Tweaking help on the MX-60

arcandspark

I have installed an MX60 charge controller and I am very impressed with this units performance. I am running ten Photowatt PW1000 95 watt panels wired up in five series pairs providing about 62 volts at 14 amps. The battery bank is 24 volts @ 3000 amp hours. I know ten panels will not do much but what they are doing is providing a little more power than the inverters are using during the day light hours. Right now I would like to tweak the MX60 to have it provide max power during sun light conditions. If I can I would like to have it stay in absorb mode continuously during the daylight conditions. I read something in the manual about a Mode One, Mode Two and Mode Three. All I have done so far is to increase the minimun Absorb time to 120 minutes and the Max Absorb time to 4 hours. Dont really know if this was a good thing or not. I see others talking about changing the park voltage? there is so many things you can change, and the unit has been doing a very good job just using the defalut setting, but I know a few of the right changes can improve the system even more. I am new to the MX60 and need to do a lot more reading and understanding about what changes have on the unit operation. Can anyone help me to understand the programming a little more. We will be adding more panels in the near future. Thanks for this forum. (arcandsaprk)

crewzer

Re: Tweaking help on the MX-60

A&S,

I can probably help you with the MX60. Just let me know what you need, and I'll do what I can to provide an explanation and/or point you to the appropriate section in the manual. It might take a day or two for me tro respond.

The operational modes (0, 1, and 2) determine if and when the MX60 controller automatically restarts itself during the day to perform an internal re-calibration and self-check. The various modes have little practical effect on how the controller operates. See page 52 of the latest user manual (Rev C) for more info.

Changing the absorption period won't have a great effect on how much energy the controller delivers. Like all similar controllers (both MPPT and PWM), the MX60 operates in a current-limit mode while functioning in the absorb or float stages. It'll only deliver enough current to maintain the target battery voltage. And, excessively long absorption periods will typically lead to extra maintenance to replace lost water from the electrolyte.

The only practical way for these controllers to deliver more power when they're in the absorb or float modes is to apply a load to the battery bank. The trick is to find a load that's the difference between the power available and what's required to charge the batteries.

HTH,
Jim / crewzer

crewzer

Re: Tweaking help on the MX-60

A&S,

Here are some suggestions for basic but important initial settings for your MX60:

CHARGER menu: Set the target voltages for the ABSORB and FLOAT modes in accordance with your battery manufacturer’s instructions.

EQ menu: Set the EQ voltage and period in accordance with your battery manufacturer’s instructions. I’d leave the EQ INTERVAL set to “000” (days). This will disable the AUTO EQ function and require that you manually initiate periodic EQ routines.

ADVANCED menu:

SNOOZE mode: select “<lowcutoff” (this tells the controller to enter it's low-power "snooze" mode when the output current is below the value set in the LOW CUTOFF menu)
PARK MPP: select 85% (the controller will operate the array at 85% of the Voc when the output current from the controller to the batteries is <5A; I've found this setting works better than the default 77% value.)
MPP RANGE LIMIT: select “1/2” for MIN, and “90%” for MAX
SWEEP INTERVAL: select “10 minutes” (this may need adjustment at a later date)
VBATT CALIBRATION: Adjust the controller voltmeter so that it matches the reading from a quality DVM taken at the battery terminals near the end of the absorption stage.
LOW CUTOFF: select “<0.4A”
MPPT MODE: select “non-GT” and “AUTO” mode
ABSORPTION LIMIT: set time limit in accordance with battery manufacturer’s instructions
WAKEUP MODE: For your array, I’d try setting the +VOC to 8.0 V, and the +MIN to 10 minutes. This will help reduce noisy relay clicking in the morning when the array voltage is high but array current is low.

That’s all for now!

