Battery Maintenance

We've been using Trojan "Traction" batteries for years in our yachts. These industrial strength batteries are designed for a full 80% discharge, and guaranteed for 1500 cycles in industrial use. Last week we removed the batteries from the keel sump aboard Beowulf and sent them back to Trojan for service. We used a combination of main halyard and boat yard hydro-crane to remove them. It is somewhat over five years ago now that we purchased these batteries, and they have sat around for the greater part of this time - not a good thing for their capacity. Trojan took them in, cycled them to the 80% level twice, and then did a voltage check. The check is done at the discharged resting voltage. Turns out that these batteries are at 105% of rated capacity. Not bad after all these years. In chatting with Mark Waycaster at Trojan about maintenance, he emphasized several things (which apply to traction batteries and their marine batteries like the L-16):

1. The batteries should be deeply cycled - to the 80 discharge level -every four to eight weeks; ideally, just before they are equalized. (We have never done this on purpose - however, once or twice by mistake.) This will increase and/or maintain capacity. The next two items apply to all flooded lead/acid batteries.
2. When topping off the batteries with distilled water, do so only after a FULL charge, to a level 1/4" above the plates (if you do this before a full charge the odds are the electrolyte will bubble over).
3. Battery acid, when it dries on the tops of the batteries, conducts electricity. This leakage will run the battery down and create potential electrolysis problems, if the batteries are in any way connected to the hull or through hull fittings. Clean the tops with a solution of baking soda and water in a spray bottle, or Windex (which contains ammonia - a base - which will neutralize the acid).

Update: Since writing this article, Trojan has stopped making this type of battery. To read about alternative sources for traction batteries, click here.

This article elicited a response from one of our readers, which we've posted here:

Just finished reading the battery maintenance article on your site and have some comments:

1. A periodic deep discharge followed by an equalizing charge is a good idea for any lead acid flooded battery, not just the Trojan.
2. Disagree! Boiling over should not be a problem on a properly filled cell during a gassing charge. If it were, the problem would still exist the NEXT full charge. I prefer to water before a good charge. The gassing helps mix the new water into the electrolyte. Stratification can cause significant loss of capacity.
3. Acid on cell tops can be insidious - but you don't find out until your clothes come out of the laundry. If you work a lot around lead acid batteries, invest in some surplus Army woolen OD's. The acid won't touch the wool.

My comments are based on being chief engineer on two diesel electric submarines. I used to own 250 TONS of lead acid cells.

- DRM (added 21 July 00)