(5-31-08)

February 4th:

     I recently got in to cycling again. To give some background on this, I'll go way back to many years ago, like age 10 or so for me. I learned to ride a bike at some unknown young age and continued to ride regularly from that age up through a little past age 15 or so when I got a learner's permit. After that, I drove cars since of course they will go farther, faster, and take people with you where you're going.

     Years passed and didn't ride bikes anymore. Then, last summer in August I had one of the tires go flat on my Civic overnight in the garage and since that was before I got married, I had no backup car at the ready and my then-girlfriend Melissa was busy at the time. It made me realize that if I had a bike, then at least I could get around my immediate area with some degree of quickness compared to walking. In my own experience, biking is at least 3 to 4 times as quick as walking for a given physical effort.

     Since I had recently seen a bike shop right by my house, I stopped by there and sure enough, they had a 2007 model year closeout on sale that fit what I was looking for. It was affordable while still being a big name brand with a lot of nice features that make it enjoyable to ride. It didn't take long before I'd spent twice as much on accessories for the bike as I had spent on the bike itself, which apparently is quite normal. Even after spending all I did from August through February, I had still spent less on the bike plus all accessories together as I once spent on a differential for my autocrossing Honda. Compared to cars, bikes are incredibly cheap.

     Now among the things I used on my bike, three use batteries. They are the headlight, taillight, and my trusty old Garmin GPSmap 76S, which I first wrote about roughly 5 years ago on this very website. Still working after all these years and some 15,000 miles logged on the GPS' trip odometer, I purchased the bicycle mount so I would have accurate trip stats for my rides. I don't use it for the navigation really, mainly just to log where I went, look at the elevation profile, and have an accurate, replayable way to see how fast I was going in certain segments after the fact, how much time was spent moving versus stopped, and so on. I love data, and the GPS gives me a way to combine my enjoyment of riding with my enjoyment of logging and reviewing data.

     It didn't take long before I was starting to see the need for some additional planning when taking battery-consuming devices. On one of my longer rides, I had my GPS start losing signal and eventually die out while I was still a good 5 miles from home. Rather than let the rest of the ride go un-logged, I pulled into a convenience store to buy some more AA batteries and swap them in to the unit. So right there I could see there was a need to carry additional batteries with me, plus I noticed that the performance of alkaline batteries was hard to predict as it wasn't reported very accurately on the unit's battery meter.

     The obvious solution was to switch to rechargeables and use those from now on and keep some spare batteries with me on rides. Never one to make a purchase without some research and of course being someone that loves data, I ended up buying a Maha Powerex C-9000 battery charger. It's generally overkill for most folks, but since it has a great charging mechanism that lets you set individual charge rates for each cell inserted as well as log battery performance with discharge and recondition cycles, the geek in me just had to have it. I purchased a couple different batteries too to round things out and start collecting data with them all.

     So far the batteries and conditions tested are as follows:

Garmin GPSmap 76S discharge testing
Battery	Test condition	Duration
Energizer 2500	Normal run, 50 degrees overnight	14:03
Powerex 2700	Normal run, 50 degrees overnight	16:59
Powerex 2700	Full backlight, 35 degrees overnight	9:49
Powerex 2700	Battery saver mode, 65 degrees when dead	22:07

     Since I was averaging 10 to 11 hours during warm temperatures from alkaline batteries and getting low battery warnings after just 5 hours of real-world usage in cold temperatures, I have decided not to even do any runtime test on alkaline batteries at this time. It does not seem worth the expense and time spent testing something that my personal usage has shown to be inferior in the kind of device I use.

     For upcoming tests, I plan to do at least two more sets of testing. First, I'd like to see how the runtime is on the Sanyo Eneloop 2000 batteries under real-world conditions. Since they are supposed to have a far lower internal resistance, this is supposed to translate into running for longer before giving a low battery warning/cutoff in digital devices such as the GPS. I plan to compare the rated and observed capacity of 2700/2600 on the Powerex to the 2000 or so of the Eneloop. This implies runtime 74-77% as long on the Eneloop, but if the lower internal resistance really does make a big difference, then the actual runtime should be longer.

     In addition to that test, I'd also like to quantify exactly how much temperature plays a role in the battery runtime. From what I've read online, you should be able to discharge NiMH batteries safely down to around -4 degrees Farenheit. Additionally, the battery charger I'm using doesn't list an operating temperature range unfortunately, but if it works at 40 degrees, then I should be able to get away with doing a discharge test with the batteries and charger in the refrigerator to simulate the cold end of the spectrum that I would be likely to use my 76S in any time soon. This gives me a data point to compare the discharge capacity of a cell at 40F versus the 75F data.

     Additionally, since I recently purchased a variety of new batteries, the bulk of which say they are "ready to use" right out of the box, I decided to run a discharge test on all of them to see exactly how much charge they really do have right out of the packaging. That table is seen below.

