Car batteries are usually replaced every 3 to 5 years on average – but as with most things in life, there’ll always be exceptions.
When changing the car battery, you need to pay attention to battery specifications – battery capacity (Ah) and cold cranking amps (CCA) and be aware of the implications should you use batteries with slightly different values than the original.
For example, can you use a battery with a lower Ah? Is it a good idea and if so what are the trade-offs?
In this post, I discuss why battery capacity (Ah) is important and whether you should consider using a battery with a lower Ah or not, and the implications should you do so all of this to help you make an informed decision.
Quick answer. A battery with a lower Ah has less available energy to power the car’s electrical systems when they are running on a battery.
This will not necessarily affect the battery’s ability to start the car, i.e supply the necessary current, the cranking amps provided it meets or even surpasses the manufacturer’s recommendations for the cranking amps.
Battery Ah | Why it is important
Battery capacity (Ah) gives you an indication of how much energy is available to power the car’s electrical systems including accessories (when the engine is not running).
It gives you an idea of how long you can expect the car’s electrical systems to run on battery.
The higher the Ah, the longer the accessories – the radio, and headlights can run.
The cranking amps (CA) is what is important in determining the battery’s ability to successfully start a car and not the battery capacity (Ah).
The CA (cranking amps) or CCA (cold cranking amps in cold climates) shows how much current the battery is able to supply to successfully start the car.
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Can you Use a Lower Ah Battery in the Car?
Always confirm that the car battery selected can deliver the required cranking amps as per the manufacturer specifications first then consider the battery capacity (Ah) second.
While I’d recommend that you stick to the manufacturer recommended battery capacity (Ah) or higher when selecting the battery capacity (Ah) or higher, a battery with a lower capacity (Ah) can work as well but will power accessories for a shorter time.
Is it better to use a lower Ah Battery?
A lower Ah battery though likely to be cheaper,will likely involve sacrificing the battery reserve capacity.
You’ll have fewer minutes of battery power available should the alternator fail or if you’re just running the radio, hazards, and interior lights with the car engine switched off.
Should you Use a Lower Ah Battery?
While it may work as well, in my opinion only consider the lower Ah battery as a temporary, emergency solution.
You may also be interested in: How long does a car battery lasts with hazard lights on
What Happens if you Use a Lower Ah battery?
If considering using a battery with a lower Ah capacity, make sure it can supply the necessary cranking amps to turn the engine over (usually over 500 cranking amps, depending on the engine capacity).
The battery with a lower Ah will provide a shorter runtime for the car electrical accessories depending on the the battery capacity.
For example, a 10Ah reduction in battery Ah capacity reduces the runtime of a pair of headlights with a combined power consumption of 110 watts by about 1 hour.
The dangers of using a battery with a lower Ah Battery
Higher risk of deep discharge resulting in premature battery failure.
Using a battery with a lower than recommended battery capacity increases the likelihood of deep discharge of the battery and premature failure.
Related questions
Should You Use a Car Battery with a Lower CCA?
While it may be possible to start a car with a battery that has slightly lower CCAs, this is not recommended.
Doing so increases the likelihood of the battery not being able to start during extremely cold weather.
Additionaly, a battery with a lower CCA is likely to fail sooner than one with the rated CCA over time.
As a battery ages, the number of CCA s it is able to supply reduces.
Where to Check for The Recommended CCA Rating of the Battery
Refer to the specifications of the original battery that came with the car and replace with a battery that has the same CCA rating or higher.
You can also refer to the car’s service manual for the recommended CCA and Ah ratings that match your car’s engine model.
When is the CCA Too Low?
This really depends on the engine capacity but many cars use batteries with a CCA rating of 500 and above.
Note: CCA rating is important for cars used in cold weather.
Final Word
To start a car successfully use a battery with the recommended CCA rating or higher.
A lower CCA rating increases the likelihood of the battery not being able to supply the required amps to successfully start during cold weather or to fail earlier.
The Ah rating gives you an indication of how much runtime you can expect from a car battery with the accessories connected.
The higher it is the longer the electrical accessories can run for when on battery.
