Trouble getting to 100% SOC

Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
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
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Comments

  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Trouble getting to 100% SOC
    Last absorb was 4 hours at 59.2v but got only to 51.2v and 1.265 SG
    Not sure what your saying, Absorb doesn't start until you get the voltage up to 59.2 volts, then the time starts, if 4 hours in not enough extend the time or raise the voltage .2 volts or so.
    (Interstate says 100% is 1.285 and 51.84v)
    51.84 must be a float voltage.
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Sorry if I wasn't clear. What I meant was that I did 4 hours of absorb with a setpoint of 59.2 then let the batteries rest and tested the SG and voltage. They read 1.265 and 51.2v.

    Interstate says a resting no load voltage of 51.84 approximates a full charge (6.48v per)
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Trouble getting to 100% SOC
    Dan_ wrote: »
    Sorry if I wasn't clear. What I meant was that I did 4 hours of absorb with a setpoint of 59.2 then let the batteries rest and tested the SG and voltage. They read 1.265 and 51.2v.

    Interstate says a resting no load voltage of 51.84 approximates a full charge (6.48v per)
    Ok, got you, after I thought about it a little I got it. I guess it could stay that high, but the actual resting voltage seems more like 50.72, but since the SG's are low then raising the voltage or extending the time will work.
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Just did a 5hr absorb at 59.2 . Tested after 30min rest. Voltage reads 52.2 (still needs stabilizing?) And SG is now only 1.250 some cells closer to 1.225
    Near end of charge there was about 4A still going in to batteries. Is that about normal?

    I need to call Interstate tomorrow to double check I'm looking at the right data
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Trouble getting to 100% SOC

    Well, the information is a little different this time. With the difference in the cells .25 SG level your probably going to have to do a Equalization. That is done at 61-62v for a hour at at time and then you check the SG level. This you do for as long as your still getting a rise on the lower cells SG level. GC-2's are are easy and you should see results in a hour or so. Your batteries are relatively new so it may be they have not completely formed their plates. You also have to watch the temperatures and not let them rise above 110 - 115 F. You also need to check the electrolyte level and add any water before you start.

    If you don't understand this , post back.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Trouble getting to 100% SOC
    You also need to check the electrolyte level and add any water before you start.
    But definitely do not overfill for two reasons:
    1. The electrolyte will expand as the temperature rises, but more important
    2. The electrolyte will be full of gas bubbles which will raise the level.
    You do not want to overflow the electrolyte in any cell during the process.

    Also, since the batteries will be getting quite warm, make sure that your hydrometer readings are temperature compensated.
    SMA SB 3000, old BP panels.
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Electrolyte levels are all good, just below or at bottom lip. Have not had to add any water in 2 months (charging every 3 days though).
    Before this I was even charging at 61.2 as recommended by Interstate. Weird to have zero water loss

    Can an eq be done with the batteries at any soc or only when full? I assume full is best but having issues getting there

    Why didn't SG come back to previous reading? Too much absorb time? Still not enough? Higher voltage needed?
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Trouble getting to 100% SOC
    Dan_ wrote: »
    Electrolyte levels are all good, just below or at bottom lip. Have not had to add any water in 2 months (charging every 3 days though).
    Before this I was even charging at 61.2 as recommended by Interstate. Weird to have zero water loss

    Can an eq be done with the batteries at any soc or only when full? I assume full is best but having issues getting there

    Why didn't SG come back to previous reading? Too much absorb time? Still not enough? Higher voltage needed?
    It's easier to do a full charge, but the EQ does not start until you get the voltage up to the 61.2v. The acual voltage the batteries see is somewhat lagging what you see on the monitor. I am still thinking if you have less than 25-30 cycles on them ( some of their Pure Lead will take more cycles ) the plates are forming. You can have Voltage from a square of active plate and still have low SG levels. If they are sulfated, you see a rise in the SG level.
  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Re: Trouble getting to 100% SOC

    If you are not using any water--You may still be under charging them. Are they bubbling a little bit when they get fully charged?

    Also, have you confirmed the charging voltages with a good DMM at the battery bank (and not just the meter on the charge controller)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Here are the Interstate specs for GC2 HD http://www.interstatedealers.com/pdf/201535.pdf

    57.6v bulk (not sure what that means since voltage is variable and increasing during bulk)
    61.2v absorb
    62.4v eq

    I am using a Victron BMV-700S battery monitor which I've tested against a reliable multimeter. Outback FXs reading was high though but has been calibrated down with mate.

