AGM vs. Gel Batteries: Which One is better. Agm battery ups

UPS battery Vs Car battery

Both UPS and Car batteries are available in lead-acid type as well as lithium-ion type. But despite the same technology used to produce these batteries, there are still many differences between them due to their application.

Most of the batteries available in the current market are still lead-acid based. Hence we will cover the difference between lead-acid based UPS batteries Vs Car batteries.

There are several types of Lead-acid batteries and some of the common types of batteries are mentioned below.

Classification based on configuration.

  • Flooded (also called Standard or Wet) battery
  • Sealed Type battery [also known as VRLA]
  • AGM Type
  • GEL Type

Classification based on application.

Both UPS and Car batteries are available in Flooded as well Sealed casing, hence to understand the difference between Car and UPS battery all you need to understand is the difference between SLI and Deep Cycle Battery.

SLI Battery (also called Cranking or Engine Battery) :

SLI stands for Staring, Lighting and Ignition. These types of batteries are developed to deliver a high burst of current for a short time [30 sec] while maintaining the battery terminal voltage of at least 12 Volt and then can be quickly recharged.

These batteries have relatively thin plates and a high plate count. This provides a large surface area of plates to react with the electrolyte to produce a higher amount of current quickly.

These batteries are also marked with CCA and CA ratings.

In a cold environment, the ability of the battery to discharge current is low as compared to in a warm environment. CCA (cold cranking ampere) rating of a 12-volt battery, defines the ability of the battery to discharge current at.18°C (-0.4°F) for a time period of 30 sec while maintaining the battery terminal voltage equal to or greater than 7.2 volts.

Whereas CA (cranking ampere) of a 12-volt battery defines the ability of the battery to discharge current at 0°C (32°F) for a time period of 30 sec while maintaining the battery terminal voltage equal to or greater than 7.2 volts.

RA or RCM (Reverse capacity minutes) rating of a 12-volt battery defines the ability of the battery to withstand the continuous discharge of 25 amperes current at 27°C (80°F) before its terminal voltage drops below 10.5 voltage.

With all these advantages SLI batteries come with one disadvantage, which that is these batteries are not designed to repeatedly deep discharge.

SLI batteries are available in both flooded (wet) type configuration and sealed [VRLA] configuration.

Deep Discharge:

Deep cycle batteries are designed for repeatedly deep discharging at a constant discharge rate and repeatedly charging. Deep cycle batteries are designed with a lower number of plates which are thicker as compared to SLI batteries (also called cranking or engine batteries).

Deep cycle batteries are also available in both flooded and sealed configurations. Deep cycle batteries are generally rated in Ah (ampere-hour), whereas they also have CCA, CA and RA ratings. But due to the application of this type of battery, these ratings are not defined.

Car battery Vs UPS Battery

UPS batteries are DEEP CYCLE type battery that provides low but steady current so that they can serve power backup for longer periods. On the other hand, Car batteries are DUAL PURPOSE type batteries, these batteries are designed to provide a balanced combination of starting ( SLI type ) and DEEP CYCLE. The car battery is designed to provide a high starting current but can also need to withstand a longer discharger period than an SLI type battery.

There are also some more noticeable differences between CAR and UPS batteries.

  • Car batteries are not designed for repeated deep discharge and their life will be reduced when subjected to this. Whereas UPS batteries are designed to discharge repeatedly without any effect on their lifetime.
  • The Ah rating of CAR batteries is relatively low as compared to UPS batteries. The Ah rating of car batteries varies from 60Ah to 85Ah. whereas the Ah of UPS batteries varies from 100Ah to 200Ah.
  • Flooded batteries are more prone to fires and explosions than a sealed battery and due to safety reasons flooded type batteries are not recommended for cars and other vehicles. Hence the car batteries are generally sealed types whereas UPS batteries are both flooded and sealed types.
  • Car batteries are also rated in craking ampere ( CA and CCA rating ) whereas UPS batteries are only made in Ah rating and Class rating.
  • UPS batteries can be discharged up to 90% without any damage whereas Car batteries are meant to ideally discharge up to 5%. And that’s the reason you should not leave your car light.

