Short answer: Tianneng and Chilwee/Chaowei have clearly documented electric-vehicle battery ranges that include graphene-labelled lead-acid products. Leoch is a major VRLA manufacturer with useful technical documentation, but a generic Leoch VRLA-AGM product should not automatically be treated as a graphene traction battery. There is no laboratory-independent ranking that makes one brand best for every scooter.
In Bangladesh, the best purchase is usually the freshest, correctly sized and properly matched set that has a real local warranty, a traceable model code and a seller willing to test capacity and load performance. “Graphene” is a product label or material claim—not a replacement for voltage, amp-hours, discharge rate, charging compatibility and service evidence.
General user-friendly section
What does “graphene VRLA” mean?
VRLA means valve-regulated lead-acid. The battery is sealed for normal use and uses internal oxygen recombination, although it still has pressure-relief valves and must not be overcharged, opened or installed without ventilation. “Graphene” generally refers to a claimed graphene or carbon-based additive, grid treatment or lead-paste formulation intended to improve charge acceptance, power delivery, corrosion resistance or cycle life. The exact recipe is proprietary and the label is not a universal performance standard.
Short comparison
| Brand/family | What the official material supports | What the buyer must still verify |
|---|---|---|
| Tianneng | Large EV battery portfolio; official material discusses deep-cycle lead-acid, special alloys/formulas and EV applications. Tianneng also provides product-code/factory-date verification. | Exact local model, Ah test rate, production date, genuine code, seller warranty and whether the offered model is graphene-labelled. |
| Chilwee / Chaowei | Official BG/Black Gold graphene-labelled VRLA gel range and EVF/premium electric-vehicle families, with claims around power, range, cycle life and temperature performance. | Exact BG/CWP/EVF model, gel versus AGM construction, rated test rate, dimensions, local importer and replacement support. |
| Leoch | Strong VRLA-AGM documentation covering maintenance-free construction, separators, grids, dimensions and electrical parameters. | Do not infer “graphene” from the Leoch name alone. Confirm that the exact model is intended for cyclic EV traction use, not standby UPS service. |
Who is the winner?
For a scooter, the winner is the battery that fits the complete electrical system and has the strongest evidence. A famous brand with old stock, a mismatched four-battery set or a weak local warranty can perform worse than a less fashionable brand that is fresh, genuine and correctly tested. A graphene label may be a useful premium range indicator, but it does not tell you the usable Wh, real cycle life or value by itself.
Bangladesh buying checklist
- Match the complete pack voltage: for example, four 12 V batteries in series make a nominal 48 V pack. Do not mix voltages or chemistries.
- Confirm Ah and the discharge test rate. A 20-hour rating cannot be compared directly with a 3-hour rating.
- Record each battery’s model, serial/batch code, manufacturing date and measured open-circuit voltage.
- Buy a matched set made in the same period. Do not replace one weak battery in an old series string and assume the set is repaired.
- Ask for the written warranty, exclusions, replacement process and whether labour is included.
- Check charger output and charge voltage against the battery maker’s specification. More “powerful” is not automatically better.
- Ask the seller to show a controlled capacity, load or conductance test. A voltage reading alone is not a capacity test.
Technical deep dive section
Why lead-acid batteries lose range
Rated energy is approximately nominal voltage multiplied by Ah, but VRLA batteries deliver less usable energy as discharge current rises. This is the Peukert effect: a high-current scooter load reduces apparent capacity. Heat, undercharging, overcharging, deep discharge, long storage at low state of charge, electrolyte drying and plate sulfation further reduce performance.
For a series pack, current is the same through every battery. The weakest unit therefore limits the pack and can be driven into deeper discharge or reverse stress before the others. That is why matching and periodic testing matter more than a single impressive label.
AGM, gel and “graphene” are different descriptions
AGM describes an absorbed-glass-mat construction; gel describes immobilised electrolyte; graphene describes a claimed material or formulation addition. They are not interchangeable terms. A graphene-labelled gel battery and a graphene-labelled AGM battery may have different charging limits, temperature behaviour and service requirements. Always use the exact model datasheet.
Charging and thermal limits
VRLA chargers need a battery-specific charge profile. Excessive voltage causes gassing, heat and water loss; too little voltage leaves the plates chronically undercharged. A scooter charger must also be matched to the number of series batteries and the manufacturer’s absorption/float guidance. Do not charge a damaged, swollen, leaking or unusually hot battery.
How to evaluate brand claims
| Claim | Evidence worth requesting |
|---|---|
| Long cycle life | Test temperature, depth of discharge, current, end-of-life capacity and whether the test was on a single cell or complete pack. |
| More range | Measured Wh or Ah at a stated rate, vehicle load, speed, tyre pressure, temperature and cutoff voltage. |
| Fast charging | Maximum current, charge profile, temperature limit, time to a stated state of charge and warranty effect. |
| Graphene technology | Exact product family, construction, datasheet, factory traceability and local warranty—not only a sticker. |
Simple field tests
Before installation, inspect cases and terminals, measure each unit after rest and document the result. Under a repeatable load, record voltage sag and recovery for every battery. For a proper capacity test, fully charge using the specified profile, rest, discharge at a controlled current to the specified cutoff, and integrate current over time. A basic DC internal-resistance estimate is ΔV/ΔI, but it is affected by temperature, state of charge, leads and contact resistance. Use it comparatively, not as a manufacturer-certified health score.
Final verdict
Tianneng and Chilwee/Chaowei are the clearest starting points when you specifically want an official electric-vehicle graphene-labelled range. Leoch is a serious VRLA manufacturer, but its generic standby AGM lines should not be compared as though they were all graphene traction products. In every case, freshness, correct cyclic specification, test evidence, matched installation and local warranty are more important than the marketing word.