Batteries (with centralized watering system) [Updated Mar-2019]

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And since we are talking about batteries, in the future our choices in this post may become dated and/or obsolete, so we will endeavor to keep this information current regarding what we have and use, and what we are researching/ considering for the future.

––––– Updated 1-Mar-2019 [by Bill] –––––
[Initial post: 2-Aug-2014]

When we were evaluating the boat for purchase, we learned the broker had once forgotten to plug the boat into shore power after moving it to a different dock. This resulted in the battery bank draining completely, killing two of the eight 6 volt Trojan T-105 [flooded lead-acid; FLA] batteries [which were ~6 years old...] Instead of replacing all batteries, only those two were replaced (contrary to everything I have ever read, heard, or understood about maintaining battery bank integrity. i.e, all or nothing…)

Therefore I figured we would soon need to replace the entire bank. After cruising a couple of weeks, this became evident; the batteries were barely getting us through the night at only ~120 AH consumption [from a 900AH initial capacity bank.] Due diligence lead me to verify the charging systems were working correctly, and they were. I also equalized and load tested the battery bank the next time we were in a marina with shore power. (Ketchikan, Alaska) My suspicions were confirmed: the bank was down to ~50% of its original capacity. Time to go shopping.

Fortunately the local Crowley fuel depot in Ketchikan is a Trojan dealer and stocked the T105 batteries (and at competitive pricing!) They even agreed to deliver the 8 new batteries [~500 lbs] to the boat, and cart off the old batteries for no charge. Done deal.

However, before committing, I needed to decide whether to change over to AGMs ["maintenance free"] or stay with wet cell batteries that require the routine addition of distilled water. This was especially important because the location of all 8 batteries is a vented, custom locker under what remains my tool and spare parts storage area. That means all that heavy stuff needs to be moved and temporarily relocated every time I inspect and water the batteries. 

AGMs offer other advantages as well, but I was most attracted to the “maintenance free” aspect. AGMs also came at a ~50% premium, so I researched ‘remote’ [single point] methods of watering lead-acid wet-cell batteries. That is when I discovered Trojan (and Flow-Rite) offer just such a system for a lot less than the price difference between the battery types (and it will fit future batteries next time they need replacement…) 

Enter the Trojan HydroLink™ Watering System (I chose the Clampless Tubing option…)
[I also investigated the offerings from Flow-Rite but stayed with Trojan in this instance due to the lower profile, seemingly more robust design– including purported spark and flame arresting capability– and availability at the time...]

Trojan HydroLink™ Watering System with clampless tubing
Trojan HydroLink™ Watering System with clampless tubing. (Photo from sales literature.)
The quick-disconnect [with internal check valve] is the large black fitting. The orange rubber caps cover unused connections on the T's, and the T's floating to the sides of the batteries [not on battery caps] must be for illustration purposes since they came pre-installed on the manifolds...
HydroLink components replace the stock single battery caps [3 on a 6 volt battery] with a single cap [manifold] that covers all 3 cells, has a built-in pivoting T fitting for the clampless tubing [which strongly resembles heavy duty 1/4” ID fuel hose…] a visual indicator [fiber optic] of water level, and small float valves in each cell that allows new water in only if below a prescribed level (and acts as a check valve to prevent electrolyte from entering the watering manifold plumbing.) 

The whole job consumed about 4 hours of my time [including polishing the battery and cable terminals.]  The most demanding portion was lifting the old batteries out and carrying them to the dock for pick-up. (Bringing in the new batteries was mostly downhill…)

I re-used the well thought-out 4/0 cables Jack [the previous owner] had fabricated for the last set of batteries, and finished the installation by figuring out the most efficient way to route the rubber Clampless Tubing between batteries. That took all of 5 minutes... [Trojan is a bit stingy with the tubing; I had 6" left over...]

I put the single quick-disconnect [with built-in check valve] for watering all the batteries in the engine room. The Hydrolink kit I purchased came with an outboard motor style fuel bulb with a clear hose with check valve on the intake end (for dropping into a bottle of distilled water) and a quick disconnect fitting mating with the one on the end of the battery watering hose I terminated in the engine room. 

I fully charged the batteries overnight [Trojan warns to only add water to fully charged wet-cell batteries because the liquid level increases slightly as the cells charge...]  The next day, while the batteries were still out in the open, I grabbed a bottle of distilled water and dropped the check valve end of the hand pump into the bottle. I next purged the fill line of air by pumping it until it was full of distilled water (holding the quick disconnect over the jug of distilled water- effectively recycling the water) then attached it to the battery fill quick-disconnect fitting. I squeezed the bulb a few times (~4) until is wouldn’t squeeze any more. I checked for leaks and found none. I squeezed the bulb pretty hard again just to make sure, and all connections remained dry.

