using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

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lamplight
lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
Hi

So i now have two 48V arrays: 710w on the MX60 and 700w on the Tristar [MPPT. -BB] charging 12V battery bank.

Both set to absorb at 12.8V , tristar set to timeout for 1 hr, mx-60 default setting of bulk time=absorb time but also set to limit time to 1 hour. on a typical summer day either controller can get the batteries to absorb.. what I've been noticing the last 3 days since i wired up the second controller is that either one might arbitrarily take control of absorbing while the other will report "absorb" but limit output to ZERO. I've seen it happen both ways: today mx-60 was charging said absorb really early at 8:30 am, tristar said "absorbing" too but amps/watts out = 0.

i saw other slightly odd things last two days... so i reset mx-60 to factory defaults just in case i messed something up previously... i set the absorb, float and EQ settings, and also turned on low shutoff <1 amp. (trying to minimize relay clicking in am but thats another issue.. just pointing out right now that that is all i changed.

BOTH have battery temperature sensors and they are right next to each other on the battery bank. additionally the Tristar has additional leads that i AM using that send a small wire to the battery terminals to help more accurately read the voltage. BOTH have default per volt compensation settings ( i actually can't see how to change these / check in mx-60 manual but it does say the default is +/- 30 milliamps (i think?) per degree of change from 25deg C/ 77deg F, on the tristar it is set as a decimal 0.03 voltage change per degree away from 77deg F i believe



doesn't seem a huge big deal but i worried that if both not working I'm still just using an array that doesn't meet the charging % threshold for my battery bank). (i.e.: 5-15% i think it is).

so i wanted to make sure both arrays pulled if a load came on at least and they did but not what i expected: turned on a large load for testing (electric dryer and here's what i have):

tristar said the battery voltage was 12.86v
mx-60 said 12.95v
battery itself measured 12.54v
each array pulling in about 400w each.
my trimetric read that -21Amps coming out of battery..
so i guess thats ok: the load was larger than the system could maintain, yet i don't see why more current wasn't allowed through.. it was morning so possibly that really is all the panels could pull..

so i turned off the load and when the battery V level stared to risse the mx-60 stopped at 13.3 (temp compensated i guess) and started limiting current to try to FLOAT: while the tristar was back in BULK mode trying to restore those lost amp hours. tristar read 13.45V, batteries read 13.2v at this time.. so MUCH less variation whiteout the load.. i understand this is due to losses and also something i read that one of the "Bill's" here posted a while ago called puekert effect when a large load is pulling...

my cables are about 6' from the 60A fuse shutoff between battery and controllers. they are 6AWG and i can't get any bigger cable in the terminals of the 60A fuse/shutoff. i CAN shorten these cables a couple/few feet which might help voltage drop, yes? i might be able to double up some of the cables depending on inputs. i can most likely add a second NEG cable to the bank/fuse connection, there is only one. might help voltage readings? I did verify at least on the MX-60 output terminals that the voltage its screen said was the same there... the drop in reading occurred between there and batteries: going through the shutoff and about 5-6' of cables. the mx-60 does have the voltage compensation setting but not sure that is needed during normal less AMP intensive usage... (??)

I did upgrade my negative cable to my inverter (advise from previous thread, both now 0AWG.. which seems to run fine.. ). all cables were room temp to the touch running above test after 15 mins or so..

im not sure if the voltage readings being different are the issue, or just part of it, but the mx-60 stopping what should clearly be a rebulk at absorb, and the fact that only one controller seems to take control during absorb seems odd. is this ok as long as both contribute to bulk? (which i am not sure is happening actually!!)..

maybe i need to have matching controllers.. I've got thousands of dollars into the battery bank and inverter so iuf i need another tristar at ~ $600 i guess thats what i have to do.

not sure if any of the above relates just reporting hat i see if useful.
if anyone has ideas or tips thanks!!

