It’s so frustrating when you dust off your car to take a ride, and you find that your car is not starting at all, and this is usually because of your car battery.
Car batteries can drain if you don’t drive your car for some time.
But if your car battery is draining faster than normal, then you must find out what is the problem.
Before you decide to buy a new battery, you should consider finding the fault.
In this in-depth guide, you will exactly know how to do it.
Plus, you will also know which battery should you buy, if recharging the battery is not possible.
Here is what you will know in this guide.
- Check the car battery terminals and check the water level (if it’s not an SLA battery).
- Check how much charge is left in your car battery (using multimeter).
- Determine whether you can recharge your car battery.
- If you can not recharge, then which battery to buy?
- Know the underlying problem, as to why your battery is draining.
1. Check the car battery terminals and check the water level (if it’s not an SLA battery).
Check the car battery terminals.
The first thing you want to do is to check whether your battery terminals are making a proper connection with the battery.
Just try to move it, if it is moving freely then you have a loose connection.
So tightening it, might solve the problem.
If you see rust on your battery terminal and connector, this might be due to acid.
You must clean and neutralize the acid on the connection.
Here is how you clean your battery terminals.
Ensure you are wearing gloves and does not have any jewelry on you.
Always first disconnect the negative terminal and then the positive terminal.
You do this to avoid electric shock.
(Because you will be using a metal tool to loosen the terminal, and if you start with a positive terminal and accidentally touch the tool to the metal part of your car, you will get a really bad electric shock.)
Neutralize the acid that might be on the terminals and connectors using a basic solution with a pH greater than 7.
(Just add some baking soda to water, you have a basic solution.)
Spray some of this solution and thoroughly wipe it off, with a wet cloth.
(Do not use a dry cloth to clean your battery, as it might build up static electricity.)
Take sandpaper (of 180 or 220 grit) and scrub it until you see fresh surface.
Do not forget to clean the inside of the connector, where the connection is actually made.
Make sure the terminals and connectors are dry, before you reconnect the battery.
Check the water level (if it’s not a Sealed Lead Acid (SLA) battery).
Now with all the cleaning done, before you connect the battery you must also check the battery water level, if it is not an SLA (also known as VRLA) battery.
Probably installed in your car is a Vented Lead Acid (VLA) battery.
You can know this type of battery if it has caps placed on it, which you can open to check the water level.
If it is, then you got to check the water level.
If the water level is low and the plates inside are exposed, then you need to add just enough water to cover the plates.
(Remember to take all safety precautions before you add water.)
Do not add more water if the plates are not exposed.
Because if the charge is low, and when you charge the battery, it will cause the water to overflow, because of the expansion of electrolyte solution.
You should only add distilled water, and not the mineral water or water from your purifier.
(Note: By the process of distillation we get distilled water, the water is heated, turned into vapor and is condensed back into liquid in a separate container, leaving behind the impurities.)
You should still not connect the battery.
Because we have one more thing left to do.
That is checking the charge of the battery.
2. Check how much charge is left in your car battery (using multimeter).
Here we are taking a typical 12 V car battery.
Now to check the charge of the battery you must have a multimeter.
Insert the red test lead of multimeter, in the slot on multimeter, that is labeled as VΩmA.
Put the black test lead in the slot, that is labeled as COM.
Set the multimeter dial to 20 V DC. This means you can test voltage up to 20 V.
(You will see DC Voltage symbol on the dial as: V⎓).
You are now ready to check the battery charge.
First connect the positive (red) multimeter probe to positive terminal ⊕ of the battery.
Then connect the negative (black) multimeter probe to negative terminal ⊖ of the battery.
Now you must make a good connection with the battery, and hold it for some time, until the reading is stable.
Make sure battery is disconnected, before taking the reading (to get Open-circuit voltage (OCV)).
3. Determine whether you can recharge your car battery.
Take your reading and compare it with the table below, to know the estimate of battery charge level this reading correlates with.
| Approximate State of Charge (SoC) | Open-circuit Voltage (OCV) | |
| 6V Battery | 12V Battery | |
| 100% | 6.32 | 12.65 |
| 75% | 6.22 | 12.45 |
| 50% | 6.12 | 12.24 |
| 25% | 6.03 | 12.06 |
| 0% | 5.95 | 11.89 |
If your battery charge level is good (that is ≥ 12.5 V), then it probably was loose battery connection problem, or the rust on it.
Now you have cleaned it, so just connect the battery, and it should work.
Charging your car battery.
If it is below 12.5 V, then you need to recharge it.
If it is below 11 V then your battery is in the state of deep discharge.
During discharge the plates become lead sulfate, this is normal process for every discharge.
But if you leave it for weeks or months in this discharged state, Sulfation can become permanent and recharging it won’t help.
To recharge the battery from deep discharge, your battery plates must be in good condition.
If that’s the case, you have a fairly good chance of recharging the battery, using a car battery charger that is capable of recovering deeply discharged battery.
You can recharge your battery from your local electrical technician, car mechanic or authorized battery dealer.
If you want to recharge it yourself you must have a battery charger, also you must take all safety precautions to do so.
(Note: It will take up to 1 day or even 2 days for the battery to fully recharge, depending upon battery charge level.)
Knowing whether each cell of a car battery is good.
A typical 12 V battery will have six 2.1 V cells, which adds up to 12.6 V.