    I've definitely done fewer than 30 cycles on the batteries. Is there a recommended process for new batteries to get plates to form? Haven't yet charged with caps off to check for bubbles but will next time. When charging at 61.2 though I can smell what I assume to be electrolyte gassing. Just weird not to see levels drop.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Trouble getting to 100% SOC

    The battery specs are, as usual, not for solar use.

    To be sure the battery is at full capacity you want to discharge/recharge repeatedly. Not partially on either side of the cycle: take them steadily down to at least 75% SOC and recharge fully. A bit of a problem if you're having trouble hitting 100% SOC. Always check charge state with a hydrometer; do not judge by Voltage alone.

    The Interstates are not a good choice for RE because like Trojan and Surrette they want a rather high Absorb Voltage and that can be difficult to achieve in the limited amount of time available from the sun.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Trouble getting to 100% SOC

    You won't get much of a answer why the Absorb is higher than the Bulk. I emailed them once because I thought it was a misprint. One of their engineers answered back that it was higher because of the Pure lead content of the HD plates. The plates are very thin, but there many more of them than a regular GC-2. I got those batteries as a trade-in on a new set I installed, they were less than a year old. I did as coot advised, I started to cycle them and did a couple EQ's on them and they were fine. I sold them and as far I know they are still working fine.
    not sure what that means since voltage is variable and increasing during bulk
    Bulk Voltage is the trigger point to start Absorb. The actual Battery voltage tends to be a lag behind the displayed voltage because what your seeing is being raised by the over voltage of the charger. But it's not as much as they advise. I think I used around 58 v to absorb them.

    I think the email was posted in a thread here several years ago. If you search there 100's

    http://forum.solar-electric.com/showthread.php?10710-Absorption-voltage&highlight=Interstate+batteries
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Interesting to read through that thread. I have contacted Interstate similarly and havent gotten the answers I'm looking for. Just about what I expected though given they're the cheapest option.

    Hydrometer I've been using is East Penn temp calibrated. Should I even trust Interstates SG figure for 100% though?

    So my issues are just related to the batteries being new and I should just cycle them more? Doesn't seem like I should go higher than 5 hours absorb...or should I?
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Trouble getting to 100% SOC
    Dan_ wrote: »
    Interesting to read through that thread. I have contacted Interstate similarly and havent gotten the answers I'm looking for. Just about what I expected though given they're the cheapest option.

    Hydrometer I've been using is East Penn temp calibrated. Should I even trust Interstates SG figure for 100% though?

    So my issues are just related to the batteries being new and I should just cycle them more? Doesn't seem like I should go higher than 5 hours absorb...or should I?
    I'd cycle them for a couple weeks and see if the SG level and the voltage begins to converge. 4 hours in absorb would be at the far end of what I have ever absorbed GC-2's. Usually 2 hours is about average. your using a fairly high voltage and that will usually cut the time back. The only have 6x6 inch plates.
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Everyone's input is much appreciated thank you.

    I read some discussion in other threads about discharging the batteries deeply to develop their plates when new. Is this advisable or should I stick with 30-40% DOD?
    Is 1.265 the 100% mark or 1.285 as interstate claims?
    I've done a few 2-4 hr 61.2v absorbs in the past. Any potential plate damage?
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Trouble getting to 100% SOC
    Dan_ wrote: »
    Everyone's input is much appreciated thank you.

    I read some discussion in other threads about discharging the batteries deeply to develop their plates when new. Is this advisable or should I stick with 30-40% DOD?
    Is 1.265 the 100% mark or 1.285 as interstate claims?
    I've done a few 2-4 hr 61.2v absorbs in the past. Any potential plate damage?
    The forming action should work just fine with a discharge to 60% SOC (40% DOD), although some manufacturers may recommend 50%. Going deeper is more likely to do harm than good through sulfation, especially if the battery stays below 50% for several days.

    As to the SG, different batteries are provided when new with different SG electrolyte, and in some cases the documentation that accompanies the batteries does not catch up with changes in the supplied SG.

    Some battery manufacturers also supply "tropical" versions of the same battery with a lower initial SG to compensate for the faster battery deterioration in high temperature environments. Or "cold weather" models with higher SG to provide more current capability in cold weather.

    Too much vigorous "boiling" of a battery can cause deterioration of the positive plates and irreversible loss of electrode material, decreasing the capacity and shortening life. It becomes even more likely if the battery temperature is allowed to rise too high during EQ. Even cool gentle EQ (almost just extended Absorb) can cause water loss requiring more frequent refilling of the batteries.
    SMA SB 3000, old BP panels.
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Just gave the bank a 3.2hr absorb at 59.2v. I opened the caps and indeed bubbles were coming to the top. SG before charge was about 1.210, after charge average cell SG is 1.240 (still very far away from the supposed 1.285 full). I was going to let the absorb go 4 hours but the current going in stayed steady at 4A for 10min so I turned off the generator. No load voltage reads 51.8v (which incidentally interstate says is 100%)

    Thinking about doing an EQ at 62.4 for an hour tomorrow
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Trouble getting to 100% SOC

    I sure hope that SG reading of 1.400 is a typo.

