How do you add water on a monthly basis to batteries you can't even reach? A battery watering system makes it easy!

Easy Battery Watering

If you have wet-cell batteries, you know what fun it can be to check and water the batteries. You’re supposed to do it every month, but when you have to remove part of the batteries — disconnecting the wires, lifting at arm’s length straight in front of you — do you really do it that often?

I’m certain that the previous owners of our boat didn’t (evidence: the two hard-to-get-to batteries lasted about 15 months).

Even if you don’t have to move and disconnect the batteries, they’re usually still hard to get to.

So in the process of doing all our other battery work, we added a battery watering system. Since it’s hard to show here on our boat, I’ll use the artists’s rendition of the Qwik Fill system:

How do you add water on a monthly basis to batteries you can't even reach? A battery watering system makes it easy!


There are a couple of brands available, but they all work pretty much the same as least as far as the ones you’d use on a boat go.

  • You replace the vent caps with the special watering ones.
  • Connect tubing from one set of vent caps to to another (generally two or three batteries can be connected).
  • At one end of the “chain” connect the fill tube which has a quick connect on the other end.
  • At the other end of the “chain” put an end cap.
  • When not in use, the fill tube is just coiled up and left in place.
  • To fill the batteries, you use a squeeze pump that’s similar to an outboard motor fuel line — connect one end to the quick connect, and put the other into the jug of distilled water. Squeeze a few times and you’re done!

The vent caps have a float valve in them that stops water flowing when the cell is full, so each cell gets just exactly the right amount of water. When the squeeze ball gets hard, all cells are full. Disconnect the pump tube.

Here is a short video fro Flow-Rite explaining the installation and use of the system:

There are fill systems made for most Group 24, 27, 29 and 31 batteries and also for 6-volt golf cart batteries. Typically you buy “battery systems” (the vent caps and tubing) for one or two batteries in a group (buying as many sets as you need — this is the part that stays permanently attached), then you need one pump unit for all and you simply connect the pump to each fill line.

The water does not stay permanently attached — it’s not a totally automatic battery watering system, simply one that makes it so that you don’t have to reach each battery. For us, it now takes about two minutes to fill our batteries, including the time to get the distilled water out, get the pump tube out and connected, and put everything away. But yes, we still have to do it every month.

It’s now this easy:

How do you add water on a monthly basis to batteries you can't even reach? A battery watering system makes it easy!

If you read the company literature and some reviews, some people talk about installing the system in just a few minutes. HA! Remember, this is a boat project. And nothing is ever easy.

Yes, it’s easy to make the actual connections (just be careful as you’re working around battery acid). But if you’re on a boat where the batteries are hard to get to, it’s going to take longer as you have to get to all the batteries and wind the connector tubing around the battery wires. It took us about 3 hours before we were totally happy with the installation and didn’t have any places where the tubing was pinched.

The two big companies offering battery watering systems are Flow-Rite and Trojan, and both offer systems for 12 volt batteries (as far as I know, up to Group 31 size) and 6- and 12-volt golf cart batteries. We went with the Flow-Rite because it was easy to order online from Amazon and I had problems making connections with the local Trojan dealer. However, from talking to some people with a Trojan system, it seems that Flow-Rite is also less expensive. One reader, Bill & Donna from Denali Rose used the Trojan system and wrote up their experience — read it here.

NOTE: Both companies also make systems for golf course operations and other commercial applications which will fill tens (or hundreds) of batteries with varying degrees of automatic operation — these are NOT suitable for a boat. You want the ones designed for boats and RVs.

Here are the links for the Flow Rite systems on Amazon. You need as many “kits” as you have batteries — that is, if you have three batteries, you need one 2-battery kit and one 1-battery kit; if you have four batteries, you’ll need two 2-battery kits, and so on). In addition, you need one of the pump assemblies, no matter how many batteries you have. Our total cost for the project (3 12-volt batteries) was about $120.

This is one of those improvements that no one every sees, yet it makes life aboard so much easier. Doing the battery water is now such an easy job — we don’t even have to open the battery compartment, let alone move batteries or disconnect the wiring. Total win!

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  • Candy Ann Williams
    Posted at 08 March 2015 Reply

    Great post! This would be a great project for La Fiaca!

  • Mark Zalenski
    Posted at 08 March 2015 Reply

    I used these on the 8 Trojan golf cart batteries on my last boat for 7 or 8 years and they worked great. If you have a high point above the batteries to put the jug of distilled water on, the system will fill by siphon after one or two pumps on the bulb.

  • Lex (Tanton43, Chesapeake Bay)
    Posted at 08 March 2015 Reply

    Thanks. You guys come up with many good suggestions. I like this one. Using this may help avoid holes in my clothes from battery acid.

  • Tina Barnes-Weida
    Posted at 01 August 2015 Reply

    We have battery watering system and it is wonderful, water both banks (8batteries) in 5minutes, with no spilling of water. 1St of every month with ease.

  • Tony Hill
    Posted at 01 August 2015 Reply

    Have one as well, love it!

  • Carolyn Goodlander
    Posted at 02 April 2016 Reply

    Unfortunately, it costs about $100 for two batteries and we have 8!

    • The Boat Galley
      Posted at 02 April 2016 Reply

      You’ve got a lot larger bank than we do. We’ve got three batteries and without the watering system we’d have to have AGMs as there is just no way to get to them. The cost of the watering system is considerably less than AGMs around here.

  • Scott Berg
    Posted at 02 April 2016 Reply

    We have the Trojan watering system for our 6 GC house bank, cost us about $200 and it’s been great…well worth it

  • James Montgomery
    Posted at 07 August 2017 Reply

    Battery watering systems come up regularly on E-bay used. Save a ton of money.

    I use an old juice jug for the filler with a 3/8″ hole drilled in the cap. The hoses are 1/4″ ID 3/8″ OD so the hose stuffs snug in the cap. All I do to top batteries is pour some distilled water in the jug put the cap on and tip the jug upside down. It pulls a slight vacuum, so I crack the cap a bit to relieve it now and then.

    Cost less me than $50 and is much faster and easier than fooling with the squeeze bulb.

  • Darlene Moore Bak
    Posted at 09 August 2017 Reply

    Previous owner had this on our boat. So easy ! 2 banks of 4 fill in no time. Can’t imagine having to fill 8 batteries each separately

    • The Boat Galley
      Posted at 09 August 2017 Reply

      I love ours. There is no way we could get to all our batteries otherwise — you’d literally have to “unwire” them all and remove two to get to the third. With this, I water the batteries while waiting for coffee water to boil. 🙂

  • Tom Kober
    Posted at 09 August 2017 Reply

    With out looking how do you know all the plates are covered?

    • Barry Ainsworth
      Posted at 09 August 2017 Reply

      The caps have a float that stops the fill at the right level

  • Ted Reshetiloff
    Posted at 10 August 2017 Reply

    We use watermiser battery caps. Have for 5 years now. We still water batteries but hardly have to add much each month.

  • Kelly Jones
    Posted at 10 August 2017 Reply

    Simon Jones

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