SBIR-STTR Award

Batteries for-nuclear submarines have traditionally been discharged to prevent sulfation. A recent attempt to float ssN2l prototype batteries in order to achieve longer battery life and reduce battery maintenance has led to sulfation of these batteries. The battery vendor has suggested the use of regulatory to allow adequate charging of weaker sulfated cells, while protecting the stronger cells from overcharge. We propose to locate the site or sites where sulfation ie occurring and to provide breadboard devices for test on the ssN2l batteries to reduce the mulfation and/or prevent the mutation from occurring. As an alternate approach to the aforementioned regulators, we propose consideration of a pulse charger which piggybacks its output on top of the normal DC charge from the motor-generator machinery.

Keywords:
lead acid battery monitoring system floating battery pulse charging sulphation impedance

BTC, Inc. has found a fundamental change in battery materials which has caused most modern lead-acid batteries to be liable to dendrite shorting. the dendrite shorts can lead to premature cell failure, overcharge of series-connected cells, excessive gassing, sulfation and a whole host of other problems. A continuation of our Phase I SBIR study in Phase II will quantify the battery material change, will develop an additive which will return the chemistry to the desired materials, and which in turn will allow the cells to float better and more reproducibly without dendrites. Tafel testing of large submarine lead-acid cells 9ASB-49A and LLL-69/SSN-21 SEAWOLF) has shown that soft, dendrite shorts and plate sulfation can be detected with fairly simple, reasonable non-destructive external electrical tests. Lead-lead dioxide-sulfuric acid reference cells have been designed and fabricated to allow the Tafel testing. The fundamental studies of the battery chemistry and electrochemistry were done in performance to studies of shunt regulators and/or pulse chargers, since we believe it is better to diagnose and threat the internal problem rather than apply an external field fix. These electrical/electronic devices will be studied during our Phase II project. Since the submission of our original Phase I proposal, a new buck-boost shunt regulator has been described in the literature that will be more useful than the original BWB buck regulator. In our Phase II effort, BTC, Inc. also proposes to gather more data on performance of Navy submarine cells under different operating conditions. This will be done by taking additional readings on cells at MINSY, at MARF, at GNB Kankakee, and on the SSN-21/LLL-69 cells after they are activated in min-1994 at Portsmouth Naval Shipyard, before installation of SEAWOLF at Electric Boat.