Eeepad charging while camping

[worwig]

I camp a few times through the year. Maybe close to a week away from an outlet. I'm using a touring motorcycle to tow a small camper.
So, for a few years now, I have had a small 12 volt lead acid gel battery in the camper. A simple diode between that battery and the taillights on the camper. So, as I drive down the road, the battery gets some charge. Then when camping, I plug a 12 volt USB adapter into that gel battery and charge my phone. I also carry a small solar panel to help replenish the battery during the day. (that is a nearly waste of time BTW) I have two issues.

1) The 12 volt USB adapter isn't going to charge the Asus Eeepad worth a crap. Anyone have any good ideas for portable chargers or such?

2) The whole 12V gel cell sucks. The motorcycle charging system is mediocre at best, so I'm lucky to get 13.5V. Add on the diode drop (a schottky) of maybe 0.3 or so. So I'm lucky to get 13V at the battery, which isn't going to really charge it.

I was just looking at something like this (see link below). I could charge this while driving using a 12 to USB adapter, then use it for my phone. Oddly, there is a comment specifically about it not working on an Asus.

Thoughts.....


Amazon.com: EZOPower Black 2-Port Ultra High-capacity Portable External Rechargable Backup Battey Pack -10000mAh (2A/2A) for IPhone, IPOD, IPad, MP3 Players, Tablet, GPS, Mobile Phone, Android Phone, Cell Phone, Blackberry, HTC, Samsung, Nokia, LG, S

 

[vicw926a4]

The TF101 utilizes a USB3 connection for higher voltage and charge rate, via its unique wall charger, and a conventional USB source will charge very slowly.

Could you use an inverter to provide 120v AC, and your regular ASUS charger plugged into that?

Sent from my DROIDX using Tapatalk

 

[worwig]

The TF101 utilizes a USB3 connection for higher voltage and charge rate, via its unique wall charger, and a conventional USB source will charge very slowly.
Could you use an inverter to provide 120v AC, and your regular ASUS charger plugged into that?

Yes, that is the current plan. But there will be a lot of inefficiencies (and more bulk to carry). I'm not sure I'll get many charges out of the gel battery.

 

[vicw926a4]

Good points about the bulk and inefficiencies, but it should work.

I suppose if you are brave, and have the skill set to do it, you could breakout the AC charger to inject DC from the battery to the rectified side, still utilizing the USB3 setup. Not sure, though, how the ASUS would behave with the lower input voltage directly from the battery, vs. the 15v nominal that it is expecting.

 

[motoprof]

I wonder why 13.5 volts at the battery is not good enough to charge the battery. Generally speaking, voltage should be between 13 and 15 volts while the engine is running.

Someone else may want to comment on this but doesn't the transformer (or most pads for that matter) require 2 amps of charging power instead of the .5 amps that phones use? This was discussed in the accessories section if I recall correctly. Check it out and good luck.

 

[vicw926a4]

I wonder why 13.5 volts at the battery is not good enough to charge the battery. Generally speaking, voltage should be between 13 and 15 volts while the engine is running.

Someone else may want to comment on this but doesn't the transformer (or most pads for that matter) require 2 amps of charging power instead of the .5 amps that phones use? This was discussed in the accessories section if I recall correctly. Check it out and good luck.

The really, really fine print on the charger specifies:

15v at 1.2 amps (the USB3 power contacts)
5v at 2 amps (using the conventional USB2 power contacts to)

I expect 12-13.5 volts would probably be just fine. It's just that I don't think ASUS makes a USB3 charger designed for car use, and they spec. it at 15v dc from the AC wall charger, so we don't have a good example to prove it. Of course if they did make one, you could just buy it, and move on.

I'm sure the 15v is a nominal value, and really not that critical. Hopefully, the AC charger is just feeding a dumb dc voltage, and the charging intelligence is in the TF.

 

[worwig]

I wonder why 13.5 volts at the battery is not good enough to charge the battery. Generally speaking, voltage should be between 13 and 15 volts while the engine is running.

That was a bit of a typo. I'm lucky to get 13V at the camper gel battery. You really need to put in a bit over 14V to charge it.
In the end, even with a charged 12V battery, I need an efficient way to charge the Transformer. I'm going to play with charging it from a good 5 volt USB source. I don't really need a fast charge, just an mediocre overnight charge should work.