Flexmax80 overvoltage

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Flexmax80 overvoltage

Postby bksumner on Sat Jun 04, 2011 10:44 am

Our inverter has twice shut itself off due to voltage in excess of 16VDC. The Flexmax80 stats page says that it has produced 16.1VDC. All the set points are at factory default and there is no equalization cycle programmed. Why would the charge controller send out this much voltage and how can i stop it? Every time it does this the fridge is lost and my beer gets warm.
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Re: Flexmax80 overvoltage

Postby petertearai on Mon Jun 06, 2011 1:14 am

Hi my fm80 also reports an over voltage 15.1 to 15.3 in the stats on regular basis.Because I don't have a Flexnet and hub and mate I cant see the duration of the over voltage. My system is often 1 to 2 weeks with no load so I suspect it may be something to do with that.
In your situation I would be tempted to do a factory reset an see how that goes.
The software level may be of use to some of the more experienced users of this forum.
Regards Peter
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Re: Flexmax80 overvoltage

Postby tallgirl on Mon Jun 06, 2011 8:41 am

bksumner wrote:Our inverter has twice shut itself off due to voltage in excess of 16VDC. The Flexmax80 stats page says that it has produced 16.1VDC. All the set points are at factory default and there is no equalization cycle programmed. Why would the charge controller send out this much voltage and how can i stop it? Every time it does this the fridge is lost and my beer gets warm.


High current and high state of charge. Voltage rises very rapidly when a full battery has even a moderate amount of current applied, and this is especially true for both AGM and Gel batteries.

Xantrex inverters are notoriously sensitive to short high-voltage transients, which for 16 volts is entirely too low anyway, due to high equalization and temperature compensation voltages.
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Re: Flexmax80 overvoltage

Postby Kent Osterberg on Mon Jun 06, 2011 9:01 pm

When the charge controller periodically sweeps to find the PV array maximum power point, it briefly quits regulating the output voltage. If the battery is nearly full, the voltage can rise quite quickly. AGM batteries with relatively large PV arrays are particularly susceptible. The duration of the high voltage is not long enough to harm the batteries, but the high voltage protection of some inverters is so low that it causes problems.

The possible solutions are not very pleasant: 1) Replace the inverter with one that is tolerant of higher dc voltage. 2) Try a different brand of charge controller that behaves differently - it might take two to accomplish what you are doing with the FM80. 3) Split the PV array into two separate sub arrays with their own charge controllers so only half as much current is involved in the MPPT sweep.
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Re: Flexmax80 overvoltage

Postby petertearai on Mon Jun 06, 2011 10:49 pm

Kent ,Thanks for that explanation,I think it may explain my situation.
Regards Peter
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Re: Flexmax80 overvoltage

Postby Gordon-Loomberah on Tue Jun 07, 2011 12:32 am

Here is what one of these voltage excursions looks like, from my Graphtec data logger (@ 1 sec sampling). This was the highest voltage peak in the past 18 days, typically the daily peaks are around 30.0-30.5V on a good charging day. With my Latronics inverter, which will handle 34V input, this is no problem at all.

Apart from Kent's suggestions, I would suggest an easier solution, using M brand relay driver. Just set it to bring in a large load if the voltage exceeds say 15V, then your inverter should not cut out at all.
Attachments
Vpeak.gif
Blue: Battery Volts, Red: load Amps, Green: FM80 Amps, Pink: SB50 Amps
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Re: Flexmax80 overvoltage

Postby Kent Osterberg on Tue Jun 07, 2011 7:29 am

Very nice data presentation! It looks like the 945-watt array is on a separate charge controller, is that right? One thing to be aware of is that with 1-second sampling of a peak voltage event that is less than 5 seconds long, the actual peak voltages are probably not being sampled - the peak voltage is probably a little higher than the data indicate.

I like the idea of using the Morningstar relay driver to turn on a diversion load temporarily. I think it is fast enough provided the time delays are set to zero. The power handled, just briefly, is approximately the peak array output power, so it'll need to be a substantial load.

Seems like the charge controller should be designed so this problem doesn't happen. The voltage rise is an indication that maximum power cannot be accepted by the battery. The sweep should terminate rather than allowing the output voltage to rise.
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Re: Flexmax80 overvoltage

Postby Gordon-Loomberah on Tue Jun 07, 2011 3:52 pm

Kent Osterberg wrote:Very nice data presentation! It looks like the 945-watt array is on a separate charge controller, is that right?


Thanks :) Yes, the 945W array is a mix of older panels I accumulated over the years, with various Vmp including two 220W Solarfun panels with Vmp of 30V, the other 3 are Vmp ~36V. A 200W WTG is also connected, but decent wind is rare here. The controller is a BlueSky SB50.


One thing to be aware of is that with 1-second sampling of a peak voltage event that is less than 5 seconds long, the actual peak voltages are probably not being sampled - the peak voltage is probably a little higher than the data indicate.


Yes, I realise the sampling can miss the brief peaks, the FM80 recorded a 31.7V peak that day. I could use 100ms sampling, but I'd be filling my HD at 10X the rate :shock:

Still, I dont see a 5 second excursion to 0.7V over the EQ voltage to be a problem at all!
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Re: Flexmax80 overvoltage

Postby sparky on Wed Jun 08, 2011 6:13 am

Nice Gordon!

I am hoping you can make time for a friend of mine down your way and do some e-commerce with another 2kw tracker. The ones I have been using 2 years ago went to an extrusion for the panels and it has really sped up the install time.
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Re: Flexmax80 overvoltage

Postby petertearai on Sun Aug 21, 2011 1:17 am

Up at my holiday house at weekend and inverter started to beep over voltage.Looked at the fm80 and it showed 42 volts in and cycling out 13.9 to 16volts out and up to 50 amps. This continued on a 5 second cycle.It was in the floating mode at the time .Watching it, it briefly said tracking then floating then back to float, then back to the cycling up and down from 13.9 to 16 volts.
I then started the 800 watt vacume , the output then settled down to 13.9 volts 60 amps and 850 wattts, full sun. After that it settled down.
Software 001.009.008

Will a newer software level sort this out.

When I check the history -1day max volts 15.4 min volts 12.6 abs .26 float 9.4
-2 day max volts 16.0 min volts 12.6 abs .45 float 8.45
And so on in a similar vane.
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Re: Flexmax80 overvoltage

Postby petertearai on Tue Aug 30, 2011 6:06 pm

Took my fm80 back to the dealer , they have replaced a board. Will connect back this weekend.
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Re: Flexmax80 overvoltage

Postby blackswan555 on Wed Aug 31, 2011 1:23 am

Not seen this one myself so I may be way off :roll:
How about using the FM`s AUX relay system to switch a mains load in @ v eg oil filled heater ?
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Re: Flexmax80 overvoltage

Postby petertearai on Sun Sep 11, 2011 12:28 am

FM80 back installed a week ago. Went up and checked it this weekend. All good, max voltage each day 14.8 , Absorb set to 14.5 but rts probably taking it up to 14.8 .
Every day the same so all good.
Firmware was upgraded to 2.00.00. Also I think a board.. All good .Great warenty service .
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