At CES 2011, we looked at and plugged into as many tablets as we could to see how they charged. Where possible, we tested four different Voltaic batteries ranging from a 5V 500mA output (USB 2.0 standard), up to 5V 2,000mA (which is what the iPad AC charger outputs).
Bottom line is that every tablet we connected to charged off our USB V11 battery outputs 5.5V 650mA. However, if you do the math, it will take a long time to charge the bigger tablets with normal USB output. Which is why most tablets seem to be following Apple with a higher power charging option and why we announced the Spark Tablet Case with correspondingly higher capacity battery and current output.
Samsung Galaxy Tab: The Galaxy has been in the market since late 2010 and is currently the main contender to the iPad. It has a 7” screen and a 4,000mAh battery (15 watt hours). The smaller battery and screen mean faster solar or normal USB charging than the iPad.
samsung tablet charging
The DC in plug is unfortunately a proprietary Samsung plug. The Galaxy is set up to charge from a USB cable which connects to a high power AC charger delivering 5V, 2,000mA (i.e. the same as the iPad AC charger). The Samsung experts told us that it will not charge from a PC USB plug (5V, 500mA), but their site and our tests suggest otherwise . The charge would no doubt be slow, but we were able to at least get the charge indicator to come on from the full range of the batteries we tested.
Blackberry PlayBook: We were keen to get a look at the prototypes on display at CES. We weren’t alone! There was a throng and the RIM staff were not letting them out of their hands so we didn’t get to test anything. The Play Book has a 7” screen. The battery capacity and play time have not yet been announced, but it seems battery woes are what is slowing down the release expected early 2011.
playbook-charging
The good news is that the PlayBook charges from a standard micro USB plug, as well as a proprietary MagSafe like magnetic plug. The unofficial word is that a Blackberry phone charger will charge the Play Book which means the same 5V, 500mA output you get from a USB plug in a PC. This would be a very slow charge for any decent size battery and it was not clear whether more power could be put through the micro USB plug. It seems likely that at a minimum the magnetic cable will allow for faster charging at higher amps (likely still at 5V), and with a bit of luck this will work through the micro USB plug. Unfortunately we were not able to get a look at the AC charger output.
ZTE Tablet: ZTE Corporation is the world’s 5th largest telecommunications company and China’s largest. They sell into 140 countries including the US. Expect to see a lot more of them. Their new 7” tablet was on display at CES. The battery capacity is relatively small at 3,400mA (12.6 watt hours), but ZTE claim it has a 10 hour life. The input plug is micro USB plug. We were able to charge the tablet without any trouble from several batteries with USB output (5-5.5V and 500-1,000mA), so it should also charge from a standard USB plug.
Amazingly as we left the ZTE booth, they handed us an iPad and asked for a hand written comment on the ZTE tablet. Ours was “get a notepad app on your own tablet”.
Sharp Galapagos: Sharp released this “e-reader / tablet” in Japan in 2010 and it is destined for the US later in 2011. It comes with either a 5.5” or a 10.8” screen with 7 to 10 hours of video playback respectively. Battery specs were not available, but are likely to be in the same 15-25 watt hour range seen in the other 10” tablets. The rep claimed that both models charge from a standard 5V USB plug, in a 3-4 hours. We were able to confirm that both models did indicate charging when connected to the Voltaic V11 battery which outputs 5.5V 650mA, but it is highly unlikely that the 3-4 hour estimate is accurate for the 10.8” tablet.
sharp-tablet-charging
Motorola Xoom: Motorola unveiled the Xoom at CES. It has a 10” screen with a purported 10 hour run time on video playback. They are not yet commercially available. What appeared to be production units were being demonstrated, but staff had them on a short leash (literally).
motorola-tablet-charging
On charging, Motorola is the outlier, having chosen not to make the Xoom chargeable from either 500mA or 2,000mA USB plugs. Rather they charge from an AC charger at 12V x 1.5A. There are no DC car chargers available, but that possibility seemed to be open and would be a logical step in the absence of the USB option.
