Reviews > Electronic Devices > Solar Chargers > Exponent Flex 5 System with Batt Pak > Stephanie Martin > Field Report

Field Report: ICP Solar Exponent Flex 5 and Batt Pak

Details in this Field Report are intended to be taken in addition to findings as listed in my Initial Report.

Contents
- Product Use and Performance
    - Exponent Flex 5
    - Batt Pak
- Continued Test Strategy
- Summary

Product Use and Performance
Before I get too far into this report, I should state that I have primarily used the ICP Solar Exponent Flex 5 in conjunction with the iSun BattPak.  On occasion, I have used each item separately from the other, but the majority of the time, they have been used together.

Coleman Exponent Flex 5:
So far, I've used the Exponent Flex 5 both in and out of my vehicle and it has also accompanied me on various hiking and backpacking trips.  At this time, it shows no wear, and appears as good as new.  All stitching has held up nicely, and I haven't observed any fading of the fabric covering of the panels.  I have not had an opportunity to evaluate the weatherproofness of the Flex 5 as I haven't been blessed with any appreciable precipitation during the test period.

In order to evaluate the Exponent Flex 5, I purchased a small multi-meter to measure voltage and amperage output of the panels in various conditions.  I set the panels out in my backyard on various days to check power output under different weather conditions while also attempting to evaluate the effect of different angles of incidence of sunlight. My discoveries?  It seemed to me that the biggest factor on obtaining good power from the solar panels was the quality of sunlight.  The panels performed poorly and output considerably less than their peak power rating of five Watts on days that the sky was overcast or even if the sun was periodically obscured by thick clouds.  In addition, early morning and late evening sunlight, even on cloudless days, resulted in low power output.  On days when the sky was clear, I noticed minor differences in power output (on the order of approximately a half a Watt) when the panels were placed flat on the ground or hung vertically facing the sun.  As I had expected, when I turned the panels away from the sun, I experienced a sharp drop in power output.

During the course of testing, I also came to realize just how little power five Watts actually is.  I don't personally own many devices that can run on five watts or less.  One item I did have was my portable CD player.  Unfortunately, my CD player must require close to the full five Watts to run as every time the solar panels were partially obscured (from clouds or tree cover or a change in direction), the CD player would stop playing - this would invariably seem to happen while I was in the midst of a particularly engaging tune.  So far, I've not found any other devices in my personal possession with a car lighter adapter-style power input that can be run off the Flex 5 solar panels - I was unsuccessful in using the Flex 5 to activate my hazard/safety light and air compressor.  So far, the best use, in my opinion, for the Flex 5 panels has been to aid in recharging my NiMH batteries while on trips.  More on that later.

In terms of affixing the Flex 5 panels to packs, I've been less than successful in managing this process to my satisfaction.  The panels seem awkward to connect to many of my packs - the Flex 5 unit is rather long when unfolded for use and, in some cases, dangles off the pack and flaps around in an annoying manner.  In addition, there isn't a clean way of connecting the Flex 5 to some of my packs as the bulk majority of them are lightweight or ultralight in design and finding high attachment points on my packs where I can attach the Flex 5 can sometimes be a challenge.  So far, the best method seems to be to run a short length of cord through the top grommets of the solar panel unit and loop the cord around the pack's lid connection points/webbing.  The bottom of the panel can sometimes be attached to the pack depending on the pack's design.  This sits the first bank of panels squarely on top of the pack lid, with the others following the contour of the pack going down - unfortunately, this does also mean that access to the lid pocket of my packs is obscured, but it does allow for good light exposure for at least half of the panels on the Flex 5 unit.  Unfortunately, for the panels to continue to supply the maximum amount of power, I have to have constant sunlight on them during peak sun hours - sometimes this is difficult due to terrain; but more often, it is difficult because my travel just doesn't allow for it.  For some reason, I often find myself hiking into the sun, rather than away from it - this means the solar panels, which are strapped to my pack, are often not facing the sun directly.
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iSun Batt Pak:
During the field test period, I've used the Batt Pak to recharge various AA NiMH batteries.  I've used it in conjunction with the Exponent Flex 5 solar panels, as well as with the AC wall adapter and also with the DC adapter plugged into my car.  I'm happy to report that regardless of power source, the Batt Pak remained cool to the touch during all charging.  I really like the fact that the unit doesn't throw off a lot of heat.  I've not yet had the opportunity to use the Batt Pak as a power source, but I have confirmed with the manufacturer to use only rechargeable batteries with the Batt Pak in this application.