Comments

  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    right now the tristar says "float"

    battery voltage 13.39, target voltage of 13.35
    (0 watts output, current is -0), so its clearly just backing off... which i guess at this stage is totally fine except they are both interpreting voltage differently.


    so if i go down to check I'm sure the mx-60 will say
  • BB.
    BB. Super Moderators, Administrators Posts: 33,532 admin
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60
    lamplight wrote: »
    Both set to absorb at 12.8V , tristar set to timeout for 1 hr, mx-60 default setting of bulk time=absorb time but also set to limit time to 1 hour. on a typical summer day either controller can get the batteries to absorb.. what I've been noticing the last 3 days since i wired up the second controller is that either one might arbitrarily take control of absorbing while the other will report "absorb" but limit output to ZERO. I've seen it happen both ways: today mx-60 was charging said absorb really early at 8:30 am, tristar said "absorbing" too but amps/watts out = 0.

    That does not make sense to me... If you told me that the controllers are set to enter Absorb/Bulk if the battery voltage falls below 12.8 volts--Yes, I can see that. But Bulk/Absorb setpoint should be something around 14.5 volts or so...

    i
    saw other slightly odd things last two days... so i reset mx-60 to factory defaults just in case i messed something up previously... i set the absorb, float and EQ settings, and also turned on low shutoff <1 amp. (trying to minimize relay clicking in am but thats another issue.. just pointing out right now that that is all i changed.

    What did you set them too?
    doesn't seem a huge big deal but i worried that if both not working I'm still just using an array that doesn't meet the charging % threshold for my battery bank). (i.e.: 5-15% i think it is).

    1050 watts panel * 0.77 derating / (1104 AH * 12 volts) = 0.061 = 6.1% rate of charge

    Certainly OK with both panels assuming a nominal maximum wattage of (1050w*0.77 panel+controller deratings = ) 809 watts.
    so i wanted to make sure both arrays pulled if a load came on at least and they did but not what i expected: turned on a large load for testing (electric dryer and here's what i have):

    tristar said the battery voltage was 12.86v
    mx-60 said 12.95v
    battery itself measured 12.54v
    each array pulling in about 400w each.
    my trimetric read that -21Amps coming out of battery..
    so i guess thats ok: the load was larger than the system could maintain, yet i don't see why more current wasn't allowed through.. it was morning so possibly that really is all the panels could pull..

    With the remote voltage sense leads, the Tristar should read the "correct" battery voltage without respect to voltage drop in the charge controller wiring (assuming the sense leads are connected "directly" at the battery bank and where you measured the 12.54 volts).

    The MX60 (as I recall) should allow you to reprogram the volt meter if it is not accurate (do this at night with no charging current to give an offset to the cable drop)...

    By the way, how long are your cables from battery bank to charge controllers?
    so i turned off the load and when the battery V level stared to raise the mx-60 stopped at 13.3 (temp compensated i guess) and started limiting current to try to FLOAT: while the tristar was back in BULK mode trying to restore those lost amp hours. tristar read 13.45V, batteries read 13.2v at this time.. so MUCH less variation whiteout the load.. i understand this is due to losses and also something i read that one of the "Bill's" here posted a while ago called puekert effect when a large load is pulling...

    Going to FLOAT does not make sense unless they load was for a very short time (the controllers may have to see below 12.xx volts for y minutes type setting?).
    my cables are about 6' from the 60A fuse shutoff between battery and controllers. they are 6AWG and i can't get any bigger cable in the terminals of the 60A fuse/shutoff. i CAN shorten these cables a couple/few feet which might help voltage drop, yes? i might be able to double up some of the cables depending on inputs. i can most likely add a second NEG cable to the bank/fuse connection, there is only one. might help voltage readings? I did verify at least on the MX-60 output terminals that the voltage its screen said was the same there... the drop in reading occurred between there and batteries: going through the shutoff and about 5-6' of cables. the mx-60 does have the voltage compensation setting but not sure that is needed during normal less AMP intensive usage... (??)

    Assuming (400 watts / 12.5 volts =) 32 amps. Using a generic voltage drop calculator, 6' one way run on 6 awg wire -> 0.2 volt drop...

    I would suggest, for a 12 volt battery bank around 0.10 to 0.05 volt drop maximum. So, shortening the wire run by 3' would do that. Or going up from 6 awg to 3 awg or thicker would do it too. With stranded wire, you can clip the excess until the ends fit into the terminal block (still fuse as if 6 awg wire even if you are are using 2 awg--You don't want to overheat the cable ends/attachments).

