HouseBank

Designing the House Bank

Along with BatteryType and BatteriesLayout, the main considerations in the design of the house bank are:

• Daily load • Capacity • Charging capacity of the alternator • Trickle charging

Total Daily Load

Load is measured in total daily amp-hours (AHAmpere-hours (A*H)), which is simply the average current drawn per hour times 24 hours. Calculating this is a major task subject to much second-guessing. The first step in calculating load is to determine the combined DCDirect current and ACAlternating current AH load for all ‘appliances’. Use a spreadsheet to list each item and its wattage or current draw, depending on which is available. For the DC, make sure you work entirely in either 12 or 24 VVolt. See ElectricalCapacityDC and ElectricalCapacityAC.

For each item, estimate the duty cycle (how long it will be used each day). Do a separate tally for fixed loads (e.ggram., instruments) and intermittent loads (e.g., coffee maker). If in doubt it is safer to over-estimate the duty cycle. But don’t go overboard. If you over-estimate too much you might have to go back and tweak the numbers more realistically when you realize that you need to tow a sub-station behind you on a barge to supply your electrical requirements.

All estimating processes must be subject to a reality check. It’sSecond better to get each number as exact as possible, then add a fudge factor to the total, rather than fudge numbers individually.

In addition, you need to calculate the peak and surge requirements. To estimate the peak demand, determine which of the largest appliances will be used simultaneously. To estimate the surge demand, determine the surge on start up of large AC motors. (DC motors do not have a surge.)

Use whichever number is the highest for all future calculations. Let’s call this the Total Daily Load.