12 hours external battery pack

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hardwarej
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12 hours external battery pack

Post by hardwarej »

i would like to build a battery for the webdt366 that lasts 12 hours. i found a 4 cell li-ion battery which is rated 15 ah,7.4V and i think it will do the job
now i would like to connect this battery to the secondary battery output connector on the device.(3 pins) because i want it to behave like a secondary battery
i checked the voltage on the connector and found 6.5 v between the first and second pin , 3.05 V between the second  and third and 9.6 v between first and third
Now i am guessing that i could safely connect my battery , between the first and third pin (9.6v) and this could charge it.
anyone can tell me how the 3 pins are used in the webdt 366(winCE) and if i can safely connect the battery as mentioned above

Thanks
akhileshss
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Re: 12 hours external battery pack

Post by akhileshss »

Just wondering... Has any progress been made on the battery-front by *ANYONE* ?
My WebDT is sitting with an excellent puppy distro installed for months now. The only reason I cannot use it is not its usability, but the battery... Sometimes, I feel that WebDT-366 is better than iPad, only if it had a good battery to last for atleast 8-10 hours :(
mistico4
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Re: 12 hours external battery pack

Post by mistico4 »

I would also be interested in knowing.

At first I thought about using a 12v battery plugged into the DC input. Turns out 12v batteries are rather scarce and probably not enough capacity for even  1 hour use. Ebay lists some 1800MaH ones for CCTV devices. I bought 1 just to try and am waiting for it to arrive.

From my almost non-existent electronics knowledge, I believe 7.4v batteries plugged into the internal battery connector or even the external battery contact pads is the way to go. Could it be as simple as plugging in 4 18650 lithium-ion cells in 2s2p (2 serial in paralell) configuration? Say 2500MAh cells, that would be a 7.4V 5000MAh battery pack. I understand it's risky to assemble off-the-shell lithium cells in bigger packs. Maybe two 8.4v RC Ni-MH batteries in parallel plus a resistor to reduce voltage to 7.4v? Ni-MH have better discharge capacity and are safer than lithium cells.

And what about the third wire (probably a thermistor, I read in another post)? Could anybody source a replacement or maybe some kind of driver hack to ignore the readings?

The pack mentioned by op (15 ah,7.4V) must be as expensive as an iPad alone!
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