    Don't Equalize unless there is a significant discrepancy in SG between cells and you've already got at least some at "full".
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Haha yes typo sorry

    What I meant was 1.240 on average. One cell measured as low as 1.230 and one as high as 1.245 but most close to 1.240 (which still seems awfully low)

    I'm still not sure if I have a faulty hydrometer, a faulty set of batteries or some fault with my procedure (doesn't seem like that).
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Trouble getting to 100% SOC

    1.240 is still too low, and the 'spread' of 0.015 between cells indicates a need for EQ.

    Go for the equalization charge.
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Alright will do

    Looked up the warranty on the batteries and its 12mo free replacements so I still have 9mo to take them back if needed
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Consumed 9Ahr since the last charge yesterday and just now did a 1hr EQ at 62.4v. I was curious whether the plastic battery casing would heat up at all but did not one bit; they were cooler than ambient air.
    EQ seems to have evened out SG, all cells now read very close to 1.250
    I bet if I was charging daily with shallower discharge (and then shorter absorb time) I'd probably be able to top it off to 100% but still yet to see it. Still no panels (hopefully this week though). Hate running the generator so only do it every 3 days or so

    What's an appropriate ending amps to look for with GC2s. So far I've seen high 3s and 4A before time ran out. Some say 1-2% bank ahr so according to that either 2.1 - 4.2A
  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    Re: Trouble getting to 100% SOC

    With Interstate GC2s I have found I need to use the recommended high voltages to get them to 100%. Running them with a grid interactive inverter didn't help either in the sell mode. As of late I have been charging, equalizing, and discharging to desulfate and get them equalized. Taking my limited experience into account they don't seem to be overly gassing using the recommended high voltages and don't seem to reach 100% soc unless I do use the higher voltages.

    Just my 2 cents.
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Much appreciated helpful to have other GC2 experiences. So by high voltage do you mean 7.65v per or 7.4v per or?
  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    Re: Trouble getting to 100% SOC

    Currently 7.65 on absorb using end amps at 3 volts, but like you I have some uneven cell SOC readings I am trying to remedy and like you I didn't properly commission my bank.
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Gave the bank a 3hr absorb today, ending amps were 4.5. Checked SG in two batteries. Within one all three cells read 1.250 and the other battery all 3 read 1.235 or thereabouts. Discrepancy probably because I haven't got the damn thing to full.
    Finally got my panels. Have 2800w but have only setup 720w temporarily until I get poles in the ground. Only using about 500whr per day. Fingers crossed for finally getting to full and no more gasoline!
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    Been charging from solar the last few days. Wonderful to charge in silence and listen to the batteries bubble.
    Everyday it seems like it's getting a full charge (I have end amps at 2) but SG is only at 1.260 (temp corrected). I believe some manufacturers consider this full or close to but Interstate says 1.285. Might have to up the voltage as verdigo does
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Trouble getting to 100% SOC

    The problem with Interstate is they have a lot of conflicting information out there. If the batteries were filled with 1.280 electrolyte then you'd have no problem getting to 1.285. On the other hand even with a EQ and massive over charge, I'v never been able to get 1.265 past 1.280. They are not clear about if their numbers are loaded or resting.

    I found this today in what they term deep cycle batteries. To me their voltage is off and the SG levels sure are.

    Attachment not found.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Trouble getting to 100% SOC

    Looks like a generic chart to me: resting Voltage and SG.

    Interstate unfortunately has batteries that are like Trojan and Surrette: high Voltage compared to mainstream. 15+ Volts for Absorb! Not a good thing for your basic 12 Volt system with a typical inexpensive inverter that will be screaming "over Voltage" every day at that level, never mind EQ.

    One reason why I don't like Interstate batteries.
  • Dan_Dan_ Solar Expert Posts: 61 ✭✭✭✭
    Re: Trouble getting to 100% SOC

    No way I will be buying cheapo GC2s again but they're so tempting given the price and local availability. Interstate seems specifically bad. How can a battery company be clueless about their batteries?
    I was suspect as well about the electrolyte numbers given. Attached is their spec sheet though


    I'm having a discrepancy between what my Victron battery meter (shunt) is reading vs what the Outback FM says. Currently 2.18A shown at the shunt but FM says 3A. I don't have the outback dc meter too expensive. Should I not use the end amps feature because of this?
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