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Old 02-12-2018, 19:16   #1
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FLA 20hr Test to 10.5v - Flooded Lead Acid

Flooded Lead Acid
20 hour Discharge Capacity Test.

One of the surest ways to test the capacity of your Flooded Lead Acid batteries is to charge them up once a year, following the manufacturer recommendations.

1. Full Charge - During absorption test and watch the trailing amps drop to below .5% of the 20ah Capacity (for T105, 20hr rating is 225ah, 225 x .005= 11.25amps) to be sure they are fully charged. For T105 I do the final charge separately rather than in series (12vdc nominal).

2. Equalize following the manufacturer specs (again it is best to equalize T105 separately). If the batteries have had partial state of charge PSOC for large parts of the summer, particularly for boats on moorings without at least some SolarPV, it is better to equalize for 2-3 hours, otherwise 30 minutes would probably be acceptable, depending on how much they have sulfated (uneven or lowered SG readings and lower charged voltage are signs of this)

3. Let the batteries sit 24 hours and then put a small 2-3 amp load on the battery for 5 minutes to take the surface charge off.

4. 20hr Discharge Capacity Test Calculation:
- 20 hr Rating: From manufacturer's literature. For T105 20hr =225ah
- Continuous Load required: AH rating/20 hours. For T105 225ah/20hr=11.25amp

5. So the goal is to maintain a 11.25 amp discharge on the batteries for 20 hours, at which point the battery should be fully discharged and at 10.5vdc (5.25vdc for a single 6vdc T106). During the discharge draw down the amperage will vary due to changes in chemistry and the fact that the voltage will be declining. Thus the resistance will need to change over the 20 hours to have an accurate test. We can discuss how it is best to do this in later posts. Using a good Digital Multimeter you should record voltage and amps every hour, and make any necessary adjustments to meet the calculated amps.

6. An accurate Coulomb counter or SOC Meter wired up with a shunt to negative is useful. Once the battery is fully charged, reset the meter. Note the conditions and try to take readings every hour for voltage and ah discharged.

I think we've covered enough territory for this post.
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Old 03-12-2018, 09:05   #2
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

I found what appears to be a very inexpensive Voltage, Current (amps), Power (watts), Energy (WattHour) meter that appears to be is accurate to within .5% for $17. It appears that it would be very useful for battery discharge testing.

MICTUNING DC 6.5-100V 0-100A LCD Digital Display Ammeter Voltmeter Multimeter Volt Watt Power Energy Meter Blue with 100A/75mV Shunt

Here are the answers to some good questions.

https://www.amazon.com/ask/questions...dp_dpmw_al_hza

If the unit measures discharged energy in watthours, to get aH is not difficullt. aH= watthours/12vdc (nominal voltage). I suppose we could assume a linear relationship between 10.5v and 12.8v and take the average of that for voltage. (12.8+10.5)/2=23.3/2=11.65v average.
So the formula would be
aH = watthours/11.65v
Here is an wH and aH calculator https://convert-formula.com/ah-wh
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Old 03-12-2018, 09:46   #3
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

I suggest editing the original post changing 'charge' to 'drain'.

5. So the goal is to maintain a 11.25 amp charge on the batteries for 20 hours
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Old 03-12-2018, 10:09   #4
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

Here is the

8in1 Digital Voltage Current Battery Capacity Tester Electronic Load Discharger Resistor 180W


which would be adequate for testing two T105 in series at 12vdc nominal with 20hr capacity rating of 225ah. Why do I say that?
12.8volts x 11.25amps (the constant amperage required to discharge draw down the batteries to 10.5 amp over 20 hours, for a good battery)= 144 watts. This device is good for 180watts. For a first test you could just test one T105 from 6.4v down to 5.25v and the watts would be 1/2 to be sure the device works well.
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Old 03-12-2018, 10:10   #5
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

Can't edit, but good point. Don't know what I was thinking. Thanks. Should be "DRAIN" or "DISCHARGE". I hope the context is clear enough so this mistake is evident.

Quote:
Originally Posted by guyrj33 View Post
I suggest editing the original post changing 'charge' to 'drain'.

