Battery voltage question

[Hillbilly Deluxe]

I built a 48 volt cart with 8 six volt t105s ( new). I broke them in correctly and at first, I was getting pack reading of approximately 51.5. Recently, about three months later, I added water for the first time and charged again. Now the charge for the pack is reading about 50.9, which is typically considered full charge. Question is, will adding water temporarily lower the pack voltage until I get a few charges on it?

[JohnnieB]

Since nobody's replied, I'll give it a W.A.G.

You stated you added water for the first time and charged again. Does that mean you charged the batteries, watered them and the charged again, or does it mean you added water to partially discharged batteries and then charged them. Water (Distilled not tap) should only be added to fully charged batteries.

When are you measuring the battery voltage?
If you measure shortly after the charger kicks off, you'll be reading something called "Surface Charge", which dissipates quickly with use or over about 12 hours when idle.
After the surface charge is gone the 6V batteries should read about 6.37 each and should be within about 0.1V of each other.
A newer battery may have a slightly higher voltage and the fully charged, open circuit voltage declines as the battery ages.
A fully charged lead acid wet cell has a Specific Gravity of approximately 1.277.

When you add water to the electrolyte of a fully charged battery, the Specific Gravity will become less until battery is recharged.
If a significant amount of the Sulphuric Acid in the electrolyte solution had been lost to boiling over and out-gassing, the specific gravity might not reach the full charge concentration.

As for the answer to your specific question:

Question is, will adding water temporarily lower the pack voltage until I get a few charges on it?

I don't know for sure, but it might.

[scottyb]

You stated..."Recently, about three months later, I added water for the first time and charged again"

New batteries charge a lot longer than when they are broken in. These long charge times coupled with the high summer temps could have depleted the water levels considerably in 3 months.
IF you let the water levels drop below the lead plates, let the plates get exposed to air, then that would explain the drop in capacity?
Otherwise, if you added a bunch of water, it should come back up in a charge cycle or two.

Check water levels once a month.

[Hillbilly Deluxe]

The water was added then charged. Also, The plates were never exposed. Next charge the voltage raised. I believe I simply diluted the acid. Thanks.

[scottyb]

yes, that could be