    Assuming the TrisStar remote voltage sense is working correctly, its voltage drop is not as critical (just a bit more loss energy due to drop).

    I am not sure the "too small" 6 awg wiring is causing your missing bulk/float stages.
    im not sure if the voltage readings being different are the issue, or just part of it, but the mx-60 stopping what should clearly be a rebulk at absorb, and the fact that only one controller seems to take control during absorb seems odd. is this ok as long as both contribute to bulk? (which i am not sure is happening actually!!)..

    Until you see your battery bank running for a fair amount of time at ~14.5 volts, something is not right. With parallel charge controllers that are not "synced"--It will be normal for one to enter absorb/float before the other... But the fact both are missing this seems strange.
    maybe i need to have matching controllers.. I've got thousands of dollars into the battery bank and inverter so if i need another tristar at ~ $600 i guess thats what i have to do.

    I would not worry about sync'ing your controllers--But they do not look to be operating ideally at this time.

    What is the Specific Gravity/Resting Voltage of your battery bank? Is it >90% charged when running these tests?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60
    lamplight wrote: »
    Hi

    So i now have two 48V arrays: 710w on the MX60 and 700w on the Tristar [MPPT. -BB] charging 12V battery bank.

    Both set to absorb at 12.8V , tristar set to timeout for 1 hr, mx-60 default setting of bulk time=absorb time but also set to limit time to 1 hour. on a typical summer day either controller can get the batteries to absorb.. what I've been noticing the last 3 days since i wired up the second controller is that either one might arbitrarily take control of absorbing while the other will report "absorb" but limit output to ZERO. I've seen it happen both ways: today mx-60 was charging said absorb really early at 8:30 am, tristar said "absorbing" too but amps/watts out = 0.

    First problem: Absorb Voltage on a 12 Volt system should be 14.2 to 14.8 depending on the batteries. Definitely not 12.8.

    Second, it doesn't really matter if the current on one of the controllers drops to zero while both are reporting Absorb. Absorb stage is a constant Voltage state; the current will fluctuate as loads come and go but over-all will head downwards.
    i saw other slightly odd things last two days... so i reset mx-60 to factory defaults just in case i messed something up previously... i set the absorb, float and EQ settings, and also turned on low shutoff <1 amp. (trying to minimize relay clicking in am but thats another issue.. just pointing out right now that that is all i changed.

    Altering the Absorb End Amps won't have any effect on the early morning relay clicking; that is a normal (but annoying) function of the MX as it detects "high enough" input Voltage to try and start charging. When it can't because the panels aren't producing any real current it shuts down, waits a bit, and tries again.

    BOTH have battery temperature sensors and they are right next to each other on the battery bank. additionally the Tristar has additional leads that i AM using that send a small wire to the battery terminals to help more accurately read the voltage. BOTH have default per volt compensation settings ( i actually can't see how to change these / check in mx-60 manual but it does say the default is +/- 30 milliamps (i think?) per degree of change from 25deg C/ 77deg F, on the tristar it is set as a decimal 0.03 voltage change per degree away from 77deg F i believe

    The Tristar's remote battery Voltage leads are a good thing. But you may have to reprogram the MX60's Voltage reading to get it to agree. It's somewhere in the advanced menu. Since the stage changes are Voltage dependent, you want to make this adjustment so both controllers agree on battery Voltage when the current is low (like the end of the Absorb stage or during Float).
    doesn't seem a huge big deal but i worried that if both not working I'm still just using an array that doesn't meet the charging % threshold for my battery bank). (i.e.: 5-15% i think it is).

    If you don't have a battery monitor, just watch both displays and add the maximum current you see on each together. Battery monitors are really useful when you're trying to use two or more dissimilar controllers.
    so i wanted to make sure both arrays pulled if a load came on at least and they did but not what i expected: turned on a large load for testing (electric dryer and here's what i have):

    tristar said the battery voltage was 12.86v
    mx-60 said 12.95v
    battery itself measured 12.54v
    each array pulling in about 400w each.
    my trimetric read that -21Amps coming out of battery..
    so i guess thats ok: the load was larger than the system could maintain, yet i don't see why more current wasn't allowed through.. it was morning so possibly that really is all the panels could pull..

