There are two common way to design a PowerWall- this booklet explains the pros and cons and helps you decide which is right for you.
This is booklet on assembling a Power Wall using BatteryBlocs in fencepost tubes.
BatteryBlocs Power Walls place a large number of cells in parallel inside of 5″ plastic fencepost tubes
We’ll call each parallel group in a tube a “stack”.
A piece of SuperStrut is secured to the wall, and short pieces of SuperStrut are secured to each fencepost tube. The fencepost tube with the batteries inside hangs from the the interlocking pieces of SuperStrut so that individual stacks can be removed for repair. Because of the modular design, the rest of the battery can still be easily connected together and used while repairs are happening.
The cells in each stack have their own voltage meter for easy monitoring.
Each stack has it’s own active balancer. This active balancer moves power from the highest stacks to the lowest stacks. It balances all the time, not just when fully charged, allowing you to extract more power from the battery and extended the batteries life. Matching the cells is much less critical when active balancing is used, also, more of the battery capacity can be used.
Using this modular technique you can start small and add on later. You can change voltages by adding or subtracting stacks. You can add more cells to a stack for more capacity. You can unbolt and remove a stack for repair, then reconnect the neighboring stacks and go on using your battery.
This particular wall powers my house. It is a 120P15S of about 18kwh. It was made from all salvaged cells of differing ages and capacities I have collected over the years. This battery is charged by an Outback Solar Charge Controller with the voltage programmed to 60 volts, four volts per stack. The battery powers an Outback 3000 watt inverter. Fusing is through a 50 amp DC circuit breaker. Low voltage shutoff occurs both through the inverter and through a trigger relay turning on and off a power relay.
Similiar BatteryBlocs Power Walls are used in tiny houses, boats, vans.