In The News #1 - 10 Things to Consider when choosing an Extended Battery

EDITOR'S NOTE: This is yet another new series of posts to appear on my blog, this time highlighting my work which has been featured by the professional tech journalism elite. I am very proud to be able to share this here.

First published - Tom's Guide 5/11/2009 (click on link to read)

Introduction to topic:

Notebooks have become increasingly predominant in recent years, and today manage to outsell desktops. It is easy to understand their popularity – notebooks are more portable, pack the same features as a desktop, can be found for under $500 and can run totally unplugged for hours on battery power.

That last point – battery power – is critical of notebooks. For many users, a notebook purchase is dependent on it’s ability to run on battery power, since they need something they can easily take with them to places where they may not be able to plug in to mains power. For others, notebook battery power will be a paramount concern as they may need to get by for extended periods, or they simply don’t want the hassle of dealing with cords and finding an outlet.

My recent experience using a HP dv4t notebook with the 12-cell extended battery gave me a great example of just how much the right battery can make a difference to not only notebook power, but also how you use your notebook. Mobile road warriors in particular will attest to this. If you’ve been thinking of getting an extended battery for your notebook, or have wished many times that your notebook had more juice in it after it went dead, this article will hopefully give you a better idea of the options available to you, and the things you should take into consideration when choosing an extended battery.

BTW: I am not affiliated with HP in any way, I’m just a satisfied user of their product.

1. Do you really need an extended battery?

This will be the first question you need to ask yourself. Your work (or play) will more than likely already define how you spend your day, and throwing a notebook into the mix will certainly change things for you. If you already have a notebook, think about how you use it and where you use it. Do you keep it on your desk plugged in constantly or grab it with the coffee before you bolt out the door every morning? Do you find yourself needing 5-8 hours of battery power every day or do you spent 5-8 hours running around town with it and just need sporadic power? Do you bring along just the notebook or have one of those fancy multiple-compartment cases crammed with accessories?

If you’re shopping for a notebook, you may want to keep these in mind as well as look at size, features and prices. Finding a notebook that has what you want for features and price is one thing, but does it have the battery power you’re going to need? Likewise, does that 8-hour notebook the sales guy’s been pitching to you for the last 15 minutes have the features/performance you need and will it be light enough to carry all day?

The bottom line you need to think about here is how long you will intend to keep your notebook powered on for while you are away from the outlet. If the answer to that is not long, or if the outlet is close by, chances are you probably don’t need an extended battery.

If, however, you know you are going to be nowhere near AC power and/or need juice in your notebook for several hours to an entire day, you will definitely be better off getting an extended battery, or perhaps even two.

2. Run time

How long your battery goes for will depend on three main factors – the battery itself, the hardware your notebook has in it, and your usage habits.

Let’s start with that last one, usage habits, since you probably already know what you’re using your notebook for. Light activities such as web surfing and office apps will give you much longer run time than multimedia tasks such as movie playback and 3D gaming. The differences in run times here can be quite staggering – using my HP dv4 I could get 5 solid hours surfing online, but that battery time got cut down to just over 4 hours for movie watching and only 2 and a half hours while gaming. If you tend to take breaks frequently while you work, you may find your battery goes longer than if you work constantly, since the notebook will be running on idle more often. Of course, you should check your Windows power settings and make sure to have “max battery” enabled to get the most from your battery.

When looking at hardware, higher-end components are not always battery friendly. Take Intel’s mobile Core 2 Duo CPU – their T-series processors are rated at 35W TDP, but their similar speed P-series processors run at just 25W. 10 watts less power means more juice left in your battery. In a similar fashion, integrated graphics will consume less power than dedicated graphics processors because of the relaxed feature set. If your display is an LED backlit screen, it will use less power than the same display that is non-LED. And opting for a more expensive SSD drive that uses 1.5W will also boost your battery times compared to regular mechanical drives that typically run at 2.5W.

It’s best to really do your research and look at the options when configuring a notebook, especially if you intend to get every bit of power out of your notebook’s battery.

This also underlines the fact that quoted battery times are almost never what you end up getting under real conditions. That’s because manufacturers will run a common synthetic benchmark such as MobileMark2007 or the older Ziff Davis BatteryMark in order to establish measurable comparisons between different batteries and different notebooks. That’s good when trying to compare a Sony notebook to a HP, but the catch is manufacturers will perform these benchmarks on a model that has bare minimum hardware, using their biggest battery, under predefined settings, and quote a simulated maximum battery time. So don’t be surprised, however, if that 8-hour battery only gives you 6 to 7-hours in the real world.

