The 12V automobile battery still remained as an important vehicle part even in modern vehicles these days. It serves as:
- start up the electric vehicle / cranking the vehicle engine
- a backup for petrol/diesel vehicle in case the alternator is down
- electric supply for electric vehicle and petrol/diesel vehicle accessories, and
- one VERY IMPORTANT function for petrol/diesel vehicle (which I will talk about in another article)
EFB and AGM batteries become a norm because of the iStop (idle stop) function and more technology added into the vehicle.
Then hybrid vehicle comes to the market and uses normal startup battery. With the rise of electric vehicles these days, they installed different types of battery, from normal startup to AGM and even 16V lithium battery.
Here, we first need to learn the types of battery and find out which exactly you are required to install for your vehicle.
Normal startup battery
Commonly used in older generation petrol/diesel vehicles, hybrid and electric vehicles these days. The only normal type of battery in the market is called “Maintenance Free” battery, printed as “MF” or “Maintenance Free” on the battery label. If your new vehicle original equipped battery have these wordings, you can choose normal startup battery to replace your original one.
But before going into MF battery, let’s learn about the past product – Flooded Battery.
Flooded Battery
Aka wet-cell battery / conventional lead-acid battery. Flooded battery has removable caps on the battery for vehicle owners to add distilled water / refill battery electrolyte.
Vehicle owners require to inspect the flooded battery routinely to prevent the electrolyte from drying out. If the battery has dried out, it will damage the battery.
People often think flooded battery lifespan is longer than maintenance free battery. Simply refilling the electrolyte and it is good to go again. However, maintenance free battery saves more time in the long run. For light truck vehicle (or heavier), it’s difficult to check the fluid level without taking out the battery. Fluid is over-filled most of the time.
Maintenance Free Battery
Commonly found in the market. Most models are tightly sealed to prevent electrolyte from drying up. The battery casing is engineered in a way to trap the vaporized gas and turn it back into liquid such that the electrolyte will not dry up. Or rather, difficult to dry up.
Flooded battery does not have such function and therefore, drivers need to routinely check the battery liquid level.
Some Japanese battery brand looks like it’s flooded battery with cap that can easily take out to refill the liquid inside. In fact, these batteries are still maintenance free battery. Their batteries label is also marked as “MF”.
Frequently Asked Questions
1. What is the indicator on top of the battery?
A: It’s called hydrometer. Hydrometer is used for flooded battery to test the voltage of the battery back in the past. Some battery brand installed with hydrometer to let driver monitor the state of charge (“S.O.C”) of the battery. It has 3 different colors specifying Good, Recharge, and Replace.
2. How does the indicator help to diagnose the battery?
A: The indicator has a ball at the bottom of the tube.
If the battery fluid is fully charged, it has higher density, and the ball will float on top of the fluid. This will show the battery S.O.C. is good.
Likewise, if the fluid is half charge, the density is lower, and the ball will fall in the middle of the meter. If the battery charge is very low, the ball goes down the bottom, giving the “Replace” color.
3. Does all Maintenance Free battery including EFB and AGM equipped with the hydrometer?
A: No. Only several brands and models still equipped with the hydrometer. Nevertheless, almost all AGM battery do not have one.
4. Why hydrometer is not accurate ?
The hydrometer shows the battery is “Good” but the multimeter shows the battery have 12V or even lower. That’s because vehicle these days require more than 12V to startup. Unlike the past, older vehicle such as Honda Fit 2012 (or before) can use 11V to crank the vehicle engine. The hydrometer no longer provides an accurate result.
In addition, the hydrometer locates just one cell of the battery. There are 6 cells (columns) in the battery and it’s possible that each 6 cells have different charge and density, causing inaccuracy of the hydrometer.
On the flip side, it can still be used as a reference for the battery electrolyte level in the battery. Although the battery is enclosed and trap the vaporized gas, there are still some that may escape. This happens especially in commercial vehicles in Hong Kong where drivers keep cranking the engine.
EFB Startup Battery
Enhanced Flooded Battery (EFB). The better version of the normal startup battery. The invention of this type of battery mainly focusing on vehicles with iStop function. A better internal structure gives this battery more charge and discharge cycle to adapt the uses of iStop.
Because of this feature, EFB battery is supposed to have better lifespan than normal startup battery.
Frequently Asked Questions
1. What is iStop function?
Idle stop (iStop) is a feature of the vehicle that will stop the engine whenever the vehicle comes to a stop such as traffic jam and red light.
2. Why vehicles with iStop feature needs EFB/AGM battery
The continuous starting and stopping the engine pose a heavy burden on the charging and discharging cycle of the battery. Hence, the vehicle needs a better battery structure to adapt into this function.
3. If I always disable iStop, can I use normal battery instead?
Practically speaking yes. But the lifespan of normal battery still depends on the owner driving habit.
Afterall, there could be times when you actually forget to disable the function.
