug, this should be very close to the sense lead voltage rather than the terminal voltage.)

Can you look at the same readings on your CC?

svNorthStar

Re: Morningstar MPPT 60 Battery Sense

InetDog, the unit is using the battery sense. When scrolling through the data on the RM2 is has a display "battery sense 13.5 V valid". According to the book, you won't see that if it isn't using it. The dip switch settings don't have anything to do with this. When you power the unit up it sees it's connected and uses it. If I disconnect them, it disappears and just uses the internal readings it gets off the charging lines as described above.

Cariboocoot, I think it is a bit disingenuous to say that .4 V on a 12 V circuit is close enough. On a battery system that is the difference between a full charge and a 50% charge. I don't think that would be close enough for you on your systems. BTW, the manual specifications page claims voltage accuracy of <= .1% or +- 50mV on 12/24V systems. This error is over 3% or > 30 times their spec.

I intend, hopefully tomorrow if we get good sun to plot the spread at various levels of charging and during the different modes. I also intend to insert a sensitive amp meter in the battery sense line to verify no current flow. Then I'm not sure. I guess something could be impressed upon the line that is making the controller read it wrong. Maybe a twisted pair would help. I'll play with it more tomorrow and report. I wish I could plugin on the software side. Maybe I'll try to make that happen. I do see that I don't have the most current firmware from the website, although the note make no mention of solving this problem.

Everyone, keep the suggestions coming.

Cariboocoot

Re: Morningstar MPPT 60 Battery Sense

Trying to wrap my mind around Morningstar's method right now. This is thinking out loud.

Battery sense wires give most accurate indication of battery Voltage. When in use the charge controller should use that value to determine appropriate charge stage relevant to settings. Readings from battery wires (those carrying current) should be disregarded.

RTS will alter "apparent" Voltage, and should do so for battery sense readings as well. Thus if the batteries are warm the Voltage should appear higher than it really is. As such the readings from the other wires would appear low, and not necessarily at the right points for Absorb/Float.

Check battery sense Voltage readings with the RTS connected vs. disconnected. Outside chance of a faulty sensor here.

niel

Re: Morningstar MPPT 60 Battery Sense

in a nutshell, it doesn't sound like the battery voltage sensor is working properly and morningstar should address your concern. when voltages are that far beyond the base voltage with the sensor attached it kind of defeats the purpose of having the sensor as it would be more accurate without it. i believe that was your point and i see no cure on your part other than making sure it is connected properly. if connected properly then the problem is either in the sensor or the controller itself and that should be the job of morningstar to find out what is at fault and fix it. you must work with them though to get this resolved.

do keep us apprised.

Muskoka

Re: Morningstar MPPT 60 Battery Sense

Again, some numbers from this morning. Mine is working fine it appears, although the controllers consistently read higher voltages than my clamp meter, and 2 other digital multi-meters. I have my sense wires connected to my common busbars, there is nothing on the actual battery bank terminals, other than busbar + - connections. I will try with the sense wires connected directly to the battery bank and see if the voltage is exactly (closer) the same as the controller readings, and report back.

The meter reading directly from the battery bank was 12.95v.

Attachment not found.

Glen

Edit: Just thought I would verify the sense voltage reading in the controllers display and this is what I got.

Controller ts-m-2 display/meter voltage sense reading - 13.16v
MSView voltage sense -13.16v
Busbar voltage from DMM - 13.25v
Actual battery bank voltage from DMM - 13.26v

Now the controller is reading lower...go figure.

Edit2: The readings are very much load / charge dependent. My fridge just kicked in and the battery voltage (actual) was almost a full tenth lower than the controller reading. As soon as the fridge stopped drawing current, the reverse happened, the battery voltage (actual) was close to a tenth above the controller. Pretty cloudy today so not getting much charge, but enough to show a 10th of a volt difference.

When the loads and charge are off, the readings are close, as per the screen shot above. I just checked again and the actual battery and busbar voltage are the same. The controller sense wires which are connected to the busbar are almost a 10th of a volt higher.

Cariboocoot

Re: Morningstar MPPT 60 Battery Sense

A DMM will not have temp compensation.

At 25C battery temp the MS's temp comp should be zero. If the battery temp is 30C (often the case when current is flowing) the battery needs less Voltage so the RTS causes the controller to read the Voltage as +0.15 (and so on). Set points do not change; only the apparent Voltage. In this manner the set points are effectively lowered.

