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BATTERY TESTING, MONITORING

AND

RESTORATION MANUAL

E-Mail:

Submitted By

MTekPRO Technologies Private Limited

B-229, LGF, Greater Kailash- I, New Delhi, PIN- 110048

[email protected],Website:www.mtekpro.com

Phone: +91 11 46173333, Fax: +91 11 41825662
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Electric generating stations and substations for protection and control of switches

and relays

Why battery backup is needed?

Batteries are used to ensure that critical electrical equipment is always on. There are so

many places where batteries are used and it is nearly impossible to list them all. Some of

the applications for batteries include:

Telephone systems to support phone service, especially emergency services

Industrial applications for protection and control

Back up of computers, especially financial data and information

Less critical business information systems.

Without battery back-up hospitals would have to close their doors until power is restored.

But even so, there are patients on life support systems that require absolute 100% electric

power. For those patients, as it was once said, failure is not an option.

Just look around and see how much electricity we use and then to see how important

batteries have become in our everyday lives. The many blackouts of 2003 and 2012 aroundthe world show how critical electrical systems have become to sustain our basic needs.

Batteries are used extensively and without them many of the services that we take for

granted would fail and cause innumerable problems.

to insure the supported equipment is adequately backed-up

Why to test battery systems?

There are three main reasons to test battery systems:

to prevent unexpected failures by tracking the batterys health

to forewarn/predict death


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Primary Battery Failure Modes:

Electrolyte Water Loss:

Dry out, vapor diffusion through container (


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Battery Life Cycle and Replacement Zone:

1. Impedance

IEEE Recommendations:

2. Voltage

3. Specific Gravity

4. Loud Test

5. Visual Inspection

1. Impedance

Lagging Indicators:

2. Voltage

3. Specific Gravity

1. Sulfation

Leading Indicators:

2.

Dry out3. Chemical Properties


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In Old UPS Battery Systems - The DC filtering capacitors usually had much lower

impedances than the batteries. Designs have changed.

Improved Battery Diagnostics- The Truth About Noise:

Because the DC capacitors and battery are in parallel, they will share the AC Ripple

(Noise).

Many UPS Manufacturers have lowered the amount of filtering capacitors.

More DC current is flowing into the battery and less into the filtering capacitors.

The majority of the AC ripple current comes from the inverter as it converts the DC

power to AC power.

Most battery manufacturers specify a maximum acceptable ripple voltage- typically1 to 2% of the DC float voltage.

AC ripple voltages will induce AC ripple currents.

High ripple currents cause Excess Heat, Reduced Battery Life and thermal

runaway.

Conclusions:


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Discharge (Load) testing remains the most reliable method to monitor the state of

health of a battery.

Discharge testing is time consuming, expensive, must be done offline and is

detrimental to the batteries.

Reduced life due to discharge testing.

Routine discharge testing is also required for accurate results.

Load testing is still considered to be required.

Cannot rely on any one test method.

New test and measurement equipment is available for testing both the electrical

and chemical properties. This will catch the chemical failure modes and is the best,

rapid-test solution.

Continuous monitoring is an excellent alternative when cost is not an issue.


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Lead Acid

Types of Batteries:

There are several main types of battery technologies with subtypes:

Flooded (Wet): Lead- Calcium, Lead- Antimony

Valve regulated Lead-acid, VRLA (sealed): Lead- Calcium, Lead- Antimony-

Selenium

o Absorbed Glass Matte (AGM)

o

Gel Flat plate

Tubular plate

Nickel-Cadmium

Flooded

Sealed

Pocket plate Flat plate

PbO2 + Pb + 2H2SO4 2PbSO4+ 2H2O

Lead- Acid Overview:

The basic lead- acid chemical reaction in a sulfuric acid electrolyte, where the sulfate of the

acid is the part of the reaction, is:

The acid is depleted upon discharge and regenerated upon recharge. Hydrogen and

oxygen form during discharge and float charging (because float charging is counter acting

self-discharge). In flooded batteries, they escape and water must be periodically added. In

valve-regulated, lead-acid (sealed) batteries, the hydrogen and oxygen gases recombine to


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form water. Additionally, in VRLA batteries, the acid is immobilized by an absorbed glass

matte (AGM) or in a gel.

