battery questions

bw125bw125 Registered Users Posts: 4
I picked up a pair of 6v batteries from a scrap dealer. They were from a telephone co that replaced their battery bank.

3KCT 180 8HR CAP 180AH. They weight 120lbs each. They had a terminal voltage of 6.15 each when I got them. Roughly 70% charged if I'm correct. Paid $250 for the pair.

They look like they are in like new condition. The outside case is clear so the plates are visible.

Does this sound like a decent price? I see the trojan t-105 seems to be roughly the same capacity but weights like 1/2 as much (62lbs). Could one conclude that the batteries I got are just heavier and designed to last longer (more cycles)?

Thanks

Comments

  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: battery questions

    FREE used batteries can be a good deal. USED expensive batteries, probably not - sorry JMHO.

    Name brand Trojan batteries are expensive. But there are plenty of other equivalent batteries for a fraction of the cost, and seem to last every bit as long.

    I have 8 6V golf cart batteries in my bank. The oldest pair of the bunch is almost 5.5 years old, and still holding up. I paid $71 each back then. The going price at Sam's Club, as of last month...

    e.jpg

    f.jpg

    These have ~220AH capacity, and come with a warranty.

    I recommend charging, equalizing, then measuring the specific gravity of the ones you bought. Hope they work out well for you...
  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: battery questions

    It is difficult to tell... At least your batteries had a decent charge on them... Many batteries that sit for ~1-6+ months without charge will self discharge and start severe sulfation--Which kills battery capacity.

    If the batteries take a charge and cycle well--Then you got an OK deal.

    This looks like the batteries you got (PDF).

    If yours are 3K"C"T with calcium, then they will have lower self discharge and less water usage.

    These batteries designed for use as "UPS" type batteries (I am guessing)... Which is short/high current discharge at random times. Not exactly as used for for solar. From another document with batteries from the same vendor (but different models), they have two types of batteries listed, one for float and another for cycle service. There is a significant difference in cycle life between them (with ~3x longer cycle life for those batteries designed for cycling).

    Do you have a brand/link for documentation on your batteries?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bw125bw125 Registered Users Posts: 4
    Re: battery questions

    Yeah BB that pdf you linked to shows the battery. It was the only documentation I could find myself. C&D Brand 3KCT 180. 08/90 P# 04-79277 is the only other
    info on the batt. Maybe I should try and contact C&D to see what they say regarding if they are designed for cycling vs float.

    2manytoyz, Im in Canada and haven't found any big box stores that sell 'off brand' 6v golf cart batteries which is kinda why I jumped on this pair. Shipping costs on deep cycle batteries to Canada kills any deal I have found.


    I have them connected in series to make 12V and have them on a 2a (rc-2a12-3) charger atm.
  • DillDill Solar Expert Posts: 170 ✭✭
    Re: battery questions

    well, if nothing else, it will be cool watching them charge!
  • bw125bw125 Registered Users Posts: 4
    Re: battery questions

    Yeah the charger seems to peak at 16v... bubbling like crazy at that point :)
  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: battery questions

    Be careful with charging at "high voltages"... Typically, the maximum charging voltage is around 14.5 to 14.8 volts (if battery is at ~77F room temperature) for flooded cell batteries.

    Equalization is done at ~15-16 volts (at about 5% of rated AH capacity maximum) and usually only done if cells are miss-matched in specific gravity (say one cell is lower by upwards of 0.030 SG vs the high cell in the series string). Once the cell's SG stops rising (check every 30-60 minutes), stop the equalization charge (some chargers have 1-2 hours automatic equalization charging timers--different folks have different opinions if this is a good or bad idea for long term battery life).

    Otherwise, Equalization should be done when needed (different vendors recommend from every 1 month to every several months to twice a year). Equalization when not needed can be pretty hard on the battery bank and reduce its overall life.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bw125bw125 Registered Users Posts: 4
    Re: battery questions

    That charger claims to 'rejuvenate' by dissolving sulphation buildup. So I was gonna try a few charge/discharge cycles to see if it improves in capacity.

    Thanks for the warning BB, don't want to be causing unnecessary damage. That charger is fully automatic so from what I can tell everytime it's used it charges all the way up to 16V if left on till it says 'charged'.
  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: battery questions

    Lead Sulftate first forms as a fluffy type material--But after a few hours (to 24 hours), it then forms into a crystalline lead sulfate. The soft form is part of charge/discharge chemistry of the battery bank. The hard crystal does not participate and can be knocked of the plates when gassing occurs (exposing active plate material again).

    Too much gassing, besides erroding the plates, can also drive Oxygen (which forms on the positive plate during charging/gassing) into the plate and its supporting framework--causing oxidation and eventually failure (battery positive terminals can actually be pushed up a bit--or extruded out the battery top cover when oxidation becomes excessive).

    Deep Cycle Battery FAQ
    www.batteryfaq.org

    Are a couple things to read...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: battery questions

    i agree with bb that you are most likely overcharging those batteries with that charger. nowhere on their specs does it say you can apply 16v to the batteries. one consolation may be if the batteries are somewhat cool as charge voltages are usually referenced at 77 degrees f.

    that 8/90 may be the manufacture date and if so they are over 20yrs old. do contact the manufacturer for some advice and facts on those batteries.
  • Earnest TilleyEarnest Tilley Solar Expert Posts: 56 ✭✭✭✭
    Re: battery questions

    I have a question about batteries. I have 4 12v batteries later im going to get 4 of the golf cart batteries and set them up as 24v. I want to keep my old batteries but dont want to mix them is there anything wrong with puting a charge controller coming from the 24v battery bank (as if it where the solar panels) and running it to the 12v bank? Using separate inverters for each battery bank would this work or am i just being silly?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: battery questions
    I have a question about batteries. I have 4 12v batteries later im going to get 4 of the golf cart batteries and set them up as 24v. I want to keep my old batteries but dont want to mix them is there anything wrong with puting a charge controller coming from the 24v battery bank (as if it where the solar panels) and running it to the 12v bank? Using separate inverters for each battery bank would this work or am i just being silly?

    Not silly: it can work. But you don't want to use a PWM type controller between the two battery banks. An MPPT type will be much better suited to adjusting the Voltage down and controlling the charging. The PWM would just pass current, and it would have a lot of current available as batteries can produces hundreds of Amps and their Voltage doesn't fluctuate much. Many of the cheaper ones would burn up.

    Somewhere on the forum we discussed doing this exact thing for a boat system that ran 24 Volts but needed a 12 Volt battery for emergency radio equipment.
Sign In or Register to comment.