Target Voltage for 24 volt system.

KJ7YMKJ7YM Solar Expert Posts: 30 ✭✭
When I got my TriStar MPPT 60 started up I noticed that according to my Crown Battery literature that the default settings all seem to be lower than Crown recommended. One of the things that I cannot seem to get a handle on is the Target Voltage setting that I should be using for my 24 volt system. I am using Crown CR-185 batteries.

Information on this seems to be all over the map. Currently my system says I have a target voltage of 29.94. Is it just me or does that seem a little high? I went to a major charger manufacturers web site, and it sad "The target voltage for a 24 volt charger for flooded batteries is 2.4 to 2.45 volts per cell, which is 28.8 to 29.4 volts."
To me that seems like a rather large spread to be guessing at. Can anyone give me a more reliable firm number? Tanks Guys.

Comments

  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    Don't go by the charger manufacturer. Go by whatever the latest recommendations from the battery manufacturer, Crown in this case. The charger mfg has wide ranges as the recommended setting varies between makes of battery. Compare Crown to Trojan for example. Call or email Crown if in doubt.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • VicVic Solar Expert Posts: 3,136 ✭✭✭✭
    Hi Larry (perhaps),

    As Mt. Don mentioned, it is always best to use the battery manufacturer's data for charge parameters.

    Guess that the "Target Voltage" is also known as the Absorb voltage. This voltage depends on several things, especially the SG of the electrolyte in the batteries. Higher SG electrolyte requires a higher Absorb voltage. It is quite possible that the Target SG is about 1.280 for a fully charged battery (when compensated for the battery temperature),

    As you probably know, if your Crown batteries are Flooded Lead-Acid (FLA), the Hydrometer readings from each cell of the battery bank is the Gold Standard on just how well your batteries are being charged in your system with your settings.

    Often, in Winter, the Absorption voltage needs to be increased in order to charge the batteries in the Solar Day that you have. You may be in the SW US, where the sun is generally very king to PV systems in the Winter, IIRC.

    The time that the Absorption stage requires to reasonably fully-charge a battery depends upon the Depth Of Discharge (DOD) that the battery experienced in the previous discharge cycle.

    Hope that the Morningstar MPPT 60 has done away with those limiting DIP Switches, and gone to a modern data entry technique.

    Opinions, Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 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.
  • VicVic Solar Expert Posts: 3,136 ✭✭✭✭
    KJ7YM wrote: »
    When I got my TriStar MPPT 60 ... Currently my system says I have a target voltage of 29.94. .[/SIZE][/FONT][/COLOR]

    Am adding this second post on this Thread (rather than Editing the first one), as it is not now possible to see if you are still on-line on this forum ...

    What part of your system is telling you that the Target V is 29.94. If the batteries are cool or cold, the required voltage needs to be increased. If you are using the essential Battery Temp Sensor (BTS), and the batts are cool, this may well be the correct voltage.

    Did look at the spec sheet for your battery model number, but Crown only specs a constant-current charge voltage. PV-charged system cannot deliver this type of charge, generally.

    Perhaps you could contact Crown Tech to see what IS the recommended charge voltage and time for a battery charged from PV. Their end-of-charge parameters cannot be used by any PV CC that I have seen. So you should try asking about the Ending Current value (also known as Finishing Current by some).

    FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 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.
  • KJ7YMKJ7YM Solar Expert Posts: 30 ✭✭
    Thanks Guys,
    I guess the first thing I need to determine is what the heck MorningStar means by Target Voltage from the report I pulled from the Controller.

    Vic this model has both Dip Switches, and like everything else in the solar game, I have discovered that unspoken and unprinted but soon realized feature that I interpret to read as this." Oh so thank you for spending a half a grand on our product. Oh yes we should let you know that our default settings are just a tad off from what anyone would actually want. Oh, you wish to be able to really use it? We have that covered, for just a few hundred dollars more........." :-) The same with my Inverter, but in that case we need to change the numbers up above 1500.00 mark. Anybody else ever feel this way?

    Just a little humor to lighten the air here. Thanks for letting me vent :-)

    I fear I am one of the probably 99% who are more at risk of doing harm than good with the programmable feature, but as you can see it has not stopped me from trying to to do it anyway. How else are we to learn? :-)

    After some of what I have learned I just wish that the controller manufactures would let you input to a program on the net somewhere the relevant facts that your Battery Manufacturer provides along with your situation and then give a suggested setting for the peripherial settings that are available. In my case I have good numbers for the Big Three from Crown. Absorption 30V, Equalize 31.2V, Float 27. But then I find that there are times for these things like Absorption so many hours, and then extended absorption time and voltage. Who the heck knows what that's about? When I pulled my controller settings it came back like this:

