When a lead acid battery sits without a charge for a while, the plates start to sulfate. This is taking the sulfur out of the electrolyte (H2SO4) and depositing it onto and into the plates (as they are often porous ot increase surface area). The plate surface sulfation ( actually lead sulfate) is an insulating layer to current flow. Some sulfation occurs during normal discharge. Recharging current reverses most of it, putting the sulfur back into electrolyte. Whenever the battery discharges (and it will do this all by itself with no load) sulfation occurs. However, when the plates are solidly sulfated (insulated), there is insuficient current to coax the sulfur deposits on the plates to recombine into the electrolyte. A sulfated battery is only interesting to a recycler who can smelt it to recover any lead that remains.
The "for certain" way to test for sulfation is to check the specific gavity of the electrolyte with a hydrometer. At 60 degrees F pure water is 1.000. Lead acid battery electrolyte will read between 1.100 (discharged) and 1.350 (charged) depending on how much sulfur is in it. The closer the number is to 1.000, the more sulfur is deposited onto the plates. Most likely your battery is not ever going to be very good again even if it does begin to take a charge with prolonged charger activity. It will never have close to the capacity of a new one as you can never completly reverse the sulfation. This means that one or more plates will always have a part of it insulated with a sulfation layer. New electrolyte will add more sulfur. But, it won't remove the sulfation layer deposited on the plates. They will still be insulated and prevent current flow. Extended charger activity is your only hope, provided the plates have enough distilled water to keep them covered. But, if it doesn't start taking current within 24 hrs, it probably never will. Cheers, Lloyd SOHC4 #11 72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F, 78 750 Kevin Hunter wrote: >I just bought an old Honda which has a 12V battery which looks brand new, >but was very dead (only about 3 volts) and apparently has high internal >resistance, since it won't take any current. However, the voltage (with the >charger disconnected) has flashed up to about 11.5 after only about 1/2 hour >of "charging". So far, the battery isn't gassing, and still not taking any >significant current. > >Should I dump the electrolyte (or water...whatever it might be), refill with >fresh acid and then charge, or just leave it go on the charger the way it is >and see what happens? > >Kevin in TX > >
