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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.
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.
12V 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:
| Voltage under load | Verdict | What it means |
|---|---|---|
| 10.0V and above | GOOD | Holds cranking load comfortably. Battery is healthy. |
| 9.6V – 9.9V | ACCEPTABLE | Still serviceable. Keep in use and monitor. |
| 9.0V – 9.5V | WEAK | Borderline. Recharge and retest before deciding. |
| Below 9.0V | REPLACE | Cannot hold load. Replace the battery. |
24V 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.
| Voltage under load | Verdict | What it means |
|---|---|---|
| 20.0V and above | GOOD | Holds cranking load comfortably. System is healthy. |
| 19.2V – 19.9V | ACCEPTABLE | Still serviceable. Keep in use and monitor. |
| 18.0V – 19.1V | WEAK | Borderline. Recharge and retest; check both batteries. |
| Below 18.0V | REPLACE | One or both batteries failing. Test each 12V block. |
Resting 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):
| Resting voltage (12V) | Resting voltage (24V) | Approx. state of charge |
|---|---|---|
| 12.7V+ | 25.4V+ | 100% — ready to load test |
| 12.5V | 25.0V | ~75% |
| 12.4V | 24.8V | ~50% — charge before testing |
| 12.2V | 24.4V | ~25% — recharge first |
| 12.0V or less | 24.0V or less | Flat — 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.
Match 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.
| Battery type | Typical Ah | Load needed | SAMCO tester |
|---|---|---|---|
| E-bike / two-wheeler | 12–30Ah | ~60A | BCT-6 (60A) |
| Small / mid car | 30–50Ah | ~100A | LoadPro 100 (CBLT-100) |
| Large car / SUV | 55–70Ah | ~200A | BCT-200 (200A) |
| E-rickshaw / inverter block | 75–200Ah | ~300A | LoadPro 300 (ERLT-300) |
| Truck / tractor / commercial | 200Ah+ | up to 450A | BCT-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 →
How 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.
Ask on WhatsApp- BCT-6 eBike Tester (60A)12V VRLA eBike and scooter batteries, 12–30Ah.
- LoadPro 100 (100A)12V car batteries, 30–50Ah.
- BCT-200 Automotive (200A)12V car and SUV batteries, 55–70Ah.
- LOAD PRO 300 Inverter (300A)12V inverter, tubular and solar batteries, 75–200Ah.
- ERLT-300 E-Rickshaw (300A)12V blocks inside e-rickshaw traction packs.
- BCT-700 HRD (450A)Selectable 100A–450A for commercial batteries.
- Carbon Pile (500A)Adjustable BCI half-CCA load, starter and alternator tests.
When to run a battery load test
- Slow or hesitant crankingThe engine turns over lazily, especially on the first start of the day. The classic trigger for a car battery load test.
- Backup time has droppedAn inverter or tubular battery that once ran three hours now runs forty minutes.
- Range loss on an e-rickshawOne weak 12V block in a traction pack drags the whole set down. Test block by block.
- Warranty claim at the counterBattery dealers and workshops settle disputes with a load reading, not a resting-voltage argument.
- Buying a used vehicleMechanics and second-hand buyers test before paying — the battery is the cheapest fault to find and the easiest to miss.
- Seasonal and fleet checksGarages, service centres and taxi fleets screen batteries before winter and before long routes.
More battery testing guides
- How to Load Test a Car BatteryStep-by-step car battery load test.
- Load Tester vs MultimeterWhich tool actually proves a battery will crank.
- Inverter Battery Health CheckTest 150Ah–200Ah inverter and tubular batteries.
- E-Rickshaw Battery Testing GuideFind the weak 12V block inside a traction pack.
Frequently 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 fully and retest before deciding.
What should a 24V system read under load?
Double the 12V figures. 20.0V and above is good, 19.2–19.9V acceptable, 18.0–19.1V weak, and below 18.0V means replace. If a 24V bank fails, test each 12V block separately to find which one is at fault.
How much load should I apply?
Roughly three times the battery's Ah rating, or half the CCA rating, held for 10 seconds. Too light a load lets a weak battery pass; too heavy a load can fail a healthy one.
Does the battery need to be fully charged first?
Yes. Load test only at 12.7V or higher at rest (25.4V for 24V). A battery at 12.4V is around 50% charged and will fail a load test that a full charge would pass.
How long should the load stay on?
10 seconds, and read the meter while the load is still applied. Allow about a minute of cool-down before the next test.
Does temperature change the pass threshold?
Yes. The thresholds above assume roughly 21°C. In cold weather a marginal reading may recover once the battery warms, and in hot weather the pass mark sits slightly higher. Always compare blocks at the same temperature.
Why does my battery read 12.6V but still fail?
Resting voltage only shows surface charge. A battery with sulphated or shed plates can hold 12.6V at rest and still collapse the moment current is drawn. That gap is exactly what a load test exposes.
Can I use these figures for a lithium or LiFePO4 battery?
No. This chart is for lead-acid batteries only — flooded, SMF, VRLA, AGM and tubular. Lithium chemistries have a different voltage curve and a battery management system that will cut out under a raw load.
Why does the LOAD PRO 300 show three bands instead of four?
The LOAD PRO 300 uses a simplified three-band scale on its faceplate — optimal, caution, critical — for quick reading in the field. The four-band chart here is the same data at finer resolution: its acceptable and weak bands together make up the caution range.
Which tester should I use for my battery size?
Match the load to the battery: 60A for 12–30Ah two-wheeler batteries, 100A for 30–50Ah car batteries, 200A for 55–70Ah car and SUV batteries, 300A for 75–200Ah inverter, tubular and traction batteries, and up to 450A for commercial batteries above 200Ah.
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