Bypass Battery Temperature Sensor and TempComp on Flexmax 100 afci

Discussion about the FM100 AFCI Charge Controller
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mattyxp@yahoo.com
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My RE system: Mate3s
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Bypass Battery Temperature Sensor and TempComp on Flexmax 100 afci

Post by mattyxp@yahoo.com »

Hi All,

If you have a Mate3s and Flexmax 100 charge controllers and need to bypass the Battery Temperature Sensor (BTS) and Battery Charging Temperature Compensation for any reason and unplugging the BTS sensor from the Flexmax 100 BTS port/jack does not work to turn off the battery temperature reading on the Mate3s, then here is how to fake out the Mate3s correctly and easily so that the Flexmax 100 battery charging temperature compensation is effectively turned off:

***I had to do this because even with my BTS sensor unplugged from the Flexmax 100 BTS port/jack, my Mate3s still was reading/detecting "ghost" temperature signals between 32 degrees F and 450 degrees F even with the BTS sensor unplugged, which Outback can not explain and/or is not willing to fix with a way to permanently disable battery charging temperature compensation for those of us using lithium batteries who obviously need to disable battery charging temperature compensation.

***You'll need to purchase a RJ11 Screw Terminal...I purchased this one that worked great from Amazon:
https://www.amazon.com/AAOTOKK-Terminal ... 886&sr=8-1

- The Battery Temperature Sensor (BTS) ohms at 10,120ohms when the temperature is at 25 degrees Celsius (77 degrees Fahrenheit).
- Pins 1 & 2 and pins 3 &4 are tied together on the BTS sensor port/jack of the Flexmax 100 charge controller.
- Simply solder a 10kohm resistor and a 120ohm resistor together in series and then put one leg in either pin 1 or 2 and put the other leg in either pin 3 or 4 of the RJ11 Screw Terminal. I used 1w resistors but understand that any watt resistor is fine. Make sure to cover any metal on the exposed resistors with electrical tape to prevent any shorting, etc.
- Plug the RJ11 Screw Terminal with the resistors attached into the BTS port/jack in one of the Flexmax 100 charge controllers.
- That's it and the Mate3s will now read a constant 25 degrees Celsius (77 degrees Fahrenheit).
- With the Mate3s now reading a constant/steady 25 degrees Celsius from the BTS port/jack on one of the Flexmax 100 charge controllers, the Flexmax 100 battery charging temperature compensation will be effectively disabled. This is perfect for lithium battery charging with no battery charging temperature compensation.

For my Simpliphi 48v 3.8kwh lithium batteries, I have set the FLexmax 100 Battery Charging Temperature Compensation settings as follows:
Battery Temp Comp Range: Limited (until Outback Power makes way to turn off Temp Comp completely)
Limited: Lower Battery Voltage: 54 VDC (Charge Controller Float setting)
Limited: Upper Battery Voltage: 56 VDC (Inverter Absorb setting...charge controller setting will be .4v higher)
Temperature Comp Slope: 2 mV/C (set to lowest until Outback Power makes turning
off Temp Comp possible, set to 0 if ever possible)

So, with the BTS sensor port on the Flexmax 100 charge controller always being at a steady 25 degree Celsius, the battery charging temperature compensation will always be automatically offset by 0v...perfect for lithium battery charging...effectively no battery charging temperature compensation.

I hope this helps anyone who needs a way around this stupid issue that could be easily fixed by Outback just having an actual on/off setting for battery charging temperature compensation for all of us using lithium batteries with our systems.

Matt :)
Last edited by mattyxp@yahoo.com on Sun Apr 04, 2021 10:02 am, edited 1 time in total.
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Re: Bypass Battery Temperature Sensor and TempComp on Flexmax 100 afci

Post by fcwlp »

Thanks for documenting the work around.
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Re: Bypass Battery Temperature Sensor and TempComp on Flexmax 100 afci

Post by sodamo »

So would this work with other components?
David
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Mike Curran
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Re: Bypass Battery Temperature Sensor and TempComp on Flexmax 100 afci

Post by Mike Curran »

sodamo wrote: Sat Apr 03, 2021 2:40 am So would this work with other components?
Yes - all the RTS is, is a thermistor, a component whose resistance changes with temperature. Any Outback component that accepts an RTS input will see this hack as if it were reading a constant 25°C.

