A portable USB battery/USB power pack (usually used to recharge your cell phone when you are off grid) can be used to power the fountain pump. They are lightweight and have a large capacity. Be sure to pack the battery into a quality Ziploc-type bag since these batteries should not under any circumstances get wet.

We do not recommend any specific battery or brand, but we’ve tested several different USB batteries (see table below.) The Anker is supposed to be the best quality with regard to lifespan, but we didn’t get any significantly better run time with it than the others. The RavPower RP-PB41 has the longest run time as a single battery but can not be used as a tandem battery (two batteries parallel) since the RavPower RP-PB41 doesn't take over automatically. If you’re already using a USB battery to recharge your mobile phone or tablet, we recommend you try it for this application before buying anything new.

These tests were run in 2016/2017. Since then models have changed, been discontinued and hundreds of new models have come on the market.

Continuous run times with pump model JT-180 are approx. 20% shorter.

Battery combinations (with double USB adapter or Pass Through *2):

(*1) iMuto X4 or X6 new generation models don't work anymore; they switch off after 45 seconds (status 4/2017).

(*2) Pass Through Charging (with RavPower as "pump-battery" only) can work for extending the continuous runtime (see below).

Batteries with problems:

As the table shows, these will need to be recharged approx. every 3 to 8 days. We suggest ordering 2 batteries, so that one can be in use while the other is charging. We have constructed a “double adapter cable” that allows 2 batteries to power the fountain in tandem – this will give you double the run time before having to recharge, but you’ll need a total of 4 batteries.

Parallel Mode

In parallel mode, two batteries are switched together running one and the same pump. The battery with the slightly higher output starts powering the pump whilst the other battery waits in stand-by until the first battery runs out of power. Then this battery starts powering the pump. You would get 16 days of continuous runtime with two RavPower RP-PB64. But the fountain needs to be build especially for these big batteries since they don't fit in standard battery compartment.

 
Here in this example Anker Astro E7 and RavPower RP-PB64 in parallel mode for 12.5 days continuous runtime.

Pass Through Charging

In essence, pass through charging involves being able to connect your power bank to a wall charger or another power bank and, whilst the power bank runs your pump, your device charges at the same time. But this works only if the "charging" battery automatically switches on when the "pump-battery" runs out of power. Unfortunately not every battery can do this. Usually you have to start the charging battery manually when the "pump-battery" is nearly out of power.  So it's good to have the bigger battery powering the pump while the smaller battery is in stand-by for charging the "pump-battery" to extend the overall runtime.
Pass through charging is a wonderful technology that enables you to make your power go further. But not every brand and model can do it.

   
Here with two RavPower batteries: model RP-PB64 and model RP-PB41 for approx. 12 days of runtime.

click to learn more about it

So how should you handle your batteries?

There is some very solid, consistent advice about getting the most out of your batteries:

1. Be prepared to replace them, eventually. Rechargeable batteries don’t last forever, and through time and use they will stop working. Thank them for saving you money, recycle them, and move on.

2. Buy a good charger. You don’t have to spend a fortune on the best charger available, but make sure you get a “smart” charger, one that electronically monitors the recharge process and prevents overcharging. Not only is it better for the batteries, it will use less power than cheap chargers, which often rely on a simple timer mechanism.

3. Remove the batteries when the recharge is complete. Unnecessary time on the charger means more “trickle” power is used to keep them charged—so more wear and tear and more wasted power.

4. Store your batteries fully loaded (never empty!) at room temperature in a dry location. Excessive heat can definitely damage your batteries and cause them to lose charge faster.

5. Every battery should be protected from water, but Li-Ion batteries (USBs) are particularly sensitive to water damage because they have electronics inside. We craft our internal battery compartments to keep the batteries dry but there is always the possibility of condensation forming, so it is imperative that the battery(ies) be enclosed in a high quality water tight Ziploc-type bag before putting them inside the compartment. And of course, if your cat has the propensity to play in the water, external batteries need to be protected as well. You have about 7 feet of cord available, so put them in a higher place, a nearby drawer or a waterproof container.

6. It's important to follow the safety guidelines that accompany your batteries!