## System OM Costs

Operation & maintenance costs consist of fixed and variable costs. Fixed costs include cooling and genera l maintenance at the site. Variable costs include recharging the batteries and periodically replacing the batteries. These O&M costs are presented as annual expenses in the prior table. The cooling charge is based on a power managemen t system which consists of eight modules, each one of which is the same size as the system being characterized here [18]. The unit must be installed in an air-conditioned room [4], and thus, the parasitic load for the cooling fans is quite small at 1.25 kW. At a peak or shoulder rate of 50/kWh, the annual cost of the cooling load for the 30 kW system is $548. The general maintenance cost of $1,000/year is based on the experience of CEMC with a larger flooded lead-aci d battery.

The recharging cost is calculated as the kW rating * discharge time * ( (1 - AC-to-AC efficiency) + 1) * off-peak 0/kWh rate * 100 days/year. The 30 kW unit requires a 37.2 kWh charge (given 76% efficiency [4]), at a 1.50/kWh off-peak rate, costs $56 annually in 1997.

The cost of battery replacement is based on an expected battery life of three years. Thus, on average, the annual cos t of battery replacement is one third the cost of the batteries. Expanded battery life increases to five years in 2000 an d ten years in 2010 and later, so replacement costs improve accordingly.

## DIY Battery Repair

You can now recondition your old batteries at home and bring them back to 100 percent of their working condition. This guide will enable you to revive All NiCd batteries regardless of brand and battery volt. It will give you the required information on how to re-energize and revive your NiCd batteries through the RVD process, charging method and charging guidelines.

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