Where I'm getting confused is that I think it should alter the reading for both the sense terminals and the charge terminals. The only Voltage variation between the two should be due to current flow difference. It is possible that this is the case, as everything agrees on Voltage when the unit is at rest. But without checking each aspect (function of RTS, function of battery sense connections, wire size & current, et cetera) you can't be certain. The only way to do that is to try the various configuration possibilities and look at what differences arise (or don't).

BB.

Re: Morningstar MPPT 60 Battery Sense

One thing to check--Measure the remote battery sense voltage at the controller. One of the sense leads could be broken (or poor connection) and you would see similar symptoms.

-Bill

Muskoka

Re: Morningstar MPPT 60 Battery Sense

The controller does not show temperature compensated voltages. The only temperature compensated voltage that's displayed is the "Target Voltage". My batteries right now are 12 deg celsius. At .028 degrees temperature compensation, your saying the controller battery voltage readings would be, actual is 13.05 + compensation (.028 x 13 = .364v), so 13.05v + .364v = 13.414v. The controller voltage readings are all within 1 tenth of actual. The controller is not showing compensated voltages. It's showing actual uncompensated voltages, according to my numbers. If they were compensated readings, they all would read close to .364 volts higher, and they're not even close to that.

And yes, the only difference in voltage readings is due to current flow, as I stated earlier. Although, the controller readings could be closer to actual as far as I'm concerned. Almost a full tenth is a bit much, especially when your trying to co-ordinated multiple controllers, and they're all a tenth out, either way.

Glen

Cariboocoot

Re: Morningstar MPPT 60 Battery Sense

That's pretty much backwards of standard practice. It's much easier for the controller to alter the "read" Voltage for temperature than to re-align the programming. "Target Voltage" should be what you're trying to achieve (i.e. a Voltage set point).

Gotta smack these engineers around a little and teach 'em proper English!

Muskoka

Re: Morningstar MPPT 60 Battery Sense

My feeling is the tolerances are a bit too loose, or something in the logic could be a little "tighter", if that makes sense. I'm still trying to get these two controllers to play nice together. The MPPT will go to float and an hour later the PWM is still plugging along in "PWM" mode, keeping the voltage at the "Absorb" voltage level far longer than it needs to be. The charge current it's putting out is matching the loads, but the voltage certainly doesn't need to be kept that high. I keep playing with the voltage settings, but when they're "jumping" all over the place due to "some" internal inaccuracy, it makes getting things co-ordinated a little tough.

The sense wires and RTS's are both in the same location for the two controllers (sense on busbar, rts on side of battery) yet the voltage sense readings are always different, and the temperature compensation is always one degree different between the two. This really causes some programming / settings issues.

I don't know what to suggest to the OP, my voltages have never been out that far, sorry I don't have an answer.

Glen

Cariboocoot

Re: Morningstar MPPT 60 Battery Sense

Getting two charge controllers to agree is difficult. More difficult if they are different brands/types. Usually it is not a critical matter, as the 'lesser' controller needs only add current for the Bulk stage. Beyond that it can whistle its own tune as long as the battery actually does get charged.

NorthGuy

Re: Morningstar MPPT 60 Battery Sense

Muskoka wrote: »

My feeling is the tolerances are a bit too loose, or something in the logic could be a little "tighter", if that makes sense. I'm still trying to get these two controllers to play nice together. The MPPT will go to float and an hour later the PWM is still plugging along in "PWM" mode, keeping the voltage at the "Absorb" voltage level far longer than it needs to be. The charge current it's putting out is matching the loads, but the voltage certainly doesn't need to be kept that high. I keep playing with the voltage settings, but when they're "jumping" all over the place due to "some" internal inaccuracy, it makes getting things co-ordinated a little tough.

When one controller goes to Float, it tries to maintain the "Float" voltage. Since the actual voltage is higher than this, it eliminates all power output completely. The other controller tries to maintain the "Absorb" voltage. Since the actual voltage is lower than this, it puts out all the power, but without help from the other controller it cannot push the voltage to "Absorb" and maintain loads at the same time. As a results, voltage wonders between "Float" and "Absorb" indefinitely.

If you make the weaker controller (with smaller array) go to "Float" first, the stronger controller (with bigger array) will have a better chance to push it to "Absorb" voltage alone and then go to Float too.

Muskoka

Re: Morningstar MPPT 60 Battery Sense

I have roughly 75 excess amps of charge current vs load, they should have no problem getting to float. The Mppt unit does on most days, it's the Pwm Tristar that's a pain. It will eventually go to float, but long after it should,. The only way I can get it to Float first is to set it's voltage about 3 tenths lower than the Mppt, shouldn't have to do that.