Discussion:
modifying a 7 inch notebook cabinet toacceptapccard
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r***@Safe-mail.net
2017-06-12 21:07:51 UTC
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About the battery. If I can find an usb power bank having the right
specifications, I could then use the power bank to power the
computer and if I wanted to be able to charge the battery and
have the computer turned on at the same time, I could get
a charger with 2 usb connectors?
With a power bank this might work, because they (AFAIK) all have their
charging circuitry inside the power bank and take a straight-up voltage
source to charge. It won't make too much difference how you connect them
as long as you have adequate gauge wires for all connections.
If you're dealing with Li-ion cells, it's not recommended. It has to do
with how Li-ion charging works. In short the charge schedule (most
notable in a "fast" charge, meaning anything less than 5 hours or so) is
constant current at a rate the battery can handle to voltage, and then
constant voltage as the current tapers off to nearly nothing.
The upshot of this is that trying to power a device with the
battery/charger combo while charging the battery will confuse any decent
charger (and if it isn't a decent charger you SHOULD NOT use it). The
only way around this is a charge controller designed for such use that
has three sets of terminals. One for a source, one for battery, and one
for load. The charge controller is then able to distinguish the load
from the battery charge current and charge it intelligently.
Your lowermost section, I do not follow.
Let us assume you somehow are able to get the battery bank into the computer's cabinet.
Let us say, you use an usb port on the usb battery bank to both charge the
usb battery bank and power supply the pc card.
In order to power the pc card, you would have an usb cable connecting the
power bank and the pc card.
I have no power banks. Looking around, it appears power banks have
a port for getting charged and one for power supplying devices.
In general, are you sure, you cannot charge a power bank and
simultaneously have it power supplying a device? If the power
bank can be charged and power supply a device simultaneously
you would connect another usb cable from the charger which charges the power bank
to the power bank.
Else if the power bank gets empty, you would remove the
usb cable connecting the power bank and the pc card.
Then connect an usb cable from the charger of the power bank to
the power bank. I suggest
to use a https://www.att.com/chargers/att-42a-dual-usb-low-draw-universal-wall-charger.html
if you want to charge the power bank and turn on the pc card at the same time.
One usb cable from the charger to the power bank.
One usb cable form the charger to the pc card.
Tor
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Tor, the Marqueteur
2017-06-13 06:34:46 UTC
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Post by r***@Safe-mail.net
The upshot of this is that trying to power a device with the
battery/charger combo while charging the battery will confuse any
decent charger (and if it isn't a decent charger you SHOULD NOT
use it). The only way around this is a charge controller designed
for such use that has three sets of terminals. One for a source,
one for battery, and one for load. The charge controller is then
able to distinguish the load from the battery charge current and
charge it intelligently.
Your lowermost section, I do not follow.
In short this is dealing with a straight-up battery pack, not a fully
integrated power bank with charger.
Post by r***@Safe-mail.net
Let us assume you somehow are able to get the battery bank into the
computer's cabinet. Let us say, you use an usb port on the usb
battery bank to both charge the usb battery bank and power supply
the pc card. In order to power the pc card, you would have an usb
cable connecting the power bank and the pc card.
Assuming a schematic that looks something like:

PC Card-\___
| Power supply
_Charger_|
|
- --Battery

This is OK. If the power bank is designed with internal charge
circuitry (required for USB powered devices because the USB voltage is
too high for Li-ion), then you should be OK.
Post by r***@Safe-mail.net
I have no power banks. Looking around, it appears power banks have a
port for getting charged and one for power supplying devices.
In this case, simultaneous charge/draw may have some losses that would
be preferable to avoid, but if the power bank is well-designed it
should be fine.
Post by r***@Safe-mail.net
In general, are you sure, you cannot charge a power bank and
simultaneously have it power supplying a device? If the power bank
can be charged and power supply a device simultaneously you would
connect another usb cable from the charger which charges the power
bank to the power bank.
It's a question of how the charger is arranged. Laptops do this all
the time.

The schematic that does not work is:

Battery
|
----+-------
| |
Computer Li-ion charger

The problem here, AIUI, is that the charger can't cut off power to the
battery once it's charged, because it can't tell. This will degrade
the battery faster, and Li-ion is the most dangerous chemistry to
mishandle. It's not without reason that there are warnings everywhere
to only use proper smart chargers for Li-ion.
Post by r***@Safe-mail.net
Else if the power bank gets empty, you would remove the usb cable
connecting the power bank and the pc card. Then connect an usb cable
from the charger of the power bank to the power bank. I suggest to
use a
https://www.att.com/chargers/att-42a-dual-usb-low-draw-universal-wall-c
harger.html
if you want to charge the power bank and turn on the pc card at the same
time.
Post by r***@Safe-mail.net
One usb cable from the charger to the power bank. One usb cable form
the charger to the pc card.
This can be done. The most important thing is to make sure the charge
circuitry has only the battery on the battery side of it.

By running off a power bank you will have some extra losses in the
boost then buck voltage conversions, quite possibly upwards of 10%.

Tor


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Tor Chantara
http://www.fineartmarquetry.com/
808-828-1107
GPG Key: 2BE1 426E 34EA D253 D583 9DE4 B866 0375 134B 48FB
*Be wary of unsigned emails*
Stop spying: http://www.resetthenet.org/
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