* Do you recharge it yourself? If you have a battery charger at home, the cost is essentially just the electricity used, which is negligible.
* Do you have it recharged at an auto parts store? Many auto parts stores offer free battery testing and charging services. This would be the cheapest option if your battery is merely discharged.
* Do you have it recharged at a mechanic or repair shop? This is the most expensive option. They'll charge for their labor and potentially for diagnostic testing in addition to the electricity. The cost could range from $20 to $50 or more, depending on location and the shop's pricing.
* Does the battery need replacing? If the battery is simply discharged, recharging is the solution. However, if the battery is old, damaged, or failing, recharging might only be a temporary fix. In this case, you'll need a new battery, costing anywhere from $50 to $200+ depending on the battery type and retailer.
In short, recharging a *discharged* battery itself is very inexpensive or free. However, the overall cost of addressing your car's battery problem could be significantly higher if the battery needs replacing.