Finally, while it is beyond the scope of this article, undervolting can also yield significant increases in battery times. Results have shown up to 25% longer performance, that’s a full hour or more in some cases. And unlike overclocking, undervolting is completely safe – the worst you’ll end up with is a BSOD. Two great side benefits to this trick are that you will also get an incredibly quieter and cooler running notebook.

3. Configuration

When it comes to choosing your battery, you may have 2 or even 3 choices for your particular notebook model. Be prepared though to face three common terms – no. of cells, amp hours and watt hours. Each determine your battery’s capacity, and understanding them will help take the guesswork out when it comes to choosing a battery.

For the HP dv4t, I had the choice of 3 options when configuring my battery:
  • Standard 6-cell battery rated at 2.2 amp hours and 47 watt hours
  • High-capacity 6-cell battery rated at 2.55 amp hours and 55 watt hours
  • 12-cell extended battery rated at 2.2 amp hours and 94 watt hours.
If you look closely, you will notice that even though the 12-cell is only rated at 2.2 amp hours, it still has higher watt hours than the 6-cell rated at 2.55 amp hours. That’s because it has more cells. Basic math here suggests that the number of cells along with the amp hours will determine your watt hours – the higher the number of cells and/or amp hours, the higher your watt hours will be. It’s always best to look at watt hours if you cannot make the determination between cells and amp hours or if the battery description is not clear.

Some notebooks may not offer you a configuration option, leaving you with just the standard battery as a second purchase. Others may have options like a 3-cell, 6-cell and 9-cell. Check your owner’s manual or go online to the manufacturer’s website to see what batteries your particular notebook can support, and look up the specs to determine your battery’s capacity.

Finally, while having more cells does translate into longer battery times, it may not necessarily give you the most efficient solution. When looking at the smaller dv3t notebook, HP offers a 9-cell extended battery rated at 2.55 amp hours and 83 watt hours - very close in performance to the 12-cell, but in a smaller and lighter configuration. It’s something to keep in mind when comparing models.

4. Size and weight

Another thing to consider is size and weight, and I don’t just mean the notebook itself. Your svelte 0.95 inch thin notebook may be light at 3.95 lbs, but if your “uber capacity” battery adds another pound and a half to it’s weight and you need to carry it around in one hand all day, suddenly it isn’t so fun anymore.

Taking my HP dv4t again as an example, the 6-cell and extended capacity 6-cell are both exactly the same size, and both weigh 0.7 lbs each. It’s safe to assume that the notebook weight that is quoted will include the standard battery, but some manufacturers may list it separately. The 12-cell, however, packs on an additional 0.7 lbs and sticks out an inch on the bottom along the rear. What this means is that while the notebook will get excellent battery times, adding a 12-cell will make it heavier and somewhat bigger.

There are several advantages though to this technique, and I’ve seen other notebooks follow this example too. Because the back is now lifted when you place the notebook down, you get a slightly elevated keyboard that is now slanted, creating better typing comfort. It also allows better airflow to the fan on the bottom making the notebook run a notch quieter and cooler. Lastly, I’ve found that extra 1-inch sticking out lets me hold the notebook more securely when I grab it.

I should mention that HP gave me the option to get both a 6-cell and the larger 12-cell battery when configuring my system. That’s good if you want to keep your notebook small and light, but still gives you the flexibility of having a second, bigger battery available when you need the extra power.

One thing you do want to be careful of is not end up getting a notebook/battery combination that is too heavy to carry at the expense of gaining battery time. That 12-cell may indeed increase your productivity while you’re mobile, but if carrying it for an hour or more gets tiring and fatigue begins to set in, it might well do the opposite and actually hamper your productivity. Sometimes a smaller notebook with two batteries works better than a larger notebook with the biggest battery. Many road warriors also fall into the trap of taking a bunch of stuff with them “just in case”, yet could be just as productive carrying only the bare essentials. My golden rule here is simple: always travel as light as you can, and if you need a case, get one!

5. Price

Not surprisingly, we should mention price in the midst of our discussion. This is something you may need to pay attention to if you are shopping on a budget, but also if you already have a notebook and are just looking for a spare battery.

Many manufacturers will give you a discount when you buy an extended battery with the notebook. HP may knock 20% off the price if you buy a spare battery with your notebook purchase. But even if there is no immediate discount, you may still want to make your choice carefully – if that 12-cell sells for $150 and the 6-cell sells for $130, guess which one gives you the best bang for the buck? If you can find coupons that give you a discount, you can make a lot of savings. One other thing you can do is surf around the web and compare prices. Even if your battery is available, you might just find it cheaper from an alternative retailer.

