Series Vs. Parallel Connections Explained

 

While researching lithium batteries, you’ve probably seen the terms series and parallel mentioned. We frequently get asked the question, “what’s the difference between series and parallel”, “can Li-ion batteries be connected in series” and similar questions. It can be confusing if you’re new to lithium batteries or batteries in general, but hopefully we can help simplify it.

Let’s start at the beginning…your battery bank. The battery bank is the result of connecting two or more batteries together for a single application (i.e. a sailboat). What does joining more than one battery together accomplish? By connecting the batteries, you either increase the voltage or amp-hour capacity, and sometimes both, ultimately allowing for more power and/or energy.

The first thing you need to know is that there are two primary ways to successfully connect two or more batteries: The first is called a series connection and the second is called a parallel connection.

Series connections involve connecting 2 or more batteries together to increase the voltage of the battery system, but keeps the same amp-hour rating. Keep in mind in series connections each battery needs to have the same voltage and capacity rating, or you can end up damaging the battery. To connect batteries in series, you connect the positive terminal of one battery to the negative of another until the desired voltage is achieved. When charging batteries in series, you need to utilize a charger that matches the system voltage. We recommend you charge each battery individually, with a multi-bank charger, to avoid imbalance between batteries.

In the image below, there are two 12V batteries connected in series which turns this battery bank into a 24V system. You can also see that the bank still has a total capacity rating of 100 Ah.

Parallel connections involve connecting 2 or more batteries together to increase the amp-hour capacity of the battery bank, but your voltage stays the same. To connect batteries in parallel, the positive terminals are connected together via a cable and the negative terminals are connected together with another cable until you reach your desired capacity.

A parallel connection is not meant to allow your batteries to power anything above its standard voltage output, but rather increase the duration for which it could power equipment. It’s important to note that when charging batteries that are connected in parallel, the increased amp-hour capacity may require a longer charge time.

In the example below, we have two 12V batteries, but you see the amp-hours increase to 200 Ah.

Now we get to the question, “Can Li-ion batteries be connected in series or parallel?”

Standard Product Line: Our standard lithium batteries can be wired in either series or parallel based on what you’re trying to accomplish in your specific application. Li-ion’s data sheets indicate the number of batteries that can be connected in series by model. We typically recommend a maximum of 4 batteries in parallel for our standard product, however there may be exceptions that allow for more depending on your application.

It’s important to understand the difference between parallel and series configurations, and the effects they have on your battery bank’s performance. Whether you’re seeking an increase in voltage or amp-hour capacity, knowing these two configurations is vastly important in maximizing your lithium battery’s life and overall performance.

The golf cart market is evolving as more and more people are taking advantage of their versatile performance. For decades, deep-cycle flooded lead-acid batteries have been the most cost effective means to power electric golf cars. With the rise of lithium batteries in many high-power applications, many are now looking into the advantages of LiFePO4 batteries in their golf cart.

While any golf cart will help you get around the course or neighborhood, you need to make sure it has enough power for the job. This is where lithium golf cart batteries come into play. They’re challenging the lead-acid battery market due to their many benefits that make them easier to maintain and more cost-effective in the long run.

Below is our breakdown of the advantages of lithium golf cart batteries over lead-acid counterparts.

Carrying Capacity

Equipping a lithium battery into a golf cart enables the cart to significantly increase its weight-to-performance ratio. Lithium golf cart batteries are half the weight of a traditional lead-acid battery, which shaves off two-thirds of the battery weight a golf cart would normally operate with. The lighter weight means the golf cart can reach higher speeds with less effort and carry more weight without feeling sluggish to the occupants.

 

The weight-to-performance ratio difference lets the lithium-powered cart carry an additional two average-sized adults and their equipment before reaching carrying capacity. Because lithium batteries maintain the same voltage outputs regardless of the battery’s charge, the cart continues to perform after its lead-acid counterpart has fallen behind the pack. In comparison, lead acid and Absorbent Glass Mat (AGM) batteries lose voltage output and performance after 70-75 percent of the rated battery capacity is used, which negatively affects carrying capacity and compounds the issue as the day wears on.

