Nuts and Volts - October 2015

Cheaper, but Not Cheap

Billionaire Elon Musk — of Tesla Motors, SolarCity, and SpaceX fame — is known for generating intriguing, long-shot business models and finding backers for them, and they just keep on coming. His latest offering — a product spinoff from Tesla Motors — is the Powerwall home battery ( www.teslamotors.com/powerwall) which stores electricity from your home solar panel array in a compact and easily installed package. As noted by the company, "The average home uses more electricity in the morning and evening than during the day when solar energy is plentiful. Without a home battery, excess solar energy is often sold to the power company and purchased back in the evening. This mismatch adds demand on power plants and increases carbon emissions. Powerwall bridges this gap between renewable energy supply and demand."

On the positive side, because the lithium-ion battery is enclosed in an outdoor-rated enclosure, it doesn't take up space in your garage or basement. Plus, it includes a liquid thermal management system, a battery management system, and a smart DC-DC converter for controlling power flow. Perhaps most interesting is that a 10 k Wh unit sells for $3,500, which puts the cost at $350/k Wh of storage. This is significantly better than competing systems which tend to run you closer to $500/k Wh. So, does it make financial sense to install one? Well, consider that the $3,500 price doesn't include the inverter, installation costs, or possible required upgrades to the home electrical system. Plus, the maximum continuous power draw is only 2,000W, which won't even run two hair dryers at the same time. The bottom line is that a plain old generator is still much cheaper for backup power. Prices are expected to drop dramatically over the next few years, though, so things might become more favorable. If you want a serious analysis now, try out the return-on-investment calculator at www.catalyticengineering.com/the-berlin-powerwall/#more-605. ▲

■ The Tesla Powerwall on an outdoor mounting.

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Easy Cable Tracing

It can be a real problem when you have a bunch of wires in the house, office, car, or other location, and need to figure out where they go and to what (if anything) they are connected. That's when you need something like Platinum Tools' new TP150 Tone and Probe set, designed to simplify cable tracing. As explained by product manager George Jang, "With the Platinum Tools Tone and Probe set's steady tone, push-to-scan button, and a clear loudspeaker, you can quickly trace and identify cable locations on jacks or through walls."

The probe features a pushbutton that activates tone scanning, and its tapered tip is designed to allow easy penetration of cable bundles. The tone generator includes a slide switch for selection of tone/off/cont modes, with the continuity mode used to determine if a wire is broken. It includes alligator clips to test wire pairs and an RJ11 connector for data and phone lines. For about $25, you get both the tone generator and probe, plus a carrying case, 9V batteries, and user instructions. ▲