    Ignore this. Tenths of a Volt difference under heavy load is nothing to worry about. Meters simply aren't that accurate.
    so i turned off the load and when the battery V level stared to risse the mx-60 stopped at 13.3 (temp compensated i guess) and started limiting current to try to FLOAT: while the tristar was back in BULK mode trying to restore those lost amp hours. tristar read 13.45V, batteries read 13.2v at this time.. so MUCH less variation whiteout the load.. i understand this is due to losses and also something i read that one of the "Bill's" here posted a while ago called puekert effect when a large load is pulling...

    If the MX60 hadn't finished Absorb when the load was applied and the battery Voltage dropped it too should have returned to Bulk until the battery Voltage rose to Absorb level then continued to the end before dropping to Float. See the first problem I mentioned above before changing anything else.
    my cables are about 6' from the 60A fuse shutoff between battery and controllers. they are 6AWG and i can't get any bigger cable in the terminals of the 60A fuse/shutoff. i CAN shorten these cables a couple/few feet which might help voltage drop, yes? i might be able to double up some of the cables depending on inputs. i can most likely add a second NEG cable to the bank/fuse connection, there is only one. might help voltage readings? I did verify at least on the MX-60 output terminals that the voltage its screen said was the same there... the drop in reading occurred between there and batteries: going through the shutoff and about 5-6' of cables. the mx-60 does have the voltage compensation setting but not sure that is needed during normal less AMP intensive usage... (??)

    Again, don't worry about V-drop under load conditions. It will matter if the controllers "see" the wrong Voltage for Absorb and Float with no or light loads. Don't "double up" wiring. For 6' on 12 Volts at full 45 Amps your drop is something like 2%, although the meters may not reflect this accurately.
    I did upgrade my negative cable to my inverter (advise from previous thread, both now 0AWG.. which seems to run fine.. ). all cables were room temp to the touch running above test after 15 mins or so..

    Different issue; inverter wiring will have no effect on controller function (unless the wiring is done very wrong, which I doubt).
    im not sure if the voltage readings being different are the issue, or just part of it, but the mx-60 stopping what should clearly be a rebulk at absorb, and the fact that only one controller seems to take control during absorb seems odd. is this ok as long as both contribute to bulk? (which i am not sure is happening actually!!)..

    First, check the Voltage set points. As before, Absorb needs to be over 14 Volts to be effective and the same on both controllers. Set the Absorb End Amps on the MX60 to zero. If it is higher than that and Absorb is "interrupted" when it comes back the current may be low enough to trigger it to end while the Voltage is high enough to cause it to go to Float.
    maybe i need to have matching controllers.. I've got thousands of dollars into the battery bank and inverter so iuf i need another tristar at ~ $600 i guess thats what i have to do.

    Nah. You just have to go over all the basic settings and accept the fact that two controllers don't act as one. Think of it as character, not aggravating flaws. If you put two MX60's on a HUB with a MATE and connect them to an OB inverter they still may not function seamlessly. But it would be the best that can be done.
    not sure if any of the above relates just reporting hat i see if useful.
    if anyone has ideas or tips thanks!!

    First tip: DON'T PANIC! :p
    I think you've got flooded cells so ...
    Absorb Voltage 14.4 at least
    Absorb time limit 4 hours on the MX60 (let the Tristar determine the max)
    Float Voltage 13.8 maximum

