Flexmax 60 ovrcurrent

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Andy Brooks
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Flexmax 60 ovrcurrent

Post by Andy Brooks »

Hi, my flexmax 60 is showing "ovrcurrent" in the screen, found some information on the forum on how to test it saying to dissconnect the panels and see what the input voltage says, after a few seconds the input voltage rises to 16volts, approx 75% of the system voltage of 24volts, according to the information I found this means the charger is not damaged and I should press the "rstart" in the "misc" menu, done this but still the same, "wake up" a few seconds then "ovrcurrent" clicks off, then repeats the cycle continuously, any help appreciated,
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Re: Flexmax 60 ovrcurrent

Post by raysun »

What is the array wattage?
Andy Brooks
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Re: Flexmax 60 ovrcurrent

Post by Andy Brooks »

Hi, There was 9 x 450s connected for ages with no problems, then this fault occurred and so now I'm trying it with only 3 x 175, regards
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Re: Flexmax 60 ovrcurrent

Post by raysun »

Andy Brooks wrote: Sat Sep 09, 2023 5:58 am Hi, There was 9 x 450s connected for ages with no problems, then this fault occurred and so now I'm trying it with only 3 x 175, regards
For array wattage:
9 × 450W = 4050W @ STC
The FM60 @ 24V: 60A × 24V = 1440W

That the FM60 experienced an overcurrent error is not surprising. That it's survived to tell the tale is surprising.

However, I'm confused. Your profile lists a 48V inverter and FM80. Can you confirm the actual setup?
Andy Brooks
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Re: Flexmax 60 ovrcurrent

Post by Andy Brooks »

Hi, yes I have 2, 48v systems, a 80 amp charger and this one with a 60 amp, the 9 panels are 6 facing directly south for the midday sun and 3 facing south west for afternoon / evening sun, I cant remember if the panels are 400w or 450w, but I can say it was working ok this way for quite some time before this problem occured, many thanks for your help. Meant to say the panels are connected in strings of 3's,
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Re: Flexmax 60 ovrcurrent

Post by SandyP »

Andy Brooks wrote: Sun Sep 10, 2023 11:35 pm ../..this one with a 60 amp, the 9 panels are 6 facing directly south for the midday sun and 3 facing south west for afternoon / evening sun../..
So even with the system voltage of 48V, as @raysun mentioned, the solar array you have can output more than the FM60 is rated for. If the panels are 400W each then potentially the 9 panel array could output ~75amps however as the array is split into 2 directions and angles/orientations are unlikely to be optimal then maybe this is why you have not encountered the overcurrent error previously. I would disconnect the string of 3 facing SW panels and see if the error recurs.
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Re: Flexmax 60 ovrcurrent

Post by 706jim »

My system has the panels split between southeast and southwest exposure. I believe this reduces the maximum surge of power and it has kept my FM80 within its current limits. Should be the case with your FM60 too.
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Re: Flexmax 60 ovrcurrent

Post by SandyP »

706jim wrote: Fri Sep 22, 2023 8:06 am .../.. reduces the maximum surge of power and it has kept my FM80 within its current limits. Should be the case with your FM60 too.
The other option to "protect" your FM60/80 from overcurrent is to change the maximum output from the default 60 or 80 amps to 2 or 3 amps below the maximum.
Last edited by SandyP on Tue Sep 26, 2023 1:47 am, edited 1 time in total.
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Andy Brooks
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Re: Flexmax 60 ovrcurrent

Post by Andy Brooks »

Hi, thanks loads, that could be the case, to try this I've disconnected all the panels and connected only 3 of 175w panel in series, but still cant get the unit to reset, tried, r'start' in the 'mics' menu but still doing the same, 'wake up'.... then straight to 'ovrcurrent' for 5 seconds, shots off, then 'wakeup' and continues to cycle the same, any ideas would be greatly appreciated, many thanks.
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Re: Flexmax 60 ovrcurrent

Post by SandyP »

