Battery CCA to Ah and Ah to CCA Guide. Whether you’re upgrading an RV用バッテリー system, speccing batteries for a boat, or comparing options for an off-grid setup, one question always appears: How do CCA and Ah actually relate? Many assume a 600 CCA battery equals ~100Ah—but starting power and energy capacity come from two different engineering worlds. Misunderstanding them leads to poor performance and costly mistakes. This guide breaks it down with real formulas and practical logic so you can choose the right battery for any application.
カマダパワー 12V 100Ah Lifepo4 バッテリー
Understanding the Difference: CCA vs Ah
To understand why a 600 CCA battery doesn’t automatically mean 100 Ah, visualize a water tank system. This analogy is crucial for understanding system limitations:
Ah (Amp Hours) = The Volume of the Tank.
It tells you how much water (energy) the tank holds. A 100Ah tank can run a small trickle of water (lights/fans) for a long time.
CCA (Cold Cranking Amps) = The Diameter of the Outlet Pipe.
It tells you how fast the water can rush out instantly. You need a massive pipe (High CCA) to turn a heavy water wheel (Starter Motor).
The Engineering Reality: You can have a huge tank with a tiny straw (High Ah, Low CCA — e.g., Solar Deep Cycle), or a small bucket with a firehose nozzle (Low Ah, High CCA — e.g., Motorcycle Start Battery).
Use this formula when you have a starter battery (rated in CCA) but need to know its capacity to run electronics like a fridge, inverter, or lights.
フォーミュラ： Ah ≈ CCA / Kfactor
Select your Kfactor (Based on Chemistry):
- Flooded Lead-Acid (Standard Car/Truck): K ≈ 7.25
- AGM (High Performance): K ≈ 9.5
- ゲルセル： K ≈ 6.5
CCA to Ah Calculation Example:
You have a standard Ford F-150 battery (Group 65) rated at 750 CCA. 750(CCA) ÷ 7.25 (K) = 103.4Ah Verdict: This aligns with industry standards for Group 65 capacity (typically 75-100Ah).
Use this formula when you have a ディープサイクルバッテリー (rated in Ah) and want to know if it has enough power to start an engine.
フォーミュラ： CCA ≈ Ah x Kfactor
Select your Kfactor:
Dual-Purpose Marine/RV: K ≈ 8.0
Deep Cycle (Thick Plate): K ≈ 6.0
Ah to CCA Calculation Example:
You have a 100Ah Deep Cycle Lead-Acid battery. 100 (Ah) x 6.0 (K) = 600 CCA Verdict: This is sufficient for small engines, but be aware that deep cycle plates may warp under sustained cranking loads over time.
CCA to Ah Conversion Chart (By BCI Group Size)
Instead of calculating manually, use this master cross-reference chart. We have consolidated data from standard BCI (Battery Council International) group sizes to provide the most accurate correlation between Group Size, CCA, and Ah.
| Application Category | BCIグループサイズ | Typical CCA (Amps) | 標準容量 (Ah) | 主な使用例 |
|---|
| Powersports | Group 14-BS | 200 CCA | 12 Ah | Motorcycle, JetSki (High Burst) |
| Compact Auto | Group 35 | 550 – 600 CCA | 45 – 50 Ah | Sedans, Small SUVs (Honda/Toyota) |
| Standard Auto | グループ24 | 650 – 700 CCA | 75 – 80 Ah | Marine Starting, Mid-size Vehicles |
| Heavy Duty | Group 65 | 750 CCA | 75 – 85 Ah | Trucks, Large SUVs (Ford/Ram) |
| European / DIN | Group 48 (H6) | 760 CCA | 70 Ah | BMW, Audi, VW |
| Marine / RV | グループ27 | 600 – 800 CCA | 90 – 100 Ah | Trolling Motors, House Banks |
| ディープ・サイクル | グループ31 | 900 – 1000 CCA | 100 – 120 Ah | Overlanding, Solar, Marine House |
| ゴルフカート | GC2 (6V) | Rated in Minutes | 215 – 225 Ah | Series Banks (Low Burst / High Cap) |
| Industrial | 4D / 8D | 1200 – 1450 CCA | 200 – 255 Ah | Bus, Large Marine, Solar Banks |
Lithium vs Lead-Acid: CCA Ratings Explained
Warning: Do not apply Lead-Acid CCA logic to Lithium (LiFePO4) batteries.
A 100Ah Lead-Acid battery might rate 600 CCA. A 100Ah Lithium battery might only list 300A “Max Pulse.” Does Lithium have less starting power? NO.
- Voltage Sag: When cranking with Lead-Acid, voltage drops to ~9V. Lithium maintains ~12.8V.
- Power = Volts × Amps: Higher voltage means the starter motor spins より速く with more torque, even at lower Amps.
- BMS Limits: The “CCA” value of lithium batteries is artificially set. This value is strictly limited by the Battery Management System (BMS) to protect battery cells from short-circuit damage.
プロのアドバイス When sizing Lithium for starting, ignore the CCA formula. Look specifically for the “Peak Discharge Current (3s or 5s)” on the datasheet.
Factors Affecting Battery Capacity: Temperature & Peukert Effect
Your calculation is only valid at standard temperature (25°C / 77°F). Real-world conditions change the math:
The Winter Penalty: At 0°C (32°F), Lead-acid batteries lose ~30% of their Ah capacity but require もっと見る CCA to turn the engine.
The Peukert Effect: If you discharge a lead-acid battery very fast (high CCA load), effective Ah capacity shrinks drastically. A 100Ah battery might only give you 50Ah if you drain it in one hour.
アドバンテージだ： LiFePO4 batteries are virtually immune to the Peukert effect. 100Ah is 100Ah, regardless of the load.
結論
Converting CCA to Ah helps compare batteries, but don’t rely on numbers alone. Pick high CCA for cold-weather engine starts, high Ah for running motors, inverters, or solar, and LiFePO4 for top efficiency.
Need a specific power profile? If your project—whether it’s a robotic fleet, an off-grid system, or specialized marine equipment—requires a specific balance of Cranking Amps and Amp Hours that off-the-shelf products can’t provide, you need a custom OEM solution. Contact Kamada Power Battery Engineering Team for a consultation on your custom battery solution.
よくあるご質問
Q1: What is the estimated Ah for a 600 CCA battery?
A: Using the right K-factor is essential. Most flooded starting batteries use a realistic K-factor of 8.0–8.7, not 7.25. With a 600 CCA battery, K=8.0 gives 75 Ah and K=8.7 gives 69 Ah, which matches the typical 69–75 Ah range for Group 24/35 batteries. K=7.25 yields 82.8 Ah, but this is a high-end estimate and not typical for modern starting batteries.
Q2: Can I replace a 600 CCA lead-acid battery with a Lithium battery?
A: Yes. A 50Ah-60Ah LiFePO4 battery aimed at starting applications often provides enough pulse current (300A+) to turn over engines that previously required 600 CCA lead-acid batteries, due to Lithium’s superior voltage retention.