After finding one battery (7 years old) out of water - and since the water level of batteries on my boat are difficult to check and maintain - I found a Qwik-Fill Battery  watering system.  I ordered the parts for 3- 12v wet cell batteries and the hand bulb pump unit needed to fill the batteries.  While a bit pricey - so far I find the system easy to use.

 

While I lack of photo of the pump unit - above are images of how the installation went.

Since my batteries are seperated by about 3' from one another - I used on system for each battery.  The yellow manifold has black floats that rise when the water level in the battery rises and shuts off the water from the manifold - preventing over filling.  The black fitting on the end of the feed tube is a one way valve and fitting to hook up the hand pump.

The air trapped in the feedlines/system is gently vented. 

After the manifold is installed in the battery you simply squeeze the hand bulb/pump until it is firm - and the battery is full. 

So far so good after 2 months.

Jay

 

When I had to replace my 4 Trojan T-105's (at a cost of $200 each in Central America) I decided to install the Qwikfill system after reading about it on an earlier forum posting

Battery Placement

I have two T-105's placed just forward of each fuel tank. Not impossible but I had to use a turkey baster to reach the fills...  just hard enough to maintain that I would just say 'I'll do it tomorrow'.

Now, they are so easy to maintain I just say 'I'll do it tomorrow''.

Seriously though, while it is pricy (about $165 for two 6v kits + bulb pump) if you have lead acid batteries that are at all difficult to maintain it is absolutely worth the cost in the long run.