With all the differences mentioned above still, you can still use your UPS battery to charge your CAR battery.

AGM vs. Gel Batteries: Which One is better?

It’s safe to say that battery technology has evolved significantly over the last few decades. The days of wooden encasements and glass cells are long gone, and thanks to new advancements and specialized technologies, batteries are now more efficient, powerful, compact, and environmentally-friendlier than ever.

One battery technology that has managed to stand the test of time is lead-acid. The simplicity and reliability of lead-acid batteries mean that they’re still a popular option amongst consumers looking for a cost-effective and long-lasting energy storage solution.

And despite the emergence of new battery technologies, such as saltwater and lithium batteries—and increasing competition from fuel cells—the global market for lead-acid batteries continues to grow. In fact, industry experts expect the lead-acid market to grow at a CAGR of 3.25% during the next four years and reach a net worth of over 70 billion.

When it comes to lead-acid batteries, two technologies are confused with each other more often than any other—gel and Absorbent Glass Matt (AGM). Even some of the leading battery websites have their information mixed up in terms of what each battery is and what it’s suited for. It’s true that both gel and AGM batteries are categorized as sealed lead-acid batteries, and share a multitude of similarities. However, they have distinctly different construction designs for different uses.

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Over the course of this blog post, we’ll provide a detailed comparison between AGM and gel lead-acid batteries in order to help you decide which one would be best suited for your particular needs.

A Brief Background

Both gel and AGM technologies are based on the lead-acid concept that was discovered back in 1869. In all these years, the underlying technology of lead-acid has virtually remained the same—the electrolyte is acidic, and the plates are made from lead.

When they were first introduced, lead-acid batteries revolutionized the concept of energy storage. These were the very first batteries with recharging capability. While lead was expensive, the basic design of lead-acid batteries was suitable for mass-production. This managed to keep the costs down to a level that was affordable for many applications.

Using thin plates meant that it could be used for applications that required strong, fast current surges (starter motors in cars), while a thicker plate made it ideal for deep cycle applications (refrigerators, power-lighting, etc.).

As we’ve mentioned above, the basic design that was invented over a century and a half ago is still in use today. However, it was not without its faults:

  • If the battery case was broken or cracked, the highly corrosive sulfuric acid could leak out.
  • The original lead-acid batteries couldn’t be installed at an angle, as this would increase the chance of leaking and reduce the amount of acid in contact with plates.
  • Since lead is a sift metal, the plates were susceptible to buckling, which causes the plate to touch and short out the entire unit or shed their active material paste.
  • In high temperatures, the electrolyte would evaporate, which meant that the cells had to be topped off periodically.

Zero-Maintenance Lead-Acid Batteries

The first zero-maintenance sealed lead-acid batteries were introduced on a wide scale in the mid-1900s. These batteries were sealed, which stopped the electrolyte leaking or evaporating. However, these batteries didn’t resolve other issues, such as shorting out due to buckling lead plates, damage caused by leaks from a broken or cracked case, or shortened life and poor performance when installed at an angle.

Absorbent Glass Mat (AGM) Technology

First developed in the 1970s, AGM batteries use glass fibres woven into very fine a mat which is saturated in sulfuric acid and then placed between the plates. This immediately solved a variety of issues in the older design, which is now referred to as flooded lead-acid (FLA). Since these valve-regulated batteries were leak-proof, they could be shipped without any hazardous material restrictions. The plates can be made flat to look like a standard FLA battery in a rectangular case, or they could be wound in a cylindrical cell.

The technology gained traction in the 1980s as an SLA battery for UPS and military vehicles and aircraft to improve reliability and reduce weight. Here are some of the notable advantages of AGM batteries:

  • If the case cracks or breaks, the acid would remain in the mat and won’t leak out.
  • These batteries could be mounted at any angle as the design ensured that the plate would be in full contact with the electrolyte at all times.
  • The mat was essentially an integral component of the batteries’ structure, holding the lead plates in place and preventing any buckling. Even if the plates did buckle, the mat would prevent them from coming into contact with each other.