5. So the goal is to maintain a 11.25 amp charge on the batteries for 20 hours
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Old 03-12-2018, 11:20   #6
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

Go here https://marinehowto.com/programming-a-battery-monitor/

and search in the text CTRL-F for

capacity test
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Old 03-12-2018, 11:24   #7
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

Quote:
Originally Posted by rgleason View Post
Flooded Lead Acid
20 hour Discharge Capacity Test

Okay we'll try this again.

One of the surest ways to test the capacity of your Flooded Lead Acid batteries is to charge them up once a year, following the manufacturer recommendations.

1. Full Charge - During absorption test and watch the trailing amps drop to below .5% of the 20ah Capacity (for T105, 20hr rating is 225ah, 225 x .005= 11.25amps) to be sure they are fully charged. For T105 I do the final charge separately rather than in series (12vdc nominal).

2. Equalize following the manufacturer specs (again it is best to equalize T105 separately). If the batteries have had partial state of charge PSOC for large parts of the summer, particularly for boats on moorings without at least some SolarPV, it is better to equalize for 2-3 hours, otherwise 30 minutes would probably be acceptable, depending on how much they have sulfated (uneven or lowered SG readings and lower charged voltage are signs of this)
I think you have to minor errors in this. First, half a percent of 225Ah would be around 1.125A, not 11.25A. A T105 that is still accepting 11.25A is not fully charged. However, it may not be possible to get the batteries to accept as little as 1.125A at 14.4VDC. I would suggest something closer to 1-2%. It doesn't matter much, but it has to be less than 11.25A.

Second, Bill Brecht described equalizing one of his lead-acid batteries like the T-105 as charging at a few percent of capacity until the voltage ceased to rise. This would occur at about 15.9 to 16.2V as I recall. This produced lots of gassing to stir up to the electrolyte as well as the best opportunity to convert the sulfate into acid. He explained in calculus terms: charge until dV/dT is zero. At least that's what I remember. I visited Trojan Battery sometime after the Rodney King riots in south LA, so perhaps 1993.

Chuck Hawley
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Old 03-12-2018, 11:40   #8
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

Relevant thread 6vdc Trojan T105 (225ah) Equalization
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Old 05-12-2018, 21:32   #9
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

Chuck thanks for your clarifying post, and John for the links , saves me from getting close to that.


I believe Trojan's T105 Equalization is 16.2v at 4% of C for 2-4 hours
  1. After acceptance, continue at 4% of C until voltage stops rising, usually 15.5-16.2v
  2. Periodically (every 30 days)
  3. When batteries have a low specic gravity after charging (<1.235), or When the range of specic gravities between cells is > 0.030 points
Which is .04 x 225ah = 9 amps I find this is quiite easy to meet with some bubbling by the batteries.



Recently I was charging in Absorption Mode at 14.7v and I am able to charge both
  • 3 year T105 pair (subjected to bad PSOC)
  • 1 year T105 pair (subject to some PSOC during the summer)
to 1.5 amps (trailing amps) after several previous full charges this fall. I am in the process of doing a shorter 1 hr equalization on both sets and then will do the discharge tests.




John,

With the $17 MICTUNING DC 6.5-100V 0-100A

lack of Peukert setting (increase discharge, available capacity decreases)
and lack of CEF Charge efficiency factor (more power required to charge than is stored)



Is this meter useable and the adjusted values obtainable using the Peukert Number Battery Life Calculator
and assuming a Peukert Number of 1.1 which is 225ah and the 20hr rate of 11.25amp?



Rated Battery Capacity 225ah
Discharge Rate 11.25a
Peukarts Number 1.1
Calculated Battery Capacity 176.63 ah
Full Discharge Time 15.701 hrs
Manufacturers Discharge Time 12.56 hrs
75% Discharge Time 12.56 hrs
50% Discharge Time 7.85 hrs
25% Discharge Time 3.92 hrs


So what exactly does this mean?


The results of my testing will not reach 20 hours?


That I need to draw down exactly 11.25 amps for 15.7 hours?


