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How to Test UPS Battery Strings with a CELLTRON Conductance Tester

Oct 21
7 min read

Updated: Oct 22

CELLTRON testers measure the conductance of the individual batteries (jars) in UPS, utility and telecom battery strings. The CELLTRON line is documented by Franklin Grid Solutions: its current manuals are issued by Franklin Electric and published on franklingrid.com. This guide follows two of them:

  • CELLTRON Advantage Digital (kits CADD-5000, CADD-5200, CADD-5500): CELLTRON Advantage Digital Battery Tester featuring UNITE Operation Guide, 167-000450 r8.

  • CELLTRON Ultra (CTU-6000): CELLTRON Ultra Instruction Manual, P/N 168-641F.

Not covered: the CELLTRON Essential, the legacy CELLTRON Advantage, and UNITE software setup. The Advantage Digital guide says it's intended for qualified persons, and both manuals say to do only the work you're trained for. This guide explains the process; it doesn't replace the manual or training.

What the testers measure

  • Franklin Electric says the Advantage Digital tests stationary batteries used in UPS systems, power utility and telecommunications. It measures voltage, conductance, temperature and strap resistance, and tests lead-acid cells and NiCd batteries at nominal 1.2, 2, 4, 6, 8, 12, 16 and 18 VDC (Operation Guide §3, p. 4).

  • The Ultra tests lead-acid batteries of 2, 4, 6, 8, 10, 12, 14 and 16 V, and measures voltage and conductance (Ultra manual, Ch. 1, p. 8).

  • Both can test batteries that are powering a load (in service) or not (not in service).

  • Why a reference value matters. Both manuals say amp-hours (Ah) are a typical measure of capacity but are hard to measure without knowing the load. Franklin Electric recommends comparing test results to a conductance reference value instead (Operation Guide §3, p. 4; Ultra manual p. 8).

Safety first

From the Advantage Digital Operation Guide (operating precautions, inside front cover; §2):

  • Batteries generate explosive gases in normal operation and when charging or discharging. Never allow smoking, sparks or flames nearby.

  • Wear PPE per NFPA 70E, including safety glasses with side shields (or a face shield), insulating acid-resistant gloves, an acid-resistant apron or shop coat, protective footwear and arc-flash protection suited to the voltage. Have an eyewash station or bottle on hand (face shield and shop coat: Ultra manual Ch. 1, p. 7).

  • If acid enters the eye, immediately flush with cold running water for at least 10–15 minutes, and seek medical attention (Operation Guide, operating precautions, inside front cover).

  • Do a pre-job hazard assessment before you start, and again whenever you return to the site.

  • Remove rings, watches and other metal jewelry. Take extra care not to drop metal tools onto a battery.

  • Keep someone within calling distance, and keep fresh water and baking soda nearby in case acid contacts skin, clothing or eyes.

  • Don't disconnect battery cables from power systems during the test without authorization. Don't place yourself in the circuit, and avoid touching a jar and a grounded rack or cabinet at the same time.

  • Battery posts and terminals contain lead. Wash your hands after handling.

The Ultra manual adds: don't operate the Ultra with its charger (AC adapter) attached (Ch. 1, p. 7).

Step 1: Pick a reference value

Franklin Electric defines a reference value as the average conductance of a sample of strong batteries similar in condition and age. Generally, about 30 new or healthy batteries are tested to get a value representative of a new online battery 90 days after installation (Operation Guide §7.1, p. 46; Ultra manual Ch. 3, p. 24).

Both manuals list the options in the order Franklin Electric says to try them:

  1. Your company's own reference values for that string.

  2. Test a sample of batteries (see below).

  3. Use one of the tester's options based on the string itself (the order differs slightly by model): Develop Reference / Reference Developer (the top 30% of the string by default), the string-summary average, Baseline Testing (Advantage Digital), or the highest conductance value in the string (Ultra).

  4. Last, use the tester's battery library. If your model isn't listed, contact the battery manufacturer or check Franklin Grid's reference-value list on franklingrid.com.

Franklin Electric says the library and website reference values are only guidelines (Operation Guide §7.2; Ultra manual Ch. 3).

Testing a sample (Operation Guide §7.3, p. 47; Ultra manual p. 25):

  1. Choose at least 30 batteries of the same make, model, power rating, age (within 6 months) and service history.

  2. Record the manufacturer, model, manufacture and installation dates, operating conditions (charge voltage, temperature, DC float current), and any visible problems such as leaking acid, corrosion or distorted cases.

  3. Test the batteries. Then test one battery 5 times in a row on float charge. The results should agree within ±2%. If they don't, an electrical signal might be present in the system.

  4. Average the results, leaving out any battery more than 30% above or below the average.

Step 2: Check conditions before you test

  • After a power outage. Don't test a string that is boost-charging after a recent outage. The Advantage Digital guide says to wait 48 hours after the outage and recharge so the string can return to equilibrium (§7.2, p. 47).

