Car batteries come in a variety of construction for a variety of applications.
The original ones were lead acid, called flooded batteries, and you could take the caps off to check the water level and use a hydrometer to see how each battery cell was doing. In fact, the term battery comes from a “battery” of cells, or a collection of cells. A car battery has 6 cells, each one at 2.14 volts or close to it. Hence the loose term 12 volt battery.
This style of car battery was useful to determine with a hydrometer which cell was bad, or if the battery just needed more charging. These types of battery let small amounts of gas out as they charge. This meant you needed to replace the water that vented out periodically.
As times changed it became less popular to have to check the water and Maintenance Free car batteries were born. They put a small built in hydrometer right in the battery with an eye for you to see the colour of the eye to know if it was good or not. Typically green meant good, white meant needs charging, and back meant dead.
The issue with this is the eye only reads one cell. So it could display green, making it seem like the battery was good, but if the cell beside it was bad, the eye wouldn’t know it. Maintenance Free car batteries have regulators that return the water back to the battery negating the need to check the water.
It is actually pretty rare for a good battery to be defective. And the convenience of not having to take the hold down bar off, and lifting the lids to check the water level in their car battery, outweighs for the average consumer the need to have to keep checking the water. The Maintenance Free batteries never need checking, the water stays in them, and not being able to determine which cell was bad, isn’t typically worth having the old style with caps.
You never ever ever put more acid in a battery. The ratio of acid to water is just right for the battery, and only water is ever lost from a battery, so only water ever goes back in it.
From there GEL batteries came along. Instead of loose sloshing water and acid, the liquid was put in a gel state. This allowed for different mounting options, lower discharge capabilities, no gassing off, and generally longer life IF it was in the right application. They work great in applications that are deep cycling, especially with a low draw and a low recharge rate. They are not suitable for a starting battery for a car.
Next was AGM batteries. Similar to GEL in that the water is absorbed by glass matting (AGM) and can handle vibration better, can be mounted inside the car (very very little gassing off when charging) as well as having many more starts to them than a typical lead acid car battery. Some specialty AGM batteries have insane cold cranking abilities, and even the typical ones can handle what a battery needs to do so much better. AGM car batteries have many more cycles (how many times it will work and recharge) than a lead acid car battery does. They also recharge faster than a lead acid.
EFB has come along now too, it stands for Enhanced Flooded Battery. This a regular lead acid flooded battery on steroids. It fits somewhere between lead acid and AGM. Vehicles with stop/start technology need them because the vehicle turns off and on so many times, the battery has to be able to handle it. Some require AGM for start/stop, it depends on what the manufacturer designed for the car.
As a rule of thumb you should replace your car battery with the type the manufacturer designed to go in it in the first place. It won’t be long before every new car sold will have start/stop technology. This means the battery has to be able to handle it. The more heavy duty a battery is, the more it costs to make.
Regardless of type of battery, it costs a certain amount to make them a certain way. More expensive ingredients in order to provide for higher demand are required. One simple thing to make a cheaper battery is to use less lead in it. If there is less lead there is less power. If there is less power, there is shorter life span. There can be lead, lead paste, antimony, calcium, sulphuric acid, lead dioxide, silica, sponge lead, tin, selenium, and so on in your car battery.
There are some things that any battery, just can’t keep up with:
- Short, infrequent trips. (alternator never charges it fully, decreasing life span)
- Listing to tunes with the car off for long. (battery isn’t meant to be drained that low)
- Very hot weather for a long time. (hot is actually worse than cold on a battery)
- Letting them sit not in use, hooked up or not. (they self discharge on their own)
- Hooking up high power stereos, winches, extra lights. (they just weren’t built for it)
Manufacturer’s build the batteries to meet certain specifications. If you were to order 1000 batteries and demand they cost you $100 each, then the manufacturer will simply make the battery cheaper. (weaker) If you were to order 1000 batteries and say I want them to be as good as they can be made, you tell me the cost, then they will be made much better. There aren’t a lot of manufacturer’s compared to battery stores, so a lot of them are a very similar battery with a different sticker. One thing we do here at Pacific Batteries, is to load test the batteries before we buy them no matter who makes them, to verify what they will hold up to.
They all have pro’s and con’s, and at the end of the day it is best to ask a battery specialist what is the best overall value battery for your car.