Abstract: A map is retrieved based on a battery temperature, a temperature rise value and an allowable current value, with which a battery can be charged while battery temperature rise is being suppressed, is obtained and the battery is charged with the allowable current value. By doing so, it is possible to charge a nickel metal hydride battery cell which temperature tends to rise during battery charge in a short time without causing deterioration due to temperature rise. This battery charger makes determinations after dividing the battery. Due to this, compared with a case of simultaneously determining all battery cells, it is possible to accurately determine the completion of charge.