Power Options for Charging Smartphones in the Field

July 2011

Cody WinnEast Africa Coffee Initiative

SUMMARY

TNS East Africa CI is evaluating the feasibility of deploying smartphones with applications for use in the field. The phones and applications can have significant benefits, and 98% of Rwanda is covered by mobile internet, but the biggest concern is the lack of power for recharging the phones.

Very few wetmills are connected to the electricity grid. Wetmill employees generally walk some distance to the nearest mobile charging station in a village, drop their phone, and pick it up at the end of the day. This is not a feasible option if they are expected to use the smartphone throughout the day.

This presentation outlines a number options for charging smartphones in the field. There is no clear product that will work successfully – field studies should be done before moving forward with this project.

Generators

Details

Some wetmills were provided with generators for powering equipment

Concerns

Generators frequently broke down and had to be returned, and are not reliable

Generator charge fluctuates, and thus is not recommended for electronics because it can fry the battery

More expensive generators with an AVR (automatic voltage regulator) or with an additional battery for charge storage would be required

Recommendation

Not a viable option, too unreliable for electronics

Solar panel + Powertank

Details

Create a kit from a solar panel plus a power storage battery (by itself, a small solar panel generates 125-500 mA of power, which is not enough to switch a smartphone into charging mode)

Sample battery: Swisscharger Powertank L

Includes multiple outputs and adaptors to charge light, radio, phone, etc

Cost

$40 (Powertank) + solar panel cost

Concerns

Would need to assemble a kit from different parts – may be support requirements

Any solar solution will require strong sunlight, so no charging can be done at night or during rains, a significant concern as the harvest is during the rainy season.

Field studies and online reviews show disappointing results using solar to charge smartphones. The power generated from solar is often not enough to meet the daily battery consumption of a smartphone

Recommendation

Probably better to use a product that combines both (see next slides). Field testing should be done with any candidate solar products to evaluate performance.

d.light s250

Details

Already used at wetmills for night lights

Solar panel + battery embedded within a light

Includes phone charger connection

Cost

$60

Concerns

Not strong enough to keep a smartphone charged if needed for regular use – solar power stored per day is less than an Android phone needs to recharge

Concerns about life of battery

Other considerations

d.light is continuously doing R&D and will come out with stronger, cheaper products over time

Recommendation

Not a viable option now, but company’s products should be monitored for 2012 season

Fenix ReadySet

Details

Can take charge input from solar panel, stationary bicycle, or grid

Low-maintenance, optimizes battery efficiency through software, will last 3 years

Can charge multiple phones, lights, radio, etc

Grameen Uganda has deployed these into the field for 4 months and is happy with results so far

Cost

$150 retail, possibly cheaper for large purchase or NGO use

Concerns

Very expensive - it is not a charge generator in itself, solar panel is also required

Other considerations

A bicycle can generate significantly more power than solar (100x per same unit cost). Wetmills have expressed opposition to biking for power but it could be an efficient option.

Recommendation

Discuss minimum cost of product + solar panel with Fenix. Re-think whether wetmills could hire day laborers to pedal a bike and charge a battery.

Solio Classic Hybrid, PowerCurve

Details

Similar products: solar panel + internal Li-ion battery

Claim to fully charge in one day of sunlight but online reviews say this doesn’t often happen

Various outputs for charging phone, light, radio, etc but only can charge one device at a time

Cost

$40-$90

Concerns

Online reviews of use of these products to charge smartphones are not positive– eg: “When fully charged from the wall the battery pack would only take my phone from 10% up to about 40%. Since it takes so long to charge in the sun, this rate of charge is unsustainable”Will only charge a smartphone up to about 75% full but some reviews say 60% is more common

Recommendation

Unlikely to be sufficient, but can try to get demo products to field test the performance

Solio Classic

PowerCurve

Great Lakes Energy – reseller of 2 solar products

Details

Solar re-seller based in Kigali, recommend 2 products:

Greenlight Planet Sun King Pro

Trony Sundial

Both are similar to d.light – solar panel + battery embedded within a light - but newer and better

Battery should last multiple years

Cost

$70 each

Concerns

Initial field test of a Trony Sundial charging a Huawei Ideos phone was not positive

After charging the battery for 1.5 days in fairly strong sunlight, the battery only intermittently charged the phone – the phone wouldn’t recognize the charger 100% of the time. Even while successfully charging, the phone battery only increased 7% in one hour.

As with all solar products, performance in rainy season is a significant concern

Other considerations

Could replace the d.light for nightlight use as well

Great Lakes also sells a larger but similar Philips product for $140

Recommendation

Continue talking to Great Lakes and do more field testing on their products