  • Temperature (Advantage Digital, §5.1, p. 35). Take a battery temperature before testing. Hold the tester within 2.5 in (6.35 cm) of the negative terminal, with the sensor perpendicular to it. In a cold (below 15 °C) or hot (30–40 °C) room, let the tester sit for about 20 minutes to match the room before testing.

  • Temperature (Ultra, Ch. 5, p. 33). The manual notes that conductance varies with jar temperature. You enter the string temperature (default 25 °C / 77 °F), and the Ultra uses it to compensate its warn/fail percentages to 25 °C, at 0.7% per °C between 0 and 35 °C.

Step 3: Set up the string

On the Ultra (Ch. 5, pp. 29–33), create a new string in BATTERY SETUP and set:

  • Jars per string (default 24). Count carefully.

  • Volts per jar (default 2).

  • Low-voltage threshold (default 12.6 V for a 12 V jar; other defaults are in the manual's Table 6).

  • Test mode: jars only, jars and 1 strap, or jars and 2 straps. Also set posts per jar.

  • Reference value (from the battery database, Reference Developer or manual entry).

  • What to measure: voltage only, volts and conductance, or volts then conductance. Use "volts then conductance" if you don't want conductance testing to affect your voltage readings.

  • String temperature.

On the Advantage Digital (§5.2–5.4, pp. 37–38), the setup covers the number of jars, jar voltage, thresholds, tests per jar, straps per test, reference value and test type. The guide says "volts then conductance" mode addresses "voltage creep".

Step 4: Connect and test each jar

  • Test one jar at a time. Both manuals warn never to use the tester on the entire string at once.

  • Test on the lead post for the most consistent results. Don't test on nuts, bolts or other battery hardware, and avoid stainless-steel hardware, which lowers or alters readings. If you can't reach the post, test on the strap as close to the terminal as possible (Operation Guide §5.1.2, p. 35 and p. 47; Ultra manual pp. 24, 35, 39).

  • Be consistent. Test each jar at the same spot every time. Changing the test point can change the result (Ultra manual p. 39). The Ultra manual says you don't need to wipe off anti-corrosion grease first.

  • Order. Start with cell one. The Advantage Digital guide prefers starting with the battery at the top of the rack, then following the series connections from the most positive cell to the most negative (§5.1.2, §6.5.4). On the Ultra, test a jar's posts and then the strap that connects it before moving to the next jar (Ch. 6, pp. 37–38).

  • Connecting (Ultra, p. 39). Attach black to the negative (–) terminal, then red to the positive (+) terminal. The Ultra won't turn on if the leads are reversed.

  • Label and record. The Ultra manual suggests putting a sticker label on each jar and strap so results line up from test to test. Record the power load, physical condition of the jars, site condition and jar rating each time you test (p. 37).

Step 5: Read the results

The Ultra beeps twice when a test is done. It beeps longer if the conductance is below the reference value, below the warn or fail percentage, or if voltage is below the low-voltage setting (Ch. 6, p. 40). Its string summary shows each jar and the string as a percentage of the reference value, with a decision of GOOD, WARN (?) or FAIL (!) (Ch. 7, p. 45).

Default warn/fail settings (CELLTRON Ultra manual, Ch. 4, p. 26, "Table 4: Defaults for a jar and string in service"): WARN below 70% and FAIL below 60% of the reference value, for both jars and strings. You can change these percentages.

What the Ultra manual recommends (Ch. 7, p. 48, "Table 7: String strength related to % of reference value"), quoted for the CELLTRON Ultra and the string-summary percentages:

% of reference value

String strength

Recommended action (Franklin Electric's wording)

> 70%

Good condition

"Check the jars for physical damage"

60–69%

Warning

"Check for problems and refer to: test results or other information about the string to determine the cause of low readings; your company procedures for jar maintenance; IEEE standard 1188-1996: Recommended Practice for Maintenance, Testing and Replacement of Valve-Regulated, Lead-Acid (VRLA) Jars for Stationary Application"

< 60%

Fail

"Replace the jars. Refer to your company jar replacement procedures or IEEE standard 1188-1996"

The Advantage Digital Operation Guide lists warn and fail percentages as user-programmable settings but doesn't publish defaults or a recommended-action table. Use your company's thresholds or check with Franklin Electric for that model.

Not sure about a reading? Retest it. Both testers have a RETEST key. The Ultra manual notes that operating and site conditions can affect results, so verifying them keeps your maintenance history accurate (Ch. 6, p. 42).

Keep a testing routine

Franklin Electric recommends setting up a testing routine to track conductance loss and prevent failures (Ultra manual, Ch. 6, p. 35). Archived results let you compare trends, spot when a string needs maintenance or repair, and provide warranty data (Ch. 7, p. 48).

Need replacement jars or a string test?

We supply replacement UPS and standby batteries and provide service across the Southeast USA. Browse SWU UPS batteries and NPX high-rate batteries, or send us the model of the jars in your string.

Request current price and availability: use the request form or email office@luxena.net.

Sources (Franklin Grid Solutions / Franklin Electric, franklingrid.com, checked 2026-10-21)

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