AGS Problems

TNBob · April 2020

Hey Guys (and Gals),
I'm writing from TN with a problem that's plagued me for a while and that I can't seem to sort out. We have an off-grid solar system for our farm, major components as follows:

24 - Canadian Solar 270 watt panels - 6.5 Kw
1 - Power Center with 2 MS4448PAE Dual Magnum Inverters (total 8800 watts) and 2 Midnite Solar Classic 150s Charge Controllers
5 - Simpliphi PHI 3.5 LiFePo batteries - 48 VDC (17.5 KW)
Magnum Energy ME-ARTR Advanced Router
Magnum Dimensions ME-AGS-N - Generator Auto Start for Network Versions
1 - Back Up Generator - Kohler Model 12RES - 12kW 120/240 VAC
(I also have an ME-ARC Advanced Remote Controls, but I haven't yet installed it)

I bought the system from Wholesale Solar about 18 months ago and installed it myself. For the most part it's working fine and more than sufficient for our needs but our situation is as follows:

We were only 'part time' residents at the farm (which is jointly owned with other family members). I got the 12 KW genny not only as 'back up' but also because I was unsure as to what our needs would be in regard to running power tools in the barn, etc, etc. The solar has proven more than sufficient for our needs and in fact, we haven't really actually needed it, even in winter. I've on really run the genny to exercise it.

When I first installed the system, I set the AGS to start the genny when VDC dropped to 20% of battery capacity (50.2 VDC) and to stop at 53.5 VDC. This and other settings I used were straight out of the Simpliphi integration guide. I also set up the system to 'exercise' the generator weekly for 15 minutes. I tested everything and everything looked cool, so the wive and I drove home (a couple of hours away). The only load running in the house was the fridge. When we drove up a bit over 2 weeks later the generator was running which I thought odd as it wasn't the day or time I had it programmed to 'exercised.' On checking the generator hour meter I was shocked to see it had run over 100 hours (with a corresponding depletion of our propane tank). Obviously that was a non-starter, so I turned off the auto start,

It became less of an issue as we gained experience with the solar and discovered we would seldom need the generator. However, I continued to run the generator manually and under load periodically, just for maintenance purposes. Also, every time we came down to the farm, I'd dig into the AGS and other manuals and try to figure out what the heck was going on. I also contacted Wholesale Solar but always ended up being told to do what the manual and their various videos said, and I've done that til I'm blue in the face. Finally, given that we always had limited time here and many other projects, I just let it slide.

Now however, thanks to the COVID-19 thing, my wife and I are here full time and I'm determined to sort this out. The problem is I have no clue how to proceed. The 'symptoms' are as follows:

1. I set the 'auto start' to kick in on 'Low VDC' of 20%, which is 50.2 VDC. (I actually have to secure the solar panels to get the batteries to drop that low). The generator DOES autostart as it's supposed to.

2. The problem is the generator stops after 15 or 20 minutes EVERY time, and no where near the set 'stop' VDC of 53.5 VDC. If I leave it alone, it will re-start on auto-start again when the VDC drops, but again it stops after 15 or 20 minutes. After 3 or 4 times, I sometimes get an 'AGS start fault' message. That clears when I cycle the AGS to off and back to auto.

3. FYI, I've also tried starting the genny manually (via the AGS) and then switching the generator to 'auto' while the genny is running. My thought there was to see if maybe the 'stop VDC' voltage set point would work then. No dice. The generator still topped after a few minutes and before the set point was reached.

4. I have only ever tried this using the battery voltage as the triggering condition, as that is what all the various manuals recommend. Every other parameter on the AGS module is turned 'off' (i.e. Exercise, SOC, etc, etc,) I going to experiment with using SOC next as I figure I've got nothing to lose.

At this point I'm at a loss so any help/advice would be most appreciated.

