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Date: 29 April 2015. Battery Primer (Tesla)


Tesla just announced a new battery is coming onto the market. With a capacity of *7kWh to 10kWh, that's one heck of a large battery capacity. How this could benefit those of us living off the grid is the question. The Tesla battery has the potential to positively effect life, however there are a few caveats.

*7kWh means 7 kilowatt hours or, 7000 watts (A/C -- your regular house electricity) [To give you an idea what that signifies in real life terms, a standard washing machine uses 2kWh and the drier takes 3kWh per load.]



First of all, don't take my word for it. The Tesla site is here:


Powerwall lithium
battery specs:

Made by Tesla company
Dimensions: 51.2" x 33.9" x 7.1"
1300 mm x 860 mm x 180 mm

Weight: 220 pounds / 100 kg

7 kWh model: $3000
10 kWh model: $3500

Voltage 350-450 volts


That final item (Voltage 350-450 volts) is the one that said "wait" to me. I know the difficulties of running a boat with both 24 and 12 volt systems. At this point this technology, though exciting has its limitations for application aboard cruising boats in my opinion.

Archie aboard M/V Irish Lady (a Monk36) said this: "The problem is adapting the new tech to old 12/24v tech in a boat. They will build inverters to go with the new batteries, but will they be acceptable to use in boats? If there is profit, someone will marinize them."

The main thing is, this Tesla battery is for a house. It is designed with A/C power considerations in mind, not the 12-volt world I live in. According to Tesla's website the Powerwall is a "Wall mounted, rechargeable lithium ion battery with liquid thermal control." Also, they state "Single phase and three phase utility grid compatible."

Basically, it's designed to supplement power used in a house. Of course the Powerwall alone is not enough. Also required are solar panels, wiring and more. The technology is exciting and if ashore I'd certainly investigate it thoroughly. 

To understand the technology you must know what exactly a battery is. Simply put, a battery stores energy. Whatever you put in can be removed, much like a pitcher water in your refrigerator. If you don't refill the jug, it will empty. So too will your battery empty of power.

Yes, solar panels can put back some of the power used and a large enough solar array will indeed keep up with usage. At this point however solar panels need to (in my view) increase efficiency too.

Patrick is carefully placing the hoist for my new engine to avoid damaging my solar panels.

Two 100 watt Renogy solar panels top the pilothouse providing power for Seaweed.

I currently have three solar panels aboard Seaweed. Two are on the pilothouse and the third cross-wise over the cockpit. Eventually I'd like two more 100 watt Renogy panels. That, with three more Group 29 marine batteries from Walmart should mean a totally decadent life off the grid for me.

Except for water. I cannot make that, yet.

This Tesla battery [http://www.teslamotors.com/powerwall] is a step and a positive one. When the costs come down and the size decreases too, well, sign me up.

Gosh, it would be good to have enough power generation to run one of those RV rooftop air-conditioning units without the Kubota engine or a generator running.

That's a maybe someday item for me. If I were tied long-term to a dock I'd definitely want an air conditioner aboard here in Florida. It gets h-o-t.

I study innovations and imagine ways the new
ideas can be used to positively impact my life.

I'd love to hear what you think of the Tesla.
And, are would you consider this for your house ashore?


2015, 2021

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