Andy Brooks wrote: Tue Sep 26, 2023 12:43 am ....\.. still doing the same, 'wake up'.... then straight to 'ovrcurrent' for 5 seconds, shots off, then 'wakeup' and continues to cycle the same, any ideas would be greatly appreciated, many thanks.
I suggest contacting Outback support as it may have been 'fried' by the initial overcurrent event.
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Re: Flexmax 60 ovrcurrent

Post by Andy Brooks »

Ok, will do, thanks, give it a try,
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Re: Flexmax 60 ovrcurrent

Post by PaulN. »

SandyP wrote: Fri Sep 22, 2023 8:06 pm
706jim wrote: Fri Sep 22, 2023 8:06 am .../.. reduces the maximum surge of power and it has kept my FM80 within its current limits. Should be the case with your FM60 too.
The other option to "protect" your FM60/80 from overcurrent is to change the maximum output from the default 60 or 80 amps to 2 or 3 amps below the maximum.
Hello. I bought 30 each 24v 250 watts used solar panels last year after a hail storm broke three of my previous panels. I have 6 old panels on my Mx-60 and 8 of the 30 panels on my Mx-80 Flexmax wired for a nominal 48v from the panels powering my 24v lead acid battery bank/ 4024 Trace. We usually have lots of sun and are usually fully charged before noon. However, we will get a series of 2-3 days of overcast skies with production of < 2KwHrs, but consume perhaps 4KwHrs per day. I'd love to take the 22 panels that aren't in use to boost my production on overcast days. If I set the Mx-80 to a max of 75 amps but hooked up all 30 250 watt panels, 7500 watts at 48 volts, capable of 160 amps, would the Mx-80 protect itself by dropping the amps to 75? I have power to burn on sunny days and don't mind the power loss then, but having three times the power on cloudy days would save my running the generator. Otherwise, is there a diversion load of some sort that could be put prior the charge controller to allow me cloudy day production but limit amps to the Mx-80 on sunny days? Thanks, Paul
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Re: Flexmax 60 ovrcurrent

Post by SandyP »

PaulN. wrote: Wed Oct 25, 2023 12:59 pm ../.. If I set the Mx-80 to a max of 75 amps but hooked up all 30 250 watt panels, 7500 watts at 48 volts, capable of 160 amps, would the Mx-80 protect itself by dropping the amps to 75? ../..
I am walking back my comment that lowering the maximum output current will "protect" your charge controller when connected to an oversized array as other issues relating to the input (and FM chip reaction delay) may result in damage to the charge controller.

Have a read of this : https://atl.my.site.com/OutbackKnowledg ... on-feature

In your case, for 100% confidence, I would be getting a second FM80 and splitting the solar array into two parts each going to their own FM80.
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Re: Flexmax 60 ovrcurrent

Post by SandyP »

SandyP wrote: Thu Oct 26, 2023 5:34 pm Have a read of this : https://atl.my.site.com/OutbackKnowledg ... on-feature
It is interesting to note this from the Outback Knowledge Base article:

"2. Hardware Limitation
Nominal value of the hardware over current is approximately 113 Amps. "

And this seems to apply for the FM60,80 and Extreme series.
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Re: Flexmax 60 ovrcurrent

Post by raysun »

SandyP wrote: Wed Nov 01, 2023 11:15 pm
SandyP wrote: Thu Oct 26, 2023 5:34 pm Have a read of this : https://atl.my.site.com/OutbackKnowledg ... on-feature
It is interesting to note this from the Outback Knowledge Base article:

"2. Hardware Limitation
Nominal value of the hardware over current is approximately 113 Amps. "

