I bought a brand new lead acid battery for my motorcycle after the previous one was at the end of its lifecycle. Just to mention the battery is of the brands associated with a good quality. It was a dry model that I needed to fill myself with the electrolyte sold with the battery. It worked well after following instructions carefully. No problem.

However after some 50h of driving and forgotting park lights on the battery was drain out. Voltage was down to some 10.5V or so. No hope for starting. No problem either. Just charge the battery. I took it apart just to check the overall condition and charge overnight.

Now, I understand that such an energy drain to low voltage can damage battery but what surprised me was that 3 cells had lost a lot of electrolyte and the rest 3 cells were at specified level. Anyway I added distilled water to specified level, charged overnight and there was again enough peak amperes to start.

Next I checked the regulator (roughly) after charging by checking the system voltage and it was (at "low rpm" like 1500 - 4500, about the rpm of of the travel speed of my bike) between 13.8 - 14.5V.

Ok, maybe for that specific battery - say 14.5V - is too much. I could understand that it could cause some (or even big) loss of electrolyte. What I can not understand is why some cells - in a brand new battery - were like nothing happened and the rest were like totally dry.

I do not know if it matters but the dry cells were at positive side of battery but not the most positive was the most dry. The amount of electrolyte (6 cells from - to +) was approximately 100%, 95%, 100%, 55%, 20%, 75%. These amounts just roughly describe the amount of electrolyte needed to satisfy the specified level average.

Is this kind of wearing in such a short time usual or should I return this battery to the dealer?

  • \$\begingroup\$ Did you use distilled water? \$\endgroup\$ – StainlessSteelRat Apr 22 at 17:00
  • \$\begingroup\$ (Initially.) Any other kind of water includes trace minerals which will destroy battery cells. \$\endgroup\$ – rdtsc Apr 22 at 17:09
  • \$\begingroup\$ I believe I wrote distilled in my question. \$\endgroup\$ – pirho Apr 22 at 17:11

When cells get oxidized from under voltage for long periods (lead sulphate) they develop higher ESR. The 14.2V is most commonly used on flooded cells to lightly agitate the plates with extra current to break down this oxide so it settles below the plates.

The weakest cell will accelerate its overcharging when there is 14.5V and instead of 14.2/6 you start to generate more heat from I^2ESR losses in one cell more than the others with lower voltage and start to boil off the acid. How well matched each cell capacity in kFarads also affects the voltage rise in each cell, so the weakest cell again overcharges and boils off more electrolyte.

The best way is to limit the voltage to 14.2 abs. Max and measure specific gravity , s.g. with a glass float and rubber hose with a sample for each cell. Quality of a battery with series cells is not only the high capacitance (Ah) and low ESR (CCA) but more importantly , how well matched they are.

Pulse discharging is an effective tool which can also desulphanate batteries when the battery is being charged >13.2V. If the sulphated condition is short term in months and ambient temperature is not too high >40’C the sooner this is done, the better your chances of recovery. Otherwise name brands mean nothing while perfectly matched high s.g. Means everything to a open flooded lead acid battery within 0.1%. 10% difference is poor.

  • \$\begingroup\$ Thanks, I understand your answer but does it actually answer to a question "How to revive your dead/sulphated lead acid battery?". I mean that I understand that when the battery goes to sulphated phase things are exactly as you said. But for a brand new battery what should have not been sulphated just after adding the electrolyte and when the charging system begins to charge what could have happened? I think battery was bad at the start. And after re-(distilled)watering it again works as expected (but for how long?). I am gonig to have a tester anyway to see individual cell charging %. \$\endgroup\$ – pirho Apr 22 at 17:46
  • \$\begingroup\$ So to clarify I understand the uneven evaporation after the drain when charging (filled with distilled water) . But if I "boiled" a brand new battery I would expect that all the cells had some roughly even evaporation. \$\endgroup\$ – pirho Apr 22 at 17:57
  • \$\begingroup\$ And to add maybe my title is not too clear... \$\endgroup\$ – pirho Apr 22 at 17:58
  • \$\begingroup\$ Unless you measured these parameters when new,or it’s still on warranty, not much can be said except to some pulse chargers work better than others. The rise time must be fast. It doesn’t need high current. The alternator does that. Your assumption that the battery quality was high could be wrong but 14.5 in high ambient temp is a reason for accelerated failure. \$\endgroup\$ – Tony Stewart EE75 Apr 22 at 18:58

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