1996 Johnson Evinrude "ED" Electric Outboards Service Manual, P/N 507119, Page 21Get this manual
Variable load High-Rate Discharge Tester (Recommended) Connect tester to battery terminal postsDischarge at rate of one-half the Cold Cranking Amps rating (CCA) (or three times the battery amp hour rating) for 15 secondsIf the voltage is 9.6 volts or higher at the end of 15 seconds, the battery has good output capacityFixed Resistance Tester This equipment has built-in load for high -rate discharge testingFollow equipment manufacturer's instructions regarding test period and meter readingsEngine load for Resistance Twist the spark plug leads and remove them from the spark plugsConnect voltmeter across the batteryCrank the engine for 15 secondsIf voltage is 9.6 volts or higher at the end of 15 seconds, the battery has good output capacityBattery Charging
While the battery is charging, it gives off hydrogen gas which will burn and cause the battery to explode if ignited If gas cannot leave battery (vents are clogged), the battery may burstTherefore, when charging batteries, make sure that battery vents are open and battery is out in open airMake sure no sparks or flames are presentDO NOT SHORT ACROSS BATTERY TERMINALS to check battery conditionTaper Charging If batteries are to be fully charged by means of quick charger, the charge rate must be "tapered" (reduced to safe limit) when the electrolyte temperature reaches 1250 (52 C), or when gassing becomes excessiveFailure to reduce the charge rate may harm the batterySlow Charging If the battery is to be slow charged, charge the battery at amperes until fully chargedFull charge of the battery is indicated when all cell specific gravities do not increase when checked at three intervals of one hour and all cells are gassing freelyCharge periods of 24 hours or more might be required