Wednesday, January 13, 2010

Quick and dirty review of Sanyo KBC-E1S Mobile Booster (as a portable iPhone charger)

(See end of post for a 6 months later update, on my final thoughts 6 months on.)

I bought an iPhone in Dec 2009, and while I've heard and thus somewhat expected of it's high battery drain, I was quite unprepared for having the phone run out of juice before the day is over.

During Christmas shopping, I came across a Sanyo "mobile booster" pack, which I bought for myself as a small X'mas gift. In essence, the pack consisted of
- 2 x Sanyo AA eneloop batteries (HR-3UTG)
- 1 x plastic housing (for charging/discharging the batteries)
- 1 x USB cable (Type-A to mini-B)
- instruction quicksheet

Since this is only intended to be a "quick-and-dirty" first look, I will only reflect on the it's effectiveness in providing emergency power for my iPhone.

Out-of-the-box, the supplied 2 x Sanyo AA eneloop batteries took around 1 hr 20 mins to charge my iPhone 3GS 32Gb from 16% to 42%, giving me a measly 26% of juice. Repeat plug-unplug managed to coax another 3% out of the batteries.

Later, immediately after a proper full-charge (using a GP ReCyko GPAR05BS battery charger), the same 2 eneloops managed to raise the iPhone battery level by 50% from 46% - 96%.

This simple test covers the two corner cases of having charged battery having been left in my bag for some time, providing approximately 25% charge to the iPhone 3GS 32GB, and freshly charged batteries used immediately, giving approximate 50% charge.

Given the results, the unit has has proved it's usefulness to me, and I am more than content to carry the small package in my bag wherever I go. The following factors/features are key to me:
- affordability: the street price is SGD30++
- (although normal NiMh rechargable batteries are cheaper and nowadays come in high capacities of > 2500 mAh compared to the 1900 mAh rated eneloops) the eneloops provide far better shelf life, which is important for batteries that I may not use soon after charging
- the small plastic housing can also also serve as a battery charger using USB from any PC or standalone USB power or car adapters (altho I strongly believe in using better chargers)
- in a crunch, I can buy off-the-shelf AA or eneloop/ReCyko, or even non-rechargeable batteries from anywhere


Is it for anyone? No. My key criteria is to make use of easily available AA batteries. Those after maximum portable charging capacity should opt for high capacity lithium-ion based rechargeable battery packs available from Sanyo, GP, etc or a variety of OEM manufacturers.

Final Thoughts 6 months later (added 8 Aug 2010)

It's 6 months later, and I thought it'll be useful to add how well the unit has been holding up.

On a proper full-charge (using the same GP ReCyko GPAR05BS battery charger), the same 2x eneloops managed to charge the iPhone by 40% from 17% - 57%. Further repeated plug-unplug coaxed another 3% out of the batteries.

The simplistic conclusion is that the batteries has degraded around 20% from "new", over 6 months of sporadic usage of once or twice per month.

Pros: I'm reasonably happy with the performance of the unit. For the primary purposes I bought this for, which is to give an emergency charge where a power socket may not be available, the device has met my requirements. (If you anticipate running out of juice near a power outlet, then the default Apple charger is definitely lighter and smaller, and more efficient.)

The unit gives me a 25-40% battery life boost, which is enough for about half a day's activity on the move (more if I do the usual optimizations like turning off wifi, dimming the unit and turning off 3G). If I need more, I can always bring 2 more AA batteries, or buy them off the shelf, which is a big plus over non-AA type chargers.

The batteries have proven to be reasonably durable, giving me a better than expected level of usefulness after 6 months of use (compared to "normal" NiMh rechargeable batteries).

Lastly, since the unit can both charge and discharge, paired with the iPhone and iPhone charger, I've survived short overseas vacations without having to bring a laptop or a separate battery charger, which is in itself quite amazing.

Cons: Of course performance can and will always improve with new technology. These is my wish list for the next product refresh.

Size: The unit seems to have quite abit of wasted space, which as a portable device, seems to be rather bad design. The whole unit seems to be rather empty and "airy", and gives me the impression that the physical siz e can be shrunk by at least 33%.

Heat: During discharge, the batteries and the unit both heat up significantly. I suspect this may be why the unit design is so "airy" and open.