4. Can a vehicle original equipped with normal battery upgrade to EFB battery?
A: Yes. Some of my customers’ vehicles upgrade to EFB battery shows an improvement in the usage. However, not all vehicles and/or person should upgrade to EFB. Those who do not use the car that often, using EFB battery is simply spending extra without extending the usage.
AGM Startup Battery
Absorbent Glass Mat (AGM) is an even better battery type compared to EFB. It uses special fiberglass mats that hold the battery fluid. It has an even higher charge and discharge cycles than EFB. European-made vehicles even including KIA Sorento originally equipped with AGM battery to better support the vehicle electrical appliances.
Frequently Asked Questions
1. Can I replace original equipped AGM battery with a normal battery if I always disable iStop function?
A: No. Unlike EFB battery, vehicles original equipped AGM because of heavy electrical appliances. Normal battery can’t keep up with the current requirement.
2. Can I replace original equipped AGM battery with EFB battery?
A: No. AGM battery is one grade higher than EFB battery. Downgrading to EFB will result in shorter lifespan.
3. Can I replace original equipped EFB battery with AGM battery?
A: Practically speaking yes. But whether AGM battery can provide longer usage still depends on drivers’ driving habit. Not all drivers can enjoy the AGM battery to the fullest. You may appear spending more but not getting the benefit of the upgrade.
4. Can I replace original equipped normal battery with AGM battery?
A: Practically speaking yes but not recommended. It’s a waste of money in fact. The price for an AGM battery costs three times more than a normal battery. With proper maintenance, a normal battery can last for 3 – 5 years. The expenditure is much lower than AGM battery in the long run.
(New) eAGM Battery
Another type of AGM battery specially for electric vehicle. It’s original equipped in Korea-made electric vehicles such as KIA and Hyundai.
It’s invented not long ago so the market may not have eAGM available except getting the original equipped one.
If your vehicles are equipped with eAGM, you can choose AGM as a substitute.
However, I just met a case which the customer’s electric vehicle was replaced by a EFB battery but his original equipped supposed to be eAGM battery. He said that the car dealership center technician told him to replace the battery because it got a low voltage (but never tell him how much voltage the battery currently has).
Although the battery can still be used, his eAGM is supposed to last for a very long time as compared to his current EFB (which is a downgrade).
Deep Cycle Battery
It is designed to deliver steady amount of power over a long period of time.
Automobile seldom uses deep cycle battery as startup battery is optimized to deliver a large burst of power for engine starting.
Old batch of Tesla such as Model S uses deep cycle battery but other electric vehicles normally uses normal startup battery or AGM battery.
You should get deep cycle battery if your purpose is to find one that keep power equipment continuously such as solar panel, boat, and even road sign.
Frequently Asked Questions
1. Can a vehicle uses deep cycle battery?
It’s not recommended because deep cycle can’t provide a large amount of current at one go to crank an engine. Deep cycle battery is also more expensive than startup battery. Besides, it takes more voltage to charge deep cycle battery that petrol vehicle may not be able to provide.
Electric vehicle nowadays use smaller size automobile battery. Smaller size = cheaper. If an electric vehicle uses normal startup battery, it’s expected to last for 4 to 5 years with proper maintenance.
Lithium Battery
Lithium battery to be used for startup isn’t a new thing. LiFePO4 (Lithium Iron Phosphate) is specially designed for start up the vehicle. Just like your mobile battery, it’s supposed to last longer than normal start up battery. However, LifePO4 is not commonly used because:
High selling price
If the startup battery is located at the front hood near the engine, LifePO4 battery degradation will accelerate in a much faster pace because of high heat.
Alternator Issue
Alternator in petrol/diesel vehicles is not designed to charge the lithium battery. Getting LifePO4 as an aftermarket battery may not give you a very long lifespan as you expect.
In addition, alternator has a part known as voltage regulator that regulates the voltage that it generates. Alternator voltage range between 13.4V to 14.6V. But this voltage alternator may fail / sometimes it can’t stop the alternator outputting even more voltage. I once inspected a vehicle alternator output voltage goes up to 15.x when the driver cranks the vehicle. In this case, a normal (lead acid) startup battery acts as a buffer to absorb this 15.x V, preventing the current damaging other vehicle parts such as ECU.
If LifePO4 is used, its battery management system (BMS) will protect the battery from getting damaged by stopping the current into the LifePO4, but it will not work as a buffer. In this case, it will direct and spoil other vehicle parts.
Electric vehicle still equips with lead acid battery because of the high cost. Yet, some electric vehicles equipped with AGM can be expected to last for more than 7 years.
Still, latest tesla model is now equipped with 16V Li-on battery. It’s expected to last very long that people believes it’s gonna to last forever.
Conclusion
Whether it’s brand new vehicle or second hand vehicles, it’s vital to learn and know what your vehicles are equipped in order to avoid getting the wrong equipment.
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-> Battery specification explained
-> Best Startup Battery Ranks in Year 2025
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