The internal resistance of AGM batteries is also very low, which means they have a comparatively long service life—even when deeply cycled—and are capable of delivering high currents on demand. over, AGM batteries are zero-maintenance, are considerably lighter than flooded lead-acid batteries, and provide superb electrical reliability. They can also sit longer in storage without needing a charge, as they’re less susceptible to sulfation. Furthermore, the battery has a low self-discharge and can stand up well to low temperatures.

The list of advantages doesn’t end here! AGM batteries also have a superb ability to deep cycle and a charge that is up to 5 times faster than their FLA counterparts. They perform admirably in the depth of discharge (DoD) department as well. While flooded lead-acid typically have a specified DoD of 50%, AGM batteries offer around 80%.

Because of their relatively lightweight and good vibration resistance, AGM batteries are commonly used in automobiles and airplanes. over, their unique design means that the chances of acid spillage in case of a collision or an accident are relatively low. AGM batteries also offer superb cold-weather performance, which makes them suitable for marine, robotics, and motor home applications.

However, just like all other types of batteries, AGM units have their drawbacks as well. Firstly, their performance suffers in warmer temperatures. In fact, many manufacturers recommend stopping the charge if the core of the battery exceeds 49°C (120°F). AGM batteries are also sensitive to overcharging.

Gel Technology

While AGM technology has certainly improved the flexibility in the lead-acid segment, it hasn’t eliminated all the flaws and issues. In applications with jarring or vibrations, the mat could end up rubbing against the plates, which can result in damage.

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While gel battery technology was first conceived in the 1930s, it wasn’t perfected and commercialized until the 1980s. Gel batteries use an electrolyte that is similar to a silicone gel in compositions and appearance. The gel enhances the battery’s structural integrity internally and keeps the lead plates and their active material in position. The gel ‘glues’ on to the plates—essentially combining the plates and the electrolytes into one single piece, so they move in synchronization if the unit is jolted or vibrated.

Gel batteries offer a multitude of advantages that make them suitable for a wide number of applications. Firstly, just like their AGM counterparts, gel batteries don’t require any maintenance. Because of the electrolyte’s viscous, plasma-like nature, the chance of leaks is very small—even if the outer case is cracked. This means that gel batteries can be placed at any angle or position. over, these batteries feature a valve which eliminates excessive pressure.

Gel batteries also have superb shock and vibration-resistance. There are no hydrogen emissions, which means you don’t have to worry about placing them in a ventilated area while they’re being charged. Also, since gel units have superior deep cycling capabilities, they also have a higher discharge feature.

Furthermore, unlike FLA batteries, gel batteries can be easily revived even after they’ve been left discharged for a prolonged period of time.

Now that we’ve discussed the advantages of gel batteries, it’s time to move on to their drawbacks—with the price being the first on the list. Compared to conventional flooded lead-acid batteries—and even AGM units—gel batteries have a considerably heavier price tag. They also have a relatively slow charge rate. over, their charging needs to be halted immediately after it’s complete as it can develop voids with its electrolyte—which can potentially result in loss of charging capacity.

Another thing gel batteries need to be protected from is heat. High temperatures can have a negative impact on the saturation and composition of the electrolyte.

Because of the numerous advantages they offer, gel batteries are suitable for a wide array of applications. The most common ones include solar energy storage, ventilators in health facilities, and perhaps the most common one: electric cars.

Gel or AGM: Which is better?

From a theoretical point of view, the answer is simple: gel is the superior of the two technologies. However, if you look at it from a practical point of view, the price tag of gel batteries is only justified if the battery has to be good at withstanding jarring or vibration.

The use of gel batteries is quite prevalent in the industry of performance vehicles—off-roading bikes, jet skis, ATVs (All Terrain Vehicles), quad bikes, etc.—areas where jarring and heavy vibrations are commonplace. For applications like these, choosing gel batteries over AGM and FLA units is a sensible decision.

However, when it comes to most other applications, such as emergency lighting, regular automobiles, emergency lighting systems, and solar energy storage solutions, AGM batteries are the better choice due to their lower costs.

Why Lead-Acid Battery Technologies are Often Confused with Each Other

As we’ve stated in the paragraphs above, sealed lead-acid batteries (SLAs) come in two different variations—gel and AGM. However, we’ve also used a number of terms to describe both of them, including ‘zero-maintenance’, ‘sealed lead-acid’, and ‘valve-regulated’. This is probably the main reason why consumers often confuse the two technologies. Allow us to explain what these terms mean.