PS When I first read the OP, I was surprised the FM100 cannot accept a temperature compensation slope less than 2 mV/°C, because Skybox does accept 0 mV/°C. In fact, without reading the post thoroughly, I'd initially drafted a response saying just set the slope to 0, but re-reading it discovered that was already tried and not possible. With Skybox it's convenient to be able to do this if you still want to track your lithium battery temperature without temperature-biasing the charging voltage .
https://smart.tigoenergy.com/p/pZXn7SZQyO45?date=2021-11-10
https://enlighten.enphaseenergy.com/public/systems/Hctc107221
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Re: Bypass Battery Temperature Sensor and TempComp on Flexmax 100 afci

Post by raysun »

I'd suggest using precision wire wound resistors instead of carbon or foil units. They will have more stability long term. Also, might want to take a peek at the resistors temperature coefficient to make sure you're not inadvertently creating a thermistor all over again.
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Re: Bypass Battery Temperature Sensor and TempComp on Flexmax 100 afci

Post by santafedave »

Afternoon Mattyxp. I am having problems with my RTS on my radian system. I put together the hack you posted here and I was wondering if you are able to read the temp on the dashboard of the OpticsRE screen. I have attached a screen shot of my screen and I don't have a temp readout anymore.
RTS hack opticre screen showing no temps.png
santafedave
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Re: Bypass Battery Temperature Sensor and TempComp on Flexmax 100 afci

Post by santafedave »

Here is a screen shot when I unplugged the RTS from the radian. Showing a unbelievable temp.
Temps when RTS is unplugged from Radian.png
mattyxp@yahoo.com
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Posts: 22
Joined: Sun Jan 17, 2021 12:11 pm
My RE system: Mate3s
VFX3648 x2 units master/slave setup w/ PSX-240 Transformer
Flexmax100 afci x 2 units
Flexnet DC
HUB10 port hub
32 REC360aa alpha solar panels with total wattage of 11,520w
20kw Perkins diesel backup generator

Re: Bypass Battery Temperature Sensor and TempComp on Flexmax 100 afci

Post by mattyxp@yahoo.com »

Hi Santafedave,
My OpticsRE shows the 77degree temp under the battery voltage in the upper right Power Flow chart and I can also see the 77degree flat line steady temp on the hourly chart if I select the "F" option from the far right drop down tab in the hourly chart.
Your inverter is a different model than mine so maybe that causes OpticsRE to display the temps differently...I don't know.
I also see your temp fluctuating in your screenshot. My hack does not allow for any temperature fluctuation so either you didn't implement the temp hack or maybe you disabled it completely for the entire day shown in your screenshot...ya got me kinda confused here.
I am using a Mate3S that is has its firmware up to date.
I am not grid tied and I see that you are grid tied...not sure if this would cause any differences in our OpticsRE displays.
You can also look at the temp directly on the Mate3S unit.
I also see that you are using FullRiver AGM batteries...when they die early which mine did, get a warranty refund (like pulling teeth but possible) and get lithium batteries...so much better.
Have you already replaced the RTS with a new unit to eliminate that potentially being the cause of your ghost extreme temps?
The "ghost" extreme temp fluctuations you are getting are similar to what I was seeing with my system. Outback could never figure out what was causing them and just blamed it on "random signals" of some sort that was not their problem.
My hack will stop the issue by forcing 77 degree temp at all times, but then your temp comp won't work with your AGM batteries...but this is better than the huge temp comp that the false extreme temps will cause.
Or Outback could get off its ass and just put in a temp comp slope setting option of 0 in our inverter settings and this would fix the problem the right way...but that won't happen, Outback has flat out refused to fix their ghost extreme temp problem.
Hope this helps...
Matt :)
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3 Canadian Solar 325W Module Mono Perc 1000VDC panels.
8 FullRiver AGM DC400-6 Sealed Batteries 415AH 6V L16 size.
Fireraptor quick disconnect.

Re: Bypass Battery Temperature Sensor and TempComp on Flexmax 100 afci

Post by santafedave »

Thanks for the update Mattyxp. I did replace the RTS with a new unit and that didn't work. I also worked with Unbound Solar my supplier of the solar system. I had the tech on the phone and he was logged into my OpticsRE and I showed him what happens when the temps get above 86.9 degrees. We went thru a few steps like unplugging the RTS and checking the temps thru Optics. I then put the RTS gauge into a bag with cold packs in it and after the temps went below 86.9 bam the system started producing and selling to the grid again. After that I ordered the new RTS and that still didn't work. I am resigned to using the mini fridge that I bought during the summer months. I don't have problems with the system during the winter time because the temps don't go above 86.9. I have my system inside my well shed so they are out of the elements. I am going to try your hack again this next spring and try and see if that works. You plug yours directly into the CC port and I am plugging mine into the Inverter Radian port so maybe that is the difference. I am saving my aluminum cans and plastic bottles so I can get me some Lithium! Hopefully the price comes down a little! Thanks again for posting your info here it really helps out! D.
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