And this seems to apply for the FM60,80 and Extreme series.
2. Hardware Limitation
Nominal value of the hardware over current is approximately 113 Amps.
When the hardware limit is reached the FETs turn off until the processor cycle is complete. When the FETs are switched off all charging stops. The FETs will turn back on with the next processor cycle. They will continue to turn on/off until the PV current is reduced.
3. MPPT vs. PWM
If the array harvest exceeds the maximum programmed current the FM will cease MPPT tracking and start a PWM (pulse width modulated) duty cycle. In most situations this should lower the charge current. if it is still over the limit the controller will continue to take similar steps until current falls below the programmed maximum.
Once current is acceptable the charge controller will go back to MPPT mode.
That is interesting, indeed. It would seem the FMs have a form of overcurrent protection, as well as "current shaving" (via PWM). The former doesn't specify where the "hardware overcurrent" would be (input or output), but I'm assuming its on the input side. The latter sounds like it may be a bit "slow" in limiting, and aligns with several accounts of the controllers overshooting their current limit settings.
I'd be interested in seeing experimental results from testing the overcurrent functions, but don't think I'll carry them out on my controllers and battery. :wink:
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Re: Flexmax 60 ovrcurrent

Post by SandyP »

raysun wrote: Thu Nov 02, 2023 10:15 am ../..
That is interesting, indeed. It would seem the FMs have a form of overcurrent protection, as well as "current shaving" (via PWM). The former doesn't specify where the "hardware overcurrent" would be (input or output), but I'm assuming its on the input side. The latter sounds like it may be a bit "slow" in limiting, and aligns with several accounts of the controllers overshooting their current limit settings.
I'd be interested in seeing experimental results from testing the overcurrent functions, but don't think I'll carry them out on my controllers and battery. :wink:
As you say, even with the current limit set lower than maximum, the FMs do record 'peak Amp' outputs in excess of the limit set and higher than their labeled maximum :sad:
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Re: Flexmax 60 ovrcurrent

Post by raysun »

As you say, even with the current limit set lower than maximum, the FMs do record 'peak Amp' outputs in excess of the limit set and higher than their labeled maximum :sad:
Thanks for confirming that. I had my suspicions, but never kept an oversided array large deployed long enough to test the throttling response. I did put up a 4400W array, and within an hour, conditions drove it to 4700W. That was enough to sober me right up, so I removed two panels that were slated for a second array anyway. The Current Limit was set to 80A, and I didn't have any idea if that was a hard limit, but it didn't behave as such. I didn't think to try a lower Current Limit, but figured the over-power condition by itself was no bueno.
The microcontroller in the FMs isn't particularly high-speed, and I think that shows up in momentary Current Limit overshoot when conditions call for throttling. I've always feared controller latency coupled with an array over-power condition could be a recipe for circuit breaker tripping, if not outright damage.
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Re: Flexmax 60 ovrcurrent

Post by SandyP »

raysun wrote: Mon Nov 06, 2023 11:42 am ../..
The microcontroller in the FMs isn't particularly high-speed, and I think that shows up in momentary Current Limit overshoot when conditions call for throttling. I've always feared controller latency coupled with an array over-power condition could be a recipe for circuit breaker tripping, if not outright damage.
One day when it is partly cloudy I will change the Victron BMV to log the current going to the battery per second to see if I can see how long these overcurrent events last.

Looking at the log of the FM60 it shows the following over a couple of weeks:

085Vp, 81.1Ap, Max V 30.3, Min V 23.5
088Vp, 64.5Ap, Max V 28.9, Min V 23.3
088Vp, 73.8Ap, Max V 31.4, Min V 23.7
088Vp, 77.9Ap, Max V 32.4, Min V 22.7
087Vp, 76.3Ap, Max V 31.0, Min V 23.3

None of the over amp figures show up in the per Minute Victron Log.
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Re: Flexmax 60 ovrcurrent

Post by SandyP »

raysun wrote: Thu Nov 02, 2023 10:15 am ../..
I'd be interested in seeing experimental results from testing the overcurrent functions, but don't think I'll carry them out on my controllers and battery. :wink:
Here is a graph showing how the FM60 clips/limits its output when the max charge current setting is lowered from the default of 60Adc.
I have ours set at 55Adc and there is a constant house load of ~3.5Adc
BMV_Thu28Mar24.jpg
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