Installing a Light-Weight Car Battery

Back when we were track-racing our cars, we used to spent nights dreaming up ways to make it go faster. One way was to lighten the battery. Reduce the overall vehicle weight and your engine had less mass to move. But we didn't learn about the additional benefits of having a light-weight battery until after we stopping racing our vehicles:

The first benefit is obvious, even if minute. Originally we never considered it, but with the huge increase in gas price, every bit counts.

Light-weight battery made for other purposes than starting cars generally cost far less than regular car battery. Most likely due to the less demand in those industries. After all, most of us need a car to get anywhere nowadays.

This third benefit is really the driving force of using these batteries in everyday driving. One of our friends left his car battery in the trunk of his car. It tipped, spilled onto the trunk carpet and a rag. The next day he found the remaining of what we guessed was a rag. It completely decomposed due to the battery acid. The following photo shows corrosion on the battery mount on my own car. I had to throw that mount away, because it could not be dissembled.

With a sealed-lead acid (SLA) battery, you won't have to worry about corrosive acid spilling in your car. You don't have to top off its water level. You can transport them in almost any fashion. Therefore, a SLA battery seems like a good candidate for our purpose.

Picking a Light-Weight Battery

It's not so easy picking a lightweight SLA battery for cars. We must find one that matches a standard car battery in as many aspects as possible. These aspects include voltage, amp-hours, longevity, charging characteristics, etc. Fortunately, those light-weight batteries are out there and we have found several replacements.

Cross-Reference
After 16 years since we started this article, SLA batteries are still prevalent today in this use. But battery technology are advancing rapidly. Could the new LiFePO4 battery technology replace the SLA in your car? Follow our "Installing a Lightweight LiFePO4 Battery in a Car" article to find out.

Hawker Genesis G16EP

When we first started looking for light-weight batteries for our cars, we found the Hawker Genesis G16EP battery. It costed about $50 bucks, but has since then drastically increased in price. It is only 13.8 pounds; About a third of the weight of a regular car battery.

Hawker Genesis G13EP

Later, we found a surplus of Hawker Genesis G13EP battery. We were able to pay $25 for each battery. The G13EP is slightly smaller than the G16EP and weighs only 10.7 pounds. We were thrilled with this battery.

Source for this battery is in the "Related Links" section below. The following photo shows the size difference between the Hawker Genesis G13EP and G16EP.

But the surplus stash of Hawker Genesis G13EP didn't last long. With the Hawker Genesis G13EP and G16EP prices sky-rocketing over the roof, we soon started looking for another source of light-weight batteries.

Universal Battery UB12180

The Universal Battery UB12180 is a good candidate. This battery is about the same size as the Hawker Genesis G16EP. It weighs about the same as well. In fact, if you look at the specs, you'd say it is the same battery. The only difference is the terminal on top of the battery. It has bladed terminals used for wheel chairs and golf carts. At less than $50 a pop (including shipping), it's an excellent car battery replacement. In fact, over the years, price has actually dropped to $40, including shipping. Source for this battery are listed in the "Related Links" section below.

After using this battery for about a year or so in three different cars, we can say that it is practically the same as the Hawker Genesis G16EP. Only minor difference is that the Hawker Genesis battery can be mounted in any orientation, while the Universal Battery UB12180 has to sit up-right. More detail about this constrain in the mounting section below.

Technical Details

The Universal Battery sealed lead acid battery requires a voltage limited charger set to the following voltages: float charge 13.5 - 13.8V, cycle service 14.1 - 14.4V maximum. The design permits rapid recharge at these voltage settings. F.A.A., C.A.B., I.A. T.A., and D.O.T. air transport approved. Ventilate well. Do not install in airtight container. 12V 18Ah.

Converting to Car Battery Post

In this section, We will explain how to convert the battery posts on these light-weight battery to the ones acceptable by your vehicle.

Hawk Genesis Batteries

The Hawker Genesis batteries comes with M6 screw posts on top of the battery. So you simply need to get a pair of battery terminals that can screw onto the M6 posts. The part you will need is the following:

You can source these parts in the "Related Links" below. You only need one set of these terminals for each car, because they can be re-used on each replacement battery.

With the part listed above, all you have to do is screw it into the battery terminals of the Hawker Genesis battery (see photo below) and you are good to go.

Universal Battery UB12180

The UB12180 battery has bladed terminals on top. The vertical battery post on the Universal Battery UB12180 makes it difficult to convert to the SAE battery posts. The first bright idea we had was to use golf cart cables. For this idea to work, you'll need the following parts:

You can source these parts in the "Related Links" below. You only need one set of these parts for each car, because they can be re-used on each replacement battery.