The Batt Pak, like the Flex 5, is also holding up well and generally not showing signs of wear other than a few scuff marks on the translucent lid.  It has proven easy, if a bit slow, to use.  It was difficult to see the status of the LEDs on the Batt Pak during bright light, so checking the Batt Pak charge condition sometimes required me to actually get up close to it to shade the LEDs for a quick check.  In an attempt to verify charge times, I drained 8 AA NiMH batteries and inserted them into the Batt Pak for charging.  The batteries were either 1600 mAh or 1850 mAh depending on the brand of battery.  Initially, I set up the Batt Pak with the Flex 5 for charging.  I found that even after three consecutive mostly sunny or fully sunny days, the batteries were still not yet charged.  At this time, I brought the Batt Pak inside and hooked it up to the wall for the remaining time.  It took an additional 1.5 hours to finish charging the batteries.  After experiencing such a discrepancy, I re-evaluated the materials that came with the Batt Pak to discover that the approximate charge times listed were assuming use with 1000 mAh batteries.  Incidentally, it lists the average charge time to be around nine hours (regardless of the number of batteries) when plugged into either a DC source or while attached to a solar source.  Using a wall AC adapter doesn't speed the charge time appreciably and only cuts an hour off the average charge time to reduce it to eight hours.  I have to admit, I personally prefer a faster charge, and in the time it takes for me to charge 10 batteries in this charger, I could have charged them much faster using my 4-battery capacity rapid charger.

On my recent trip to Death Valley, I used the Batt Pak to recharge my AA's for my camera and GPS by combining DC and solar power.  While the car was running or while we were nearby, we left the Batt Pak attached to the car to charge; while we left for a hike, I rigged the Flex 5 in the south facing window of the truck to charge the batteries in our absence.  Even with one of the Flex 5 panel sections fully shaded, the combination of the two power sources provided fully charged batteries over the course of a day. 

Combining the solar power provided by the Flex 5 along with another power source is, for me, the best application of this pair of products.  I say this because I don't carry enough electronic devices with me to justify the weight of the setup.  The minimum operating weight of the Flex 5 and Batt Pak is 19.6 ounces (555.7 grams).  Each of my AA batteries weighs 0.9 ounces (26.6 grams) and each of my AAA batteries weighs 0.4 ounces (11.3 grams).  With this in mind, in order to justify the weight of the Batt Pak, I need to be on a trip long enough that I would require the use of more than twenty-one AA batteries - otherwise it's simply lighter for me to have extra batteries on hand.
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Continued Test Strategy
Most of the remainer of my testing will occur in the desert southwest of the United States in the states of Arizona and Utah.  I plan on continuing to evaluate the Exponent Flex 5's durability, resistance to UV damage and hopefully its weatherproofness (Arizona is not exactly known for precipitation).  In addition, I'll continue to evaluate its ease of use - seeing if I can come up with other ways to strap the Flex 5 to various objects as well as re-evaluating the effect of angle of "exposure" to the sun on performance.

Specific to the iSun Batt Pak, I'll be continue to evaluate its battery charging performance on NiMH batteries in conjunction with the Exponent Flex 5 as well as when plugged into a car lighter socket in a vehicle as well as via the AC adapter.  I hope to be able to get a better estimate of charging times required when using these various methods of power.  The ability to power other small devices via the Batt Pak continues to intrigue me, so I still plan to attempt use it to run my portable CD player and other devices that I evaluate to have an appropriate power requirement.
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Summary: Whoo Hoo's and Boo Hoo's  
I really am glad to have had the opportunity to test out a portable (and environmentally clean!) power source.  While it does not make sense to me to carry it along on backpacking and hiking trips, it has proven to be quite useful to have in my car to charge batteries while I'm off exploring.  I'm glad to see the progress that portable green power has made, and look forward to seeing the technology continue to improve.  With that said, here are my "Whoo Hoo's" (likes) and my "Boo Hoo's" (some room for improvement).

- Woo Hoo: I like the idea of having a clean and renewable power source at my fingertips
- Woo Hoo: I like the fact that the Batt Pak remains cool during charging
- General Comment: Five Watts really isn't that much power, however ICP does make other portable solar panels that have higher power output available.
- General Comment: It takes quite a long time to charge batteries using the Batt Pak regardless of quantity of batteries or power source used.
- Undecided: Attaching the Flex 5 to packs can sometimes be difficult and an annoyance due to its length and the lack of places on my packs to hold it in place.
- Boo Hoo: the weight to power ratio of the combined Flex 5 and Batt Pak system just doesn't make sense for short backpacking trips - it's the equivalent of carrying 21 AA batteries!
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My thanks to BackpackGearTest.org and ICP Solar Technologies for this opportunity to test out a renewable energy technology.

Reviews > Electronic Devices > Solar Chargers > Exponent Flex 5 System with Batt Pak > Stephanie Martin > Field Report