Valve Regulated Lead-Acid Batteries

Although AGM and gel batteries are categorized as ‘sealed lead-acid batteries’, the fact is that they’re not truly sealed. For instance, if the unit overheats because of excessive charging, it could lead to a gas build-up which could result in the battery exploding. To prevent this from happening, both gel and AGM batteries have pressure valves that allow gases to escape once the core of the battery reaches a certain temperature.

Sealed Lead-Acid (SLA)

Technically speaking, even closed FLA batteries can be termed as sealed lead-acid batteries. But with that being said, many consumers reserve the term ‘sealed lead-acid’ for gel or AGM batteries. However, don’t assume that this is universally true. Whenever you purchase a battery, always ensure you understand what the seller or manufacturer means by SLA. You can do this by verifying how the electrolyte (the battery acid) is stored within the battery:

  • As a liquid:this is an FLA battery which cannot be used in applications with excessive jarring or installed at an angle.
  • In a glass mat:this is an AGM battery and isn’t suitable for applications that involve heavy jarring or vibrations.
  • As a silicone gel:This is a gel battery that can virtually be used anywhere.
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Final Word

The better option ultimately depends upon the consumer’s requirements and the intended use. The following things should be considered when deciding which type of battery to purchase:

  • The application the battery
  • The environment in which the battery will be placed
  • How the battery will be recharged
  • If you require bursts of power or a slow discharge rate

Once you answer the following questions, you’ll be able to determine which type of battery would be best for you.

If you’re looking for the best energy storage solution for your solar power generation system, or want to learn more about the properties of lithium and lead-acid batteries, get in touch with the experts at CANBAT. We’re one of Canada’s leading battery manufacturers and suppliers.

How To Charge AGM Battery

AGM battery, also known as VRLA battery, is a sealed valve-regulated lead-acid battery with AGM material as the separator. There are mainly three types. One is used as a starter battery for automotive due to its high current performance. One is focused on deep cycle performance, used in solar renewable energy, UPS backup power, telecom base stations, CCTV, and other BESS(Battery Energy Storage System). The 3rd type is focused on higher current discharge as for motive power.

Deep cycle AGM battery is a type of VRLA battery focused on deep cycle performance. Sealed, maintenance-free, the biggest advantage, excellent deep cycle life, achieve more than 1000 cycles at 50% DOD.

AGM battery is very sensitive to overcharge and over-discharge, improper charging and discharging will lead to the reduction of battery life. So the proper charging process is very important.

The Charger

If you are using a VRLA battery Smart charger, it is certainly the best choice. Can we use a regular charger?

Well, it depends. You have to be very professional and careful, as well as follow the principle of three-stage charging.

The whole process could be very complicated, so in general, it is still recommended to have a dedicated Smart charger.

Three Stages Charging

The THREE STAGES CHARGING are Constant Current charge (bulk charging), Constant Voltage charge (absorption charge), and Supplemental charge (float charging).

The 1st stage is constant current charging, CC for short name. We set the charger voltage to the battery (pack) cycle charge voltage, and the current to the cycle charge current. Please note that too high voltage or too high current will overcharge the battery and damage the battery. The specific voltage and current will be explained in detail in the next 2 parts. During this phase, the battery voltage rises to a constant number.

The 2nd stage is Constant Voltage, where the battery voltage remains at a constant value and the charge current decreases. After the current is reduced to a very small value, stage 3 begins, reducing the voltage to the float voltage.

The 3rd stage is supplemental or trickles charge. The battery current is shallow, and this phase is critical to activate the whole materials inside the battery, which helps to maintain a good health condition of and extend the lifetime.

For more detailed information, please visit this link:

Charge Voltage

The charge voltage includes cycle charge voltage and float charge voltage, fast charge voltage. In general, the float charge voltage is used for daily floating charges, the lowest. Cycle charge voltage is used for recharging after discharged to a certain depth, it is higher. Fast charge is the voltage of Rapid full charge under an emergency condition, the highest, not commonly used.

