The Un-Official Segway Battery FAQ - Last updated 9/10/2004

"Segway batteries are like girlfriends- they're much better when they're new" - Chris Johnson

Common Questions

1.1 How do I charge my battery when my HT first arrives?
1.2 How do I charge my batteries
1.3

How do I keep my batteries in top shape?

1.4 How long does it take to charge?
1.5 What should I do if Iím not going to use my HT for an extended period?
1.6 What do the blinking lights under the charging port mean?
1.7 I plugged in my Segway, but it wonít go into steady charge mode, why?

 

Performance Questions

2.1 Why was my battery better at first than it is now?
2.2 How much range should I be getting?
2.3 How long is my battery going to last?
2.4 When will I know my battery is dying?
2.4.1 How much do new batteries cost?
2.5 What is the deal with heat?
2.6 What is the deal with cold?
2.7 My first bar lasts long than my last bar- why is that?

Tips & Tricks

3.1

Can I "Top-Off" my battery?

3.2

How about charging in my car?

Technical Questions

4.1

What are the battery specifications?

4.2

How much current do the charging batteries draw?

4.3 How much does it cost to per charge?
Geek Questions
5.1 Can I use power from my batteries for external accessories?
5.2 Can I change the cells in my battery myself?
5.3 Can I piggyback external batteries to my HT?

Purpose of this document- Maintainer Comments


*** Required reading: Segway's Battery Care Booklet ***

Common Questions

1.1 - How do I charge my battery when my HT first arrives?

  1.  Charge 12 hours without interruption before first use
  2.  The first 5 charges use up at least one bar but no more than 3 bars.
  3.  For the first 5 charges, charge at least 8 hours without interruption.

Following this initial conditioning procedure is believed to be one of the most important factors to getting best overall performance and lifespan out of your batteries. Itís hard to wait 12 hours on day one, but do it anyway.

1.2 - How do I charge my batteries

The simple answer is- Just keep your Segway plugged in when it is not in use. The Segway's batteries were designed to need minimal attention and if you are completely un-interested in details, you donít need to know much more than this.

But there is more to know if you want to get the absolute best results from your batteries, which you probably do if you are reading this.

If possible, let the your batteries cool down before you charge them. Ideally, after coming in from a long ride you would allow three hours for them to completely cool down, but even as little as 15 minutes of cooling  is better than nothing. If you have the choice of charging  in a cool place or a hot one- choose the cool spot. If you are charging outside on a hot day and  have the choice of charging your machine in direct sunlight or a shady spot- choose the shade.

Real world experience has shown that pulling the rubber mat off the Segway allows everything to cool down more quickly. Upon removing the mat after a long ride you will notice the powerbase itself is warm/hot to the touch. A fan blowing cool air across the powerbase is also effective in cooling everything down more quickly. Some owners have reported good results in cutting the "ears" off the rubber mat to allow easier removal and re-installation.

1.3 - How do I  keep my batteries in top shape?

Re-conditioning your batteries is widely reported to improve performance.

Perhaps every 20 charge cycles, run your HT down to empty.  The important  part of running the batteries down for re-conditioning is to slowly deplete the last remaining charge. Wait until you have a bar or two left and then lean the machine against the wall while in balance mode and leave it there. This slowly depletes the remaining charge evenly. After a period of perhaps hours, when practically all remaining charge has been used up,  the machine will automatically shutdown. 

Once the machine has shut off this first time repeat the process again.  Start the machine, balance it against the wall and let it run until auto shutdown. This time around the machine should run something less than 20 minute before shutting down. Now charge your Segway for 8 to 12 hours, or longer. If possible unplug for a minutes to re-start the fast charge cycle and leave it plugged in for at least a few hours.

 Doing the second round of discharging as described in the procedure above has been debated in the user community. The information was received on good authority, but slightly conflicts with other previously released information. In any case, a single discharge conditioning  procedure will improve your battery performance.

Note that a fully charged Segway sitting  in balance mode against the wall will run for something like 24 hours before completely discharging.

The theory behind the conditioning procedure is that running the batteries down very slowly will allow all the individual battery cells to deplete evenly and completely. This will allow the battery packs to accept a fuller charge on the following charging cycles.

1.4 - How long does it take to charge?

Roughly six hours if the battery is completely drained and you want to fully charge it. In real life you will almost never drain your battery all the way to the bottom, unless you are conditioning it. For a halfway depleted battery, two hours will probably get you past the main charging cycle.

