Powering a USB device from a battery

[Deleted User]

I have a cats water drinking fountain coming from Amazon
It is USB powered and supposedly consumes 2watts
Rather than running it from a mains adapter - I am considering trying a power pack battery
How long would a 20,000ma battery run 2 watts for - if fully charged 

molerat

Amps = watts / volts.  2 / 5 = 0.4 amps or 400 ma.  Your 20000mah power pack will only provide around 66% of that quoted figure due to losses in conversion so 13200 mah.  13200 / 400 = 33 hours. What are you going to do when you need to recharge ? Get a power supply, much easier.

coffeehound

Does the fountain run all the time or do the cats somehow trigger it?

matelodave

Be aware that most battery packs only deliver power when there's an actual load - do you need to press a button to activate it.

If your cat toy doesn't consume current continuously then it will switch off and have to be manually reset.(try it with a mobile phone or something - unlpug the load and then plu it it again after say five minutes and see if it starts to charge or whether you need to press a button to restart it). 

getmore4less

If you have already ordered you could have provided a link

If you wanted one to run off battery why not order one of the rechargeable ones?

[Deleted User]

coffeehound said:

Does the fountain run all the time or do the cats somehow trigger it?

It runs constantly

and a USB lead is supplied to plug into the mains - via an adapter

But the reason for the question is positioning - We would prefer to put the drinking fountain in a place that is some distance from a mains socket !

Mickey666

There are plenty of rechargeable "USB power banks" available, often sold for recharging mobile phones when camping etc.
Here's a review: https://www.techradar.com/news/top-portable-chargers
And lots on Amazon: https://www.amazon.co.uk/usb-power-bank/s?k=usb+power+bank

[Deleted User]

Mickey666 said:

There are plenty of rechargeable "USB power banks" available, often sold for recharging mobile phones when camping etc.
Here's a review: https://www.techradar.com/news/top-portable-chargers
And lots on Amazon: https://www.amazon.co.uk/usb-power-bank/s?k=usb+power+bank

I have one already - hence my question

It's a 20, 000 mAh one!

I was wondering whether it would be worth "trickle charging" from a small solar panel ?

Amazon have them from less than £10

forgotmyname

No. Lithium batteries do not like trickle charging.  Yes it will trickle charge but you will reduce its

lifespan considerably.

20,000 mAh for £10?  Fake or really poor quality?

pbartlett

400mA continuous is quite a big current drain, even for a big battery. Mains power is your best bet.

[Deleted User]

forgotmyname said:

No. Lithium batteries do not like trickle charging.  Yes it will trickle charge but you will reduce its

lifespan considerably.

20,000 mAh for £10?  Fake or really poor quality?

No - not the USB power bank - that cost me £20 from 7 day shop and it is a genuine Xtorm 
The £10 is for the solar panel ( there are some for less too !)