Charge Rating

Knowing a bit about batteries can help fine-tune how you handle them.

Andy Bolig - June 09, 2014 01:45 PM


The D1200 charger can charge and/or maintain a battery using the maintainer cord or the heavier charging clips. Both store in a convenient compartment in the rear of the charger.


The D400 also has maintenance and charge clip cords. The D400’s major selling points are its smaller size and lower cost.


A nice touch on the D1200 is this charging clip light, which allows you to see battery markings for the proper terminals.


For the D1200’s little extra coin, you get a higher charge rate (using charge clips only) and this handy USB charging port as well as a maintenance cord hook-up.


Many new charger/maintainers use push-button selectors and digital, multi-use gauges. The Optima units use the newest microprocessor technology as well as back-lit gauges for ease of use.

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If there’s ever been an unsung hero of the automotive world, it most likely would be the battery. The only time that most of us think about them is when they give us trouble, but we hardly bat an eye their way for their years of loyal servitude.

Consider the environment that a car battery calls home. In close proximity to heat generators like your car’s radiator, exhaust manifolds, water hoses and other components can make for a tough existence for a car battery. Then, when you consider our tendency to drive collector/show cars sporadically, the torture test is two-fold. Long-dormant sessions can be equally devastating to a battery’s life cycle as the heat and environment in which it resides.


Working Within the System

Many folks simply think of a battery as a powerhouse, a storage bin to hold the magic current that makes your car start. But when your car doesn’t crank, or the starter fails to turn over due to low current, there must be a problem. Not really. At the risk of over-simplifying things, there are several components that are designed to keep your car’s battery in top shape under normal conditions.

Of course, there’s the battery. It’s designed to have a large enough capacity to withstand the deep current draw that occurs when you crank the engine to get it started, but most of the time, it lives in a much less drastic state of charge/discharge as accessories such as fans, radios, lights and whatnot strive to pull power from the black box under the hood. A quick look at the different sizes of wires that feed the various components will tell you quickly which ones carry more current.

Replacing the energy removed from the battery is the job of the alternator (or generator for earlier cars). It uses mechanical energy from the engine to produce electrical energy that will be stored in the battery until needed.

Batteries have a desired range of operation and do not like to be pushed beyond those parameters. Draining a battery below 80 percent of its rated capacity and conversely over-charging a battery can cause severe damage. Making sure that the battery does not receive too much energy, but does get enough to keep the battery “fully charged” under normal operating conditions is the task given to the voltage regulator. As the name states, it regulates the amount of current sent to the battery. Some cars use a separate regulator, mounted somewhere in the engine compartment while many newer cars have the regulator embedded within the alternator.

The most important factor of a properly working charging system is the term “normal operating conditions”. Keep in mind that engineers design cars to be driven, with only a slight consideration to the fringe parameters of what is considered “normal”. What that means is that engineers use things like math and physics to determine when an alternator should be charging and how much charge it should send back to the battery. They plan on a certain amount of engine idling and stop and go traffic (maybe more so today than 30, 40 or 50 years ago) but mostly, they plan on folks driving their cars with engines operating at higher rpm.

Extended parade-driving or idling can actually begin to drain a battery since the alternator might not be producing enough energy to replace what is being used. This becomes more apparent as electric fans, A/C and other components come on the scene. A quick answer might be to simply pump up the charge potential of the alternator to compensate for this, but you have to remember, we’re talking engineers here. They also have to consider the additional heat that will be produced within the alternator and at the lower rpm, would the alternator’s cooling fan/ventilation be sufficient to ensure the unit’s longevity?

Likewise, increasing the efficiency of an alternator’s low-rpm performance will likely influence its higher-rpm output as well, where those same engineers intended for it to spend most of its life cycle. Pushing the additional energy into the battery over a long term can also have negative repercussions related to excessive internal heat and wear.


An Answer to the Abnormal

That helps explain why our daily drivers are reliable, but what changes when we start talking about collector cars or less-frequently driven cars? Keep in mind that batteries simply store energy; they do not make it. They also lose some of their charge if they are not maintained, which is sufficiently done during the aforementioned “normal operating conditions”. If they do not see normal operation, a lead acid battery will lose some of its charge gradually and over time.

This is why a car may not start if it has been stored for a long time, possibly over the winter. When you also take into account many of today’s cars also have various other forms of parasitic loss to the battery, like radio station pre-set memory, digital clocks and such, it’s easy to see how a battery can lose a charge if not used regularly or maintained.