Each cell contains lead plates and electrolyte, and it is possible that any one cell could go bad.
So as a consequence, the battery might not fully recharge to 12.6 V, and will be below 11 V, no matter how much you charge it.
So you have damaged plates in one of the cells.
This means you should already start reading about, buying a new car battery.
After the battery recharge.
After recharging, ensure the water level is just below (up to 25% below) the inner part of the opening.
Connect the positive terminal first and then the negative terminal, and yes, connecting the battery is the reverse of disconnection of the battery.
Now you have a clean connection and a charged battery, so your car must start if there are no other problems.
4. If you can not recharge, then which battery to buy?
Now you are sure your battery is dead, so you should consider buying a new battery.
First, check your car owner’s manual.
Whatever specifications it says, you should get that battery.
You don’t want to damage your car’s electrical system by installing a wrong battery.
Now the question is which type of battery you should install?
Types of Lead acid batteries.
VLA (Vented Lead Acid) and SLA (Sealed Lead Acid).
VLA (Vented Lead Acid) car battery.
Also known as flooded battery.
It has really good battery life, and is easy to troubleshoot.
This battery is cost-effective than all other types.
But it comes at the cost of maintenance.
You must ensure to maintain the battery water level.
Usually you need to check the water level every three months, to make sure the plates do not expose to air.
Plus, there is a chance of spillage, which will also lead to corrosion.
VLA is further of two types, depending upon plates used (mostly relevant to inverter battery).
Flat plate battery and Tubular plate battery.
SLA (Sealed Lead Acid) car battery.
Also known as VRLA (valve regulated lead–acid) battery.
These are sealed batteries, which does not require water topping.
There are two types of SLA battery.
AGM (Absorbent Glass Mat).
AGM battery has electrolyte absorbed in fiberglass mat.
Gel cell (Gel battery).
This battery has gel like electrolyte, which is made by adding fumed silica to sulfuric acid.
The advantages and disadvantages of these both batteries over VLA battery are similar.
Advantages.
They recharge faster than VLA battery.
No spillage, so you can install in any orientation.
No water topping required.
Better resistant to vibration, which is also a common cause of failure of a battery.
Disadvantages.
Not cost-effective.
Less tolerance to overcharging, which can lead to failure of the battery.
Battery life is shorter than VLA battery.
Types based on thickness of plates in lead acid battery.
Starter battery and Deep-cycle battery.
Starter battery.
Designed to have thin, but more number of plates, to lower the resistance and increase surface area.
So that it can provide high power output, to crank the engine.
This battery design cannot handle deep discharge.
This type of battery comes with a CCA (Cold Cranking Amps) mark on it.
Deep-cycle battery.
Designed to have thick plates so that it can give continuous power with a medium power output.
Also, it can handle deep discharge.
Mark of Ah. (Ampere Hour) will be present on this type of battery.
(So both Starter battery and Deep-cycle battery has its own applications. But a combination of these two is also available.)
Concluding with types of batteries.
Now you know all the lead acid battery types.
So when you come across any type, while looking to buy a car battery, you know what it is suitable for.
5. Know the underlying problem, as to why your battery is draining.
Now, you might have recharged your car battery or bought a new one.
In either case, if you won’t fix the root cause of your battery drain, you will be back to square one.
There are two main reasons as to why your battery might be draining.
Parasitic draw and Bad alternator.
(Parasitic draw is the current being drawn by some of your electrical system even when you turn off your car.)
To check for Parasitic draw.
Leave your car hood open, turn off your car, keep your car’s remote key away from your car, so that your car’s remote key-less system (RKS) goes to sleep.
Set the multimeter to test the current.
To do that, insert the black test lead of the multimeter at COM slot.
And insert the red test lead of multimeter at 10 A DC or 10 A⎓ slot.
Set the multimeter dial to 10 A DC or 10 A⎓.
Now disconnect the negative battery connection.
Connect one multimeter probe to battery cable and other probe to negative battery terminal.
On average, the reading must be below 50 milliamps or close to it, like 60 milliamps or 70 milliamps, which is also a good reading.
Your multimeter is set to 10 A so your reading will be shown in decimal.
So for 50 milliamps it will show as 0.05 (this reading is in amps and not milliamps).
This current draw is usually by your car’s remote key-less system (RKS), and this is required, so that your RKS works.
But if your reading is higher, like 100 milliamps, then you need to get it checked by your mechanic.
To check the bad alternator.
Ensure your car battery is charged to max.
Connect the multimeter’s positive probe to positive terminal and negative probe to negative terminal of the battery.
Start the engine and leave it for 15 minutes.
Check the voltage reading, it should be between 13.5 V to 14.5 V.
If it is more than 14.5 V say 15 V then the voltage is not regulated properly, and this is bad for your battery.
So your voltage regulator inside the alternator might be bad, so get it replaced.
If it is less than 13.5 V, then you must test the voltage at the alternator.
Check your owner’s manual to locate the alternator.
Connect the positive probe to the positive wire-connection of the alternator, and connect the negative to the outer casing of the alternator.
If the voltage at the alternator is also less than 13.5 V (same as at the battery), then you have a bad alternator.
If the voltage at the alternator is more than the voltage at the battery, then there might be a problem, with wiring connection between alternator and battery.
Conclusion.
So now you have enough knowledge not just to buy the best car battery, but also diagnose and repair the fault that is draining your battery.