The matte is much like the fiberglass insulation used in houses. It traps the hydrogen and

oxygen formed during discharge and allows them to migrate so that they react back to

form water. This is why VRLA never need water added compared to flooded (wet, vented)

lead-acid batteries.

A battery has alternating positive and negative plates separated by micro-porous rubber in

flooded lead-acid, absorbed glass matte in VRLA, gelled acid in VRLA gel batteries or plastic

sheeting in NiCd. All of the like-polarity plates are welded together and to the appropriate

post. In the case of VRLA cells, some compression of the plate-matte-plate sandwich isexerted to maintain good contact between them. There is also a self-resealing, pressure

relief valve (PRV) to vent gases when over-pressurization occurs.

2 NiO(OH) + Cd + 2 H2O 2Ni(OH)2 + Cd(OH)2

However, in NiCd batteries the potassium hydroxide (KOH) does not enter the reaction like

sulfuric acid does in lead-acid batteries. The construction is similar to lead-acid in that

there are alternating positive and negative plates submerged in an electrolyte. Rarely

seen, but available, are sealed NiCd batteries.

Nickel- Cadmium Overview:

Nickel-Cadmium chemistry is similar in some respects to lead-acid in that there are two

dissimilar metals in an electrolyte. The basic reaction in a potassium hydroxide (alkaline)electrolyte is:


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Failure Modes:

Positive grid corrosion

Lead-acid (flooded) failure modes:

Sediment (shedding) build-up

top lead corrosion

Plate sulfation

Hard shorts (paste lumps)

Dry-out (Loss-of-Compression)

Lead-acid (VRLA) failure modes:

Plate Sulfation

Soft and Hard Short

Post leakage

Thermal run-away

Positive grid corrosion

Gradual loss of capacity

Nickel-Cadmium failure modes:

NiCd batteries seem to be more robust than lead-acid. They are more expensive to

purchase but the cost of ownership is similar to lead-acid, especially if maintenance costs

are used in the cost equation. Also, the risks of catastrophic failure are considerably lower

than for VRLAs.

The failure modes of NiCd are much more limited than lead-acid. Some of the more

important modes are:

Carbonation

Floating effects

Cycling

Iron poisoning of positive plates


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Best way to test and evaluate your battery:

1. Make a test and benchmark its values when the battery is new as part of the

acceptance testing.

Test intervals:

2. Make an impedance test at the same time to establish baseline values for the

battery.

3. Repeat the above within 2 years for warranty purpose.

4. Make an impedance test every year on flooded cells and quarterly on VRLA cells.

5.

Make capacity tests at least for every 25% of expected service life.6. Make capacity test annually when the battery has reached 85% of expected service

life or if the capacity has dropped more than 10% since the previous test or is below

90% of the manufacturers rating.

7. Make a capacity test if the Impedance value has changed significantly.

1. Replace cell if the impedance is more than 50% above baseline. Make a capacity test

if 20-50% of baseline.

Evaluation:

2. Replace battery if capacity test shows less than 80% of rated capacity.

Practical Battery Testing:

The battery testing matrix below may help guide even the most skilled battery testing

technician and will help simplify the recommended practices.

The following is a description of some of the tests or maintenance parameters.

Impedance, an internal ohmic test, is resistance in AC terms. With regard to DC battery

systems, impedance indicates the condition of batteries. Since it tests the condition of the

Impedance Test:


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entire electrical path of a battery from terminal plate to terminal plate, impedance can

find weaknesses in cells and inter cell connectors easily and reliably.

Basically, impedance test is determined by applying an AC current signal, measuring the AC

voltage drop across the cell or inter cell connector and calculating the impedance using

Ohms Law. In practice, not only is the AC voltage drop measured but so is the AC current.

The AC current is measured because of other AC currents in a battery that are additive

(subtractive). Other AC currents are present from the charger system. The test is

performed by applying an AC test signal to the terminal plates. Then measure both the

total AC current in the string and the voltage drop of each unit in the string by measuring

each cell and inter cell connector consecutively until the entire string is measured. The

impedance is calculated, displayed and stored. As the cells age, the internal impedanceincreases as depicted in figure 1. By measuring impedance, the condition of each cell in the

string can be measured and trended to determine when to replace a cell or the string

which helps in planning for budgetary needs.