Thanks,

Bob in TN

mcgivor · April 2020

Welcome to the forum Bob

Since you've proved to yourself that the generator is not needed, the best thing would be to disconnect the AGS and run it manually if required. The added complexity increases the possibility of something going wrong and when something dose go wrong, it has an uncanny way of doing so when there is nobody there.

AGS should only be used for critical backup with complete monitoring including communication to notify the operator of any faults along with run notification.

TNBob · April 2020

McGivor,

First, thanks for the welcome and I'm very pleased to be here. I've been scratching my head a lot on this DIY journey and this forum seems like it will be a tremendous resource so I thank you and all the many other active and knowledgeable members for sharing your knowledge.

Regarding your very practical suggestion, that's exactly what I did when we weren't in full time residence (though I just disabled the AGS rather than removed it).

However, things are changing. We're here full time now because of the COVID thing but that really just sped up a previously planned time table of events. We always intended to move here full time eventually anyway. Likewise, our two sons and their families will be in mostly full time residence beginning over the next year or so. We have a nice 'cushion' now but as we add full time residents (not all of whom are 'power conscious') I anticipate usage increasing and I do foresee an eventual need for the AGS. Obviously, I can always 'work around' it but I did pay for the dang thing so I'd like to see it work.

stillchillin · April 2020

Hi Bob have the same invertor with the AGS, I have the setpoints different than you and have not had any issues. I will agree that the manual is a bit confusing. I have the generator come on at 65% and off at 90%. I also have the generator come on at 47.5 volts and off at 53.7 volts. You do have a fairly small battery bank for all that invertor and a larger load say a coffee maker can drop the voltage considerably. Try changing your setpoints. I would be happy to discuss setpoints with you if you need more help. Good luck, Stillchillin

mcgivor · April 2020

stillchillin said:

Hi Bob have the same invertor with the AGS, I have the setpoints different than you and have not had any issues. I will agree that the manual is a bit confusing. I have the generator come on at 65% and off at 90%. I also have the generator come on at 47.5 volts and off at 53.7 volts. You do have a fairly small battery bank for all that invertor and a larger load say a coffee maker can drop the voltage considerably. Try changing your setpoints. I would be happy to discuss setpoints with you if you need more help. Good luck, Stillchillin

Don't think a coffee maker would drop the voltage by 1mvV of a 17.5 Kw LiFePo4 bank. ...... you may have missed that part, 5 × 3.5 kw

softdown · April 2020

Perhaps I misunderstood. This is how I read things: 50.2 volts is 80% of battery capacity as opposed to "20%". 12.55 volts/battery. Most of us reach that before the sun comes up. So your genset turns on and quickly charges them up to 53.5 volts. "The problem is the generator stops after 15 or 20 minutes EVERY time" I'm thinking it runs until the batteries register a surface charge of 53.5 volts - then shuts off. It would need to continue charging them for another couple hours to get a truly full charge,

By comparison stillchillin has a start point of 47.5 volts.11.87 volts/battery. That is still a pretty aggressive intervention point for the genset to kick in. One could hit that while running the microwave or well pump if the batteries were somewhat depleted.

Again, perhaps I misread things but I'll persevere nonetheless because, well, why not? I'd set the genset auto. on at ~ 46 volts. Or 11.5 volts/battery. Then consider having it shut down around 53.5 volts. It would run for a few hours at an interval closer to a couple times a year or so.

Is there another way to "make it exercise" once/month or so? If not one could devise a suitable intervention value - maybe ~ 49 volts or so.

I hope it is this simple.

mcgivor · April 2020

@TNBob What charge current is being used and where is the reading for the cut in/out voltage being taken from? The reason I ask is because if the voltage is measured at the inverter side as opposed to the battery side, there may be voltage drop sufficient enough to cause short cycling. The voltage drop would be greater at higher currents, the target of 53.5V is 3.343 volts per cell, if there were for example a 1 volt drop the charging would stop at 3.281 volts per cell, which may see insignificant bt that represents a huge part of the overall capacity on a LiFePo4 bank.

