On 10/06/17 06:03, ronwirring@Safe-mail.net wrote:
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-charge... 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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On 12/06/17 11:07, ronwirring@Safe-mail.net wrote:
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.
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.
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.
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.
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.
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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Loading sharing is the ability to draw power from battery but when the battery is being charged, the load switches seamlessly to being powered from the same power input that is powering the battery charger.
Products that do this: *adafruit make a 5v boost + charger with load sharing. [1] *nitecore make a 18650 li-ion charger + usb power bank which also has load sharing. which is a rare feature for power banks. [2]
Example load share circuit: http://blog.zakkemble.co.uk/a-lithium-battery-charger-with-load-sharing/
[1] arr search youll find it, called powerboost i think. note that its not good for OTG phone use. i damaged one of mine when my device was sending power back down to the powerboost. :( [2] https://www.banggood.com/Nitecore-F1-Flexible-Micro-USB-Outdoor-Power-Bank-S... (where i bought mine from.)
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Alexander Ross -
ronwirring＠Safe-mail.net -
Tor, the Marqueteur