Financing is another option you may want to consider if buying your spare battery with your notebook. Best Buy for example offers 18 months no interest for many of their purchases, letting you enjoy your new mobile freedom and make comfortable monthly payments.

One thing I would certainly not recommend is buying batteries that are used, even if the savings are substantial. It’s difficult to know what condition that battery may be in - you don’t want to end up with a dead “paperweight”, or worse, a battery that was on a recent recall list that could potentially damage your equipment. Always buy batteries that come with the full manufacturer warranty in the event you encounter issues and need a replacement later on.

6. Cell technology

Older notebooks used nickel-metal hydride batteries, or NiMH. Over the years manufacturers began replacing this design with Lithium-Ion (Li-ion) batteries, and now many manufacturers are moving on to Lithium-polymer (Li-poly) batteries, such as the new 17” MacBook Pro from Apple.

Li-ion batteries are superior to NiMH because the more advanced chemistry offers better performance - energy density of Li-ion cells are higher than NiMH, and Li-ion cells exhibit relatively low self-discharge (5%) rates compared to NiMH (30%). Li-ion batteries also don’t suffer from memory effect. In layman’s terms, Li-ion batteries will store more energy than same sized NiMH cells and hold that energy longer. The downfall for Li-ion is if they are shorted or overcharged, they are susceptible to explosion, and thus require integrated circuitry to carefully monitor voltage.

The move to Li-poly batteries was made notable recently by Apple, although the technology has been available for use for over a decade. Li-poly differentiates itself from Li-ion in that it does not require a hard casing and can be shaped to fit as needed. The fact that there is no cell spacing allows energy density to improve by over 20% compared to Li-ion designs. Finally, Li-poly is cheaper to manufacture than Li-ion and more robust to physical damage.

I would be hesitant, however, to buy a notebook with a built-in Li-poly battery compared to a removable Li-poly or Li-ion, simply because you are left with a useless notebook when the battery dies. The ability to swap batteries midway through your workday and maintain your productivity without being near AC power is an important consideration to keep in mind.

Finally, regardless of which chemistry your battery uses, all batteries will degrade over time. A reasonable ballpark figure to work with is approx. 10%-20% per year. You may not notice after a year or two, but a 4 or 5-year-old notebook will more than likely need a battery replacement.

7. Brand name or after-market

You may have noticed traditional battery manufacturers like Duracell offer notebook replacement batteries. While my recommendation would be to stick with a manufacturer-branded battery for best performance and compatibility, after-market batteries often sell for far less, sometimes at half the price of what the notebook manufacturer may charge. These may be worth a look if you are on a tight budget, but also if your manufacturer no longer offers batteries for your particular model. For many older notebooks, after-market batteries may be your only option when looking for a battery replacement. It’s also not unlikely uncommon that an after-market battery will be available with bigger capacity than the original battery that came with your notebook.

Another rather innovative idea has been the use of external slab batteries that connect thru the AC jack – Tom’s did look at such a battery from APC a while ago. I have to admit these products are hard to find today and are all but discontinued.

Would I use such an external slab battery? I’m not so sure. While they do have the advantage of offering universal compatibility with just about any notebook via adapter tips and voltage settings, your notebook won’t know it’s on battery power – it will still think you have the AC adapter plugged in! This opens up a proverbial can of worms, most notable being that you now create a situation where if your main notebook battery is down and you then plug your external battery in and it also runs out, your notebook will just turn off cold and kill whatever you were working on at the time – much the same way your notebook would turn off if you remove your main battery while the notebook is on and then pull out the power cord.

The reason this can happen is because unlike an AC adapter, these slab batteries may only pass power to the notebook, not power the notebook and charge the battery at the same time. With my HP dv4t, the original battery was rated at 2.2 amp hours, but the AC adapter can provide 4.1 amps DC, powering both the notebook and the charging circuit. So even if you match the voltage, your external “dumb” battery may not have the amp capacity to feed power the same way your AC adapter does. If you decide to go with an external battery like this, my best advice is to plug it in first, let it run down and then continue working off your notebook’s own battery, so that if it is time to shut down, your notebook can go into hibernation mode properly.

