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Old 11-11-2010, 10:15   #1
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How Often Do You Check Your Water and How Low Is Too Low ?

I just dropped four new T105's in and am doing some finishing touches on the installations. So far, so good. I'm determined to set these up the "right way" rather than just eyeball it and hope for the best. My two current (pardon the pun) questions:

1) According to this link: Electrical Study Hall: , 50% is around 12.25 volts. So if you're "never supposed to drop below 50%", making sure the voltage is higher than 12.25 volts is good, right?

1)a. Won't temporary loads drop the voltage a bit lower perhaps, then when that temporary load is stopped the voltage could come back up?

What is "too low" and how are you measuring?


2) How often are you checking and adding water? Anything charging the batteries is "smart" and has temperature sensors and throttles amperage based on the battery type and voltage. Will once a month be fine / overkill?
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Old 11-11-2010, 11:47   #2
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I use 75% as a rule rather than 50%. Batteries last much longer then.

Fairly easy with solar panels. (And sun )

Check the water 1 or twice a month in the summer, batteries are 90 degrees and will use water even with no load and no charge.

Got the same 4 golf cart batteries, but Deka instead of Trojan.
Previous set lasted 5 years, could have gotten more, but I accidently let one cell down below the top of the plates.
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Old 11-11-2010, 11:54   #3
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I use 75% as a rule rather than 50%. Batteries last much longer then.

.

Hard to do when living when living on the hook. I go down to 50%. I find I'm using the band from 85% to 50% as the last 15% takes a lot of time to charge up.
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Old 11-11-2010, 11:59   #4
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anything lower than 10 volts and the battery will not fully recover is general rule but deep cycles will do better than cranking batteries. Best to keep above 12 volt but most will not be harmed by 11.5 or so
As for how often to add fluid? when they need it of course lol but i do mine once a year and check more often but if you are heavily charging it could be once a week just have to keep an eye on it till you find your needs.
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Old 11-11-2010, 12:09   #5
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G'day, mate. Your 12.25 volts is a good target point. At the end of the refrigeration cycle using the inverter, I see voltages under 12, once the large load is removed, they quickly come back up to the target point. Hasn't been an issue over the 13 years so far on these AGM's, plus you don't have to worry about checking the water levels. Cheers.
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Old 11-11-2010, 12:15   #6
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Checking voltage

By definition, the voltage used to gage a battery's state of charge is the "resting voltage" that means no load for a few minutes.
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Old 11-11-2010, 12:16   #7
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The lower the discharge level, the shorter the battery life. Keeping you batteries above a certain point can be expensive, noisy, and smelly. A good battery monitor can pay for itself quickly.

As for battery levels, when I replace my personally damaged T-105s (not enough water ), I started checking the levels weekly. After a few weeks I had an idea of when I needed to top off.

Also, if I ran a movie marathon or used gobs of power via the inverter, I'd check more often. I check them every 2 weeks regardless, though. I get a look at the wiring, check the terminals for tightness and lack of corrosion, and top off the batteries with either distilled water or RO water directly from the RO.
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Old 11-11-2010, 12:34   #8
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By definition, the voltage used to gage a battery's state of charge is the "resting voltage" that means no load for a few minutes [sic: HOURS].
The battery voltage chart refers to resting open circuit voltage. Open circuit voltage is generally measured 12 hours after charging to allow surface charge to dissipate.

If the electrolyte liquid level drops too low, the plates are exposed to air, lose capacity, and are damaged.
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Old 11-11-2010, 13:02   #9
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Okay, thanks gentleman. In regards to adding water, I know the plates are supposed to be covered, but exactly how much am I supposed to add? Is there a little mark or something inside if I flash light around in there?

And do I need to test the specific gravity, or just add distilled water?
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Old 11-11-2010, 13:14   #10
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I always use distilled water and add it to the bottom of the fill holes. Hard to describe but the fill holes have "collars" (for want of a better word) on them, going into the batteries. I fill till the water just touches these collars.
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Old 11-11-2010, 13:15   #11
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Get yourself one of these.
It stops filling at the proper level.

Battery Filler Bottle

Filling to the collars is ok, but not if you're going to equalize.
The batteries will blurp out electolyte.
Don't ask how I know.
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Old 11-11-2010, 13:18   #12
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Get yourself one of these.
It stops filling at the proper level.

Battery Filler Bottle

Filling to the collars is ok, but not if you're going to equalize.
The batteries will blurp out electolyte.
Don't ask how I know.
Well look at that.
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Old 11-11-2010, 13:48   #13
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Gord, the OP was looking for the time to begin charging. Presumably many hours after charging but possibly under load.

I was saying that the voltage under load is not an indicator of state of charge.

Determining state of charge, during a charge is better tested by the aceptance rate.
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Old 11-11-2010, 14:03   #14
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Different battery types will have a different voltage at 50%. For example, Rolls batteries ( Voltages, Specific Gravity and State of Charge (609) | Rolls Battery ) will show 11.6 v under load at 50% of charge. Back when I used lead acid batteries I always used 12 v even as the 50% point when I considered recharging to be urgently needed.
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Old 11-11-2010, 14:21   #15
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... Is there a little mark or something inside if I flash light around in there? ...
Usually.
Electrolyte levels should be just below the bottom of the vent well, about Ĺ - ĺ inch above the tops of the separators.


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... I was saying that the voltage under load is not an indicator of state of charge.
Determining state of charge, during a charge is better tested by the aceptance rate.
I agree, only suggesting a longer resting period.
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