The nominal voltage of a single AGM battery cell is 2V. In different combinations, the popular voltages are 2V, 6V, 12V. 24V and 48V are also found in battery banks. Specific cycle charge voltage and float voltage refer to the following table. All parameters are generally based on 25°C. Please note that the appropriate voltage is different for flooded or gel batteries.

Temperature Compensation

Temperature compensation is.30mV/°C for cycle charge voltage.20mV/°C for float charge voltage

At low temperatures, the charge voltage may be slightly higher. When the temperature is high, it is extremely important to be careful of overcharging due to high voltage.

Conditions without Print

If the charge voltage is not indicated on the battery, the reasonable cycle charge voltage can be estimated according to the open-circuit voltage (OCV) when the battery is fully charged. Generally, the open-circuit voltage of the 12V battery when fully charged plus 1~1.5V is a reasonable cycle charge voltage.

If you do not know the open-circuit voltage when the battery is fully charged, you can occasionally charge with 2.4V per cell blindly, but it is more difficult to judge when the battery is full. There may be overcharge, causing certain damage to the battery. Note that it’s 2.4V per cell, NOT 2.4V per unit.

If you only need to charge the battery once in the way described in this article, you can skip this step. If you want to use it for a long time, it is recommended to perform this step carefully to determine the open circuit voltage when the battery is 100% fully charged. We call it as OCV (open circuit voltage) at 100% SOC (stage of charge).

There are several ways to know this value:

First, use a DC voltmeter to measure the voltage of the battery that remains more than one hour after fully charged, and the value is directly obtained.

Second, get from the documents. The value will not be printed on the battery, but usually we can get it from the manufacturer’s operating instructions or MSDS.

Third, for a flooded battery, it can also be obtained by testing the density of the electrolyte of the battery when fully charged. The method is OCV=SG0.84, for example, the density of the electrolyte is 1.35 g/mL, and the open circuit voltage of the battery is OCV=1.350.84=2.19V.

It is important to get the voltage when the battery is fully charged. It can be used to verify that if the battery is fully charged, to determine the battery charge and the depth of discharge.

Charge Current

The charge current is related to the rated capacity of the battery. It is generally 0.1C~0.4C, which is 1/10 to 4/10 of the rated capacity.

If it is a 100Ah battery, it is 10A~40A. It can be measured with a DC ammeter, a clamp meter.

Well, some of the most advanced manufacturers on the market today use thin plate technology. They increased the charging current to 1C, which is equal to the rated capacity. High-current charging will greatly shorten the charging time, but these high-end batteries are not popular enough.

Still, 0.1C~0.4CA are considered in most of the applications.

Charge Temperature

The charge temperature of AGM battery is between 0℃ and 40℃, please keep the charging temperature within this range, otherwise, it is harmful to the battery.

Battery Capacity

Battery Capacity can also be found from the print o label.

In general, the print will indicate the rated capacity of the battery, as shown in the photo, the battery is marked as 200Ah, but the UPS battery is sometimes represented by W. For this kind of battery, the simple calculation method is the wattage divided by four.

Charge Connection

There is not much to say, the positive pole of the charger is connected to the positive pole of the battery, the negative pole of the charger is connected to the negative pole of the battery, then the charger and the mains are turned on, then the battery is charging.

It is worth mentioning that for multi-cell battery charging, I recommend parallel charging. Because parallel charging can improve the consistency of the battery, and low-voltage charging is also safer.

It should be noted that when charging in parallel, the cable should adopt the diagonal method to improve the consistency of the current shunt. The so-called diagonal connection method is as follows.

Determine the charging time, or when to stop charging

If it is not blind charging or charging with an excessive voltage, the charging current is reduced as charging progress.

If the battery is charged by the manufacturer’s recommended charge voltage, in general, the charging current can be considered to be fully charged when it is reduced to 0.03C. For example, a 100Ah battery, if using the voltage recommended by the manufacturer, is considered to be substantially fully charged when the charging current is less than 3A.

Alternatively, the time required to charge 1.2 times the required amount of power is the charging time. For example, a 100Ah battery, fully discharged, needs to be filled with 100Ah to be full; 1.2 times 120Ah; if the charging current is 0.15C or 15A, then 120÷15=8 hours can be almost fully charged.