 

No Maintenance

One of the major benefits of lithium batteries is that they require no maintenance whatsoever, whereas lead-acid batteries regularly need to be checked and maintained. This ultimately results in saved man hours and the extra costs of maintenance tools and products. The lack of lead-acid means that chemical spills are avoided and the chance of downtime on your golf car is drastically reduced.

 

Battery Charging Speed

Regardless if you’re using a lead-acid battery or a lithium battery, any electric car or golf cart faces the same flaw: they have to be charged. Charging takes time, and unless you happen to have a second cart at your disposal, that time can put you out of the game for a while. A good golf cart needs to maintain consistent power and speed on any course terrain. Lithium batteries can manage this without a problem, but a lead-acid battery will slow the cart down as its voltage dips. Plus after the charge has dissipated, it takes an average lead-acid battery roughly eight hours to recharge back to full. Whereas, lithium batteries can be recharged up to 80 percent capacity in about an hour, and reach full charge in less than three hours.

 

Plus, partially-charged lead-acid batteries sustain sulfation damage, which results in significantly reduced life. On the other hand, lithium batteries have no adverse reaction to being less than fully charged, so it’s okay to give the golf cart a pit-stop charge during lunch.

Eco-Friendly

Lithium batteries put less strain on the environment. They take significantly less time to fully charge, resulting in using less energy. They do not contain hazardous material, whereas lead-acid batteries, as the name suggests, contain lead which is harmful to the environment.

 

Battery Cycle Life

Lithium batteries last significantly longer than lead-acid batteries because the lithium chemistry increases the number of charge cycles. An average lithium battery can cycle between 2,000 and 5,000 times; whereas, an average lead-acid battery can last roughly 500 to 1,000 cycles. Although lithium batteries have a high upfront cost, compared to frequent lead-acid battery replacements, a lithium battery pays for itself over its lifetime. Not only does the investment in a lithium battery pay for itself over time, but big savings can be made in the way of reduced energy bills, maintenance costs, and possible repairs that would otherwise need to be made to heavy lead-acid golf cars. They also just perform better overall!

 

Are Lithium Golf Cart Batteries Compatible?

Golf carts designed for lead-acid batteries can see a significant performance boost by swapping the lead-acid battery to a lithium battery. However, this second wind can come at an instillation cost. Many lead-acid equipped golf carts need a retro-fit kit to operate with a lithium battery, and if the cart manufacturer doesn’t have a kit, then the cart will need modifications to operate with a lithium battery.

What Maintenance Do Electric Vehicles Need?

 

What maintenance?!

 

One of the main benefits of owning an electric vehicle, besides caring for the environment by not using gasoline and emitting fumes into the atmosphere, is the fact that it requires less of your time and money to make sure it runs smoothly.

The initial cost of purchasing such a vehicle is still quite high, but it pays off in the long run. EVs have fewer moving parts than Internal Combustion Engine vehicles, which means they have a smaller number of components in need of regular checkup and repair.

However, a few things will need your attention from time to time:

1) Monitor the battery

In an electric car, the battery takes up most of the space under the hood. While it may be bulky, heavy and complex, it doesn’t require day-to-day maintenance, but it will in time. As with any electric device, the more time passes, the less charge the battery holds and there’s nothing much you can do about it. You may not even notice it at first because it will take a lot for your EV to break down in the middle of the road, but eventually, you will realize that you can cover less mileage than before with a single battery charge.

Electric car batteries usually have a warranty of 8 years, but there are cases where it took 15 years for the battery to be officially faulty. When that happens, you will have two options. You will either return your car to the dealership, or you will find a battery specialty shop to replace your battery pack where you will faint from the sight of the bill. The cost of replacing perhaps the most important part of your electric vehicle is in the thousands or tens of thousands of dollars, which can still be too much for electric car owners depending on how much you had spent on purchasing the vehicle, to begin with. However, if you have grown accustomed to driving cleanly, you probably won’t go back to ICE cars.

2) Assess the brake wear

The interesting thing about electric vehicles is that they use the regenerative braking system, a process involving harnessing energy from the parts stored in the battery system for later use. Thus, brake wear on your vehicle’s pads and rotors is very limited and they will probably last twice as long as on an ICE vehicle.

