This is specifically important for sealed systems because they are less tolerant to overcharge than the swamped kind. https://e785s8hz.micpn.com/p/cp/1087d8162eb8be6c/r?url=www.dbdxjjw.com%2FGo.asp%3Furl%3Dhttp%3A%2F%2Fwww.aiki-evolution.jp%2Fyy-board%2Fyybbs.cgi%3Flist%3Dthread