Poll on battery size.

[JRP3]

while this is technically feasible, it doesn't make sense in a financial way.

I don't think Level 3 makes sense at home financially no matter how it's configured :wink: It's going to be a large investment for a capability that will rarely be used, unless you intend to turn your home into a public charge station.

 

[WhiteKnight]

I do like the idea of having battery backup for the house - especially if the power goes out and I can't drive anywhere because I can't recharge. More likely to consider a natural gas generator though, since they're only about $5K.

And my house is the one place where I do not really need the quick charge capability.

 

[VolkerP]

A quick google search shows 100kWHr of lead acid can be bought retail for $15k USD. I wonder what kind of control electronics you would need to DC fast charge, given that you already have DC from the batteries.

Control electronics will be cheap. Just a micro controller to implement the DC charging protocol.

Fast DC charging must feed 250 amps to the 300 mile pack, following the voltage curve of the battery pack as the SoC goes up, then finally cut back the amps as the pack nears 100% SoC. An empty Tesla battery pack starts to charge near 325V and cuts off at 375V. Your lead acid battery bank will end up at ~ 1.8V cell voltage after a C/1 discharge, so you need ~ 220 cells in series. Thus, your start voltage is near 440V.

You need some DC/DC converting power electronics to step down from 440V to 325V at 250A. If you burn the delta, you must get rid of 28kW and need an even bigger battery bank.
For a more efficient way, look into a Pentium 4 desktop computer. Near the processor socket you can see fat electrolyte capacitors and semiconductor devices with bulky heat sinks. They are for converting 150W DC from 12V to around 1.25V. Scale it up 600 times.

 

[mnx]

aren't you on TOU billing? We've been on it for over a year now here in Hamilton...

Check your power bill, and make sure there aren't any additional charges - there often are.

Here in Ontario electricity is 7.5 cents per kwh, but there are also delivery charges, a regulatory charge, a debt retirement charge, and sales taxes, for a grand total of 13.4 cents per kwh. (Yes, it's horrible - Quebec charges half that.) It will cost me about $12 to fill the pack.

 

[Doug_G]

aren't you on TOU billing? We've been on it for over a year now here in Hamilton...

Only just started this month. It reduces the price by 1.5 cents at night, and raises it by 2.5 cents during the day. And they're now talking about a rate increase. :cursing:

 

[VolkerP]

go get solar.

 

[Robert.Boston]

Canada isn't the best place for solar. Nor is Germany, but for the insanely high feed-in tariff rate that subsidizes solar.

 

[Doug_G]

Canada isn't the best place for solar. Nor is Germany, but for the insanely high feed-in tariff rate that subsidizes solar.

You'd be surprised. In summer the daylight goes on and on. It's also peak sunlight when we have peak demand - when the air conditioners are all cranked up.

 

[Robert.Boston]

You'd be surprised. In summer the daylight goes on and on. It's also peak sunlight when we have peak demand - when the air conditioners are all cranked up.

I guess I should have said "compared to other parts of North America, ..." Southern Canada has a potential of about 4kWh/m^2/day, about 60% of the potential in southern California. See http://www.nrel.gov/gis/solar.html

 

[neroden]

Tesla owners can gather to fund some fast DC chargers in a highway station, though.

This is really the sort of thing I was thinking of regarding level 3, getting together to fund a public charger in a key location. It's not at all clear what standard to push for when talking to governments or businesses though. Sigh... standards wars strike again.