HTH,
Jim / crewzer

boB

Re: Tweaking help on the MX-60

arcandspark wrote: »

If I can I would like to have it stay in absorb mode continuously during the daylight conditions. (arcandsaprk)

If you would really like to do this, an equivalent way would be to simply raise the FLOAT Voltage to equal the Absorb Voltage.

boB

System2

Re: Tweaking help on the MX-60

But if he cares about his batteries, he won't go there.

arcandspark

Re: Tweaking help on the MX-60

Thanks for the help Crewzer and Bob, that is exactly the kind of information I was looking for. With each helpful hint I am able to better understand the in's and out's of the MX60 and how it can be tweaked. With the system set up the way it is right now, even if the charger was in Absorb all day it would not harm these batteries because the demand of the inverters to run the home, which is completely off grid, will never allow the batteries to ever get over charged, due to the size of the PV output. As we add to the PV size I will teak the MX60 so it will be able to apply a good charge to the batteries, but it will take a lot more PV panels than we currently have on line. Thanks again for the useful information. I am working on a design to use an MX60 or Flex80 with a 48 volt alternator, capacitor bank and small propane engine as a backup charge system, instead of running a much larger backup AC generator and using the inverters to charge the batteries for times when weather keeps the PV panels from delivering full power. Thanks again, Dave R. (arcandspark)

System2

Re: Tweaking help on the MX-60

arcandspark wrote: »

With the system set up the way it is right now, even if the charger was in Absorb all day it would not harm these batteries because the demand of the inverters to run the home, which is completely off grid, will never allow the batteries to ever get over charged, due to the size of the PV output. (arcandspark)

Then I don't understand why you would want to disable the float mode if it never goes there anyway. What if the inverter loads were to fail when you were away, or otherwise not monitoring your system? Wouldn't it be great to have the MX pop into Float and protect the batteries once they became fully charged?
It can easily be programed to revert to Absorbing if the voltage were to drop one volt below Float.
OK, I'll say no more on this thread, I'm moving on.
Peace

arcandspark

Re: Tweaking help on the MX-60

Wayne, You make a very good point, and one I had not given much thought. Thanks it is well taken and you are right. I will try to figure out how to program the MX60 to do just that, go back into Absorb when it falls one volt below Float, should it ever get to a Float state. Also I read something in the manual about how the unit can revert back to a restart or back to Absorb after 1 1/2 hours or some time frame. That is what I would like it to do, but I am not use to program the MX60 yet and that is why I am asking for help with these issues. Wayne, thank you for your input and reminding me about situations where the system owner by be out of town or not on site for a few days, and what coutld happen. I usually try to think of all the what if situations, but it is hard to remember all of them. Dave R.

crewzer

Re: Tweaking help on the MX-60

With the system set up the way it is right now, even if the charger was in Absorb all day it would not harm these batteries because the demand of the inverters to run the home, which is completely off grid, will never allow the batteries to ever get over charged, due to the size of the PV output.

Dave,

This may be a semantics issue, but I don’t agree with your statement. It’s my view that the batteries would be harmed and/or require additional maintenance if the “charger was in absorb all day”.

One the other hand, if the PV array isn’t large enough to meet energy demand during the day, which in turn would prevent the charger from reaching the absorb stage, in which case the absorb timer settings would be moot, then that’s a different issue.

Part of the solution here might be to understand more about how the MX60’s absorption timer operates. Generally, the timer counts down (decrements) when the controller is in the absorb mode until it hits its calculated end time (= min time setting + time in bulk/MPPT mode) or the maximum time limit setting, which ever comes first. However, if the controller enters absorb mode, then falls back to bulk mode (i.e., due to high loads), then re-enters absorb mode, then the counter will initially decrement while in absorb mode, then increment (count up) when it falls back to bulk mode, and then begin to decrement again when the controller re-enters absorb mode.

In other words, if the controller were to switch back and forth between bulk/MPPT and absorb modes several times during any day, the controller will automatically extend the cumulative time it spends in absorb mode.