Building Up the Battery

Treating a dead battery, or even a battery with a low charge, can be handled in several different ways, depending on the reason for the re-charge. Handling a stored vehicle’s normal parasitic power loss or a battery’s normal loss of charge should not be handled in the same manner as if the lights were left on your daily driver and you need to get to work.

The different ways of handling each situation have kept engineers working late into the night, trying to devise ways to best handle each instance without doing damage to the battery under your hood. Today’s battery chargers and maintainers have much more sophisticated circuitry than earlier models with only a plug and possibly one or two dials or switches. Batteries actually respond positively to differing rates of charging, depending on the situation. A brief understanding of how lead-acid batteries work might help shed some light on this.

A 12-volt battery is actually made of six individual “cells”, wired in such a way that each cell adds to the voltage supplied by the previous cell(s). Each fully charged cell produces approximately 2.1-volts, meaning two cells produce 4.2-volts, three produce 6.3-volts and all the way up to the six cells in our 12-volt batteries actually producing 12.6-volts when fully charged. Each cell consists of two lead plates (one positive and one negative), which are submerged in electrolyte consisting of water and sulfuric acid.

As a fully charged battery is connected to a load, a chemical reaction between the electrolyte and the lead plates produces energy. This chemical reaction also begins to coat both positive and negative plates with a substance called lead sulfate, also known as sulfation. This build-up increases as the battery continues to discharge until the plates are almost fully covered in sulfate. At this point, the battery is considered “fully discharged”.

As the battery is re-charged, the lead sulfate reverts back into lead and sulfuric acid. If a battery is excessively discharged and not sufficiently re-charged, the lead sulfate can form hard crystals, which will not revert back with only a fixed-rate charge. A higher rate of charge is required to adequately re-convert the crystals. By increasing the charge rate, the amount of time necessary to fully recharge the battery is shortened as well. As with batteries themselves, there’s always a negative to go with the positive.

If a charger is left at this high charge rate, the battery will over-charge, resulting in excessive heat, over-gassing and loss of electrolyte. This is why many chargers today utilize circuitry that senses a battery’s charge level and tailors the amount of charge sent to the battery.


Charge or Maintain

So, what’s the difference between a charger and a maintainer? The line between the two does cross a little bit, and there are a few differences as well. The answer as to which one is best suited for you depends on what you will be using it for primarily.

If you’ve got a car that is used infrequently and you simply want to keep it at the ready for when the sky is clear and the roads are dry, a maintainer would most likely be your best bet. If you’re wanting to bring a battery back from the dead in a relatively short time, the increased charging rates provided by a charger would do much better for you. Usually, their increased grunt in charging rate is witnessed by their larger size as well.

Just because various chargers and maintainers have specific benefits to their respective styles, doesn’t mean that they don’t have similarities. To keep this comparison apples-to-apples, we looked at two relatively new chargers available from Optima. Many enthusiasts know about their brightly-topped batteries and a few of those also know they offer chargers, but fewer still know why they offer two different types of chargers and why each exists.

Before we get into the differences, let’s take a look at what you will get from both the Optima Digital 1200 charger and the Optima Digital 400 maintainer. Both can be set to quickly adjust for differing types of batteries, both are micro-processor controlled and provide protections from reverse-polarity hook up, both have pre-charge battery condition and spark-free hook-up safeguards. Both chargers can bring back deeply discharged 12-volt batteries (down to 1.25-volts left in the battery) and both will work to maintain the battery in your car or motorcycle or ATV, but the differences dictate which one suits you best.

When it comes to making a decision here, size does matter. If you want something small (in both price and stature) to simply keep a battery in tip-top shape, the Digital 400 maintainer might be to your liking. It works well for maintaining a battery and can charge a discharged battery, but will take some time to do so.

The Digital 1200 charger offers a much higher output (12 amps) than the smaller Digital 400’s four, so long as you use the supplied charging clips on the D1200 and not the auxiliary charging port on the side, which is limited to only four amps as well. The Digital 1200 charger also has other features not found on Optima’s maintainer, like the light on the charging clip so you can see battery markings and make correct hook-up, even in low light. If you need to call in the D1200 for long-term battery maintenance, there is also a supplied six-foot maintaining cord so you don’t need to fidget with charging clips each time. There is also a USB charging port available on the D1200, just in case your cell phone needs a little pick-me-up.

Of course, all these additional bonuses can equally be found in the additional cost of the D1200, but if your battery is dead and your boss is staring at your empty chair at work, the additional cost for shorter charge times is money in the bank. For more information about Optima’s batteries, chargers and which one fits your garage best, check out their website.


For Your Information 

OPTIMA, (888) 867-8462