Discharge test from newly delivered cells
Battery	Rating	Discharge Rate	Capacity	Percent of rated
Powerex AA #5 - #8	2700 mAh	200mAh	174	6.4%
Eneloop AA #1 - #4	2000 mAh	200mAh	1346	67.3%
Eneloop AA #5 - #8	2000 mAh	200mAh	1362	68.1%
Eneloop AA #9 - #12	2000 mAh	200mAh	1373	68.7%
Eneloop AAA #5 - #8	800 mAh	100mAh	585	73.2%

     From the above table it's pretty clear that the Sanyo Eneloops have a very useful amount of charge right out of the box, especially in stark contrast to the Powerex batteries which are for all intents and purposes, totally flat upon arrival. Further giving evidence to Sanyo's claims of long storage life, they claim batteries are only charged to 75% before shipment and all my AA packs had a manufacture date of August 2006, and the AAA's a date of October 2006. This would mean the AAA's lost just 1.8% of their charge in some 14 months, and even the AA's only about 7% over 16 months.

     Next was to test how the batteries performed after going through the C-9000's break-in charge. With that mode, you input the rated capacity of the battery then the charger gives it a 0.2C charge to about 145% of rated capacity (much chrage is lost as heat), 1 hour rest, 0.1C discharge, followed by the 0.2C charge again. The end result is a fully topped off and "activated" battery, along with the capacity achieved during the discharge cycle. It takes about 36-45 hours per each set of batteries, so it's rather time consuming. Also it is worth pointing out that NiMH batteries are supposed to need around 5-10 cycles to reach their maximum capacity, so if anything, the first time break-in rating will be lower than the maximum capacity achieved after some use.

Break-in charge reported capacity
Battery	Rating	Capacity	Percent of rated
Powerex AA #5 - #8	2700 mAh	2585	95.7%
Eneloop AA #1 - #4	2000 mAh	1946	97.3%
Eneloop AA #5 - #8	2000 mAh	1996	99.8%
Eneloop AA #9 - #12	2000 mAh	1935	96.7%
Eneloop AAA #5 - #8	800 mAh	805	100.6%

     So far it looks like the Eneloops show a bit of an advantage in terms of how quickly they can be used at their maximum capacity as well, showing a couple percent closer to their maximum than the Powerex cells, but that still doesn't change the fact the Powerex cells have an average capacity some 30% higher than the Eneloops, at least immediately after charging. Still, at the projected charge detereoration rates, the Powerex wouldn't fall behind the Eneloop cells until they had been in storage for about 5 weeks, so for things like my GPS and bike lights, the Powerex cells are probably the best bet. For most of the rest of stuff in my household however like optical mice, clocks, and things where I only replace batteries ever 6 months or so, the lower self-discharge rate of the Eneloops wins.

     So what's next? Well once I've used all the batteries enough and evaluated their cold-weather performance, I'll check their capacity again and then maybe even set some aside in storage and see what their real-world self discharge rate appears to be in regular storage. Then I may even test self-discharge when kept in the refrigerator, which is supposed to slow the rate of self-discharge in batteries. All in the name of science and data collection.

February 21st:

     It was time to add some new photos and information about my bike, so I'll start with the photos, seen below.

     

   

     Next pic over is one of my bike mounted up on the rack for my car. While it's true that I can fit my bike in my car if I take the front wheel off, it's a pain to do so, plus it just kind of flops around in the back of the car when it's like that. It can't be safe either if I got in a car wreck and had 40 pounds of aluminum bicycle flying from the back into my head. While I haven't done this yet, I can quickly throw the bike on my car, then drive somewhere with a nice bike trail and do the trail, then throw the bike back on my car and ride home.

     Next up is a picture of my bag with the pannier unfurled on one side and a big beefy sweatshirt in it. If you rolled it up, you could probably fit both a sweatshirt and a pair of jeans on a single side. I've actually carried two gallons of water home from the store - one on each side - with the only trouble being the bike tries to fall over when you're stopped if you don't securely put your feet down. Lighter stuff like clothing shouldn't be a problem though. I also have a closeup shot of the pannier on the second row. This also lets you dress in layers and have somewhere to put clothing as it warms up.

     Lastly is an older picture of my bike at night with the camera flash. What you're looking for here is mainly how well the reflectors work. You'll see the reflector on the bag as well as the front tire throw back a ton of light. This was when I had only swapped my front tire and not the rear, so you can really tell the difference between the reflective strip tire and the factory one with no reflector strip. I now have matching reflective tires front and rear. Also I had both my standard and my insulated water bottles on the bike in that pictures. Between the two, it's 3 pounds of water. The bike bag has a pouch for another 24 ounce bottle on the back too, so my capacity is around a half gallon of fluids in this configuration.

     So that's about it for now. I recently downloaded the SRP Canal System PDF from their website and have some plans maybe to ride with some friends on canals, maybe the Scottsdale Greenbelt, and maybe the South Mountain ride on one of their "Silent Sundays" when cars are banned from the park all day. The South Mountain ride would be the biggest challenge since it's 7.5 miles and I think a 1400 foot climb. The climb is of course the hard part, not so much the mileage, so I'm a little excited to test myself with such a ride. Stay tuned....
Page last updated: February 21, 2008