In the real world you may end up plugging in for short periods such as maybe 20 minutes when you stop for a break (waiting for the batteries to cool  is impractical in these cases). Even a short charge such as this can add a nice little boost to your range.

1.5 - What should I do if Iím not going to use my HT for an extended period?

Just leave it plugged in, in a cool spot if possible. Leaving you Segway plugged in for a long period of time is believed to actually help "heal" the batteries to some degree. NiMH batteries will slowly discharge if left just sitting for an extended period of time. It is understood that some permanent damage can result in neglecting NiMH batteries.

In the real world, several users have reported leaving their Segway unplugged for weeks or even months with no noticeable change in performance. But this is not recommended.

It has been reported that after left plugged in for an extended period of time, a Segway may show slightly unexpected battery  results on the following ride. This may manifest itself in slightly reduced range, or quicker than expected discharge.  This phenomenon is reported to go away after a charge/discharge cycle.

1.6 - What do the blinking lights under the charging port mean?

This is the battery-charging indicator. There are actually two sides to the blinking light. If you look very closely you will see that they are labeled F and R for Front and Rear battery.  There are three modes of charging. When you first plug your Segway into the wall it starts in trickle charge mode while the on-board electronics evaluate the battery state. In about a minute it will usually go into full charge mode. After full charge mode is completed it will switch to a balancing mode which evens and balances the charge in all the individual battery cells. Upon completion the Segway returns to trickle charge mode and stays there indefinitely.

  • Slow Blink - Trickle charge
  • Fast Blink -  Cell balance process
  • Steady light - Fast charge

1.7 - I plugged in my Segway, but it wonít go into full charge mode, why?

The batteries are too hot to charge. Segway batteries have built in thermometers that monitor their temperature and prevents them from charging if they are hotter than 120 F. If too hot they will stay in trickle charge mode for what can be up to an hour or more. They need to cool down before they can take a charge.  If possible, cool them down even further than what is needed for them to start charging.

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Battery Performance Questions

2.1 - Why was my battery better at first than it is now?

Real world experience indicates that after you initially condition your new batteries, the following 10-20 rides are going to be the ones that give you exceptional range.  This is in the nature of the NiMH batteries. Nope, youíre not doing anything wrong, this is what everyone seems to be getting.

2.2 - How much range should I be getting?

This is probably one of the most debated topics in the Segway user community. The stock answer is from Segway LLC is 8-12 miles on a full charge. There are so many variables that the range you are getting may or may not be related to the state of your batteries. Based on a sampling of real world experience, getting less than 8 miles on a full charge may not indicate any problem with your machine or batteries.

A slew of variables that come into play regarding range, for example: Weight of the rider, riding style, terrain, wind speed, wind direction, overall speed, frequency of stops and starts, tire pressure, etc. Based on real world experience, it would possible for a rider to see a range of less than 6 miles if several conditions stack up against then. Likewise, many riders report consistently getting better than 10 miles out of a charge.

Real world experience indicates that getting range of less than 8 miles per charge does not specifically indicate a problem with your batteries. You would be well advised to look at the other variables closely before blaming the batteries.

2.3 - How long is my battery going to last?

Current wisdom has it that the NiMH batteries in your Segway will last 500 full charge / discharge cycles. What this means in the real world of partial charges is less than clear. Some riders have reported over a year of daily riding with no loss of battery performance. One owner reports killing a set of batteries with 8 months of use and abuse. It's too early to know what the real-world life expectancy will be, but the jury should be in by the end of 2004 when many owners will be hitting the end of their expected battery life.

With the initial release of Segways coming up on one year as of this writing (2/2004) it will be interesting to watch the real world patterns of wear and tear on a wide scale. Please submit your experiences with Segway battery life and stay tuned for updates.

On the topic of battery cost, here are some points  to consider.

Let's make some basic assumptions.

  • A set of batteries costs $600
  • Their life will be 500 full charges.
  • Each charge will take you 10 miles.

