Trouble getting to 100% SOC



  • VicVic Solar Expert Posts: 2,993 ✭✭✭✭
    Re: Trouble getting to 100% SOC


    Generally, CC's output current readings are only approximate. A quality meter/monitor on a quality external Shunt should me more or considerably more accurate.

    The MN Classic CC appears to have a quality shunt for output current built-in. Older CCs seem to approximate output current.

    Would tend to believe that your Victron battery meter is much more accurate than an FM or MX CC's output current reading, and a meter on an external Shunt in the negative lead of the battery, should be measuring only the current going into the battery, as opposed to the current being sent toward the battery (which could include inverter idle and load currents).

    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.
  • boonhaulerboonhauler Solar Expert Posts: 35
    Re: Trouble getting to 100% SOC

    Dan, I just read through the entire thread and can somewhat sympathize with your SG pain.

    I too have a large bank (10) of CG-2's, mine are Crown 260's. The highest SG I've seen so far is 1.260 and IIRC last time around I didn't even get there.

    My voltage readings are high (12.8-9) 24 hrs after charging. I've tested my bank capacity and have verified DOD with my TriMetric. All the numbers pencil out but the SG readings so I've kind of backed off from getting freaked about it.

    I'm currently charging with a Magnum 2812 (125 amp) and have the Absorption set at 4 hrs IIRC. I too spoke with the tech guys at the factory and they went to an outside consultant. They came back saying it was okay to go with higher charging voltages than stated. I have my absorption set at 14.8 and think the float is at 13.8.

    When the solar is installed and handling the recharging I'm thinking I'll roll with the MS CC default settings but that remains to be seen. Here's a link to a site where I've discussed it in a little detail (post# 279 near the bottom of the page is where it starts)

    Dan_ wrote: »
    8 Interstate GC2-HD 208Ahr 6v in series charging from generator hooked to Outback FX3048 (panels arrive next week)

    First time managing batteries so learning the ropes. Have been charging and monitoring SG for full and if not upping the absorb time. I typically take 50-60Ah then charge. Last absorb was 4 hours at 59.2v but got only to 51.2v and 1.265 SG (Interstate says 100% is 1.285 and 51.84v)

    Should I up to 5hr absorb? What am I doing wrong? Haven't got the batteries to 100% since I've had them (2mos), are they damaged now? Glad I'm learning on the cheap batteries

    As always, thank you for your guidance
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Thanks for the reply. That is basically where I'm at as well. 1260 (temp corrected) is about the highest I see. Been going into absorb early everyday with little usage. Have it set to 4 hr, may need to back off. End amp seems to be around 3.5-4A which seems in line with what's normal.
    By the meters tally of ahr going in and out I'm always back to 100% but the benchmark for that is questionable. Without reliable SG readings it seems impossible to know true state. Having an unreliable/untrustworthy data sheet for the batteries sure doesn't help
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