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Ultimate Guide to Battery Basics

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Ultimate Guide to Battery Basics

We all know the feeling of getting buried in information when purchasing battery for the first time, in an attempt to get the correct one. Well, let’s clear that information a bit so you can get the most out of it.

This guide simply aims at making clear what lead acid batteries are, what they need and of course, how they work. The truth is battery specifications can differ from manufacturer to manufacturer so the generalization here can’t be avoided.

The utilization of commercial lead acid batteries started more than 120 years ago and they haven’t changed much since then. It is 2018 and the chemical composition that is being used to store the energy required is the same as it was back then. We often fail to appreciate just how timeless an invention can be. Take for example the landline telephones - the design has changed slightly over time but when it was the last time you lost signal on your landline phone or accidentally dropped it into the pool? It is just as effective as it was back then, same goes for the lead acid batteries. What we’re trying to say is that both batteries and landline phones function precisely the way it did a century ago.

However, what changed is how energy requirements have increased over time. Before, a 12 V house battery was just enough to use in trailers but today’s standards have drastically increased and 1 battery is just not sufficient. As a consequence, average battery life is becoming shorter and its life cycle is greatly dependent on usage, charging and maintenance. One way to prolong the life cycle is to hook it up to a trickle charger during the months it isn’t in use. Also keep in mind that the average shelf life of a battery is 3-6 months.

We suggest to take your time and read the article below.
  1. Lead Acid Battery Precautions
  2. Battery Construction
  3. Battery Types
  4. Lead Acid Battery Variations
  5. Cold Cranking Amps, Cranking Amps, Amp Hours & Reserved Capacity
  6. Charging SLA Batteries
  7. Connecting Batteries

A. First of all when you’re working with batteries you must remove jewelry and wear protective equipment - gloves, goggles, polyester clothing (cotton can be easily burned). These precautions are very important because these batteries create hydrogen gas when charging which is highly explosive. Second, make sure battery terminals are secured with graded insulation tape. Last but not least important - always keep away from children and away from inflammable materials.

Also, when working on vehicles with batteries make sure to disconnect the ground cable. After all, don’t forget you’re just inches away from corrosive acid, explosive gases and high electrical current.

B. These lead acid batteries are internally consisted of 3 x cells connected in series where each cell produces approximately 2.1V in a 6V battery and 6 x 2.1V cells in a 12V battery. A battery cell consists of two lead plates - positive covered with lead dioxide and negative made of sponge lead, with an insulating material between them. These plates are placed within a plastic case and submersed in an electrolyte consisting of water and sulfuric acid.

C. Essentially, there are 2 types of lead acid batteries - starting (or cranking) and deep cycle (marine and golf cart) batteries. The SLI stands for Starting, Lightning, Ignition which purpose is to either power a starter motor, the lightning/accessories of vehicles and the ignition system. They can be either flooded cells or maintenance-free where flooded ones required distilled water to be added overtime and monitored. The Deep Cycle battery doesn’t provide a high amount of initial current but greater energy delivery for a long period of time. The main difference between SLI & Deep cycle batteries are the thicker plates which help the deep cycle battery service a number of discharge cycles. SLIs have much thinner plates which are inclined towards warping.

D. Lead Acid Battery Variations are the so called - Wet Cell (or flooded), AGM (Absorbed Glass mat) and Gel Cell. All of the versions are filled with electrolyte and look alike with few differences.

Usually you will find that AGM & GEL batteries cost twice as much as a flooded due to the fact they are “maintenance-free”. Don’t be mislead because “maintenance-free” batteries, still require regular cleaning and testing. The greatest benefits of these two types is the minimal chance of explosion or corrosion hence, they are safer. Another benefit of the AGMs is they charge 5x times faster, have the ability to deep cycle and they also stand up well to cold temperature as opposed to their counterpart - flooded battery. The better choice would be considered the AGM battery type if you won’t be using it daily since they hold charger better than other types and will provide you with a with a longer life span. 

In addition, the AGM construction allows the electrolyte to be suspended in close proximity with the plates active material which enhances the discharge and recharge efficiency. There is one specific feature of the AGM batteries that needs to be taken into great consideration - for best life performance it should be recharged before allowing it to reach 50% discharge rate. This will enhance the life cycle up to 300-400 plus cycles.

When it comes down to GEL cell batteries, they’re similar to the AGMs but have a silica additive in the electrolyte of the gel cell that causes it to stiffen. GELs are the most sensitive cell in terms of reactions when over charging.


  1. Cold Cranking Amps or CCA is measurements of the number of amps a battery can deliver at 0°F for 30 seconds and not drop below 7.2Volts.
  2. Cranking Amps (CA) also called MCA (Marine Cranking Amps) or HCA (Hot Cranking Amps) are measured the same way at 32°F.
  3. An Amp Hour (Ampere Hour - AH) is the standard rating taken for 20 hours. That means for a 50AH rated battery we will draw from it 20 hours and it will provide us a total of 100 AH which is 5 amps an hour or 5x20 = 100. However, as the load increases your realistic capacity decreases.
  4. Reserve capacity (RC) is the number of minutes a fully charged battery at 80 will discharge 25 amps until the battery drops below 10.5V.

F. There are two things you need to remember when charging a battery. First, charge the battery back to the level it was before any discharge. Second, to charge a 12-Volt battery you will need a 12V charger and for a 6-Volt battery you will need a 6V charger In other words you have to make sure that the voltage of the charger matches the voltage of the battery. You can also connect 2 x 12 volt batteries in series to get 24 volts, then you use a 24 volt charger, or charge the batteries separately. 

One common question regarding charging SLA batteries is for how long you have to charge them. There is a simple formula you can use to get an estimate of the needed charging time. Multiplying the amperage of the battery by 1.3 and then dividing the total by the amperage of the charger will give you the hours for which you have to charge the battery, assuming it was completely discharged. When connected to the charger, SLA batteries reach 70% of their capacity in the first couple of hours (rapid charge stage). The remaining 30% of the charge is completed at a much lower speed during. 

Battery chargers can come with different connectors or clips. Some of the most popular ones are the 3-pin XLR connector and the Alligator clip. You have most likely seen XLR connectors, as they are very popular in audio and video equipment. They come in male and female versions. Chargers use the male version. Alligator clips are named that way due to their resemblance of the jaws of an alligator. You have most likely seen a large version of these clips at the end of jumper cables.

G. In Series
By connecting the batteries in series you are doubling the voltage and maintaining the same capacity (amp hours). Connect the positive terminal of the first battery to the negative terminal of the second one. From the two free terminals connect the positive to the power lead on your devise, and the negative to the ground connection of your application.


Parallel Connection
By connecting the batteries in parallel you are doubling the capacity (amp hours) and maintaining the same voltage. Connect the positive terminal of the second battery to the positive terminal of the first battery. Do the same with the negative terminals. Connect your application to the positive and negative terminals of the first battery.

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