The UB12180 battery comes with screws and nuts. You can use them to fasten the golf cart cables to the battery. Then screw the "Odyssey 3217-0006" posts to the other end of the golf cart cable with two nuts..

The golf cart cables conversion is good if your existing battery cables don't reach. And it allows you to orient the battery the way you like. But after driving with it for a few days, it occurred to me that having moving parts (golf cables wiggling) may not be a good thing in the long term.

The next solutions was to use L-brackets. You'll need the following parts to implement this solution:

You can source the parts from links in the "Related Links" below. You only need one set of these terminals for each car, because they can be re-used on each replacement battery. Following photo shows the L-brackets screwed onto the terminals.

The UB12180 battery comes with screws and nuts. You can use them to fasten the L-brackets to the battery. The photo below shows the L-brackets mounted onto the battery.

With the terminals mounted to the top of the UB12180 universal battery, you can mount it into your car much like any car battery. It's just one third the size of a regular car battery. The following photo shows the battery mounted upright in the car battery compartment.

Mounting in Your Vehicle

Cross-Reference
Before you remove your old battery, if it hasn't died yet, you might want to save your car's computer data and settings. See our "Preserving Your Vehicle's Computer Memory" article.

If you get the Hawker Genesis battery, you can mount them sideways in your vehicle, which lowers the center of gravity.

To lay the Hawker Genesis battery down, you have to screw the battery cables onto the battery post first, because they are too hard to work with when the battery is laying down.

Once the cable has been screwed onto the battery posts, you can lay the battery down as shown in the photo below.

We have to get a special battery bracket (see photo below) that can mount a battery that low. The battery bracket that came with the car has threads that ends too early. Note that we added wing nuts to the top for additional cover.

This battery is mounted into a 2001 Subaru Impreza 2.5 RS, where the engine hood had ventilation holes. We installed a sheet of plexiglass on top, using additional wing nuts, to route water away from the battery post (see photo below).

Laying UB12180 Down is a Bad Idea

Apparently, UB12180 didn't not like to lie down. In one of our cars, we mounted the light-weight battery sideways in order to lower the center of gravity and provide a larger mounting surface. This car has difficult starting, whereas the other cars that mounted the batteries upright started just fine. Swapping UB12180 batteries with other cars showed that the problem didn't move with the battery, it stayed with the car. After mounting the UB12180 up-right the problem went away. We destroyed one battery in the process of troubleshooting this problem; we crank the engine too many times.

Our guess is that the chemical in the battery may lose contact with the battery terminals when it is lying down. It's obvious this battery is not designed for mounting in any orientation, whereas the Hawker Genesis batteries could be mounted sideways.

Experience

It's fun to talk about sourcing and installing these lightweight SLA racing batteries. But how do they really perform in the real world? In our experience with the lightweight SLA battery in our 2001 Subaru Impreza 2.5 RS, we notice no real adverse effect in this daily driver. The car is able to sit for a week and still start. However, the battery lasts only one year in daily service in sunny Southern California. So we put an annual reminder in our Google calendar to remind us to replace the battery. For $40, it's very cost effect compared to today's car battery price averaging $250. We've been using SLA batteries in this car for over 10 years now.

Thoughts
It's not clear why the SLA battery only lasts one year in a daily driver. Is it due to the number of charge cycles? Or is it due to the engine heat? Further experiment is needed to determine how to extract maximum value from these SLA batteries in a vehicle. Possible tests:

Place the SLA battery outside the engine bay. For example, the Prius 12V battery is located in the trunk. But the Prius may not use the 12V battery to start the gasoline engine; it is a hybrid.
Will the battery last longer if it is not a daily driver? Hence, pointing to charge cycle.

We have a 2021 Subaru WRX STi. And it's OEM battery just recently worn out. We've installed a 12V 18Ah SLA battery into this car, given the excellent experience we had previously. The newer model Subaru has too many new electronic technology and drains the battery a lot quicker than the previous generation Subarus. The new battery was drained in 3 days. But we traced the problem to the aftermarket alarm that the dealer put in. After removing the alarm, the car can sit for 4 days and still start.

If you need the car to sit longer than the time frame quoted, you can use the ExpertPower 12v 33Ah SLA battery. It's about twice the size and weighs twice as much (21.6 lbs). But it's still smaller and lighter than a normal lead acid car battery. See "Related Links" below for this battery.