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Tedx

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Posts: 6
Reply with quote  #1 

I go to Battery University and read that the most comprehensive way to test the health of a lead-acid battery is with a hydrometer.  I check every cell of my 3200+ amp/hr battery bank and every cell tops the charts at 13.  Yet, my 3200+ amp/hr. battery bank cannot hold a charge AT ALL.  My battery bank is made of used batteries that I bought half price after checking them with a hydrometer to insure they were good.

I go to forums and the guy at the end of the bar tells me that used batteries, even with good electrolyte, will not hold a charge very well.  No explanation, no physics or chemistry, just personal experience.

From my experience the guy at the end of the bar is right and the authorities at Battery University haven’t the slightest idea where they are or what’s going on.

I’ve got two 48v pv arrays feeding the 24v battery bank through two MTTP controllers. One pv array does 1200 watts and the other does 1400 watts, which equals 2600 watts.  Each controller processes a little over 1000 watts at a time. 

On a sunny day by 10:00 a.m. the bank is stuffed full with juice at 29v. One controller has cut off to prevent overcharging and the other has reduced output.  The icons on my remote MT-50 meters show the batteries blacked out full.  I can do about anything with that power:  run my 1500 watt deicer in my water tank, run the 1500 watt electric heater in the cabin and operate my household water pump, transfer pump and power tools. 

As the sun sets, the voltage drops respectively.  At sunset it’s down to 26v and dropping.  At that time I cannot use anything that puts a heavy load on the bank.  I can’t run my water pump to wash the dishes till the next day unless I run the generator.  I actually had to run the generator because a meal I was making in my slow cooker was draining the bank. 

At night I use one energy-saving light for the entire cabin.  A small 3-amp fridge is the only other load unless I use my computer and modem.  That’s with 12 200 amp/hr+ golf cart deep cycle batteries and two giant 12v deep cell batteries from floor-cleaning machines in 4 sets of 24 v series, then in parallel, going through combiner boxes to a 5,000w inverter.

I really want to get a REAL college educated explanation to how lead-acid batteries work. I need to know what chemical reaction occurs as electrons run through lead plates from negative to positive polls in a solution of 75% H20 and 25% sulfuric acid. 

The manager of an auto parts store told me that even if the electrolyte is good, sulfated, damaged or consumed plates will prevent the battery from holding a charge.  If the plates are sulfated, damaged or consumed, how could the battery retain enough sulfuric acid in the electrolyte?  He didn’t know.  Neither does the guy at the end of the bar.  There must be a reason.

 

stmbtwle

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Posts: 2,872
Reply with quote  #2 
Try here:  http://www.trojanbattery.com/tech-support/


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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
colinmcc

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Posts: 167
Reply with quote  #3 

From the web....  I loved the final line :"Recharging a sulfated battery is like trying to wash your hands with gloves on."


"
When the active material in the plates can no longer sustain a discharge current, a battery "dies".

Normally a car (or starting) battery "ages" as the active positive plate material sheds (or flakes off) due to the normal expansion and contraction that occurs during the discharge and charge cycles. This causes a loss of plate capacity and a brown sediment, called sludge or "mud," that builds up in the bottom of the case and can short the plates of a cell out. This will kill the battery as soon as the short occurs. In hot climates, additional causes of failure are positive grid growth, positive grid metal corrosion, negative grid shrinkage, buckling of plates, or loss of water. Deep discharges, heat, vibration, fast charging, and overcharging all accelerate the "aging" process. Approximately 50% of premature car battery failures is caused by the loss of water for normal recharging charging due to the lack of maintenance, evaporation from high under hood heat, or overcharging. Positive grid growth and undercharging causing sulfation also cause premature failures.

Normally well maintained and properly charged deep cycle batteries naturally die due to positive grid corrosion causing an open connection. The shedding of active material is an additional cause. If deep cycle battery is left discharged for long period of time, dendrite shorts between the plates can occur when the battery is recharged. The low resistance bridge in the shorted cell will heat up and boil the electrolyte out of the cell causing a high volumes of hydrogen and oxygen. That is why proper venting and ventilation is so important when recharging batteries. Approximately 85% of premature deep cycle and starting batteries failures that are not recharged on a regular basis is due to an accumulation of sulfation. Sulfation is caused when a battery's State-of-Charge drops below 100% for long periods or under charging. Hard lead sulfate crystals fills the pores and coats the plates. Recharging a sulfated battery is like trying to wash your hands with gloves on."

Tedx

Registered:
Posts: 6
Reply with quote  #4 
My plates look clean.  I keep anti-sulfators on every 24v array in my system.  Here's the question:  If any of the compromising events you listed:  sulfation, sediment on bottom and  consumption of lead plates, would a deep cell battery be able to produce electrolyte that a hydrometer reads between 12.75 and 13.00? Battery University says if the electrolyte is good, the battery is good.
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