Turning JC40 into EB40 via IC

[mozzwald]

Has anyone thought of turning the JC40 charger into an EB40 by using an integrated circuit that is designed specifically for charging? This design would be similar to Hippo's design but no modification to the UX50 would be required. I did some research and found several companies that make an IC designed to charge Lithium batteries via USB (or AC Adapter.) One in particular is the LTC4053 (http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1003,C1037,C1078,C1088,P2256). In the Datasheet (pg 16) it has a schematic for USB/Wall adapter charging that uses a 5V AC Adapter (just like the UX50.) The problem with this design would limit you to one external battery, not two as in Hippo's design. I don't really have the technical skills to redesign it for two batteries.

It seems to me that this would work. Any input?

[palo1]

I see no problems with your idea on the surface, the only reason Hippo modified the UX50 I believe was to be able to charge it from a usb source

p

[djboa]

its not only the charging that is the problem ... the ux expects 5v as input ... and the batteries only gives 3.6-4.2 ... so you need to also add voltage regulation, or mod the ux which is what hippo did ...

[mozzwald]

What about using a step-up IC as well? Something like the LT1300 (http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1003,C1042,C1036,P1449) ?

Also, if anyone is interested, I have a virtually unlimited supply of screws that will replace your UX50 star screws with a Philips head screw.

[palo1]

Can't locate a 4 cell battery?

p

[djboa]

sure, but how much energy and money have you spent on this when it is finally done ... and the result is an 1200mah battery working sub-par because of wasted energy in the step up ...

actually, apart from the whole need-to-mod-the-ux part, hippos mod is seriously elegant in it's simplicity - use the existing charging circuit in the ux, and eliminate the need for a step up, along with removing the need for cradles for charging ...

[mozzwald]

It may seem like a waste of time, but I'm doing mostly for fun. MAny of the IC's I've looked at say they can step-up at about 90% efficiency which seems pretty good to me. Also, you could double-up the battery for extra long life.

I was wondering if anyone had more info about how the EB40 works. In Hippo's mod he mentions:

Pin 1 : +5V regulated output at battery power mode, +5.2V when in cradle
Pin 2 : +3.6V~4.2V unregulated battery out for tracking battery status &
switch UX50 to draw power from extended battery until voltage lower than 3.6V.
Pin 3 : trigger (activating EB40 stepup circuit when connected)
Pin 4 : ground

How exactly does pin 3 trigger the EB40 to kick in? I've tested this with a volt meter using 3 AA batteries connected to pin 2 to fool the ux into thinking that an EB40 is connected (battery status window on ux will show that extended battery is present at 100%). Pin 3 has 0V all the time whether the AA's are connected or not. Can anyone explain what exactly is happening?

Thanks

[djboa]

could be a connect to ground trigger ...