Some cases during charging

The battery is warm.

During any stage of charging, if you feel the battery is warm to your touch, it is normal, no need to worry.

But if you feel it is very hot, even like burning, you have to stop charging immediately or reduce the charging voltage or current, or both.

A sound like bubbling.

Energy is released in the form of heat when the current passes through the electrolyte causing the water particles to break down. H2 is released, O2 is released, and steam is released. There are other gases like hydrogen sulfide that smells like rotten eggs, it is toxic (especially in a small room). That’s why it is important to keep the battery room ventilated.

If the VRLA batteries are making a bubbling sound but are still within safe charging range, they should be able to recombine the evaporated electrolyte internally. If there is a hissing sound, then you know that it’s gone too far and have to lower the voltage or current or both of them. Or stop for a while and then re-try.

Constant Current Stage only allows the cells to reach 80% SOC. The Constant Voltage Phase is to get the cells to 99%, where some slight bubbling is acceptable. Be sure to monitor the battery voltage and temperature and keep it below 35℃ and ensure that all battery cells have plenty of electrolytes.

Charging in Systems

Solar Renewable Industry

Victron Charge Controller

For Solar Charge Controller, it will perform 3 functions:

Regulate the output charge voltage, converting the unstable voltage generated by the solar panel into a stable charging voltage out. It also follows the three-stage principle.

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Monitor the battery voltage. If the battery voltage is too low, cut off the load.

Cut off if there is reverse current at night.

UPS chargers and other energy storage system charging equipment, also have similar functions of regulating voltage, protecting batteries, and cutting off the reverse current.

Important Notes

Watch your charging voltage and charging current

Pay attention to special events, stop charging or lower the voltage or reduce the current in time.


If you are in AGM / VRLA battery business, it is quite important for you to be experienced in the charge discharge, it will help to extend your battery life and gain more trust during the sales.

Another useful kit to extend the life of batteries in series is the balancer, for more details please check the below link:

Hi, I’m Andy. Since the year 2015, I’ve been working in SunOn Battery, a manufacturer in China that makes various batteries for 15 years now. The purpose of this article is to share with you the knowledge related to batteries and energy storage solutions from a Chinese supplier’s perspective.

Rework a UPS With Massive Capacity

Those UPS devices you buy for your computer usually have a gel-cell battery that lasts for a few years. Less if your power goes out a lot. When you replace them, you pay a bundle, even if it’s a standard cell. This short Instructable will demonstrate how to rework an older UPS for more capacity with cheaper battery power.

The picture shows some sample UPSs and an example of the gel cell from one of them. The UPSs come in various capacities and, although you can boost the capacity, the output power is fixed. When you start out, make sure that the UPS you’re going to modify will provide the volt-amps and power that you need. Also note that the volt-amp rating is higher than the power rating. The difference is because AC powered devices have a power factor. Check online for more info about this. Another, similar Instructable, also warns against trying to max out the capacity of your UPS because some use transformers that will run continuously at the rated output. It really depends upon the quality of the UPS, but plan to run at not more than about 75% of rated output capacity.

Another thing to consider is whether or not your scrap UPS has AVR or Automatic Voltage Regulation. You’ll want this if you can find it.

Step 1: The Guts

First, for safety’s sake, unplug the UPS. This pretty much goes without saying. Also realize that the battery inside the UPS may be charged, so do not short circuit any metal parts inside the box.

When you open the UPS box, you’ll usually find either one or two gel cell lead-acid batteries. You’re going to replace it / them.

What you’ll need:1 scrap UPS. but it needs to be a WORKING UPS!4 feet of #10 copper wire (2 feet of red and 2 feet of black if you can) You may need to adjust this length, but keep it as short as you can tolerate.4 spade lugs (two mating pair2 ring lugs for single battery or 4 if you have two in the UPS1 or 2 marine, deep-discharge batteries (85. 120 AH capacity)

Tools:A drill with bit setCrimper for the lugsWire stripperSandpaper or a small file to smooth out holes in plastic

Some notes on the parts: look at the pricing of the batteries and get the capacity that gives you lowest cost per amp-hour. Sometimes the 110-140 AH batteries are only a little more than the 70-90 AH ones. Check warehouse clubs for good pricing. Sometimes you can reclaim the core charge with an old motorcycle or car battery you have lying around. Make sure that what you get is a deep-discharge type battery. Some batteries are labeled as marine, but not deep-discharge.