The Balmar SG-200 was not available on Mainesail's website unfortunately, but I did find one eventually on Pkys and I should be able to connect it to the T105's and try a discharge first part of next week.
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Old 05-12-2018, 23:58   #10
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

The Peukert value for a Trojan T-105 is 1.24

1.1 is mote typically the Peukert for an AGM battery.
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Old 06-12-2018, 04:47   #11
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

The BM vs cheap AH counter distinction is just for ongoing SoC estimating accuracy.

The fact you use a standard .05C rate for load tests makes the latter fine for that purpose
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Old 06-12-2018, 09:50   #12
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

So for a Trojan T105 with Peukarts Number of 1.24 (Thanks Mittiemp for the correction, the calcullator filled the wrong number) using the

Peukert Number Battery Life Calculator


Rated Battery Capacity 225ah
Discharge Rate 11.25a
Peukarts Number 1.24
Calculated Battery Capacity 125.86 ah
Full Discharge Time 11.18 hrs
Manufacturers Discharge Time 8.95 hrs
75% Discharge Time 8.39 hrs
50% Discharge Time 5.59 hrs
25% Discharge Time 2.79 hrs


With the new corrected numbers the "Full Discharge Time 11.18 hrs"
Is that the actual time to reach the 10.5volts given the Peukarts number of the batteries? So the 20hr capacity test doe not require 20 hours? I am still confused about this.
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Old 06-12-2018, 10:10   #13
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

Quote:
Originally Posted by rgleason View Post
So for a Trojan T105 with Peukarts Number of 1.24 (Thanks Mittiemp for the correction, the calcullator filled the wrong number) using the

Peukert Number Battery Life Calculator


Rated Battery Capacity 225ah
Discharge Rate 11.25a
Peukarts Number 1.24
Calculated Battery Capacity 125.86 ah
Full Discharge Time 11.18 hrs
Manufacturers Discharge Time 8.95 hrs
75% Discharge Time 8.39 hrs
50% Discharge Time 5.59 hrs
25% Discharge Time 2.79 hrs


With the new corrected numbers the "Full Discharge Time 11.18 hrs"
Is that the actual time to reach the 10.5volts given the Peukarts number of the batteries? So the 20hr capacity test doe not require 20 hours? I am still confused about this.

There is no Peukert calculation needed at the 20 hour discharge rate & 75-80F. In other words a 225Ah battery should discharge to 10.5V at an 11.25A constant current and run for 20 hours IF the battery is at 100% SOH.

20 Hours X -11.25A = 225Ah

The ONLY time Peukert is applied is at rates that exceed or are less than the discharge rating you are testing for.

If your 225Ah battery (20H rate) runs for less than 20 hours, at 11.25A and 75-80F, then the battery is not at 100% state of health. Simple stuff... For example if it lasted 16 hours before hitting 10.5V then the battery is at 80% SOH.

You don't need anything other than a discharge current kept as close to the discharge rate as you can, a stop watch, volt meter and the battery at approx 75-80F. You';ll also need a charger to recharge as soon as it hits 10.5V...

Even if the battery is at room temp/70Fish the difference in deliverable capacity is negligible. You do not need any fancy equipment to do a discharge test.
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Old 06-12-2018, 10:39   #14
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

Well the ammeter is needed to keep the discharge rate on track. 8-)

Some other points here from a past thread, I especially like the idea of a smartphone taking timed snapsots

Absorbtion Time for AGMs
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Old 06-12-2018, 18:45   #15
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Re: FLA 20hr Test to 10.5v - Flooded Lead Acid

Thank you all . Thank you Mainesail for the simple approach and explanation to use the Peukart equation only when you are discharging outside of the batteries specs which adjusts the time to the lower capacity with the faster discharge beyond manfacturer spec. Thanks for the idea of using time lapse app or intervalometer so I can get some sleep.



Equipment for the Discharge Test:
S4 Samsung Phone & Cell Camera with Intervalometer.
Discharge equipment 15a inverter.
Lightolier 7watt bulb strip (15 bulbs) to screw/unscrew as needed.
3-5 60 watt Incandescent bulbs.
Good clamp on Amp Meter and Volt meter.
Thermometer.



I'm going to try the Balmar SG-200 during these tests too.
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