8. Availability and feasibility

Depending on your notebook, you may run into the situation where a new or replacement battery isn’t available. This is most common on older notebooks, but I could also imagine this same situation occur with a recent but more obscure notebook model from a foreign brand. Notebooks from well-known manufacturers are supported quite well, and even if your battery isn’t listed for sale, a quick part number search online will most likely locate what you need. On the other hand, if you’re looking for a battery match that has the only English letters on the label saying nothing except Made in China, it’s possible your notebook battery may not even be available in the US. This is certainly true for import notebooks sold by gray-market retailers. It’s also something to keep in mind next time you pull out the plastic on that Asian shopping spree.

When determining availability, always start with your notebook’s manufacturer and contact their support. Rather than running around to your local Best Buy or Fry’s, you’ll get better luck if you let your fingers do the walking. A quick Google search will usually get results if you know your notebook’s model number or use the part number shown on the battery. While I do not want to recommend retailers that I haven’t purchased from, online suppliers such as, and have a vast selection on their website that should get you pointed in the right direction.

There may be circumstances though where even if your notebook is old and a new battery is available that it simply wouldn’t be feasible. If you have a 4 or 5-year-old notebook and have looked at the price of a replacement battery, that cost, especially if it is between $100-$170 or higher, might be better invested in the purchase of a new notebook. Another example of where it makes little sense to invest in a new battery is when the run time will have only negligible effect. This is especially true for older, power-hungry notebooks with obsolete hardware. If you’re only getting an hour at best on battery, it may be better to put your money towards a new, more efficient notebook that can give you 3 or 4 hours of battery time rather than spend money on a second battery that will only give you another hour as before.

Finally, if you’re using a large desktop replacement, consider downsizing to an economical 13 inch or smaller. It’s not uncommon for folks these days to have a second computer, and with notebook prices starting below $500, picking one up with a second battery could be just what you need to regain your freedom and productivity.

9. Portability

As I mentioned with regards to size and weight, portability will be a key factor. You want a solution that will let you move freely, but at the same time give you the power you need without necessarily anchoring you to one spot.

If you are traveling light, chances are you’ll probably have just your notebook and a spare battery to switch midway through the day. This works fine for many folks, especially since that extra battery can be stashed inside a jacket pocket. The smaller and lighter your notebook is, the easier it will be for you to get around. Anything more than a notebook and spare battery though, and you probably will be looking for a case to hold everything in, including items like mice and power adapters.

You also want to select carefully the size and type of notebook case. It makes little sense buying a larger, heavier case designed for a 17 inch notebook if your device is a 13 inch, so match the case size as close as you can inch-for-inch with your notebook. If you are concerned about carrying gear, you can pick a case that has multiple compartments or pockets to hold your items. If your choice is for a form-fitting sleeve, make sure you take your notebook along and try it for size with your extended battery attached – batteries that stick out may not fit well for certain sleeves.

Finally, depending on where you are going or how far you are going, you may want to opt for a roller case in lieu of an over-the-shoulder bag. Backpacks, slings and vertical messengers also work great when you want to keep both hands free. Ideally, you want something that doesn’t hinder either your work or your mobility. Whatever type of case you choose or however you take your notebook around with you, the important thing is to choose what works best for you and what is most comfortable for you, while avoiding any fatigue from tiredness.

10. Productivity

In the end it all comes down to how your choices impact your productivity. Your solution should be one that let’s you get around freely without interrupting your journey. It should give you the power you need without having to plug in or cut short your time. And it should allow you to keep focused on what you do rather than take your mind elsewhere.

You may find you need more than two batteries to get through the task, a more powerful notebook, or just need a basic notebook alone without all the extra gear. Perhaps the roller case lets you bring more items along and boost your productivity, or going for that smaller, lighter notebook has made running around all day more effortless.

It is important to regularly monitor your tech lifestyle and make changes as necessary. You may find your notebook has been replaced by one that offers more power for the same battery time, or you can now buy a newer model that’s much lighter. Maybe you’ve discovered a new place open nearby where you can work that offers free wifi, and saves you using your expensive and capped 3G. Or you’ve just been given a new assignment and need to change your workday from being in a cubicle to being on the go.

Whether you measure your productivity in hours spent sitting in front of a screen, miles driven in a car or blocks walked from one office to the next, the right choice in notebook and battery will be one that gets you through it all, with minimal effort and no thought.

Because if you are thinking about battery life, if you are thinking about where do I find power, if you cannot get away from the cord, find yourself lugging around a concrete slab, your mind is constantly being distracted by fatigue and your productivity is being hindered by tiredness – if any one of these has been on your mind, then you will need to take a look back and make changes to your routine.

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