Figure 1: Impedance V/S Discharge Current


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The impedance test is a true four-wire, Kelvin-type measurement that provides excellent

reliability and highly reproducible data on which to base sound decisions with regard to

battery maintenance and replacement. Impedance is able to find weak cells so that

proactive maintenance can be performed. After all, the battery is a cost but it is supporting

a critical load or revenue stream. If a single cell goes open then the entire string goes off

line and the load is no longer supported.

Therefore, it is important to find the weak cells before they cause a major failure. The

graph in figure 2 shows the effect of decreasing capacity on impedance. There is a strong

correlation between impedance and capacity so that weak cells are ably and reliably found

in sufficient time to take remedial action.

The graph shows the reorganized impedance data in ascending order with each cells

corresponding load test end voltage. (Impedance in milliohms coincidentally is the same

scale as the voltage, 0 to 2.5). This view, that is ascending impedance/descending voltage,

groups the weak cells on the right side of the graph to find them easily.

Figure 2:- Ascending impedance with corresponding end voltage


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High power battery capacity test system

Battery testing using BTS 200 MKII and ELU 200 MKII

Electrical power plants are normally equipped with batteries of different types and regular

test according to international standard are requested in order to assure the standby

power for relays, circuit breakers, measuring equipment and telephone exchanges.

Discharging current up to 1300A with external loads (up to 9)

Graphical display showing test parameters, curve and results

Internal memory

Light and easy to carry, with handles and wheels Shunt or clamp metering of an additional current

Suitable for all battery types

Application:

The most reliable method for the determination of battery capacity is to perform a

discharging cycle periodically. BTS 200 MKII allows performing such test combining

efficiency with portability. It can test any type of battery with a discharging current op to1300A with external loads.

Battery Nominal Voltage (in Volts)

Specification:

Maximum discharging current with BTS 200 MKII

Maximum Current Discharged (in Amperes)

240 70

220 70140 130

110 130

48 130

24 130


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It is possible to parallel up to 9 external loads ELU 200 MKII. The test set shows on the

large back-lighted LCD display the following parameters:

Battery voltage;

Minimum voltage threshold (adjustable),with automatic stop;

Discharging current, power or profile;

Ah (ampere-hour) discharged;

Test time duration with automatic stop at time out;

Test conditions are all displayed;

Discharging curve is displayed;

Test parameters are entered via the functional pushbutton and the graphical displayon the front panel.

Constant discharge current

Load patterns:

Constant power

Current profile (up to 20 steps)

Power profile Manual control

Range: 0 - 130 A;

Measurement of the discharging current:

Display: 0 - 130 A (0 - 1300 A with external loads);

Accuracy: 1 % of the value, 0.2 % of the range.

The discharging activity can be stopped and started again later from the same level.


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External Load ELU 200 MKII (OPTIONAL):

When higher load current is necessary, it is possible to use the BTS 200 MKII in connection

with external load ELU 200 MKII.ELU 200 MKII is an active programmable burden as BTS

200MKII. BTS 200 MKII allows the connection up to 9 external loads ELU 200 MKII.

Nominal

Battery

Voltage (V)

BTS 200 MKII: Discharging Examples:

Nominal

Capacity (Ah)

Constant

Current (A)

Constant

Power (kW)

Test

Duration (in

Hours)

Discharging

Capacity (Ah)

End of Test

Voltage (V)

24 500 50 1 10 500 20

48 500 50 2 10 500 40

110 500 50 4.7 10 500 94

120 500 50 5.1 10 500 102

220 500 50 9.4 10 500 188

240 500 50 10.2 10 500 204

Battery

Voltage

Maximum discharging current with BTS 200 MKII with external loads ELU 200

MKII:

Maximum Discharge Currents of BTS 200 MKII with ELU 200 MKII External Loads

No. of

ELU 200

MKII

1 2 3 4 5 6 7 8 9

24 VDC 260 A 390 A 520 A 650 A 780 A 910 A 1040 A 1170 A 1300 A

48 VDC 260 A 390 A 520 A 650 A 780 A 910 A 1040 A 1170 A 1300 A

110 VDC 260 A 390 A 520 A 650 A 780 A 910 A 1040 A 1170 A 1300 A

120 VDC 260 A 390 A 520 A 650 A 780 A 910 A 1040 A 1170 A 1300 A220 VDC 140 A 210 A 280 A 350 A 420 A 490 A 560 A 630 A 700 A

240 VDC 140 A 210 A 280 A 350 A 420 A 490 A 530 A 630 A 700 A

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