Make sure that your battery has adapter studs that clamp to the lead posts. Then, get ring lugs from your hardware store, electronics store, or online store that will fit over the threaded studs and also accept #10 wire.

You can either get two pair of mating spade lug connectors, or get one set that are the mating connectors to the ones that come from the UPS. In the picture, these are the black and red wires that connect to the batteries.

Note the blue wire. The batteries are in series in this UPS, so it requires 24 volts (black terminal connected to red terminal). Do not try to power it with one battery if it comes with two! Get two more ring lugs if you need two batteries.

Step 2: Tap Into the UPS

Since the battery / batteries will not fit into the old case, you’ll use the lugs and wire to extend the wires outside the case. In the picture here, I’ve replaced the spade lugs that previously connected to the gel cells with connectors that I know will mate together and accept #10 wire. It doesn’t cost much and it’s easier than trial and error, so spend the extra 25 cents.

Drill two holes in the side of the case. The holes only need to be large enough for the wire to pass through. You don’t want the connectors to be able to sneak outside the case, to be safe. Make sure there are no sharp spurs or edges around the holes that might cut or damage the insulation. Thread the wires from the inside out, with the connection inside the case as shown.

As noted in the parts list, you’ll want to keep the wires short to minimize voltage drop, but long enough that you can place the UPS and batteries comfortably near each other and the device you’re powering (computer, stereo, etc.). Lay everything out, including battery box(es) if desired, and clip the wires to an appropriate length.

Step 3: Connect the Battery / Batteries

Here’s where you connect up the battery or batteries. Remember that the batteries are likely charged and can supply a LOT of current. I think there’s another Instructable that tells how to use them for welding. You do NOT want to do any welding, so make all crimped connections before you connect them to the batteries!

If you have two batteries, make sure to cut a short piece of wire before you add the ring terminals to the other end of the wires you connected into the UPS wires in the previous step. Make sure that this jumper wire is not too short if you are putting the batteries in containers (see end of article).

Note: You might have to ream out the inside of the ring terminals if you could not find terminals with the right inside diameter.

Once you know that the ring terminals will fit, crimp them to the red and black wire ends. If you have two batteries, make the jumper with the other two ring terminals and the small piece of wire you cut off.

Connect the red wire to the positive terminal of one battery. Connect the short jumper between that battery‘s negative terminal and the positive terminal of the other battery. Then connect the black wire to the negative terminal of the second battery. If you do not connect them this way, you will not get any power into the UPS.

Step 4: Use It

That’s pretty much it. Simple, right? The hard part is finding the right parts and connecting everything in the right order without welding anything.

You should now be able to plug in the UPS and go.

Some additional thoughts and enhancements:

You are using lead-acid batteries. In the photo, I’ve shown a plastic layer under the batteries. Even though marine batteries are typically sealed, you do not want to take the chance of a leak. Spend 8. 20 and get a plastic battery box for each battery you use. It will protect the batteries. and your floor.

In the first step I claimed this would improve the capacity, massively. By how much you ask? The largest gel cells I’ve found in UPSs are 20AH. Others are more like 7 AH. Using an 85 AH marine battery to replace a 20 AH gel cell, you should expect to get at least four times the runtime. HOWEVER, do not plan to run the batteries down by more than 50% or you will severely shorten their life. Figure more than a doubling of capacity, but less than 4 times. If you use a 115 AH battery, figure at least 3 times the run time and a much longer battery life.

I have not had any problems with the UPSs recognizing the new batteries or keeping them charged. If you have the UPS monitoring software, use it and try some tests. See how long your new rig will run before hitting the 50% charge level.

Expect the total cost to be about 80 for a single battery setup with 85 AH battery and battery case. Double battery setup with 115 AH batteries should be about 160, max. These are using battery in summer 2009. Battery spiked briefly last year, but have come back down.

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