The 53.5V is very conservative and below the Simpliphi 10K cycle warranty recommend value of 54.8V or 3.425 VPC, with Outback equipment. Was the installation done by yourself or others?

TNBob · April 2020

First, thanks to all for the feedback/comments. In the interest of efficiency I'll combine responses in this reply as follows:

stillchillin said:

You do have a fairly small battery bank for all that invertor and a larger load say a coffee maker can drop the voltage considerably. Try changing your setpoints. I would be happy to discuss setpoints with you if you need more help. Good luck, Stillchillin

stillchillin - Agree that set points might be the problem but as mcgiver pointed out, it's a 17.5 Kw LiFePo bank (48 VDC)

softdown said:

Perhaps I misunderstood. This is how I read things: 50.2 volts is 80% of battery capacity as opposed to "20%".

Is there another way to "make it exercise" once/month or so? If not one could devise a suitable intervention value - maybe ~ 49 volts or so.

softdown - More likely I did a poor job of describing the system. As I read your post, it sounds like I gave you the impression the battery bank is 5 - 12 Volt batteries connected in series. However, the battery bank consists of 5 - Simpliphi 3.5 kw LiFePo batteries each rated at 48 volts and connected to the system in parallel (not series) via cables of the same length (Simpliphi is anal about that). The Simpliphi data indicates 50.2 volts as a 20% charge and 55.6 volts as a 100% charge.

Also, with us now in full time residence, the 'exercise' is no longer an issue as I can just set a schedule and exercise the generator manually.

mcgivor said:

@TNBob What charge current is being used and where is the reading for the cut in/out voltage being taken from? The reason I ask is because if the voltage is measured at the inverter side as opposed to the battery side, there may be voltage drop sufficient enough to cause short cycling. The voltage drop would be greater at higher currents, the target of 53.5V is 3.343 volts per cell, if there were for example a 1 volt drop the charging would stop at 3.281 volts per cell, which may see insignificant bt that represents a huge part of the overall capacity on a LiFePo4 bank.

The 53.5V is very conservative and below the Simpliphi 10K cycle warranty recommend value of 54.8V or 3.425 VPC, with Outback equipment. Was the installation done by yourself or others?

mcgivor - I bought this system pretty much in a 'plug and play' configuration from Wholesale Solar, with the 'Power Center' already built containing the two 4400 inverters and two Midnight Classic 150 charge controllers pre-wired and with the ME-ARTR Advanced Router (to make it all play nice together) already installed. The ME-ARTR is the control interface and I'm not actually sure where the various inputs are being measured. When I measure voltage I'm doing it with a digital voltmeter right at the battery bank.

That said, when the 'home screen' is up on the router it displays voltage and amperage in/out of the battery bank. As memory serves, when the generator is running/charging that's around 45 to 60 amps (off the top of my head - that may be wrong).

However, the way the system is set up, it monitors power to/from the battery and calculates SOC based on Ah-in/Ah-out of the battery bank. And since the source of that charging power can be either via the charge controllers (solar array) or the generator (via the charger built into the inverter), it would seem only logical that the measurement would be done at the common point, i.e. the battery side. (That's an assumption, it seems logical but it may be wrong. I'll see what I can dig out of the technical docs.)

I get what you're saying about short cycling. The thing is, when you set both the 'generator start' and 'generator stop' voltage values via the ME-ARTR router, you also program in a 'delay time' to guard against nuisance start/stops. I have them both set at 5 minutes. Therefore the genny should not start until the battery bank has been below 50.2 volts for longer than 5 minutes. Likewise the genny should continue to run/charge until a voltage of 53.5 or greater has been maintained for 5 minutes. Is this what you're talking about or have I misunderstood your point?

That said, I've certainly got nothing to lose by raising the 'stop generator' point. I haven't tried it so far because I reasoned that if the genny was already stopping before it hit the current stop point, raising that point even higher seemed somewhat counter-intuitive.