Based on these (assumed best case) variables we can calculate:

  • A set of batteries will carry you 5000 miles
  • The amortized battery cost  will be  12 cents per mile. ($600 / (500x10))

Lets make some different assumptions (perhaps more realistic, perhaps not)

  • A set of batteries costs $600
  • Their useful life will be 450 full charges (perhaps too unreliable, limited or disappointing beyond this point)
  • Each charge will take you 7.5 miles. (In the real world you don't usually run the battery all the way down)

Based on these (assumed real world) variables we can calculate:

  • A set of batteries will carry you 3375 miles
  • The amortized battery cost  will be 18 cents per mile. ($600 / (450x7.5)

The general thinking seems to be that the Segway is expensive, but the cost of running it is minimal. Even if you write off the whole cost of the machine upon purchasing it, by the time you get your second set of batteries you are still going to pay 12-18 cents a mile in amortized battery cost. Perhaps a little more cost than you expected, but still a solid deal.

If this perspective seems overly negative- do a similar analysis against the total real cost of running an automobile, and prepare yourself to be shocked at the expense. It's probably *way* more than you  believe.

2.4 - When will I know my battery is dying?

Your range will seriously decrease. Perhaps as low as 3 or 4 miles on a charge, or less. Current wisdom indicates no amount of charging, conditioning or complaining  will bring them back to their original condition. There is some early indication that random shutdowns may be a possible symptom of a bad battery.

Real world experience has a set of dying batteries becoming half depleted in a trip of roughly two miles. Experience has also shown that one best ways to judge your range is to ride with others Segway owners, with everyone starting on a full charge. Differences in range may become glaringly apparent, even when taking into account riding style, body weight and other factors.

As their batteries age, some owners report getting good range on their first indicator bar, but having the other bars peeling away more quickly than when their batteries were new. This appears to be consistent with the general life cycle of NiMH batteries.

2.4.1 - How much do new batteries cost?

Replacement batteries currently cost roughly $600 a pair. Segway LLC is currently the only outlet for replacement batteries. You *will* need to eventually replace your batteries. For all practical purposes this is the only real consumable component of a Segway, except perhaps the tires, which should last for years.

2.5 - What is the deal with heat?

Heat is a dual edge sword with NiMH batteries. To get the most range/performance your battery temperature should be somewhere between 50-100 degrees with the best performance coming at the higher end of this range. Getting your NiMH batteries hotter than 120 degrees can cause damage.  The other side of this is that charging your batteries when they are hot will reduce their lifespan. Ideally, you would  ride with warm batteries and charge only cool batteries. By cool we mean an ideal temperature  range of 50-70 degrees/

2.6 - What is the deal with cold?

Extreme cold can do  permanent damage to NiMH batteries. Donít leave your HT out in the bitter cold for extended periods. Never let the temperature of the batteries fall to -4 F. Permanent damage can occur to NiMH batteries at this low temperature.

If your batteries cool to below 50 F. you will likely notice some sluggishness in performance.

2.7 - My first bar lasts much longer than my last bar- why is that?

The battery gauge on a Segway is not exactly linear. You will get most of your range on the top three bars and you will see the bottom two bars peel away much more quickly. Don't plan on going for a joy ride and only turning back when you have two and a half bars left, unless you don't mind the risk of getting stranded. Real world experience has been that the top two bars are roughly equal to the bottom three bars as far as the range goes.

For maximum range it is recommended to ride the last bar or two at a slow, steady pace. Crawling along on the last blinking bar at an extremely slow pace will extract the maximum range from the remaining charge. Before the dial flashes red, stopping for a period of 10 or 15 minutes to give the battery a rest will give also give some additional range. It beats pushing.

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Tips & Tricks

3.1 - Can I "Top-Off" my battery?

To some small degree, yes you can "Top-Off" your battery. Unplug your fully charged Segway, let it sit for 15 or so seconds and then plug it back in. Within about a minute it should go into steady charge mode and stay there for something over 15 minutes. Youíve now got a warm, completely topped off battery and should see improved range. At SegFest 2003, a Segway LLC engineer explained that this procedure is OK to do once in a while, but should not be a frequent practice.

It has been reported that is possible to repeat this procedure more than once in a single session by repeating the "unplug, wait 15 seconds, re-plug" cycle after the first top off. This is probably not best way to increase your overall battery life.

3.2 - Can I charge my Segway in the car?

Yes, buy an AC inverter. Plug it into your lighter and you can charge while you motor/boat/fly/etc. It is advisable to use at least a 150 Watt inverter. Note that while you could charge two Segways in your car, you would need at least a 300 Watt inverter and an inverter of this rating should be wired directly into the vehicle's power system, not plugged into the lighter. You would be wise to have your inverter separately fused with spare fuses in the glove box.

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Technical Questions

4.1 - What are the battery specifications?

