- The only number that determines starting power is the CCA (Cold Cranking Amps), the starting current with a cold battery.
- The peak current in amps (for example 3750A) is a short burst of power and can't be compared between brands.
- mAh, Ah and Wh are about capacity, so about the number of starts, not about the power.
- Compare the CCA of the jump starter with the EN value on your own battery.
On the box of a jump starter there's a row of numbers with little explanation. 3750A, 620 CCA, 12000mAh, 88.8Wh. Which number actually tells you if your car will start? Most numbers are marketing, only one really counts. Below we break them down one by one, so you can see at a glance what to look for.
CCA: the only number that determines starting power
CCA (Cold Cranking Amps) is the starting current that a power source delivers for 30 seconds at minus 18 degrees Celsius. The higher the CCA, the more power to turn over a cold engine. It's the most honest measure of starting power.
The CCA is the power that turns your engine over when it's cold, at the moment you start it. A starter motor needs hundreds of amps to get the pistons moving, and in cold weather it needs even more. That's exactly why we put the CCA first. The rule of thumb: the CCA of your jump starter should be equal to or higher than the EN value on your battery. You can read more about this on our page what is CCA and why does it matter.
Peak current (A): the big number on the box
The peak current is that eye-catching number, like 3750A or 12000A. It sounds impressive, but it's a short burst of power that only lasts an instant. There's no fixed measuring method for it, so one brand measures it differently than another. That makes peak current impossible to compare. A jump starter with a high peak current number can in practice deliver less starting power than a model with a modest but honest CCA. We explain why that number is so often misleading in peak current or CCA.
mAh and Ah: the capacity, not the power
The capacity is expressed in milliamp hours (mAh) or amp hours (Ah). This number tells you how much energy is stored in the jump starter, and therefore how many times you can start your car before you need to recharge it. It says nothing about how powerful a single start attempt is. A jump starter can have a large capacity and still not deliver enough CCA to start a diesel engine. So always look at the CCA for power, and use the capacity only to estimate the number of starts.
Wh: the total energy content
Watt hours (Wh) is another way to express capacity. You calculate it by multiplying the voltage by the amp hours. Wh is useful if you want to compare two jump starters by content, for example when taking one on a plane, where a limit of 100 Wh often applies. Wh makes no difference to starting power. Here too: the number is about content, not about power.
Number of starts: what does that tell you?
Some manufacturers list a number of starts, such as up to 30 times on a single charge. That's an estimate under favorable conditions and with a small engine. In winter, with a bigger engine, or with a deeply discharged battery, you'll get less out of it. See it as an indication, not a hard promise. We prefer honest numbers over a nice round figure.
Overview: which number really counts?
| Number | What it means | Does it count? |
|---|---|---|
| CCAthe power | Starting current at minus 18 degrees | Yes, this is the starting power |
| EN | European standard for that same value, printed on your battery | Yes, compare with the CCA |
| Peak current (A) | Short burst of power without a fixed measuring method | Barely, not comparable |
| mAh and Ah | Capacity, how many starts per charge | For the number of starts, not the power |
| Wh | Total energy content | Only for comparing capacity |
- 620 CCA, the value that determines starting power
- No inflated peak current, just an honest CCA value
- Ordered before 5:00 PM, shipped the same working day
"If you only look at one number, look at the CCA. On the Boost Mini 3750, next to the 3750A peak current, it clearly states 620 CCA. That 620 tells you whether your car will start, the 3750 is mostly there to catch your eye."
Frequently asked questions
Which number on a jump starter matters most?
The CCA (Cold Cranking Amps). That's the starting current with a cold battery and determines whether your engine starts. Compare the CCA with the EN value on your own battery.
What's the difference between CCA and peak current?
CCA is a standardized starting current measured for 30 seconds at minus 18 degrees, so it's comparable. Peak current is a short burst of power without a fixed measuring method and differs per brand. Look at the CCA.
What does mAh mean on a jump starter?
mAh (milliamp hours) is the capacity. It tells you how many times you can start on a single charge, not how powerful one start is. For power, look at the CCA.
What does the A, for example 3750A, mean on a jump starter?
That's the peak current, the short maximum burst of power. It's an eye-catcher without a fixed measuring method. The CCA that's often listed next to it is the value that really matters.
How much CCA do I need?
For a small petrol car, often 480 to 620 CCA, for a diesel or larger car, 960 CCA or higher. The CCA should be equal to or higher than the EN value on your battery.
