Battery State Of Charge (SOC) determination

[kippered]

Hello all

While doing some preliminary testing with my energizer kit from the conference I observed first hand what I have always known is true for lead acid type batteries: The battery voltage level after a rest is not an indication of SOC

It seems many people working on this technology take just a pure voltage measurement and assume it represents the charge level

From my work experience SOC (lead acid) can only be determined 2 practical ways:

- Observe how much work you can get the battery to do
- Check the specific gravity of the electrolyte using a hydrometer

My question is do these traditional methods apply to a Energized battery or do I need to drop that and go specifically by the amount of work I can get out of the system?

Thanks for your input

[SeaMonkey]

Hello all

While doing some preliminary testing with my energizer kit from the conference I observed first hand what I have always known is true for lead acid type batteries: The battery voltage level after a rest is not an indication of SOC

It seems many people working on this technology take just a pure voltage measurement and assume it represents the charge level

From my work experience SOC (lead acid) can only be determined 2 practical ways:

- Observe how much work you can get the battery to do
- Check the specific gravity of the electrolyte using a hydrometer

My question is do these traditional methods apply to a Energized battery or do I need to drop that and go specifically by the amount of work I can get out of the system?

Thanks for your input

By "Energized battery" do you mean a Sealed Lead
Acid battery (SLA) sometimes marketed as Valve
Regulated Sealed Lead Acid (VRSLA) or Gell Cell
battery?


With the sealed lead acid batteries it is necessary
to determine how much energy is contained within
it by measuring "discharge" power into a load.

By monitoring Voltage and Current readings at the
load it is possible to deterimine the energy capacity
of the battery as it discharges.

Battery Capacity tests are ordinarily done at a
specified current level (some fraction of C or
battery rated Capacity in Ampere/Hours) until
the battery terminal voltage decreases to
10.5 Volts for a 12 Volt battery. There may be
several variations on this procedure as recommended
by the various battery manufacturers.

It is also possible to determine the internal resistance
of the battery which is a very good indicator of its
health.

It is very good of you to ask these important questions.

Hopefully others will add more to the discussion from
their own experiences.

[kippered]

By Energized battery I was referring to a battery that has been charged via an Bedini (or similar) energizer.

At work our batteries have cap's to take off for each cell so that you can check the specific gravity of each cell and top up the fluid level if necessary.

A sealed lead acid battery it is more difficult and like you mentioned should really go through a discharge test or internal resistance measurement...
There are some youtube vids on how to do this that might be handy like this one: YouTube - How to test the internal resistance of a battery
but I need to study it further first

I am a novice at batteries but I think that if I am going to determine COP levels then I need to make sure and take the right tests.

I tend to see allot of people on various forums talking only about voltage level and it is concerning to say the least. I have a 12v 7AH lead acid battery that is completely unable to do any work but the voltage with nothing connected reads 12 volts and at full charge is about 12.6 Volts.

I am guessing from 12.6 to 12 volts is not a linear relationship ie 12.3V = half charged

[Aaron]

draw a load

From my work experience SOC (lead acid) can only be determined 2 practical ways:

- Observe how much work you can get the battery to do
- Check the specific gravity of the electrolyte using a hydrometer

My question is do these traditional methods apply to a Energized battery or do I need to drop that and go specifically by the amount of work I can get out of the system?

I think to see what work you get from the battery.

Almost no 2 hydrometers will give you the same reading, close but
not good for really seeing what is there. I might use one to see what
is a promising battery to grab from the scrap yard for rejuvenation but
drawing a load is much better in my opinion.

[aussieaussieaussie]

Can we also add Aaron,

People putting lights directly connected to the charging batteries while the device is running are also getting FALSE positive results. You need to put an inverter to convert back to normal AC sine wave, if you are using the rated power usage of the light as a result. Or you could just disconnect the battery from the charger for your tests!

Sorry I have just seen this WAY too many times!

Ozy

[kippered]

Yep that is the method I am going to use... put it to work and that will be the most definitive test

Time to make an excel spreadheet and chart the batteries performance

[john_g]

Good site for battery info

Hi
Here,s a good site with a lot of info on batteries, although marine slanted:

Comparing marine batteries (Gel, Absorbed Glass Mat (AGM), flooded lead acid)

[SeaMonkey]

Hi
Here,s a good site with a lot of info on batteries, although marine slanted:

Comparing marine batteries (Gel, Absorbed Glass Mat (AGM), flooded lead acid)

Excellent resource john_g. Many thanks.

[theremart]

Best test...

I agree load testing is the best way. With my computer monitored tests I can see the curve of discharge. It seems to tell the whole story.


One must be careful not to always trust the battery when connected to a circuit. Digital meters are not fast enough to keep up with most pulse motors and can give erroneous readings. Analog meters much better but not immune from such devices like the SEC by Dr Stiffler.

The best readings I have gotten is the resting voltage ( on good batteries not junk ones with surface charge ) after about 1/2 hour of rest. That seems to be a good indication of the state of charge, but better is to have a bar graph of the battery from fully charged to 10.5 V ( better to stay above 12.5 ) for the health of the battery.

Once you have done a couple of these baseline tests, then you can try other testing.

My testing has shown me that I get the most amp hours out of the battery with a slow amp draw verses a large one. The C-20 rate that Bedini recommends is a very wise idea for prolonging battery life.

As well slow charge back up is the best idea, you can get very good charging with conventional charge if you just use 3 amps of charge for the standard car battery, for a long duration of time.

Cycling also improves batteries the more you do on a "consistent basis" the better the battery is, but if you stop, even for a small amount of time it seems the battery looses the momentum of getting better.

But beware of testing batteries that are still in circuit, this often leads to many false conclusions. And if you think you have OU, be sure to put in fresh batteries in your multimeter :-) You may have but often the battery dies and gives you a false high reading.

[sucahyo]

To detect surface charging, I would measure the voltage before and after adding 100 ohm load or something.

[kippered]

This is all quite usefull information thanks all. It will hlp greatly in making sure to take accurate tests

[kippered]

After some (to this point) brief reading my question has been answered by this page:

Car and Deep Cycle Battery FAQ, Battery Manufacturers and Brand Names List, and

A sulfated sealed battery's voltage often will read higher than the SoC actually is, so load testing maybe required to determine the battery's actual performance or capacity

This explains what I was seeing with my old sealed battery that cannot do any work.

As you all mentioned the proper testing takes a decent understanding of your particular battery, its characteristics and proper determination of SOC.

I did find it good to know that I was wrong, you typically can use just a voltmeter to detect general SOC but is not the definitive test rather just gives you an idea of where you are at.