Power Efficiency: The iPhone battery is 1200 mAH, and yet, 2 units of the 1900 rated eneloop's can only charge 40-50%. The only explanation is the energy loss in converting from the 1.2V of each AA to the 5V-out of the USB specifications.

<-- This paragraph was rewritten. My appreciation to Anonymous for pointing out that I oversimplified and neglected to mention the how the different output voltages of the different batteries affected the comparison. -->

Power Efficiency: The iPhone battery is unofficially rated at 1219 mAh 3.7 V, and yet, 2 units of fully charged 2000 mAh 1.2V rated eneloop's can only charge 40-50%, while in theory they can deliver 106.4% charge. Two factors apply here:
- energy loss in converting twice from the 1.2V of each AA to the USB 5V followed by USB 5V charging the 3.7V iPhone battery
- the usage of the iPhone during the time the charging takes place, which is in itself a significant 1+ hour

Configuration: I've seen 4-AA battery dischargers, but I would love for Samsung (or anyone) to release a 4-AA unit that both charges and discharges. This would indirectly address the power efficiency and heat issues since presumably 4 * 1.2V means minimal step-up conversion to USB 5V, and in solving the heat problem, reduce the amount of wasted space necessary for air cooling.

Charging time: The time needed to charge 2 batteries are quite long, taking 6-10 hours (ie effectively overnight). This may be related to the USB specifications only allowing for 500mA max output current.


Anonymous said...

Hi. Wish to share something i know about this "power" and Current thingy...hope you don't mind.

Quote :"Power Efficiency: The iPhone battery is 1200 mAH, and yet, 2 units of the 1900 rated eneloop's can only charge 40-50%. The only explanation is the energy loss in converting from the 1.2V of each AA to the 5V-out of the USB specifications."

Power = Voltage X Current

so, Iphone battery, which is 3.7v, 1200mAh, Power is = 3.7v * 1.2Ah = 4.44wh

while for the eneloop, at 2 X 1.25v, 1900mAh, Power = 4.75wh

taking 4.75/4.44 = 107%

That is, assuming there is no loss in transfering power from the AA battery to iphone, the iphone can be charge to 107%.

But since there are no "no-loss" machine in this world, and as you mention the AA battery heat up quite a bit, Thus there are a lot losses, which explain why there can be only 25%~40% percent of charges in the iphone.

However, I really appreciate your this blog entry as in helping me to getting mobile booster for my Gadgets. Is that i just want to share something i know (hopefully its correct, LOL!!!). Thanks and Have a nice day :-D

Ho Hock Jim said...

Thank you, Anonymous.

You're right, I did oversimplify on the battery comparisons, and I've edited the paragraph hopefully doing the topic justice (albeit using slightly different battery ratings).

I'm glad my short review helped. :)

Anonymous said...

For anyone looking for a charger that will power all your USB devices, my company, PC Treasures, makes one called the ChargeIt. It comes with four AA batteries that have 2700 mAh of power, and they're rechargeable so you don't have to keep buying batteries. It's only 29.95 on our site:

Anonymous said...

Thanks for the report, I've been looking for the performance on this item on the net but with no luck until I reach your blog. Thanks for good work and review.

By the way, have you tried out the other mobile booster products from Sanyo? Are they any better performance than this AA one?

Ho Hock Jim said...

Sanyo has since released KBC-E3A and KBC-E2B. Both are much higher performing (ie. greater capacity), but neither are AA, which formed the basis of my original requirements.

At the same time, Sanyo has also refreshed the eneloop batteries, which means you may get marginally better results than I did (assuming you buy the units with the new eneloop batteries), but still nowhere near the non-AA units above.

Matthew S said...

You say "the small plastic housing can also also serve as a battery charger ... (altho I strongly believe in using better chargers)"

Actually, the KBC-E1S is a good charger in its own right. It's microprocessor-controlled with -dv charge termination and a thermistor to monitor cell temperature. It also charges the cells independently (separate monitoring for each cell rather than just putting them in series as cheap chargers do). If you disassemble it, you will see a circuit board covering whole area of the device almost entirely covered with components. So, this is not a cheapy charger, and will take care of your batteries! Sanyo do not skimp on their chargers.

Raghu Ram S S said...

I have brought this product in Jan-2012 and already it has failed. It does not discharge at all. Only the charging function works now. A bad experience for the SANYO TAG this carries!!!