Unless there’s an external charging source that can be used to regularly fully recharge the batteries, then I believe that a bigger problem is that the deficit recharged battery bank will begin to lose useful capacity as well as suffer a shortened overall life expectancy.

Finally, if you want the MX60 to return to bulk/MPPT mode when the battery voltage falls to 1 V below the FLOAT voltage, then set the "ReBulk" voltage (MISC menu, screen #3) for that particular value. See page 42 in the manual.

HTH,
Jim / crewzer

arcandspark

Re: Tweaking help on the MX-60

Thanks for all the information. I will play with the settings as time goes on. Right now the system is working great. It might not provide enough power to fully charge the batteries but is does provide enough power to allow the owner to only have to run the generator for about one hour per day to be able to run the water pump for showers. We are installing a Dc water pump next month. I have my friend run the generator for a full charge using the generator if the batteries get in the low 23 volt range. Currently they have been staying in the mid 25 volt in the morning to the mid 26 volt as the sun goes down. We are adding another 850 watts of solar panels in the next two months. Thanks again for all the help. my friends propane bill has been reduced by 85%... arcandspark

BB.

Re: Tweaking help on the MX-60

See if you can get them interested in a battery monitor... The Xantrex XBM has been getting some recent love here...

Problem with measuring battery voltage, it need to be taken with no load, after resting several hours for accurate readings.

If, a resting battery shows below 24 volts, it has already been discharged by more than 50% (I guess, the measurement is measured under load--so is not an accurate measurement of State of Charge).

If not, and the batteries are wet cells, then using a good hydrometer (water saving battery caps here too) every so often will accurately determine the battery State of Charge.

Wind-Sun has a great battery FAQ here.

-Bill

System2

Re: Tweaking help on the MX-60

Will be interesting to hear the input from others, but to me, it sounds like your batteries are never, or almost never getting a real good, full charge. Thus they may be sulfating, or have already suffered sulfation damage. I do hope not however, because batteries are expensive to replace.
If your batteries are of the flooded type, the absorbing voltage should run around 29 volts at a battery temperature of 25C. When the batteries are cooler, the voltage should be even higher.
Really does sound like your battery bank is chronically undercharged, and that is bad!
Peace
Wayne

mike95490

Re: Tweaking help on the MX-60

Wayne from NS Cana wrote: »

Really does sound like your battery bank is chronically undercharged, and that is bad!

If you've got a generator, try running it for an hour or 2 in the morning, to BULK the batteries, and then the solar can manage the Absorb portion of the the charge. After you finish absorb and get to Float, you can then switch on your loads.

You've GOT to get a full charge into the batteries, or they WILL be ruined.

arcandspark

Re: Tweaking help on the MX-60

Thanks guys, the batteries are Hawker Gell VRLA, the factory spec says minimum of 70 amps max of 120 amps for charging. For the past eight years the batteries have been charged using a generator and Trace SW inverters providing about 60 to 70 charging amps. Using the bulk, absorb, float method from the inverters and charging for between four to five hours, four to five times per week. The only problem in eight years was once when his generator died and he was not able to charge the bateries for over five days. The batteries were running down in the 1.65 to 1.75 volt per cell range which is not good but he is off grid. After a new generator was installed, all but two of the twenty four cells recovered without any noticable problems. The generator issue was two years ago. Those two cells will not take a full charge. they have since been replaced. All the other cells will come up to 2.099 to 2.108 volts no load with no problem. I have installed a Desulfator unit about three years ago, not sure if it really does anything or not but its on and running 24 hours a day. Again thanks for all the feedback, that is what is so great about this forum. (arcandspark)

niel

Re: Tweaking help on the MX-60

that extenuating time period didn't just kill 2 cells as it probably weakened the others too and you may now start seeing others fail soon, but it's hard to say when for it may have only just shortened their lifespans abit to alot.
the desulphator isn't doing anything except putting an unecessary drain on the batteries. this extra drain could've meant the difference between those cells surviving or not for even a small drain over 5 days is appreciable.