Not only that, but it will even charge your car’s battery a bit since it captures kinetic energy that would have been lost in ICE vehicles. It cannot replace a charging session, but it can save you when you find yourself away from a charging station with a dangerously low battery level.

3) Check the tires

It doesn’t really matter the type of vehicle you own, tires have to be checked regularly to avoid having to replace them too often. However, tires on electric vehicles get to see extremes for various reasons. Firstly, EVs are 20-30% heavier than ICE cars because of the massive electric battery. Secondly, they deliver instant torque, which can be hard on the tires. Thus, it is common for the tire tread to wear out more quickly than on ICE cars. Your mechanic should pay attention to the inside edge of the tread since this area of the tire is sure to endure considerable damage.

Moreover, good tire pressure ensures a smooth ride and longer tire lifespan, so don’t be lazy and examine them every once in a while. Make sure the pressure is not below or above the recommended value so as not to ruin the tires. Keep the external temperatures in mind when checking, since their variation causes tire damage as well.

Make sure your wheels are aligned every 6 to 12 months, but especially when you hit a hard pothole or a curb. Proper wheel alignment is bound to make the tires last much longer than when they are not all pointing in the same direction.

Rotate your tires in accordance with the owner’s manual and don’t wait for the seasonal tire change. Still, it is important to follow the pattern of the tire tread. If they have the same pattern, and front and back tires are the same size, then it’s easy, just swap them front to back and back to front. But, if not, then you have to put the “left tire” on the right side wheel and vice versa. This can end up costing you more than simply replacing the tires, but if you want to go that way, keep in mind that the tires rotate in the right direction while spinning.

4) Top-up the fluids

Firstly, EVs with a liquid thermal management system will need you to check and replace the coolant regularly in accordance with the owner’s manual, just like with ICE cars. The reason is that, unlike ICE vehicles, electric cars have massive batteries which mustn’t be over or under heated, thus preventing vehicles from functioning properly.

Secondly, brake fluid requires the same amount of attention. Because of the specific braking system on EVs, there is significantly less degradation. You can get away with not changing it up to two years, depending on the make and model of your electric vehicle.

Thirdly, windshield wiper fluid is to be added more often, with taking into account temperature changes which come with different seasons. Choose between summer and winter blends according to the external temperature in order to avoid fluid freezing in the winter.

5) Replace cabin air filter

With EVs spearheading the green revolution and keeping the air outside of the car as clean as it can get, it is not surprising that the air inside the cabin has to be of high quality as well. Some of the electric vehicles that come from production lines these days have a special type of filters which create positive pressure inside the cabin and are capable of making and keeping the air clean as it is in hospital rooms. Not only are outside smells reduced to a minimum, but also are sub-particles and allergens that could enter the cabin. In order to keep such a level of comfort and health care, you mustn’t neglect to change your cabin air filters at least once a year. You can even do it yourself after 30k or so miles of driving, by spending up to $50 on the new filter and an hour of your time.

6) Update the software

If you look at your electric vehicle as a giant gadget, then you understand the importance of regular updates. They ensure that EVs run longer and more smoothly, schedule and reschedule maintenance appointments, but also take care of various security issues that tend to come up more and more these days. For the vehicles that require you to get them to the dealership for an update, don’t be lazy, and get that taken care of as soon as you hear there is an update for your car’s software. If you have the option of the over-the-air software update, then you have nothing to concern yourself with – the update will be run without you.

7) Take care of the body

As long as you take good care of the chassis of your car, you can minimize both your bill at the mechanic and your worry about having to replace your vehicle for a new one. Also, the better your car looks to you, it’s owner and driver, both inside and out, the greater the pleasure you will have in driving it. From there, it goes that if it looks good and it runs well, you will not have to replace it prematurely if you don’t want to.

On the other hand, issues you don’t need to concern yourself with if you own an electric vehicle are as follows:

1)   Fuel

2)   Muffler

3)   Spark plugs and wires

4)   Motor oil

5)   Automatic transmission fluid

6)   Radiator fluid top-ups and fixes

 

Your EV doesn’t have the mentioned components. Therefore, your life is easier because you don’t have to run to your mechanic worrying they can cause you to be stranded on the side of the road with a broken down car.

