Equalize

RussellJRussellJ Registered Users Posts: 15 ✭✭
I have two Sun 120's, a harbor freight 45, SunSaver 20 and two 100ah lead acid deep cycle batteries wired in parallel. My daily dod is 15-20% and my Trimetric says I'm getting a full charge almost every day, might only miss 1 day in 10 due to weather. I've read here that equalizing the batteries once in a while is good for them but my charge controller doesn't have an Equalize mode. So my question is, how can I equalize my batteries?

Comments

  • TnAndyTnAndy Solar Expert Posts: 249 ✭✭✭✭✭
    Re: Equalize

    Either get a supplimental charger if you have grid power available and use that ( Like an Ioata....be sure you get the IO4 chip in it ) or buy a programable charge controller.

    http://store.solar-electric.com/ioen12vo15am.html
  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Re: Equalize

    According to the SunSaver manual... If you have the controller configured for Flooded Cell batteries, they are designed to charge at a higher voltage (14.4 volt nominal) to keep the battery well mixed.

    If the batteries have a pretty good bubbling action and you need to add distilled water every month or so--the batteries may be doing OK.

    If you want to manually equalize the batteries--follow the battery equalizing instructions and just jumper the solar panel + input connection directly to the battery + connection for the appropriate time/voltage for your battery bank every month or so. Typically, 2-3 hours at around 15-15.5 volts.

    If you do jumper (or add an "equalize bypass switch")--you need to make sure that the area is well vented (no hydrogen gas) and sparks do not get near the battery.

    As always, be very careful around the batteries. Hydrogen gas and very high available short circuit current can ruin your day if you do something wrong.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,373 ✭✭✭✭✭
    Re: Equalize

    Sunsaver = no EQ function. That's a bummer. These are Flooded Batteries, with water fill caps right ?

    If this was my system, and I had to do it manually, this is what I would do.

    Give the batteries a night off, so they are full charged in the AM

    As soon as the Charge controller thinks they are in float, I'd bypass the controller, and
    connect the batteries directly to the panels, and verify the batteries are still charging (with a voltmeter). Open doors to ventilate the hydrogen gas. After an hour of this, I'd check the battery voltages again, and get my ear down close to them, and listen for bubbles and gurgles as the cells bubble. I'd then let this go on for a couple of hours, you don't have a lot of PV, and they are pretty big batteries. Then just connect batteries back to the charger in the normal mode. Give them an hour to calm down, and pop the caps off, and refill with distilled water. Mop up any acid mist or spillage.
    Id' repeat every other month, since it's a pain to do, and maybe look into a controller that will do it. I know even the C-12 will do it, manually with a push button, and maybe has a 30 day auto timer to do it too.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Equalize

    if you have the batteries cross wired then you may not need to eq them. the interconnecting wires must be equal in size and length to do this though. after that the power can be applied or taken from opposing battery posts. more specifically that means the negative post of one battery and the positive post of the other battery. if you disconnect the batteries and measure their voltages with a dmm after a few hours at rest, this will show if one battery has charged up differently than the other. what you could do in this case is to charge the 2 batteries separately one at a time and then recombine them for parallel operation. odds are your batteries are probably not very out of kilter being there's only 2 of them.
  • icarusicarus Solar Expert Posts: 5,244 ✭✭✭✭
    Re: Equalize

    You can also use a hydrometer to check each individual cell. ( A good idea to do every once in a while anyway). If there is a significant difference between cells, the do an Eq.

    I personally check my cells frequently and almost never is there much of a difference between them. I do a have assed Eq now and again, but I don't know that I need to.

    Tony
  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Re: Equalize

    Equalization has two major tasks for flooded cell batteries.

    One is to "equalize" the charge between cells in series (and parallel) by charging any slightly undercharged cells while wasting energy in over charging the already charged cells.

    The second is to mix the electrolyte which can stratify (heavy/dense electrolyte at the bottom of the cell, the "water" at the top of the cell) by creating hydrogen gas to mix the electrolyte evenly throughout the cell... More of an issue for "tall" batteries.

    For AGM's... The standard recommendation has been to never equalize, because they can vent hydrogen gas/electrolyte if there is too much energy pumped into a cell during equalizing.

    However, recent experiences (and some mfg. recommendations) do suggest that a "light" equalization once or twice a year will help batteries with cells that have individual charge variations (some cells less than 100% charged).

    Following the mfg. recommendation for equalization (time and voltage based on battery type and current cell temperature) and making sure that distilled water is added as needed (flooded cell) is key to keeping the batteries operating well.

    Batteries that are part of parallel (or series/parallel) strings, especially those with unbalanced wiring (some batteries short cables, others with long cables to the bus bars) can be helped with equalization--However, the battery cabling should still be fixed/modified to help ensure that all batteries equally share the work. Equalization, by itself, will not "fix" an incorrectly wired/configured battery bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RussellJRussellJ Registered Users Posts: 15 ✭✭
    Re: Equalize
    niel wrote: »
    if you have the batteries cross wired then you may not need to eq them. the interconnecting wires must be equal in size and length to do this though. after that the power can be applied or taken from opposing battery posts. more specifically that means the negative post of one battery and the positive post of the other battery.

    Cool! That's exactly the way I set them up. The batteries do make bubbles during the afternoon so I guess they're doing ok. I didn't see anything in the SunSaver operating instructions for jumping the + terminals. I tried connecting the panels directly to the batteries once but in less than 30 min. the input voltage was up over 16! Seemed too high to me, I was afraid of warping something.

    Using a tempurature compensted hydrometer, it shows all the cells around .1230-.1240 at the end of the charging day. I thought it should be higher than that? The Trimetric shows <1 amp into the batteries by late afternoon so I assume the SunSaver thinks they're full.
  • icarusicarus Solar Expert Posts: 5,244 ✭✭✭✭
    Re: Equalize

    According to the NAWS battery info site: State of Charge (Depending on temp, it sounds like you may be a bit low)

    "State of charge, or conversely, the depth of discharge (DOD) can be determined by measuring the voltage and/or the specific gravity of the acid with a hydrometer. This will NOT tell you how good (capacity in AH) the battery condition is - only a sustained load test can do that. Voltage on a fully charged battery will read 2.12 to 2.15 volts per cell, or 12.7 volts for a 12 volt battery. At 50% the reading will be 2.03 VPC (Volts Per Cell), and at 0% will be 1.75 VPC or less. Specific gravity will be about 1.265 for a fully charged cell, and 1.13 or less for a totally discharged cell. This can vary with battery types and brands somewhat - when you buy new batteries you should charge them up and let them sit for a while, then take a reference measurement. Many batteries are sealed, and hydrometer reading cannot be taken, so you must rely on voltage. Hydrometer readings may not tell the whole story, as it takes a while for the acid to get mixed up in wet cells. If measured right after charging, you might see 1.27 at the top of the cell, even though it is much less at the bottom. This does not apply to gelled or AGM batteries."

    I suggest that you might read :http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries
  • PhotowhitPhotowhit Solar Expert Posts: 4,996 ✭✭✭✭
    Re: Equalize

    "...Specific gravity will be about 1.265"

    Only true when adjusted for Temperature, the OP is correct to worry about the temperature when equalizing.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
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