bulk to fast ?

offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
On sunny days Im zooming through the bulk stage of charging in about an hour or so. The voltages for bulk absorbe and float are set to battery specs. I am over paneled (4200watts for 450amp hr 48v) so I was thinking I need to set my cc to a lower charge level. I usually see 45 to 50 amps in bulk but have seen as high as 79amp. Should I set my cc at a lower level and if so how low. It does not let me set max amps just a percentage value. Darn xantrex. I do have a batt temp sensor hooked up.

Comments

  • Joe_BJoe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    Re: bulk to fast ?

    I have about 2.5 KW of panels on a 24 volt system with 740 AH of FLA batteries. From a DOD of 85% it takes me about 3 hours to get into absorb. I run my AC charger at 60% and my solar at 100%. Basically you want to shoot for about 10-15% of the batery capacity as a max bulk charging current. So 45 to 75 amps is good for your bank size of 450 AH.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: bulk to fast ?
    offgrid me wrote: »
    On sunny days Im zooming through the bulk stage of charging in about an hour or so. The voltages for bulk absorbe and float are set to battery specs. I am over paneled (4200watts for 450amp hr 48v) so I was thinking I need to set my cc to a lower charge level. I usually see 45 to 50 amps in bulk but have seen as high as 79amp. Should I set my cc at a lower level and if so how low. It does not let me set max amps just a percentage value. Darn xantrex. I do have a batt temp sensor hooked up.

    That 79 Amps is a 17.5% charge rate. It will destroy the batteries.
    If your Xantrex controller does not allow you to set a charge current limit, take some panels off. You don't need more than about 3000 Watts for 450 Amp hours @ 48 Volts.
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: bulk to fast ?

    If you set the CC to a lower voltage, it will reach that level even quicker and go to absorb even sooner.
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: bulk to fast ?

    Its not a voltage setting its a charge current level. However there is no definition in the instructions as to what the %'s are. I would assume they are based on the max charge level of 80 amps. So would I set it to 50% so I would get a max of 40 amps. This is for the xanterex 80 600. Would this setting also reduce the output during float. Would it reduce how much I can draw for loads during charging. Where are the xanterex experts when you need them
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: bulk to fast ?

    I just had a look through the manual.
    Yes, the % limit on the output is based on its 80 Amp maximum capacity so 50% would limit the output to 40 Amps.
    As near as I can tell that is the output limit; there is no difference whether the current is going to charge batteries in Bulk or supply loads in Float. 40 Amps on a 48 Volt system is roughly 1920 Watts. Keep in mind the batteries can contribute to power draw by the inverter; you are not dependent on the charge controller's output for maximum power usage. In theory the DC side could handle twice that amount (40 Amps from he controller plus 40 Amps from the batteries) for a total of 3.8 kW +/-.
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: bulk to fast ?

    It just seems such a shame to choke down the output from my panels. On the plus side I can almost fully charge my batteries even on a rainy day. I guess Ill have to set it down to 60% to protect the batteries. Just a question but what is the damage done by charging the batteries to quickly besides thermal runaway which should be controlled by the temp sensor?
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: bulk to fast ?

    offgrid me,
    i am assuming you have fla type batteries and although it is over the high side of our normally recommended range, it will most likely be fine. you may have need of checking the water levels more often. if you want to reduce it it may be easier to just put a load on the batteries while they charge from the sun for the load will subtract from the overall charging amps. yours is indeed a rare case as few have too much power, so to speak.

    i was not aware that the xw 600 had the ability to cut back on its current output. can you guys confirm that with me?
  • VicVic Solar Expert Posts: 2,970 ✭✭✭✭
    Re: bulk to fast ?

    Hi OGM,

    In looking at the manual for the Schneider XW MPPT, It says, "Advanced Settings>Charger Settings (under the label) Max Chg Rate"

    Set a number from 1 -- 100 which appears to be the percentage of the of the MAX charge current (I assume it is the percentage of the 80 A max value). Under the description it says, "sets the maximum charging current limit"

    Why not change this value and see what happens. The manual says that the Default is 100.

    I do agree with niel, that probably no harm would occur to your batteries in charging @79 Amps, And you did say that with the high observed. But, it might not be best to have the bank Bulking at or near this value every day. Pehraps we sometimes get a bit hung up on the exactness of rule-of-thumb values. Altho, batteries seem expensive, and some caution seems in order.

    You are one of the few who acutally meets or exceeds the Rule of 10% of capacity minimum charge rate ... congratulations.

    Have Fun, 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.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: bulk to fast ?

    very interesting feature.8) try setting it to 75 as that will put it a touch over the 13% mark. confirm this is the case as that corresponds to 60a.
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