    Regulation Voltage: 15.00 V (12V), 30.00 V (24V), 60.01 V (48V)
    Temperature Compensation: -0.030 V/degC (12V), -0.060 V/degC (24V), -0.121 V/degC (48V)
    Max. Compensation Temp.: 80 deg C
    Min. Compensation Temp.: -40 deg C
    Absorption Time: 2:30:00 h:m:s
    Absorption Ext. Voltage: 13.40 V (12V), 26.80 V (24V), 53.59 V (48V)
    Absorption Ext. Time: 3:00:00 h:m:s
    Battery Service Reminder: 30 days
    Float Voltage: 13.50 V (12V), 27.00 V (24V), 54.01 V (48V)
    Float Timeout: 30:00 h:m:s
    Float Cancel Voltage: 12.60 V (12V), 25.20 V (24V), 50.41 V (48V)
    Equalize Voltage: 15.60 V (12V), 31.20 V (24V), 62.40 V (48V)
    Equalize Time: 1:00:00 h:m:s
    Auto-Equalize Interval: 28 days
    Equalize Timeout: 3:00:00 h:m:s
    HVD: 15.50 V (12V), 31.00 V (24V), 62.01 V (48V)
    HVDR: 14.50 V (12V), 29.00 V (24V), 58.01 V (48V)
    Maximum Regulation Limit: 15.65 V (12V), 31.30 V (24V), 62.60 V (48V)
    Maximum Battery Current: 45.00 A
    Array Voltage Fixed Target: disabled V

    Right now I see I have my Absorption extension voltage (26.8) set lower than the Float Voltage (27). Does that seem weird? A typo maybe?
    And that thing called Float Cancel Voltage (25.2) is lower than the actual float voltage setting of 27 volts. These things may be right, but I am clueless.

    Kinda heavy stuff for a new guy :-)
  • VicVic Solar Expert Posts: 3,136 ✭✭✭✭
    Hi Larry,

    Thanks for the added info.

    Morningstar has been around for a long time. They do make some good products. Sure do not know just why they do not include an LCD Display as standard equipment.

    Believe that they do have some software that will allow custom charge settings, via computer, which may help.

    For many, like me, Morningstar has their own special language for traditional charge stages. This can make it difficult for those of us who do not have/use Morningstar equipment, to help in situations like yours. I do not know just what is the Absorption Extension voltage ... it may well be the voltage used to finish the Absorb stage (at the end of Absorb) - guessing.

    Perhaps you should try contacting Morningstar Tech Support for recommendations on Charger settings, or at least ask for your Decoder Ring, so you might be able to translate their words to more traditional terminology used on other CC

    In poking around on the Net, it does look like your batteries use 1.280-ish SG electrolyte, which will increase charger voltage settings a bit.

    You will want a good Hydrometer. These are available at Auto Supply stores. The sponsors of this site carry the Hydrovolt, which is accurate, repeatable and easy to read, FWIW.
    Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 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.
  • VicVic Solar Expert Posts: 3,136 ✭✭✭✭
    Larry,

    Bet that you have seen this Thread, also on MPPT-60 Set Points:
    http://forum.solar-electric.com/forum/solar-electric-power-wind-power-balance-of-system/advanced-solar-electric-technical-forum/330211-mppt60-morningstar-setpoints

    Mike, who replied in the Linked Thread did mention that there is information in the MPPT-60 Manual about setting these parameters.

    FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 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.
  • HandyBobHandyBob Banned Posts: 31
    I use Crowns and have installed many. They are a great company and growing at an impressive rate. Ditto for Tristar's. Both companies will confuse you if you get the wrong guy on the phone. Crown has one pc of literature that will tell you up to 2.7V per cell is acceptable, but you need to consider many variables and that is a bad idea for daily automatic charging. On another pc they say 30V for a 24V system and that is what I use on my 6CRP525's with great success. For a 12V battery, use the 14.7V (29.4V) algorithm & leave auto EQ off. If they were tall L-16's the answer would be different. Using a hydrometer will verify to you this works fine with the Tristar. It has a very smart automatic self adjusting algorithm, but you won't find any good explanation of what it does. It works, period. I tried to get Morningstar to address this many years ago. If they could do a better job of marketing they would be even bigger, but they still are the worldwide leader.
  • KJ7YMKJ7YM Solar Expert Posts: 30 ✭✭
    Thank You Guys,

    Vic thank you, I had discounted that thread earlier because it looked like it was addressing AGM batteries. But re-reading it did provide me with some vital pieces I was missing, which coupled with Bobs comments enlightened me enough to go and reset the areas that I obviously had set wrong. Thanks again guys.
    Larry
  • KJ7YMKJ7YM Solar Expert Posts: 30 ✭✭
    Well guys, I went back and looked into the manual from MorningStar for the TS-MPPT-60 and a lot of the answers I did not think were there actually are.The document looks a lot different a month into the hobby, compared to when you first read it with zero knowledge or experience :-)
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