# DIY battery gravel vac, or hacking a ready made one



## captmicha (Jul 12, 2009)

I want to be able to touch up my tanks in between water changes, especially with sponge filters not grabbing up the mulm, without having to grab hoses and buckets. But I have an Eheim battery vac and the suction sucks (see what I did there?), and it's always breaking down. None of the others on the market are supposed to be as "good" as the Eheim either. 

I tried making one with an electric water pump, but the 1/2" return hose required knock things around my tank, and it's a pain to have to keep plugging and unplugging it when I go from tank to tank. Hence why I still want a battery powered one. 

Has anyone done a DIY battery powered pump, or seen a tutorial for one? Or hacked one of the ready made ones to take more powerful batteries?


----------



## Gone missing (Aug 26, 2017)

Sorry that I have not seen this post earlier. DIY, hacking, changing is a favorite game and I might have some ideas. Still interested? 
Some things that might change the operation? 

Needs to be more "powerfull" to pick heavier debris? Perhaps using a smaller intake? The smaller diameter makes for faster flow even though the amount is the same. Faster flow can appear to be more powerful as it may pick up stuff better. 

Stronger batteries? That can mean two things. Are you hoping for longer lasting batteries. That could be solved with larger capacity batteries still using the same voltage. But if spinning the motor faster is wanted, that can be pressed some but not too far to burn the motor. 

Interesting idea and I'm open for "brainstorms" if this is still an idea for you.


----------



## captmicha (Jul 12, 2009)

Yes, still very interested. A smaller intake is a good idea, also speed for more thrust. Any ideas? 

The electric plug in one I tried making was just a cumbersome waste of time.


----------



## Gone missing (Aug 26, 2017)

A couple random thoughts, then! 
One is that a smaller tube will be passing near the same amount of water so it will be a faster flow and appear stronger. Some paying with different sizes might find one you like. This idea is why they build the big tube on the end of the commercial siphons. It lifts the sand but then drops it before it gets caught in the smaller tubing and removed completely. 
For a longer lasting battery one might play with adding more batteries connected in parallel so that the voltage remains the same but the total capacity is doubled. Depending on what is wanted, it might be good to find some of the higher capacity dry change batteries of the same voltage as the siphon. Things like those used for emergency lighting or alarms systems, Motorcycle or RC cars might be prospects for higher capacity. 
For higher voltage to make the motor spin faster, we begin to get over into burning the motor if we push it too far but most take tank a bit more than rated. Cars are rated at 12VDC but often see 14 volts for long periods when running. Danger here is you begin to run a 12V motor on 20 volts, though!!! 
Got any thoughts on what type and voltage the tiny motor currently runs on? Two "D" cells put end to end to give about 3 volts, maybe?


----------



## Gone missing (Aug 26, 2017)

Any more thoughts or progress on this project?


----------