    The "dual charge" should allow the MX60's clock to run up fairly quickly, reducing its Absorb time to less than the Tristar will run. That will depend on the Tristar's Absorb settings of course. The goal here is to set it so that the MX60 basically contributes current during Bulk charging and when loads are drawing and defers to the Tristar for other limits.
  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    sorry.. first of all i meant absorb at 14.8 , EQ is 16v, floor 13.1, I think i got the 14.8 number here... someone said the larger batts seemed to do better a little higher.. i get to float real quick every day so i thought id try running at only 1 hour absorb for now... looking closer at the manual they are pretty vague:
    Table 2 – Charge parameters
    Note: The most common type of charge method at present is the three stage plus equalization. This outline is based on this type of charging method. Check with your charger manufacturer for specific settings for their equipment. Please note, if “topping up” with water is required more than once every two (2) months, the voltage settings are too high on your system.
    Temperature/Volt per cell Example: 12V (6 cells)
    Bulk/Absorption
    0 ̊C to 16 ̊C 2.5 Volt 15.0 Volts
    17 ̊C to 27 ̊C 2.4 Volt 14.4 Volts
    28 ̊C to 40 ̊C 2.36 Volt 14.16 Volts
    Float
    2.19 13.14 Volts
    Equalization
    2.58-2.67 15.48-16.02 Volts

    but on closer looking at this i think I'm going to try 14.6v..
    Altering the Absorb End Amps won't have any effect on the early morning relay clicking; that is a normal (but annoying) function of the MX
    i didn't say that.. i changed "snooze mode" to "<low cutoff", and then in the advanced menu set <Lowcutoff to 1 Amp :
    The Low Cutoff is adjustable from .2 amps to 1 amp; .6 amps is the default Low Cutoff current. Raising this value will assist the MX60 in entering Sleeping mode at night.
    hoping this will help minimize clicking.. i know not related to my problem jus clarifying.
    The Tristar's remote battery Voltage leads are a good thing. But you may have to reprogram the MX60's Voltage reading to get it to agree. It's somewhere in the advanced menu. Since the stage changes are Voltage dependent, you want to make this adjustment so both controllers agree on battery Voltage when the current is low (like the end of the Absorb stage or during Float).

    i verified today when everything was floating that they do all pretty much agree.
    If you don't have a battery monitor, just watch both displays and add the maximum current you see on each together. Battery monitors are really useful when you're trying to use two or more dissimilar controllers.
    i do and mentioned that.. thats how i knew amps out was larger than incoming..

    If the MX60 hadn't finished Absorb when the load was applied and the battery Voltage dropped it too should have returned to Bulk until the battery Voltage rose to Absorb level then continued to the end before dropping to Float. See the first problem I mentioned above before changing anything else.

    this is what I'm pretty sure isn't happening.. it seems like maybe a bug in mx-60? after shutting off the load mx-60 said mppt, but when it passed over the programmed FLOAT voltage, even though system hadn't reached float that day. the tristar was bringing the voltage back up to absorb again (normal), but when the mx60 got to 13.2v it started limiting current and letting the tristar try to bulk charge up to absorb again, by itself. seems the mx-60 gets confused. i don't know if this will happen again if i try it after both are reporting a full charge and in "float".

    am i making sense? there was other anomalies but they may be normal.. ill try to watch it.. i guess as you say if bulk and load sharing work the rest doesn't matter. i noticed i did have to start eq manually on both to use both arrays, but thats no big deal.

    First tip: DON'T PANIC! :p

    ok :)
    Absorb time limit 4 hours on the MX60 (let the Tristar determine the max)

    going to stay with one hour for now since summer and i get very rapidly to absorb.. they both seem to float eventually... i guess i have to monitor it more but thanks on the voltage readings being wrong under load info... i was wondering if that was a big problem... doesn't seem to be now that you and Bill clarified



    The "dual charge" should allow the MX60's clock to run up fairly quickly, reducing its Absorb time to less than the Tristar will run. That will depend on the Tristar's Absorb settings of course. The goal here is to set it so that the MX60 basically contributes current during Bulk charging and when loads are drawing and defers to the Tristar for other limits.