 

Overview

Lithium iron phosphate batteries pack a lot of power and value into a small package. The chemistry of these batteries is a big part of their superior performance. But all reputable commercial lithium-ion batteries also include another important element along with the battery cells themselves: a carefully designed electronic battery management system (BMS). A well-designed battery management system protects, and monitors a lithium-ion battery to optimize performance, maximize lifetime, and ensure safe operation over a wide range of conditions.

At RELiON, all our lithium iron phosphate batteries include an internal or external BMS. Let’s have a look at how a RELiON BMS protects and optimizes the operation of a lithium iron phosphate battery.

1. Over and Under Voltage

Lithium iron phosphate cells operate safely over a range of voltages, typically from 2.0V to 4.2V. Some lithium chemistries result in cells that are highly sensitive to overvoltage, but LiFePO4 cells are more tolerant. Still, significant overvoltage for a prolonged period during charging can cause plating of metallic lithium on the battery’s anode which permanently degrades performance. Also, the cathode material may oxidize, become less stable, and produce carbon dioxide which may lead to a buildup of pressure in the cell. All RELiON battery management systems limit each cell and the battery itself to a maximum voltage. The BMS in the LiFePO4 battery, for example, protects each cell in the battery and limits the voltage in the battery to 15.6V.

Undervoltage during battery discharge is also a concern since discharging a LiFePO4 cell below approximately 2.0V may result in a breakdown of the electrode materials. Lithium batteries have a recommended minimum operational voltage. In the Himax 12.8V 100Ah, for example, the minimum recommended voltage is 11V. The BMS acts as a failsafe to disconnect the battery from the circuit if any cell drops below 2.0V.

2. Overcurrent and Short Circuit Protection

Every battery has a maximum specified current for safe operation. If a load is applied to the battery which draws a higher current, it can result in overheating the battery. While it’s important to use the battery in a way to keep the current draw below the maximum specification, the BMS again acts as a backstop against overcurrent conditions and disconnects the battery from operation.

Again, using the RB100 as an example, the maximum continuous discharge current is specified at 100A, the peak discharge current is 200A, and the BMS disconnects the battery from the circuit if the load draws about 280A.

A short circuit of the battery is the most serious form of overcurrent condition. It most commonly happens when the electrodes are accidentally connected with a piece of metal. The BMS must quickly detect a short circuit condition before the sudden and massive current draw overheats the battery and causes catastrophic damage. In the RB100, the battery shuts down within 200-600 microseconds of an external short circuit, then resumes normal operation if the short circuit condition is removed.

3. Over Temperature

Unlike lead-acid or lithium cobalt oxide batteries, lithium iron phosphate batteries operate efficiently and safely at temperatures up to 60oC or more. But at higher operating and storage temperatures, as with all batteries, the electrode materials will begin to degrade. The BMS of a lithium battery uses embedded thermistors to actively monitor the temperature during operation, and it will disconnect the battery from the circuit at a specified temperature. In the example of the RELiON RB100, the BMS disconnects the battery at 80oC (176oF) and reconnects the battery at 50oC (122oF).

4. Cell Imbalance

Lithium-ion batteries have a major difference from lead-acid batteries when it comes to balancing the voltage in each individual cell during charging. Because of small differences in manufacturing or operating conditions, each cell in a battery charges at a slightly different rate. In a lead-acid battery, if one cell charges faster and reaches its full voltage, the typical low end of charge current, along with the excess charge-return, will ensure the other cells get fully charged. In a sense, the cells in a lead-acid battery are self-equalizing during charge.

This is not the case with lithium-ion batteries. When a lithium-ion cell is fully charged, its voltage begins to rise further which may lead to electrode damage. If the charge of the entire battery is stopped when only one cell is fully charged, the remaining cells do not reach full charge and the battery will operate below peak capacity. A well-designed BMS will ensure each cell safely and fully charges before the entire charging process is complete.