Battery Vent Caps

In an earlier post we showed how we cleaned up all the primary wiring to the two 6 volt L-16 batteries and put them in a secure enclosure built from starboard. That upgrade was a major improvement, but we still had some problems keeping the tops of the batteries dry.

We considered replacing the lead-acid batteries with AGM's but the Trojans were in really good shape and holding charge well. Also, we keep reading that lead-acid batteries are best suited to our situation, where the DC system is run with dock power plugged in for the majority of the time. 

Difficult to see in this shot but there is 'weeping' or 'sweating' on the caps of a couple of cells on the forward battery.

We fussed with the acid levels for several months but never found an ideal condition. If we kept the acid just barely above the lead plates it eased the problem considerably but we had to watch the levels very closely and top the cells up frequently to avoid exposing the plates. If we were more generous with the distilled water and let the level come up, even a quarter inch above the plates, the sweating started. It got worse with a heavy equalising charge and/or a bumpy ride, such as motoring into steep chop. 

Things came to a head when we found that despite our efforts to keep them dry, the moisture on top of the batteries had been enough to rot the hold-down straps and corrode the strap anchors. The acid had slowly wicked along the straps and corroded the buckles and anchors. The stitching on one webbing strap actually disintegrated.

Corroded buckle on one of the hold down straps.

Corroded anchor bracket for hold down strap.

Corroded buckle on second hold down strap.

A poor photo but it shows the stitching on the strap above that actually fell apart due to the acid!

We had to do something. While surfing the net for solutions we found several products that promised to fix our problem, which evidently is quite a common one with lead-acid batteries. After a bit of research we decided to try the Water Miser made by Flow Systems.

http://www.flowsystemsusa.com

The Water Miser vent caps are designed specifically to eliminate misting from escaping gas during charging cycles and are a direct swap with the standard 1/4 turn caps on most wet cell batteries. They are also very inexpensive.

  

We sent of for a half dozen caps figuring we couldn't get hurt too badly. Here they are, installed, about two weeks ago. We topped up all the cells to a level that previously would have guaranteed some weeping and, at the time of publishing this post, we have seen no sign of any problem.....Yippee!  

The old caps on their way to the dumpster, another item crossed off 'The List'!