【再発防止】インジケーターでは液レベル正常なバッテリーを充電中に爆発！CCAを復活させるはずの激安OBEST バッテリー充電器でサルフェーション除去中の爆発事故と原因の考察。

While pulse charging an AC DELCO battery using a very cheap OBEST battery charger, available for around ¥2,000 on Amazon, the battery exploded and the case was destroyed. We identified the cause and devised measures to prevent recurrence. Previously, pulse charging with an AC DELCO AD-0007, purchased for around ¥30,000, had successfully restored the battery and prevented any accidents. Therefore, we assumed the OBEST battery charger was the culprit and investigated the cause using an oscilloscope. As expected from an AC DELCO manufacturer, it only adds extremely short pulses to the charging voltage. On the other hand, the very cheap OBEST battery charger generated longer waves in addition to the pulse waves. This was similar to the extra waves generated by a simple circuit I once built. In addition to the pulses, it also added an ineffective integral voltage, which, while effective, resulted in a relatively large amount of hydrogen gas being generated. This may have been an indirect cause of the explosion. However, the OBEST battery charger was not the only factor contributing to the explosion. Compared to the AD-0007, the pulse voltage applied is nearly twice as high, and naturally, hydrogen gas is generated, resulting in a significant decrease in battery fluid. While the battery fluid level was checked using an indicator before charging, the indicator only shows the fluid level of a specific cell. Therefore, if a problem occurs with a specific cell, it cannot be addressed. It is suspected that the explosion occurred due to an air spark caused by an unfortunate combination of a cell with a low fluid level and electrode deformation due to previous sulfation. At the end of this article, we provide a summary of points to be particularly careful of when charging batteries.