Lexmax 60. What happen when input watts are exceeded

Discussion about the FM100, FM80, and FM60 Charge Controllers

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sirfuzzy
Forum Junior Member
Posts: 2
Joined: Mon Jan 11, 2021 3:20 am
My RE system: Conext SW 2524
FlexMax 60
Eight(8) trinia 285w modules
six(6) outback energycell 106NC (12x2)x3

Lexmax 60. What happen when input watts are exceeded

Post by sirfuzzy »

Hi,
I am new to this forum. I am a DIY solar installer. This is my first time touching Outback equipment.
I was called in to look at an off-grid system as the owner was noticing a drop in system performance. Unfortunately, he could not locate the user manuals.

the system is
8 trina 285w poly. Arranged as 4 strings of 2 modules each
1 Midnitesolar combiner box
1 Flexmax 60A CC @24vdc
1 Conext 2524 inverter
6 Outback energycell 106NC battery (12vdc x 2)x3

The literature says that the FM60 maximum solar wattage@ 24vdc is 1500w. This system at the peak may supply 2280w.

Q1. What does FM60 do when it receives input wattage greater than the 1500w.
Does the CC shutdown; does it dump the excess energy; etc

When I tested the voltage on the 6 batteries four(4) of them were 13.5vdc to 13.7vdc, however, a connected pair that made the 24v bank had individual readings of 12.7v and 15.1v, and the battery with the 15.1v was a little warmer to the touch than the others. The owner said the batteries are four(4) years old at the least.
I have noticed some build-up on the connections on all the battery poles, but the levels are different at each pole.

Q2. The 15.1v reading and 12.5v reading are odd in my opinion. What can I do or have done to confirm my suspicions?

Any feedback or possible solutions will be appreciated.
fcwlp
Forum Czar
Posts: 732
Joined: Wed Jan 22, 2020 9:40 am
My RE system: GS8048A, FM80 w/3,600W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed.

I install and maintain grid-tied and off-grid systems in my area and consult on solar system design/operation.
Location: 80 miles NE of Phoenix at 5500'

Re: Lexmax 60. What happen when input watts are exceeded

Post by fcwlp »

sirfuzzy wrote: Mon Jan 11, 2021 3:54 am Q1. What does FM60 do when it receives input wattage greater than the 1500w.
Does the CC shutdown; does it dump the excess energy; etc
If system is in bulk charge mode (max current to battery) it will attempt to limit the current to 60A output. Second line of defense is a "hopefully" a 60A breaker on the CC output. As bulk charge is usually in the morning, the 2,280W of PV are at STC, and the FM60 has not blown up yet, system is probably o'k.
sirfuzzy wrote: Mon Jan 11, 2021 3:54 am Q2. The 15.1v reading and 12.5v reading are odd in my opinion. What can I do or have done to confirm my suspicions?
Not much. Time to budget for some new batteries. You may have to take that string out of the system in the interim. Most of the current is going in and out of that string causing the one battery to heat up.
raysun
Forum Emperor
Posts: 4104
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Lexmax 60. What happen when input watts are exceeded

Post by raysun »

sirfuzzy wrote: Mon Jan 11, 2021 3:54 am Hi,
I am new to this forum. I am a DIY solar installer. This is my first time touching Outback equipment.
I was called in to look at an off-grid system as the owner was noticing a drop in system performance. Unfortunately, he could not locate the user manuals.

the system is
8 trina 285w poly. Arranged as 4 strings of 2 modules each
1 Midnitesolar combiner box
1 Flexmax 60A CC @24vdc
1 Conext 2524 inverter
6 Outback energycell 106NC battery (12vdc x 2)x3

The literature says that the FM60 maximum solar wattage@ 24vdc is 1500w. This system at the peak may supply 2280w.

Q1. What does FM60 do when it receives input wattage greater than the 1500w.
Does the CC shutdown; does it dump the excess energy; etc

When I tested the voltage on the 6 batteries four(4) of them were 13.5vdc to 13.7vdc, however, a connected pair that made the 24v bank had individual readings of 12.7v and 15.1v, and the battery with the 15.1v was a little warmer to the touch than the others. The owner said the batteries are four(4) years old at the least.
I have noticed some build-up on the connections on all the battery poles, but the levels are different at each pole.

Q2. The 15.1v reading and 12.5v reading are odd in my opinion. What can I do or have done to confirm my suspicions?

Any feedback or possible solutions will be appreciated.
The FlexMax60 is rated at 60A maximum charging current. For a 24V system the nominal array power that can be accepted is 24V x 60A = 1440W.

Exceeding the array limit may lead to one of two outcomes:
#1 The excess power is dissipated in the controller's circuitry damaging components from overheat.
#2 The unit loses control of the conversion process and dumps the raw input to the battery.

Hopefully, there is a 60A circuit breaker between the charge controller and the battery bank. In the event of an overload, it may open quickly enough to protect the battery.
sirfuzzy
Forum Junior Member
Posts: 2
Joined: Mon Jan 11, 2021 3:20 am
My RE system: Conext SW 2524
FlexMax 60
Eight(8) trinia 285w modules
six(6) outback energycell 106NC (12x2)x3

Re: Lexmax 60. What happen when input watts are exceeded

Post by sirfuzzy »

Thanks for the feedback.

Regarding the thought that the Flexmax CC has gotten damaged due to possible overheating etc. What do I look for regarding the performance or non-performance of the CC itself?

Are they any tests that I can perform with a multi-meter for example that will confirm any of the two scenarios?
raysun
Forum Emperor
Posts: 4104
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Lexmax 60. What happen when input watts are exceeded

Post by raysun »

Here is a simple diagnostic for controller health:
viewtopic.php?f=29&t=14942
fcwlp
Forum Czar
Posts: 732
Joined: Wed Jan 22, 2020 9:40 am
My RE system: GS8048A, FM80 w/3,600W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed.

I install and maintain grid-tied and off-grid systems in my area and consult on solar system design/operation.
Location: 80 miles NE of Phoenix at 5500'

Re: Lexmax 60. What happen when input watts are exceeded

Post by fcwlp »

@raysun's post is a good diagnostic if the unit is not working at all.

A "wounded" electronic device, whether a CC or something else is difficult to test and quantify.

On the FM60 you can view the "Charge Controller Stats" and see what the historical maximum wattage was (MaxWatt). Look at p.55 & 76 of current manual.
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