uneven topping up of lead acid batteries in series.

Tunis0101

Hello,
I have two 12v 200A lead acid batteries connected in series, after a good equalization charge on a sunny day from my solar panels I thought I’d top the batteries up since it’s been a year since I’ve done that (they are low maintenance)
I bought 1 liter of distilled water and it was only enough to refill one battery, I can’t get another liter until tomorrow morning, can I use the bank normally until I refill the other one?

Foxxie

the specific gravity will be slightly different between the two. so the batteries will not behave identically until you get that other one filled.
One will want to charge/discharge faster than the other causing them to get further away from each other each charge and discharge.
As long as its above the plates on both batteries. the battery with more water will have a slightly lower specific gravity.
If the plates are exposed on one battery due to low water level it will not be a good idea to use them in this state at all.

You can keep them on float charge until the water arrives. to prevent discharging.
Battery with lower specific gravity (higher water level. lower acid concentration) so one battery may become overcharged while the other one is not quite full yet. and gas and bubble vigorously. before the other one catches up. causing it to gradually drift further apart..
if you have no choice and must use them as-is. you may be able to extend the absorption time by 1-4 hours for the lower battery to catch up. without equalizing. but you’ll be potentially causing extra water usage and corrosion of the battery plates than if they had the same amount of water in each and reached full at a more equal time.
You want the batteries to stay in almost identical states and condition for them to stay a matched series string and work well together.

Foxxie

I can’t seem to read the entirety of your reply. it cuts off after “I don’t” and it completely disappears when I click on it.
This website has been acting very screwy and problematic lately.

It may of been charged or equalized too aggressively. if it has muddy reddish brown water.
See if it clears up after a few days of being in floating stage with no extra charging or discharging. no equalizing.
You may also want to independently charge both batteries to full one at a time with a 12v charger if one is significantly lower than the other and unable to “catch up” when charging normally.
Also how does it function? Does both batteries behave normally. or does one of them drop voltage a lot when a load is applied.
Murky or cloudy water is caused by charging at a high rate or equalizing. with the fluid stirring up loose particulate material in the battery. either from the lead plates or sulfate being stirred up by the bubbles.

dark Black or very dark brown cloudy water is what you want to avoid. Severe damage to the battery plates has ocurred if this is the case.
How does it look with a bright flashlight?

Very aggressive or prolonged equalizing can cause corrosion of the positive plates causing reddish brown cloudyness.

Does it clear up if you leave the battery sit a while on float?