Battery Load Test Readings Chart — 12V & 24V | SAMCO
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Battery Load Test Readings Chart

This battery load test readings chart gives the voltage numbers that decide good, weak, or replace — for 12V and 24V lead-acid batteries. Bookmark it as your workshop reference.

Reference by SAMCO Battery, Delhi 12V & 24V lead-acid Updated 15 July 2026
Quick reference: Use this battery load test readings chart as follows. Under a matched load, a healthy 12V battery holds 10.0V or above (9.6–9.9V is acceptable); below 9.0V means replace. A healthy 24V battery holds 20.0V or above (19.2–19.9V acceptable); below 18.0V means replace. Always test from a full charge, hold the load about 10 seconds, and read the voltage while the load is still on.

0112V battery load test readings chart

Voltage measured while the load is applied, on a fully charged 12V lead-acid battery at the 10-second mark:

12V lead-acid — voltage under load
Voltage under loadVerdictWhat it means
10.0V and aboveGOODHolds cranking load comfortably. Battery is healthy.
9.6V – 9.9VACCEPTABLEStill serviceable. Keep in use and monitor.
9.0V – 9.5VWEAKBorderline. Recharge and retest before deciding.
Below 9.0VREPLACECannot hold load. Replace the battery.

0224V load test chart

For 24V systems — trucks, buses, some commercial equipment. If your tester works on 12V blocks, test each 12V battery separately and use the 12V chart instead.

24V lead-acid — voltage under load
Voltage under loadVerdictWhat it means
20.0V and aboveGOODHolds cranking load comfortably. System is healthy.
19.2V – 19.9VACCEPTABLEStill serviceable. Keep in use and monitor.
18.0V – 19.1VWEAKBorderline. Recharge and retest; check both batteries.
Below 18.0VREPLACEOne or both batteries failing. Test each 12V block.

03Resting voltage vs state of charge

Before you load-test, the battery should be fully charged. Use this to check charge level with a multimeter at rest (no load, engine off, ideally after the battery has sat an hour):

12V lead-acid — resting voltage vs approximate charge
Resting voltage (12V)Resting voltage (24V)Approx. state of charge
12.7V+25.4V+100% — ready to load test
12.5V25.0V~75%
12.4V24.8V~50% — charge before testing
12.2V24.4V~25% — recharge first
12.0V or less24.0V or lessFlat — do not load test yet
Why this matters: A load test on a half-charged battery fails for the wrong reason — it looks like a bad battery when it is only low. Always bring the battery to full charge first, or you will condemn a good one.

04Match the load to the battery size

The load has to be heavy enough to stress the battery. The rule of thumb is a load of roughly three times the amp-hour rating for about 10 seconds. Too light a load lets a weak battery pass.

Load current vs battery size (12V lead-acid)
Battery typeTypical AhLoad neededSAMCO tester
E-bike / two-wheeler12–30Ah~60ABCT-6 (60A)
Small / mid car30–50Ah~100ALoadPro 100 (CBLT-100)
Large car / SUV55–70Ah~200ABCT-200 (200A)
E-rickshaw / inverter block75–200Ah~300ALoadPro 300 (ERLT-300)
Truck / tractor / commercial200Ah+up to 450ABCT-700 HRD (450A)
Step-by-step guides: How to load-test a car battery in 10 seconds → How to test an e-rickshaw battery pack, block by block →

05How to use these numbers

This battery load test readings chart only holds if the test is done right. Four things decide whether the reading is trustworthy:

  • Full charge first. Read the resting-voltage chart above and charge to 100% before load testing.
  • Matched load. Use the sizing table — an undersized load makes a weak battery look fine.
  • Read under load. The number that counts is at the 10-second mark while the load is still applied, not after you release it.
  • Mind the temperature. Batteries read lower in cold weather; a marginal winter reading may recover in warmer conditions.

Pick the right tester

SAMCO Battery Load Testers

From ₹2,415

Fixed and multi-level resistive load testers for 12V lead-acid batteries — two-wheeler, car, tractor, e-rickshaw and inverter. Delhi dispatch, Pan-India delivery.

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Browse: LoadPro 100 · BCT-700 HRD · LoadPro 300 · Carbon Pile
Battery load test readings chart infographic — good, acceptable, weak and replace voltages for 12V and 24V lead-acid batteries.
Battery load test readings at a glance

06Frequently asked questions

What voltage is a bad 12V battery under load?
Under a matched load, a 12V lead-acid battery that drops below 9.0V is failing and should be replaced. Between 9.0V and 9.5V it is weak — recharge and retest. 9.6–9.9V is acceptable, and 10.0V or above is healthy.
What should a 24V battery read under load?
A healthy 24V system holds 20.0V or above under load, with 19.2–19.9V still acceptable. Below 18.0V, one or both batteries are failing — test each 12V block separately to find which.
Why must the battery be fully charged before testing?
A load test on a partly charged battery reads low because it is low, not because it is bad. Charge to full (about 12.7V resting for 12V) first, or you risk condemning a healthy battery.
Do I read the voltage during or after the load?
During. Read at the 10-second mark while the load is still applied. The voltage recovers once you release the load, which hides the weakness you are testing for.
How much load current do I need?
Roughly three times the battery's amp-hour rating for 10 seconds. A 100A tester suits 30–50Ah car batteries; 55–70Ah needs 200A; 75–200Ah blocks need a 300A load; 200Ah+ needs up to 450A.

Voltage thresholds and state-of-charge figures are standard references for lead-acid batteries and are guidance, not a guarantee for every battery, temperature or condition. Prices are subject to availability. © 2026 Samco Battery

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