Wow. I just watered my 8 new batteries from my engine room in less than 30 seconds- including set-up time. It took longer to put the bottle of distilled water and the pump hose assembly away…

Lessons learned? 
  • Do your own research. The Trojan dealer, while great to work with, admitted no knowledge of remote watering systems. If I hadn't pursued this on my own [and I had no idea if such a system existed at the time...] I wouldn't have discovered these watering systems. 
  • This experience seems to reinforce the all-or-nothing strategy when it comes to replacing weak batteries in a bank.
    • In a pinch [e.g., this happens 'out there' where new batteries are not readily available...] removing the weak battery(ies) (in proper numbers- pairs in this case) would reduce bank capacity but also prevent the weaker batteries from weakening the entire bank.
  • If I could have it would have been great to take delivery of the batteries with the HydroLink manifolds pre-installed instead of having to order the kit from a different supplier and install them myself. While the installation is trivial, they do snap tightly into place giving the impression there is a possibility of breaking a manifold component if you aren't cautious when applying the required pressure.... 
    • Don't take this wrong: the manifolds are very sturdily constructed...
    • On the other hand, perhaps it makes sense to install the manifolds yourself after the batteries are placed into position- eliminating the opportunity to break a manifold while handling the heavy battery.
I can highly recommend this single-point watering system for anyone who desires to use wet-cell lead-acid batteries. [Total cost of the watering system for all 8 batteries was just under US$200 including shipping to Alaska in summer 2014...]

Future Considerations: 

  1. Wiring Changes: [Added 18-Apr-2017]
    1. I plan to install two battery combiner switches [Off, 1, 2, Both] in order to individually isolate the 4 pairs of 6 VDC batteries wired in series to yield 12 VDC. [Visualize wiring 4- 12 volt batteries in this way to simplify the mental wiring scheme...]
      1. This will allow us to isolate one or more bad batteries [in 12 volt pairings] from the main bank in an emergency. It will also allow us to isolate the 4 pairs for individual testing, equalizing, etc. as needed in the future.
  2. Future replacement battery considerations:
    1. Trojan Smart Carbon: [Added Aug-2016] I recently learned Trojan has introduced their 'Smart Carbon' technology for their 'RE' [Rural Energy] battery line. And they offer a direct replacement for the T105 battery we are using; the T105RE . These Smart Carbon batteries are purported to tolerate not always reaching a full state of charge better than the standard battery line, yielding a longer useful lifetime. [~15%]
      1. I will be researching this further, and watching for first-hand accounts. In the meantime, were I ordering new batteries today, I would probably go this direction assuming pricing is not out-of-line...
    2. Trojan Lithium Batteries: [Added 1-Mar-2019]
      1. Trojan is now marketing a line of lithium batteries [Trillium]  touted as 'drop-in-place' replacements for lead acid batteries. They sound promising, and at this time the smaller of the two offered sizes also has CAN buss comms built-in meaning they could plug into an N2K network in the future. 
        1. I will wait for others to report their real world experience before increasing my interest. 
        2. Even though our battery bank could get by with fewer lithium batteries vs. FLA [e.g., 6 vs. 8 batteries] the cost is so high with the initial release [~US$900/92 AH 12V DC battery] that I could replace my FLA bank 3 times for the same cost, so this is not a likely change for us in our cruising lifetime unless the prices become more competitive per Watt-Hour of lifespan vs. FLA.

Additional information and resources: [RE: Our current bank of FLA batteries...]
  • Related articles/posts (that we know of) that are worth reading:
  • Flooded Lead Acid battery watering systems:

Photos of our project:
Dry fit of new Trojan T-105 batteries for Denali Rose's house bank
Looking down into Denali Rose's battery bank right after the new Trojan T-105 batteries were placed into position. [Showing original battery caps.] The HydroLink watering line with the quick disconnect will be lead through the hole the battery cables go through in the upper right of this photo, terminating in the engine room.

Some of you monohull sailors may be wondering if we are going to have issues with the 7 batteries with their long dimention fore and aft on our boat... [i.e., The long dimention of flooded lead acid batteries should be athwartship on a sailboat to help prevent the tops of the plates from becoming exposed to air at extreme angles of heel...]  Well, our boat is pretty stiff, and we rarely heel more than 15° [20+° in sportier conditions...]

Here is what Trojan has to say:
How far can I tilt my batteriesFor flooded batteries, 22 degrees from vertical is the maximum recommended tilt. AGM and Gel batteries can be operated vertically or horizontally.

Completed installation of new Trojan T-105 batteries for Denali Rose's house bank
Here is the same view showing the finished installation of the HydroLink battery cap replacements plumbed with the small diameter black tubing and red rubber caps on all unused T connections. 

Also showing are the 4/0 battery cables wiring 4 pairs of 6 volt batteries in series (yielding 12 volts DC [nominal]) and then paralleling those 4 pairs into the [nominal] 900 amp-hour house bank we enjoy.

Note the through-bolted blocking securing the batteries in place.

All that remains to be done after this photo is to install the top of the battery locker and re-stow the tools and heavy parts boxes on top of it.

I can't figure out why the boat has a slight list to this [port] side...


  1. Did your new batteries come with the "Smart Carbon" technology? I can't find much info on the specifics of Smart Carbon.
    With the watering system handling maintenance, i guess the cost/weight/PSOC/density balance still goes to Lead Acid?

    1. Thanks for your inquiry, Richard.

      We purchased our batteries before the Smart Carbon versions were available. I added the Smart Carbon note 2 years after we updated our batteries so readers would be aware while researching.

      Answering your second question [which I will refrase as AGM vs. traditional Lead Acid]: for us lead acid is still the best choice since we have a sealed, vented [externally] battery locker and the centralized watering system.

      Everyone's needs are different, however, and AGM, Firefly, or even Lithium batteries may be best for their needs.

      Cheers! Bill


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