Guido and JohnT want to explain this?

Geo-TH,In

Well-known Member
I've been using two batteries in parallel in dump trailer for 6 years. Charging both at the same time. Charger says it can handle up to 4 batteries at once. No problems until recently.

The other day I decided to remove connection between batteries and test each separately. The 6 year old battery, only 70 amps and 12.03 volts. Other battery good, passed all tests.

I always thought a hydrometer was a good tool until it said all my cells were between 1.230 and 1.25 after compensating for temperature of electrolyte. It did confirm there was no dead cell, 1.000. Hydrometer said all cells were good or on the fine line between good and fair. So I used my cheapie hydrometer. It a male hydrometer, has 4 balls. All 4 balls floated. My digital conductivity tester confirmed hydrometer test, the battery didn't have a dead cell. The batteries plates have to be covered with sulfate crystals. It doesn't have enough juice to lift an empty dump trailer bed.
I'm really calling into question the validity of a hydrometer test. I'm also calling in questions the instructions saying my batteryminder can safely charge 4 batteries in parallel. BTW, I will add the batteryminder has never boiled out the electrolyte. Batteryminder also confirmed there were no dead cells.

Anyone care to explain to me how a battery that can't produce 10% of it's rating, can't produce enough juice to dump the trailer, pass a hydrometer test. I sure can't explain it.
I've learned another lesson, only charge, desulfate and equalize one battery at a time.

Come spring, I'll be looking for another battery.
geo.
 
The hydrometer only tells you the state of charge of each cell, not the battery condition.
I suspect that a month or two of the desulphator may restore capacity if that does not cause a short in one of the cells. I have had that happen where attempting to desulfate a badly sulphated battery resulted in a shorted cell.
 
Jon,
I have ran it through a few desulfating cycles. My battery conductivity tester is showing more amps, battery is coming back a little. However the hydrometer readings are still the same. Still don't understand the value of using a hydrometer when says electrolyte is good and battery is carp. I've lost confidence in a hydrometer.
geo
 
Here you go!

One will FAIL!!!!
a248051.jpg
 
I consider a hydrometer as an instrument to measure the specific gravity OF EACH INDIVIDUAL CELL and you can find a dead or weak cell using one, BUT ITS NOT GONNA TELL YOU THE ENTIRE OVERALL BATTERY CONDITION. That's why I prefer the COMBINATION of 1) a good load tester PLUS a 2) Voltmeter PLUS a 3) Hydrometer as a more complete tool set to evaluate batteries including cell by cell specific gravities. I own all three and after all these years and a gazillion batteries (was a used tractor dealer and farmer) I'm hanging onto all three, but yall are free to use one or none or any other instruments as you well please, I'm stickin with what has served me well for years however........

Good chattin with ya neighbor George

John T

John T
 
JohnT,
I agree a hydrometer can find a dead cell. I agree it measures specific gravity. I always thought if battery was discharged, the electrolyte was more like water. sp 1.000 . How can the specific gravity show good, yet no Juice in battery. Doesn't appear to me the hydrometer is worth much if it can't tell the charge in battery. My battery tester can spot a bad cell too.
geo
 
"I've lost confidence in a hydrometer. geo"
Don't underestimate hydrometers based on your experience with with floating ball types. Test your ball floater against a quility hydrometer. If one could own only one battery tester,hydrometer win's.
 
That's why I like owning all three instruments (Hydrometer, Voltmeter, Load tester) each with different purposes NOT just one, but to each their own methods as long as it suits their needs and works for them I say.

John T
 
JohnT, I still don't understand why a hydrometer can only tell you if you have a dead cell and can't tell you if a cell is good. I always thought the H2SO4 acid concentration was proportional to the charge and obviously it isn't.
geo
 
I have a very good hydrometer I purchased from NAPA. It even measures the temp of electrolyte and you can get the actual specific gravity of the electrolyte. I was making a joke about my male hydrometer.