    RIGHT. thats what i really want. will report..
  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60
    BB. wrote: »

    1050 watts panel * 0.77 derating / (1104 AH * 12 volts) = 0.061 = 6.1% rate of charge

    going to change my tagline now Bill.. sorry for the confusion.. its bigger now..(1410 W DC)
    BB. wrote: »
    With the remote voltage sense leads, the Tristar should read the "correct" battery voltage without respect to voltage drop in the charge controller wiring (assuming the sense leads are connected "directly" at the battery bank and where you measured the 12.54 volts).

    they were connected directly to bank, but.. it is POSSIBLE this wire was loose at the time... ill verify again when opportunity arises.
    BB. wrote: »
    I am not sure the "too small" 6 awg wiring is causing your missing bulk/float stages.

    me neither gave some more info in coot's reply.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    From the battery data you gave it looks like 14.4 is the right Absorb Voltage for these batteries (17 to 27 C is normal operating range).

    You've already discovered that adjusting the "snooze" settings doesn't help the morning clicks. It's for "helping" the MX60 to shut down at night. I don't know what would stop that repeat AM sampling. I've tried lots of things, short of installing a timer to keep the PV off the input until 8:00. :p

    If the MX60 goes to Float after an Absorb interruption and the Tristar can continue the Absorb, I wouldn't worry about it. Otherwise it may be necessary to set the minimum Absorb time on the MX60 to the same Absorb Time as the Tristar (not the Absorb extension though).

    Actually it sounds like they are working together fairly well. Let it run a few days and see if anything goes out of whack.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    Hi lamp,

    Generally agree with the foregoing comments.

    BUT, believe that Rebulk in the MX-60 comes with default of about 8.5 volts -- to disable it. You will need to determine just what voltage YOU want for a re Bulk IIRC.

    Did not see anything about you measuring your SGs. You need a good glass Hydrometer, of perhaps the more accurate Refractometer to measure SGs of all of your cells. AND use it/them. It is a huge benefit to actually be able to measure the SOC of the batts, and these readings will help you calibrate your Bat Monitor (forgive me if you are doing this).

    These Surrette batts need Surrette charge parameters:

    Asorb 14.2 to 14.7 MAX
    Float: 13.2 to 13.4 MAX.
    EQ: 15.5 - 16MAX (EQ at the lowest voltage that does the job.
    ALL of these charge voltages need to be temp compensated of course.

    It will help you set the charge parameters of the two CCs if you can watch the behavior. It may well change with differing loads when in Asorb. It will never, nor does it need to be perfect.

    You should download the SUrrette Solar Battery Manual if you have not yet done so:
    http://www.rollsbattery.com/content/battery-user-manual

    Click on Solar Battery Manual.
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    Hi
    first off thanks.

    yes i read that 14.4v seems the right starting ranging but there was a huge thread on batteries here once where some people were saying the big batts like i have seemed to get stirred up better on higher end... still 14.8v seems high going to change them to 14.6 as a compromise.. ;) regarding another recent thread here i was going to try less lengthy absorb times thus the 1 hour. BUT plan to do some serious EQ'ing over the next few sunny days to deal with sulfating.. and then make sure i start doing it per recommendations more regularly.

    regarding the relay click on mx60, this is the part in the manual before the park where it describes the low cutoff (under advanced menu):
    The MX60 wakes up when an optimal amount of open circuit voltage (Voc) is available. The Voc varies with external conditions, primarily the weather and time of day, which affect solar panels. If the Voc is insufficient, the MX60 enters Snoozing until either a five-minute (default) period passes or there is a 1.5 volt (default) increase in Voc at which point the MX60 reevaluates
    the Voc for recharging purposes. What is the optimal amount? The MX60 tries to recharge when the Voc is greater than the battery voltage by 2 volts, but voltage alone isn’t sufficient. An array might have a big increase in voltage first thing in the morning— more than 2 volts difference—but not enough ampacity to recharge.

    it KIND of implies this low cutoff might help decrease sweeps on wakeup.. I'm also going to try setting the sweep time to 15 mins... just because of the clicking... the noise is not an issue I'm just thinking wear and tear... thats a lot of clicks!!
    Actually it sounds like they are working together fairly well. Let it run a few days and see if anything goes out of whack.