(cut and pasted from official Segway information)

The Segway HT uses twin NiMH battery packs, designed in partnership with SAFT (a division of Alcatel), running at a nominal 72 volts. These nickel-metal hydride cells deliver the highest power of any currently available chemistry, optimized to maintain the Segway HT's balance under severe conditions. These are not your cell phone batteries! 

Each pack consists of an array of high-capacity cells and a custom-designed circuit board that constantly monitors the temperature and voltage of the pack in multiple locations. This assembly is enclosed in another unique application of GE thermoplastics--the battery box is sealed using a vibration welding technique that makes the outside of the pack a single, continuous structure--sealed from moisture and strong enough to survive the most extreme tests our durability engineers could throw at it.
 

The internal electronics in the battery incorporate "smart" charging--the customer need only plug the Segway HT into the wall and the battery will choose the appropriate charge rate based on temperature, voltage, and level of charge. The batteries will quick charge, then automatically transition into a balance and maintenance charge mode. The Segway HT customer does not need to worry about memory or timing their charges--just plug it in.
Under normal operation, the Segway HT carefully monitors both batteries and automatically adjusts to drain the batteries evenly. In the unlikely event of a battery failure, the system is designed to use the second battery to operate the machine and allow it to continue balancing until it is brought to a safe stop.

Segway Chat user W9GFO adds the following:

FYI, each block of 10 cells is charged independently. Each block also has a temp sensor. The charging circuit is based on the Microchip PIC 16F876.

Segway Chat user W9GFO corrects himself:

According to Mike Gansler of Segway LLC the above is not true. Turns out that the 60 cells in each battery pack are charged in series. You can read the transcript here
 

4.2 - How much current do the charging batteries draw?

The power supply, located at the base of the control shaft, delivers up to 600 mah to each battery pack.

The full charge portion uses about 120 watts

On slow/float charge, it uses pulses of power that vary between about 10W and 20W.

Trickle charging cycles between 8W and 13W every second or so, sometimes faster.

The full charge portion of the cycle uses  half a kilowatt of electricity.

4.3 - How much does it cost to per charge?

A fully drained Segway has been reported to consume about 0.8 kWh during a 12 hours charging cycle

 At $0.16 per kWh (California Rates) that's thirteen cents.

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For the Geeks

5.1 - Can I use power from my batteries for external accessories?

Weíve heard no reports of anyone successfully tapping into the Segway batteries to power external accessories. Current wisdom holds that attempting this may cause serious safety concerns if not outright damage to the machine. Attempt this at your own peril.  (but send us an update if you make it work)

5.2 - Can I change the cells in my battery myself?

Weíve heard no reports of this being done. The external battery shell is ruggedly sealed and Segway LLC explicitly discourages breaking open this battery case. Looking forward, as batteries age and become value-less someone out there is certain to attempt a cell reload.

Segway Chat user W9GFO adds the following:


The case is not too difficult to crack open. The really hard part is liberating the cells from the case without damaging either. They are fixed in place with a liberal amount of "gorilla snot" type glue.

The battery that I tore apart was bad. By bad I mean that one side measured something like 8 volts. After extricating the cells and running them through a series of charge/discharge cycles, they are performing at 93% rated capacity. Not so bad after all.


If one were to replace the cells, just the cells alone would cost around three hundred bucks, per battery. That's assuming they would replace them with 3300's rather than the stock 3000's. Why not upgrade, right? You could save a hundred bucks by using the cheaper 3000's but I think that's not enough savings to justify having to live with a hacked battery.


 

5.3 - Can I piggyback external batteries to my HT?

Weíve heard no reports of anyone piggybacking external batteries to power their HT. Several owners have successfully attached wet cell batteries and inverters, in an external case, to their HT. This arrangement is used  to charge while not near a power outlet.

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Purpose of this document

This document was created to help increase public awareness of the  Segway and the batteries that power them. This document is intended to supplement official Segway LLC technical and support documentation with a specific slant towards "real world" experiences gathered from the Segway community. In every case please accept any information conveyed here as inferior to official Segway LLC documentation.

Maintainer Comments

Thanks to SegwayChat members mrleisure, DHugger, Antoni, Groundloop, W9GFO and others for assistance.

Please e-mail all comments, additions, suggestions, etc to rich at spinfoot dot com.

Maintained by  Rich Harman

http://www.spinfoot.com/SegwayBatteryFAQ.html