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Basic Orientation of Lead-Acid Batteries

By Emanuel Hillmann

    
I get many questions about batteries, especially lead-acid batteries. I understand people’s curiosity, because with so many options out there, you can really get confused. I decided to write a simple article about the subject.

I do not endorse any particular type of batteries.  The statements in this article are intended only to give a general briefing about types of lead-acid batteries and their most common applications.

The simple lead-acid battery has evolved from the simple cell with plates and acid solution to complexly liaised multi-cells being adapted to hundreds of different applications. But it is good to know that, simple or complex, they follow the same basic principles.

Types of Lead-Acid Batteries.

You need to know that there are two types of lead-acid batteries:

 1. Starter Batteries (cranking batteries): These are batteries that can generate a high amount of energy in a short period of time. They are commonly used in vehicles to start the engine.

2. Deep Cycle Batteries: A deep cycle battery can generate a smaller amount of energy for a longer period of time. Deep cycle batteries are constructed with thicker plates and can withstand a deeper discharge. This makes them more prone to sulfate build-up. These batteries are commonly used in golf carts, fork-lifts, RV’s (for the house batteries), off grid solar and wind systems, Uninterrupted Power Source (UPS) and scooters and electric chairs, among others.

      Beside the 2 types of lead-acid batteries, there are also different versions where the lead is mixed with other metals or it is used in a more pure form. This alters a bit how the charge or discharge of the battery happens. There are the so-called hybrids that have properties of starter and deep cycle batteries. Despite all complexities that can be found to increase or modify performance, a lead-acid battery is a lead-acid battery.

Common Battery Technologies

There is a second classification useful to know; no matter if batteries are starter or deep cycle. The two most common technologies are Flooded and VRLA (valve-regulated lead-acid), most commonly called “Sealed lead-acid batteries,” The VRLA is divided further into Gel and Absorbed Glass Mat (AGM).

Wet cells or flooded batteries: They are the most popular because have been around longer, are less expensive and, in some cases, the easiest to regenerate. These batteries are used on cars, boats, golf cars, solar banks, wind banks and back up systems. The marine type is not sealed so users can refill any water that was lost while charging. Special care should be taken while operating any non sealed batteries; first to prevent getting burned with the acid solution inside the battery (follow the safety instructions and use safety gear) and second to prevent the battery from getting contaminated with external agents (sea water, rain water, soil etc). Non sealed batteries are not the strongest, mechanically speaking. They crack more easily than others. Make sure to fully charge them before a long winter. Even better, charge them at least once a month during the winter months, as you run the risk of battery cracking due to freezing. We will cover winter battery maintenance in the next issue.

VRLA (valve-regulated lead-acid): You can not refill these batteries.  They are designed against spills. As mentioned before they are divided in two types.

Gel Cells: The electrolyte is mixed up with a jellifying non-reactive agent like fumed silica that immobilizes the electrolyte. If for any reason the battery cracks, the cell will continue operating. Do not use any charger to charge gel cell batteries as you can ruin them easily by overcharging. These kinds of batteries require lower charging voltages compared to flooded batteries.  Read the instructions on charging to make the most of your batteries.

Absorbed Glass Mat (AGM): These kind of batteries use a glass mat to contain the electrolyte.  They are basically spill-proof compared to the flooded type. Mechanically speaking, AGMs are the strongest batteries in the market. Although the charging voltages are very similar to the flooded ones, you still need to be careful while charging, as overcharging can shorten their useful life dramatically. The AGM offers a long list of advantages like shorter charging time, resistance to vibration, continuous operation even if the container cracks or breaks, lower self discharge than other types (around 3% per month vs. 1% per day on flooded cells), low energy conversion into heat (around 4% vs. 15 to 20% on flooded or 10 to 16% of the Gel cells) and minimal fume production. On the other hand, they are 2, 3 to 4 times more expensive than the flooded ones.

VRLAs are favored by owners of boats, electric scooters, golf car and Neighborhood Electric Vehicles (NEV). AGMs are particularly favored with off grid solar and wind systems as well by RVs, aviation and jet skis. There is one more emerging market; truckers are starting to use deep batteries to power their small refrigerators, AC/heat units or ovens.

Hopefully this clarified some of your confusions on lead-acid batteries. You can always contact me if you have more questions.

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