As far as why I set the 'stop generator' set point at the conservative value of 53.5V, that was actually based on some advice I got from a video on the Wholesale Solar site. The reasoning was thus:

1. The genny will kick in to charge the battery bank at some time of no (or limited) sunlight but you can't really predict when that will be. If it turns out to be 4 AM in the early hours of a sunny day and your genny charges your battery bank to full capacity just as the sun rises, you'll have likely burned fuel for nothing. Rather the more sensible strategy would be to try to find the 'sweet spot' where your genny charged the battery bank sufficiently to carry you to the next sunny period without wasting fuel. That was the logic I was using for the 'stop generator' setting and it was experimental.

2. From a practical standpoint, since this occurs so rarely in my case anyway, I don't think it makes much difference. If I had a much smaller battery bank and the generator was cycling on regularly to satisfy additional demand, that would be one thing but for now I think I can ignore that advice. At this point I'm far more concerned with the generator actually reaching the programmed 'stop generator' set point. I'll certainly give the higher set point a try.

Also, in regard to your final question, yes I installed the system myself, though I did hire out installation of the panels on the barn roof. I hated heights when I was 20 and that hasn't gotten any better in the 50 years since, though I did go up to supervise the wiring connections LOL.

I'm a retired marine engineer (ocean going ships) which means I'm a jack of all trades and semi-competent in one or two. I can usually figure most things out given a tech manual. That said, electrical and control systems are absolutely where I'm weakest, so make no assumptions about my competence there. I typically invest a lot of time trying to figure out where I might likely kill myself or someone else, then invest an equal amount of time ensuring I don't do any of those dumb ass things. Beyond that, the list of things I don't know is likely much longer than the list of things I know. If it appears I may be overlooking something you think is basic, don't hesitate to point that out. I will be grateful and not irritated.

TNBob · April 2020

Hey Guys,

Just an update. Before experimenting with the upper set point on the battery voltage, I decided to try the auto start feature based on SOC parameter. I had been using VDC before instead of SOC because I reasoned VDC was a better choice as it was actually a 'measured' parameter instead of 'calculated' as is SOC, and thus (I thought) a more accurate parameter on which to base generator starting. Turns out I may have been 'over thinking' that a bit. I set up the AGS to come on and off based on SOC and then turned off the solar panel input to test how it would behave and the genny turned on/off and maintained SOC between the chosen levels as advertised, so problem solved.

It still bugs me a bit that I wasn't able to figure out the problem the AGS was having with the VDC parameter, but that's something to contemplate for another day. Thanks to all for the feedback.

Bob

mcgivor · April 2020

The problem with using voltage is, as previously stated, depends where the reading is taken, if at the inverter, it wouldn't take into account the voltage drop between it and the battery. Larger current values will increase the voltage drop, since LiFePo4 accept the maximum available until the target is reached, the actual battery voltage could be significantly lower.

This phenomenon nay not have such a significant impact when using lead acid because the current tapers down in the absorption stage, thus offsetting the voltage drop, then again voltage, in and of itself, is a poor indication of state of charge. Having said that even battery monitors tend to drift, requiring a periodic reset to zero when fully charged charged, as they too, are not 100% accurate.

Personally I don't use AGS as I've no need for generator charging, but if I did I wouldn't, simply because there are too many things that could potentially go wrong Monitoring trends on a regular basis provides insight into what is going on with your system, my advice, for what it's worth is perform manual control, particularly if on site, it will result in less dissapointment, this coming from someone who spent decades devoted to automation, outside of solar though with much more sophisticated applications, but did include commercial standby power generation.

The generators were integrated with the central fire alarm/security monitoring, a 24/7 service with 3 modes of communication, land line, cellular and Internet, with maintenance staff on duty to respond to any faults should they arise. Understandably you want to get value for the money spent and include the AGS, but use this feature as a last resort, just my opinion, others may vary.

AGS Problems

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