    If you say so :) ok will watch.. going to stick a webcam on the mx60 so i dont have to run to the cellar all the time...love having the tristar's web access!
  • BB.
    BB. Super Moderators, Administrators Posts: 33,532 admin
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    Do you know the battery bank's current state of charge? What your normal range is? Are you getting it 90% at least once or twice a week. Avoiding going below 50% state of charge unless really needed (bad weather, generator broken down, etc.) and get the bank back above ~75% state of charge the next day...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    Hi Vic

    thanks.. will check the rebulk.

    Vic wrote: »
    These Surrette batts need Surrette charge parameters:

    Asorb 14.2 to 14.7 MAX
    Float: 13.2 to 13.4 MAX.
    EQ: 15.5 - 16MAX (EQ at the lowest voltage that does the job.
    ALL of these charge voltages need to be temp compensated of course.

    I actually quoted from it above earlier in the thread.. where are you getting the EQ number? the manual doesn't give temperature for float it only says 13.14. I've got it at 13.1
    Ive got my absorb reset, and down to 14.6v on both controllers.

    I guess I should dust off the hydrometer.. i do have one. never used. I'm lazy it seems like such a pita.. i have usually just based health on how well the bank holds a charge. but it has been very undercharged through the last couple winters.. sounds like i need to do that and then reset the battery meter so that i know its accurate and to get the true SOC. sigh... problem with asking for help is you have to take the suggestions lol

    Bill: I get 100% according to controller often, more han once a week. i try not to go below 75% ever though there were a few times last winter when i forgot to do maintenance and they were low. Im going to get out the hydrometer.



    today is a rainy day and both are doing a bulk , so all looks good on that department.
    mx-60 array getting ~35w and tristar getting ~30w
  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    2nd rainy day in a row and I'm going to hit absorb and possible float today.. i love it :)

    ( don't run too much on it when its raining just the inverter and the website , about 22-25w).

    SOC WILL be measured later in week/weekend.
  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    hi so I finally did my first ever SG measurement. I shutoff all loads for a few minutes after batteries have been fully charged. I have a glass float model with a thermomeeter on it but forgot to check the temp as I was having problems getting the electrlyte to suck up for some reason.. must be doing something I'm doing wrong..,anyhow finally got it to fill up enough to float and it read 1.275.
    manual for the battery says SG for 20 hour rate should be 1.28

    temp on the controller says 18 deg Celsius but I'm drawing a big load now so don't know If affected temp. 64.4f ,
    hydrometer temp setting says subtract about 4 from the reading if that temp: so SG would be 1.271

    I can't be sure about the temp but assuming its close I'm in bad shape.. is that really bad? what can I do? I think I read in rolls manual somewhere to keep EQing until SG rises..

    I have to figure out how to more efficiently draw the fluid up.. to test all cells.. the bulb isn't creating strong enough suction.. I wonder if I should snip some of the end of the tube that goes into Batt..


    the temp sensors for tristar and mx60 are touching the batts but I wonder if the electrolyte actually varies a bit inside the battery.. I have to test again it seems..
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    There's no practical difference between an SG of 1.275 and 1.280. You could read the same cell twice in a row and get that much variation. And there's nothing that says your hydrometer is 100% accurate either. Heck, I can't even see 0.005 on my hydrometer. I only worry if it's in the wrong colour zone! :p

    The time to worry about SG readings is if you just charged the batteries to full Voltage and get 1.260 instead of 1.275 or you have cells reading 0.010 or more difference. Don't start equalizing batteries due to very small differences in SG between cells. EQ is hard on batteries and best done on an as-needed basis (although some manufacturers disagree and recommend regular EQ cycles). If it is an across-the-board low SG reading upon charging add Absorb time, don't EQ.
  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    ok awesome.. I did just find this which indicates my reading isn't so bad:
    http://www.rollsbattery.com/content/motive-power-bulletins?q=node/51&phpMyAdmin=0610e516bf803196b5feee0b1ad65c08&phpMyAdmin=3jSJ-jdC5E7b53DHgV8TGvpSCF6

    it's a good glass model I got from a solar dealer.. here maybe I forget..

    still I'll check all cells to check for variations sometime soon. thanks!
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    Hi ll,

    Couple of things. Looks like you are fully charging your batteries, at least based upon the SG(s) you noted.