There are two input plugs, a micro USB (which is apparently only for data) and a plug the same size as used on current Nokia cell phones (2.0mm outside and 0.5mm inside). We actually plugged one in to confirm the size. It seems an odd choice for such a high powered plug. Hopefully Nokia phones have sufficient protection for over current and over voltage, since some are sure to get plugged into the Motorola 12V x 1.5A AC charger. It is a shame to see Motorola take this approach, but the good news is they seem to have limited company so far.
Panasonic Viera: Panasonic had 3 prototypes tablets on display at CES, a 10”, 7” and 4” version. They are expected to be released commercially in 2011.
panasonic-tablet-charging
No announcement has been made about how they will charge, or whether they will charge from USB. The prototypes did not necessarily reflect what will be seen in the final version. The power input plugs on the 10” and 7” versions were larger barrel shaped plugs, like those more typically found on laptops. The 4” version used a micro USB plug, suggesting it is more likely to charge from USB.
Toshiba Tablet: Toshiba had a couple of prototype 10” tablets in glass cases and staff standing by to tell everyone that the specs are not yet determined. So they were not able to give any battery or run time specifications, or to indicate whether they will charge from USB. They were able to say that it is expected to be released in Spring 2011 and that it will come with a removable battery, so users can carry a spare.
toshiba-tablet-charging
The samples on display were running / charging from what appeared to be AC chargers for Toshiba PCs. This is a bad sign, suggesting they may go with laptop chargers which are typically 16-19V and harder to match up with solar panels.
LG: LG announced they will be releasing a tablet, but there was nothing on display.
Sony: Sony have not even gone as far as to announce a tablet, but are saying that “it is part of our strategy”.
ASUS: We didn’t make it to their booth. If anyone has details, let us know.
HP Topaz: This was not on display at CES, it is expected to be announced February 9. Early word is that it has a mini USB plug, which is a good sign, however it leaked out today that it will include inductive charging i.e. wireless charging using an electromagnetic field rather than a wired plug. This is not great news for solar charging. Induction charging is less efficient than a direct electrical connection so energy will be wasted. The dock will contain the electronics for the induction charging, and our bet is it will have an AC plug on the other end, not a USB plug. So we hope HP have at least had the foresight to allow charging through that mini USB plug from a 5V DC source.
Apple iPad: C’mon, Apple don’t display at CES! That said there were more iPads displayed in various booths than any other tablet and no tablet roundup would be complete without them. The iPad has a 10” screen, larger than most, and a 25 watt hour battery, also larger than most and necessary to deliver 10 hours of video playback.
Apple is setting the standard when it comes to tablet charging. Fortunately others are once again following.
There is a lot of talk about iPads not charging from a standard USB (5V, 500mA), Apple claims they do. It may have been that early models needed to be in sleep mode to charge from USB, but this seems no longer to be the case (presumably a software change). We have of course tested all of our batteries on the iPad and the results have been great. Everything from a AA battery delivering 5V, 500mA to a 40 watt hour battery with a 5V, 2,000mA output gets the charge indicator going on the iPad. Our early attempts at direct solar charging were not as successful, but we will revisit that soon.
For now, Apple has effectively led the market to adopt USB based charging for tablets, setting the voltage at 5V and up to 2,000mA. That is good news for solar charging, since there are already compatible solar panels that charge batteries delivering 5V via USB plugs. These systems can now be adapted to charge most tablets. However please note, what has always been true for cell phones is going to be even more obvious for tablets, if you skimp on the solar power you will not get a good result. A full charge of an iPad is going to require at least 8 watts of solar power and a long sunny day. Don’t bother plugging into a 1 watt solar cell phone charger unless you are prepared to wait more than a week.
Overall it was encouraging to see so many tablets coming onto the market with USB charge cables and standard mini and micro USB plugs. While standard USB plugs will charge these large batteries very slowly, Apple’s approach of making a 5V 2,000mA USB / AC plug seems to be getting traction.

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