Dual MPPT FX80's operation

adas

Aloha, as you know my setup on the sig line, I have two FX80's charging. One goes off and says "charged", while the other one is still cranking 75amps. Force starting it only puts it into float or absorb, even though the other one is still on bulk.

I think it occurs after both are on absorb and our electrical demand forces one to go back into bulk and later the problem one tapers off into "charged" while the good one is still maxing out in bulk. I looked at both settings and seem to be the same and even tried "reset", but still the same. Also the two units are .2V difference in battery voltage charging. Suggestions?

frank

BB.

Re: Dual MPPT FX80's operation

Use an accurate DVM and measure the voltages at the FM's terminals--charging and when done... Sounds like you either have a bad lead (high resistance), or, possibly more likely, the two units are off by 0.2 volts (I am assuming you are reading the 0.2v from their internal meters?).

Is the one that reads +0.2v higher the one that is shutting off sooner?

If so, you may just have to program that one 0.2volts higher charge parameters (or the other 0.2 volts lower--depending on which one seems to agree with your calibrated DVM better).

Are they using external battery temperature sensors? Try switching them between the two FM's... (temp sensors should be pretty accurate--they should not read differently unless one is broken, shorted, corroded)...

-Bill

adas

Re: Dual MPPT FX80's operation

Aloha, Bill

FYI the FX80's run parallel to the battery panel which is an ac 6 breaker box 60 amp each. (I can shut off each battery individually). I am using #4 wire from combiner PV box to FX80's and from FX80's I use #2 wire to the battery combiner box. All leads are 18 inches or shorter.

I kinda solved the problem by setting the one FX80 that reads .2 high to 29v bulk and the other to 28.8. Now they seem to be in harmony. Since it is a new system, with rejuvenated batteries, I am still working out the bugs. Right now we are using a 12 amp blower, airless paint sprayer, 8A fan, vehicle battery charger, fridge, various lights, and still it is running off the sun at 3:30 Pm partial cloudy, whereas I would be dipping into the batteries at this usage a week or two ago. Point is I need to realize I may be fully charged at 11am and the FX80's are throttling down. (maybe time to get a couple more 875AH batteries on line for a rainy day!

Also I think i will email Outback to see about re-calibrating the unit.
Really solved it now. i re-calibrated the unit for +.2. (under the menu recalibrate) duh.


Frank

crewzer

Re: Dual MPPT FX80's operation

Frank,

You got it. 8) Using the MX60 / FM80 controller's "Vbatt Calibration" feature in the Advanced Menu to normalize multiple voltmeters usually takes care of issue you experienced.

Regards,
Jim Goodnight
"crewzer"
Eastern Regional Sales Manager
OutBack Power Systems