Everyone is missing my point which is a hydrometer really can't tell if cells are good by measuring the concentration of the H2SO4. Only thing it can do is show when a cell is dead, then the acid is converted to water for the most part.

So much for a good hydrometer. I lost all confidence in using them to prove cells are good.
geo
 
Geo,
Here's a portion of a Wikipedia article that may explain your situation.

Note the mention of charge "level" and charge "capacity" in the last paragraph. With 6 year old batteries this may be the reason for your situation.


" A hydrometer can be used to test the specific gravity of each cell as a measure of its state of charge. Because the electrolyte takes part in the charge-discharge reaction, this battery has one major advantage over other chemistries. It is relatively simple to determine the state of charge by merely measuring the specific gravity of the electrolyte; the specific gravity falls as the battery discharges. Some battery designs include a simple hydrometer using colored floating balls of differing density. When used in diesel-electric submarines, the specific gravity was regularly measured and written on a blackboard in the control room to indicate how much longer the boat could remain submerged.

The battery's open-circuit voltage can also be used to gauge the state of charge.If the connections to the individual cells are accessible, then the state of charge of each cell can be determined which can provide a guide as to the state of health of the battery as a whole, otherwise the overall battery voltage may be assessed.

Note that neither technique gives any indication of charge capacity, only charge level. Charge capacity of any rechargeable battery will decline with age and usage, meaning that it may no longer be fit for purpose even when nominally fully charged. Other tests, usually involving current drain, are used to determine the residual charge capacity of a battery."
 
It's simple - take a fully charged battery apart and wrap the plates in plastic so only 1 square inch is exposed then put it back together.

It measures fully charged. The acid would weigh in as fully charged. Load the thing and it won't perform well the amps will be terrible. Deposits/Age impairs the ability of the acid to strip lead off the plates like that plastic does.

RE the twin batteries, a charger has no way to tell where its juice is going with batteries in parallel. It's been my experience its a recipe for a failed battery without isolator or charge controller etc. Even brand new well matched parallel batteries have more problems than singles. One cell fails and the other battery discharges into it etc.
 
(quoted from post at 23:20:52 01/11/17) It's simple - take a fully charged battery apart and wrap the plates in plastic so only 1 square inch is exposed then put it back together.

It measures fully charged. The acid would weigh in as fully charged. Load the thing and it won't perform well the amps will be terrible. Deposits/Age impairs the ability of the acid to strip lead off the plates like that plastic does.

RE the twin batteries, a charger has no way to tell where its juice is going with batteries in parallel. It's been my experience its a recipe for a failed battery without isolator or charge controller etc. Even brand new well matched parallel batteries have more problems than singles. One cell fails and the other battery discharges into it etc.

And the good battery will take on all the high freq pulse so the sulfated battery will get little or none...

Yes it can keep up to 4 batteries from going dead in the charge mode.. BUt it can only do so if they are all good. a shorted cell will mean that one battery will drag the rest down and assorb all of the charge and turn it into heat.

And in the desufate mode... the BEST battery will take on the high frequency pulse.. As the best battery will exhibit the lowest impedance to the AC style pulse and the other batteries will not see much or none of the pulse. parallel charging will ALWAYS hide the weak batteries. And as others said.. as the battery sulfates up.. it can still go to full change chemically but the surface size of the available cells is greatly reduced, meaning you 1000 amp battery will lose a bit of capacity each year as the cells are slowly covered and rendered usless... untill your 1000 amp battery now test like a tinyt battery of 50 amps.. still charges up to full but will not carry a HIGH load very long anymore. And only one cell needs to go wonky to ruin the whole process.

another point... in the ole days... you could see the engine begin to crank slower when the battery got close it the end. Now the computer controlled cars,, simply will not all the crank cycle to happen if the voltage starts to drop too low, so one day the computer controlled car started fine, then next time it refuses to crank... as the computer see too much voltage drop, cannot tell the timing, or run other sensors and spark timing, so it simply cuts off the attempt to crank over the engine... so now batteries appear to fail "immediately" with no slow crank warnings.
 
