UniEnergy Technologies Battery » What Does A Battery Tender Do? (Ultimate Guide)

What Does A Battery Tender Do? (Ultimate Guide)

We have all been there: you leave your bike or car for long periods and come back to it. It never occurs to you that the battery no longer has any charge, so you put the key in the ignition and get…nothing. You try over and again with the same result.

The most probable reason is a dead battery. So, your first reaction would be to jump-start the battery, right? But what if there is no other battery or car to use at that moment? Do you have another option? This is where Battery Tender comes into the picture.

This article is a detailed explanation of what a Battery Tender does and how to use it. You will better understand why you should have one handy for times when your vehicle battery or motorcycle battery fails you.

What Is a Battery Tender?

You may have seen this term and wondered what it means. You are not alone, as more people veer towards more innovative technologies to make their lives easier. To understand what a Battery Tender does, you must know what it is. 

A Battery Tender is basically a “charger with brains”. In other words, it works better than your typical battery charger. It uses microprocessor technology to keep your battery charging and powered when not in use. 

That way, the battery does not run down or discharge before you can use it again. It also ensures the battery does not overcharge, preventing damage from excessive charging.

What Does a Battery Tender Do?

A Battery Tender charges any large battery. It works the same way as a trickle charger, providing voltage in small amounts to the battery over a long period. But unlike your everyday charger, it uses a technology that does not permit it to overcharge the battery or damage it.

You can use it for a normal battery charging job, as it works like any other charger. However, its best use is for prolonged and sophisticated charging duties because of its electronic circuitry controlled by a microprocessor.

Benefits of Using a Battery Tender

Benefits of Using a Battery Tender
Image Credit: vwt2_1970

A Battery Tender provides many benefits that an ordinary battery charger cannot provide. 

1. Prolonged Battery Life

One benefit is that it can prolong the life of your car battery. Apart from age and wear, one of the primary reasons a battery gets damaged is overcharging. 

Since a Battery Tender prevents overcharging using its microprocessor technology, your car battery tends to last longer if you use it in place of the typical charger. While you may still have to replace it within the usual five years, it will not be out of necessity but maintenance because it will be in good condition.

2. Efficiency

Battery Tenders are typically efficient, knowing when to slow charging and whether or not to charge a battery. If a car battery is defective, a Battery Tender does not charge it. The device does not spend time trying to power a battery that may end up damaging other car parts.

3. No Sparks

One of the banes of charging car batteries is the possibility of sparks flying from the connection points or terminals. It uses spark-free technology to achieve this, which is not the same as other chargers.

4. Ease of Use

A Battery Tender uses easy-to-understand signs and indicators to help you know what is happening without needing a manual. The simple red and green indicators tell you when the battery is full if there is a charging problem, or when you need to disconnect the charger.

Indicators and What They Mean

Each flashing or steady light on a Battery Tender means something. Understanding them will help you use the device better. It is pretty simple to grasp.

  • Green Flashing Light: When you see a green flashing light on the Battery Tender, it means the battery is almost fully charged. This also means the red light is on and steady at the same time. You can use the battery at this point, although it is best to leave it until full charge.
  • Green Steady Light: When the green light stops flashing and becomes steady on the Battery Tender, it means the battery has reached full charge. You can opt to leave the battery connected for as long as you want or disconnect it at this point.
  • Red Flashing Light: A red flashing light on the Battery Tender indicates that AC power is available on the charger and the microprocessor works well. Connect the battery to charge and monitor the light. If it continues blinking after connecting the charger, it indicates that you did not connect the ring terminals or output clips properly. It may also mean that the voltage from the battery is lower than recommended.
  • Red Steady Light: When the red light is steady, it indicates that you have properly connected the battery and it is charging well. It is this red light you see when the green light starts flashing to indicate an almost full battery.

How Do You Use a Battery Tender?

How Do You Use a Battery Tender
Image Credit: flat.thunder

We would like to point out that there are several Battery Tender models. The product is from the US company Deltran and has been around for some time. There are other Battery Tender manufacturers. But over the years, these manufacturers have produced other similar products that can get confusing.

They sell batteries and chargers for specific purposes, such as batteries for marine and industrial uses. They also produce and sell wires, cables, and harnesses, but the problem is that these products all carry the name Battery Tender. Therefore, simply asking for Battery Tender without specifying what you need may get you the wrong product.

In other words, ensure you specify that you need a Battery Tender charger to get this product. Most cars use 12V batteries, so the charger should match it. To use the Battery Tender charger for your vehicle battery, take the following steps:

Step One

First things first: take the necessary precautions. Ensure you take every safety step required for installing or charging a large battery. Keep water and soap close to you to wash off battery acid if there is an accidental spill. 

Also, have an assistant standing by to help you in case of an emergency, and wear protective gear for your hands and eyes. In addition, ensure you work in a properly ventilated area.

Step Two

Position the battery and charger the way you want to use them. But ensure there is some distance between the charger and battery, as much space as the charger cables will allow. 

Ensure the charger is off and not connected to a power source and position the DC and AC cords from the car’s moving parts. It helps to keep the cables from getting tangled and damaged in these parts.

Step Three

Check the battery’s polarity, that is, the battery terminals. This is the point where you find out which of the battery’s posts connects to the chassis and which is grounded. And when you do, connect the alligator clips on the charger according to the battery connections. 

  • If your car is positively grounded, ensure you connect the charger’s negative clip to the battery’s negative ungrounded post. The negative clip is typically black, so you can differentiate it from the positive one. After that, connect the positive clip to the engine block or vehicle chassis. 
  • But if your vehicle is negatively grounded, the positive charger clip goes to the battery’s positive ungrounded post. Next, connect the negative clip to the engine block some distance from the battery or the chassis. The positive clip is red, differentiating it from the black negative clip.

The best step is to connect this clip to a strong metal part of the vehicle’s frame or engine block to control the charge. Ensure you keep the clip away from the carburetor, parts made with sheet metal, and fuel lines.

Step Four

Now, you can plug the charger into an electric outlet to begin charging the battery. Note that the 12-volt battery must produce at least 9 volts if it is not currently supplying voltage or charging. If it produces any voltage output less than 9, you need a new battery. 

Also, the battery voltage must be at least 3 volts for the Battery Tender to work. In other words, any battery with less than a 3-volt output cannot charge with a Battery Tender. This is why it is an excellent charger choice for every typical 12-volt car battery.

Can You Charge a Dead Car Battery with a Battery Tender?

Can You Charge a Dead Car Battery with a Battery Tender
Image Credit: batterytender

It is usually difficult to charge a dead car battery with a typical battery charger. But it may work with a Battery Tender because it produces a trickle charge for the battery over a long period, which is what dead lead-acid batteries need. 

Lithium-ion batteries typically need faster chargers. But there is no danger of battery damage because of excessive charging.


Using a Battery Tender is one of the best ways to charge any battery, as long as it meets the recommended voltage output. If you have extra batteries, you can use them for long-term charge storage, so you do not run out of batteries to use.

However, you must carefully read and follow the usage instructions because every Battery Tender product has specific directives to follow. But once you get a hang of it, you can use your battery longer than others because of its preservation.

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