You will need
  • Charger
If the battery is discharged, remove it and try charging in a warm room. Pre-determine battery capacity by Bosch, which is indicated on its case. If it has a conventional design with the acidic electrolyte when charging, adjust the charger current that is not more than one tenth of the battery capacity. For example, if you charge the battery with a capacity of 65 ampere-hours, on the charger, adjust the charging current not more than 6.5 amperes. In this case you must ensure that it does not overheat. Remove the battery cover. If the electrolyte boils in it, the battery can permanently malfunction. Fully charging the battery should take 10 hours.
A feature of the modern car batteries from Bosch is that many of them are helium. The electrolyte in the banks of such batteries is in a condensed state. Such batteries are dead are more environmentally friendly, easy to maintain, have an increased capacity. The special valve system allows you to release them from the excess gas. But while charging to avoid overheating of the gel, otherwise the battery will fail.
In sealed gel batteries the charging current is set at 2.5% of the battery capacity and longer charging. For the battery a 65 ampere-hours, the charging current will be more than 1,625 amps, the charging time is 40 hours. When you do this, be sure to monitor the temperature of the battery banks. If you allow the gel to become liquid, the battery will be ruined. Therefore, if you do not want the fastest charging, use the smallest possible charging current.
If the charger has a quick charge function, it can only be used on batteries with liquid electrolyte. But even they cannot continue to charge this way, because it reduces the battery life. For gel batteries, this method of charging is strictly forbidden.