Good morning neighbor George, My short answer is because it ONLY measures the SPECIFIC GRAVITY of one cell alone. I cant explain all the physics and chemistry to you in a paragraph and besides chemistry was my worst subject lol maybe you can research and study up on the chemistry and physics of lead acid batteries its NOT my favorite subject grrrrrrrrrrrrrr. I am hanging onto my 40+ years of checking batteries with THREE not just one instrument (but others can do as they please fine by me) Hydrometer, Volt Meter and Load tester even if I cant fully explain all the chemistry and physics to lay persons as I'm very much a lay person myself when it comes to electrochemical energy storage, so sorry, I JUST CANT ANSWER YOUR QUESTION maybe some chemical engineers can help us????

Keep warm neighbor, sorry I cant explain it to you.

John T
 
Pete,
I went to college to become a chemical engineer. Everything you posted I learned in my first chemistry, chem 205, decades ago. The specific gravity, of the electrolyte determines the state of the battery.

Up to the other day, I trusted what the hydrometer until I got hydrometer readings from 1.230 to 1.250m the battery didn't have enough poop to run the pump to get the dump bed up, the voltmeter only showed 12.03 volts, and my digital conductivity tester showed battery is only putting out 70 amps, 10% of what it used to produce. How can I have a dead battery and good hydrometer readings? This contradicts everything I was taught about the chemistry of a battery. When a battery is discharged the H2S04 is converted to H2O and SO3, sulfate crystals on plates. Density of H2O is 1.000.

Does everyone see my point, I have acid in all cells, no shorted cells and the battery is crap?
geo
 
I have been having my batteries die quick deaths of late. I used to have them with slower deaths. I would say all your cells have good acid readings but whatever holds the plates together could of let loose shorting it out ? Or some are just plugged up and don't function just like when an artery clogs up.
 
A 12 volt battery is just a box with six battery cells inside, hooked in series. The cells themselves might be fine but their series connections can be bad. That situation will not show with a hydrometer or any kind of individual cell tester. Only a real load tester (not a simulation tester) can prove if the battery can make rated power.
 
sotxbill,
I think you nailed it, can't effectively desulfate batteries in parallel, even
though the charger says it can handle up to 4 batteries.
The newer model of my charger says it can handle up to 6 batteries.

The lesson I learned is you can't believe everything you read I'll charge and
desulfate one battery at a time.

And I Learned I can't trust what the hydrometer either.
geo
 
Hello John T,

You can measure INDIVIDUAL cell voltage with a volt meter. You can use two pieces of household copper wire to dip in the electrolyte solution, saving the meter's leads from damage. Excersice in futility as far as TOTAL battery power output under load,

Guido.
 
A real load test is the motor on the pump, it's better than a resistor. Battery failed the motor load test.

As for battery tester I trust my digital and gave away my resistor tester. Buy a digital tester, you may like it. It will tell you when you have a bad cell too.

I've yet to see a resistor tester give you the actual amps the battery is able to produce, mine will.

Don't understand why people say my tester is bad if you don't have one. geo.
 
Hello da.bees,


Like I told Jonh T, checking total battery state of charge with an hydrometer, is an exercise in futility! You can do another INDIVIDUAL cell state of charge test. Take a piece of copper wire and use it to check a cell's voltage. Wrapping a piece of copper on each lead, it will keep your leads from the acid. You can find a bad or low cell this way as well, but if they are all the same voltage means NOTHING! When you crank the engine check the voltage at the stater. If all else is O.K. you not only will measure 9 + volts at the starter, bug the engine will be cranking. Now you have done a real world-condition load test, and the only instrument you used is a VOLT METER. You can sell that hydrometer to someone that thinks its the way to test a battery. In only tests INDIVIDUAL cells state of charge not battery capacity.

Guido.
 

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