27DCs and SG Lag Problems

LittleBill wrote:
so question, does SG drop as the battery gets sulfated? how do you know when to stop charging if the sg is lower then what full is suppose to be?

If the SG will not rise any more with the charger doing its best after a decent time to give it a chance to work, then stop the charge. All you are doing after that is heating things up and damaging the plates.

Yes, it is normal for the plates to get sulphated as the battery is discharged while at the same time the electrolyte becomes less acidic and so less dense, which makes the hydrometer float lower showing less SG.

On recharging, the sulphate is supposed to go back into solution, making the plates less sulphated and the electrolyte more acidic and so more dense, making the hydrometer float higher showing more SG.

Recharging is never fully complete so after so many cycles, the plates get clogged up and you need a new battery. The name of the game is to get as many cycles as you can with the least fussing over the batteries. Convenience and money.

If you don't fully recharge the battery that means the electrolyte is not fully acidic and SG is lower. Sulphate is still on the plates which is hard to get off and after a while can't be got off.

Even if you get the electrolyte fully acidic, if it is not mixed well, the bottom will be more dense than the top. This will have the hydrometer only picking up the top stuff which is less dense and so showing less SG.

Now you have a mismatch between your resting voltage showing full SOC, but the SG saying you are not there. (Which is where my 27s OP problem seems to be)

The cure for that is called "de-stratification" to mix it up and get the top part dense too. This is not "de-sulphation".

If you do not de-stratify, the top of the plates will still have some sulphation and the bottom of the plates will be in over-strong acid.

So you will be getting new batteries sooner.