- Your battery label shows an EN value (for example EN 540): that's your battery's cold cranking current, and that's the number that counts.
- Choose a jump starter whose CCA is equal to or higher than that EN value.
- EN and CCA measure almost the same thing, so you can compare them directly.
- The Ah or Ah capacity on the label says something about the battery's capacity, not about its starting power.
The label on your battery shows a row of numbers and codes that almost nobody explains. Yet one of those values determines exactly which jump starter you need. Below you'll find where to look and what each number means, so you choose your jump starter based on facts, not on the biggest number on the box.
EN (European Norm) is the standardised cold cranking current of your battery, measured at minus 18 degrees Celsius. The higher the EN, the more starting current your battery can deliver. On most European batteries this number appears prominently on the label, for example EN 540 or 540A EN.
Where do you find the values on your battery label?
Look at the top or the side of your battery. There's a sticker with the brand, a type code and a block of numbers. The most important one for starting power is the EN value in amps, often shown with the letters EN next to it. You'll usually also see the voltage (12V), the capacity in amp hours (for example 60 Ah) and sometimes a reserve capacity in minutes. Note down the EN value, since you'll need it to choose your jump starter.
What exactly does the EN value mean?
The EN value tells you how much current your battery can deliver for 30 seconds at minus 18 degrees, without the voltage dropping too far. That's exactly the toughest moment for your car: a cold engine with thick oil needs the most power to turn over. A car with an EN 540 battery has a starter motor built around that figure. Go below that with your jump starter and you won't turn the engine over smoothly. Match it or go higher and you're fine.
EN and CCA: are these the same numbers?
EN and CCA (Cold Cranking Amps) both measure cold cranking current at minus 18 degrees. The test methods differ slightly, but the numbers sit close enough together that you can compare them directly in practice. That makes choosing simple: if your battery shows EN 540, look for a jump starter with at least 540 CCA. You can read more about that measure on our page what is CCA and why it matters. Note: the eye catching peak current figure on a jump starter, such as 3750A, is something completely different and not comparable to the EN on your battery.
Ah and reserve capacity: what do they stand for?
The capacity in amp hours (Ah) and the reserve capacity in minutes aren't about starting power, they're about how long your battery can supply current. A higher Ah means more buffer, for example for the lights and onboard electronics when the engine is off. You can ignore these numbers when choosing your jump starter. They're useful when you buy a new battery, but for starting power you only look at the EN.
From battery label to the right jump starter
Once you've found the EN value, the rest is simple. Find the jump starter in the table below whose CCA is equal to or higher than your EN. If you drive a diesel or a larger car, add an extra margin, since those engines need more starting current than a small petrol engine.
| Your battery (EN) | Recommended | CCA | Price |
|---|---|---|---|
| up to 480 EN, small petrol | Boost Basic 3000 | 480 | €64,95 |
| up to 620 EN, most cars | Boost Mini 3750popular | 620 | €94,95 |
| up to 960 EN, diesel and SUV | Boost Pro 8250 | 960 | €189,95 |
| up to 1.440 EN, large diesel | Boost Max 10200 | 1.440 | €249,95 |
- 620 CCA, covers most petrol and diesel cars
- Smart clamps with protection against reverse polarity and short circuits
- Ordered before 5pm, shipped the same working day
Frequently asked questions
Which number on my battery decides which jump starter I need?
The EN value, the cold cranking current in amps. Choose a jump starter with a CCA equal to or higher than that EN value. The Ah capacity doesn't matter for starting power.
Is EN the same as CCA?
Almost. EN and CCA both measure cold cranking current at minus 18 degrees, with a small difference in method. The numbers sit close enough together that you can compare them directly.
Where do I find the EN value on my battery?
On the sticker on the top or side of your battery, usually shown with the letters EN, for example EN 540. If you only see an Ah value, check whether a starting current in amps is listed too.
What does the Ah value on my battery label mean?
The amp hours (Ah) show the capacity, so how long your battery can supply current. It says nothing about starting power. For choosing your jump starter, look at the EN value.
What if the EN value isn't shown on my battery?
Look up the battery by brand and type code, or choose based on your engine. For a small petrol car, 480 to 620 CCA is usually enough. For a diesel or larger car, go for 960 CCA or higher.
