PROBLEM WITH A BATTERY BANK/PACK.

[cicero]

Hello all, Can someone give me some advice. I have a battery bank which has two usb outputs from which I can charge camera phone etc. I wish to charge my electric razor which has a wallwart charger at 5 volts. I have a spare usb cable wich I have cut in halve and on the cut end I have four wires, I assume two for the voltage output and two for data. If I plug the usb end into the battery bank I get very little voltage out but 5 volts when I plug it into the usb on my computer so I assume that the data wires require data from the unit to be charged but the razor does not have this. I am sure that one of you will give me ideas or solutions so I thank you all in advance.

 

[Martaine2005]

The battery bank probably needs a load.
Connecting an open wire is akin to having nothing connected.

martin

 

[cicero]

Hello, Thank you for the reply but what you said is obvious. I was expecting a more in depth answer.

 

[WHONOES]

You could diode or the outputs of your power supplie together using Schottky diodes such as VS-100BGQ-100 or VS-!00BGQ-15.
They are made for exactly this purpose. Both are rated at 100A. The former is Rated at 100V and will have a forward drop of about 700mV at 30A, the latter is only rated at 15V but has a forward drop of abot 350mV at 30A. If you guarantee that the supplies will not exceed 15V then the latter item would be the one to use.
Whichever is used. they would need to mounted on a small heatsink as they would be dissipating up to 20Watts..
I have attached copies of the datasheets.
2189509.pdf (farnell.com)
2614081.pdf (farnell.com)