    Am certain that you must have one of the older Freas brand SG/thermo Hydrometers. They are notroious for having a bulb volume too small for the volume of the tube. Have two of them here ... stopped trying to use them, as is it very difficult to float the float. Altho I do not like doing so, you can take two pulls per read -- take one pull of electrolyte, invert the hydro, such that the bulb is below the tube, wait a bit for the electrolyte to run into the bulb, and take a second draw, expell the air in the bulb carefully... and so on, being careful to not spill of squirt the electrolyte!. This should allow the float to float. There is a three-holed stopper, IIRC) at the top of the tube, so it can take a bit o time for the fluid to run into the bulb. And, as you know, usually a good idea to take the reading on the third draw of electrolyte. The first two pulls need not float the float, just one bulb's worth of fluid into the glass tube, and expell it back to the cell.
    As an aside, you might try contacting Freas to see if they can provide you with a larger volume bulb which could fill the tube with enough electrolyte in a simgle draw. Believe that some here have had good service from Freas Glass in this regard (I have not tried doing this). I simply bought the Freas thermoter-less Hydro which works fine, as the adjustment factor for reasonable temp variations is small, and use a chart on the wall ... the temp variations cell to cell are usually insignificant if you are lucky. And, as you, use the CC or inverter's temp readout.
    Freas Glass Works:
    http://www.freasglass.com/battery.htm
    Scroll to the bottom for a WebForm contact page ...
    Am guessing that you do have a Freas Hydro. Black bulb, and tip, might even say so on the float scale.

    Regarding the target SG for your batteries:
    The Capacity of the batteries are rated as if the SG of the electrolyte was 1.280, BUT the target SG for fully charged batts is 1.265. This difference is just a little specmanship that all batt manufacturers seem to play to make their batts seem equal to or better than the competition. This 15 point SG difference makes the AH capacity seem 5% better than it is. IMHO, the 1104 AH is a 1050 AH battery with the electrolyte as shipped. And, 1.265 SG is generally better for battery life for our off grid banks.

    And, personally I'd place both temp sensors on the same battery, midway down the case. Here use a chunk of 1.5 inch thick styro sheet insulation strapped over the temp sensors to attempt to get the temp measured closet to that of the electrolyte, and less influenced by ambient.

    All in all, looks like you are doing well, hope you can take the time to measure the SG of each cell and record them. The variation in SG tells a lot about how well the bank is behaving.

    And as Coot said, EQs are generally done then SGs start to diverge too far ... about 15 or so points. Surrette has seemed to back off a bit on the frequency of EQs, but still erring on the side of a bit foo frequent vs a bit too infrequent is good, but, knowing just when the time to EQ is a bit difficult for me.

    Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60

    Vic that is what I have! the name rings a bell.. and that is what I did to get enough in there to float the float. no other option... quite messy spattered electrlyte all over.. I did notic the end of the tip was small I cut off a half inch and openings bigger.. MIGHT help draw in more.. my problem is ALSO that the bulb wasn't even pulling adequately.. in addition to not enough... I'll contact them to see if I can get a bigger bulb. thanks!
  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
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    Re: using two controllers on the same battery bank : MX-60 and Tristar MPPT 60
    Vic wrote: »
    And, personally I'd place both temp sensors on the same battery, midway down the case. Here use a chunk of 1.5 inch thick styro sheet insulation strapped over the temp sensors to attempt to get the temp measured closet to that of the electrolyte, and less influenced by ambient.

    I actually just did this with some 1" foam board scraps and tape, as I noticed mx60 and tristar wanted to float at slightly different voltages.. they are now more in line.

    also contacted freas about a bigger bulb.

    everything is running great, thanks.. only thing really left to do is shorten my battery to controller runs (between fuse shutoff and batts specifically) a few feet to minimize voltage drop. did some good testing saturday after both controllers reporting float with the washer AND dryer... i noted how under the high amp load BOTH controllers reported inaccurate voltage readings on the bank, but they kept the bank "floating" successfully at least (even though the actual bank voltage according to the battery meter was around 12.5x or so... didn;t really seem to be a problem though as they went right back to the TRUE float voltage after the load turned off.

    !! :D